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The Coordination Committee formed by GR No. Abhyas - 2116/(Pra.Kra.43/16) SD - 4, Dated 25.4.2016 has given approval to prescribe this textbook in its meeting held on 3.3.2017, , SCIENCE, AND, , TECHNOLOGY, STANDARD NINE, , Maharashtra State Bureau of Textbook Production and, Curriculum Research, Pune., , The digital textbook can be obtained through DIKSHA APP, on a smartphone by using the Q. R. Code given on title page, of the textbook and useful audio-visual teaching-learning, material of the relevant lesson will be available through the, Q. R. Code given in each lesson of this textbook.

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Preface, Dear students,, Welcome to Std IX. We have great pleasure in offering to you this Science and, Technology textbook based on the new syllabus. From the Primary level till today, you, have studied Science from various textbooks. From Std IX onwards, you will be able to, study the fundamental concepts of Science and Technology from a different point of view, through the medium of the different branches of Science., The basic purpose of this textbook can be said to be ‘Understand and explain to others’, the science and technology that relates to our everyday lives. While studying the concepts,, principles and theories in Science, do make the effort to understand their connection with, day to day affairs. While studying from this textbook, use the sections ‘Can you recall?’, and ‘Can you tell?’ for revision. You will learn Science through the many activities given, under the titles such as ‘Observe and discuss.’ and ‘Try this’ or ‘Let's try this’. Activities, like ‘Use your brain power!’, ‘Research’, ‘Think about it.' will stimulate your power of, thinking., Many experiments have been included in the textbook. Carry out these experiments, yourself, following the given procedure and making your own observations. Ask your, teachers, parents or classmates for help whenever you need it. Interesting information, which reveals the science underlying the events we commonly observe, and the technology, developed on its basis, has been explained in this textbook through several activities. In, this world of speed and technology, you have already become familiar with computers and, mobile phones. While studying the textbook, make full and proper use of the devices of, information communication technology, which will make your studies so much easier., While carrying out the given activities and experiments, take all precautions with regard, to handling apparatus, chemicals, etc. and encourage others to take the same precautions., It is expected that while carrying out activities or observation involving plants and, animals, you will also make efforts towards conservation of the environment. You must, of, course, take all care to avoid doing any harm or causing injury to any plants or animals., Do tell us about the parts that you like as well as about the difficulties that you face as, you read and study and understand this textbook., Our best wishes for your academic progress., , Pune, Date : 28 April 2017, Akshaya Tritiya, Indian Solar Year :, 8 Vaishakh 1939, , (Dr Sunil Magar), Director, Maharashtra State Bureau of Textbook, Production and Curriculum Research, Pune

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For teachers, l, l, , l, , l, , l, , l, , l, , The real objective of science education is to learn to be able to think about events, that are happening around us, logically and with discretion., In view of the age group of Std IX students, it would be appropriate now, in the, process of science education, to give freedom and scope to the students’ own curiosity, about the events of the world, their propensity to go looking for the causes behind, them and to their own initiative and capacity to take the lead., As experimentation is necessary to learn the skills of observation, logic, estimation,, comparison and application of available data, which form a part of science education,, deliberate efforts must be made to develop these skills while dealing with laboratory, experiments given in the textbook. All observations that the students have noted, should be accepted, and then they should be helped to achieve the expected results., These two years in middle school lay the foundation of higher education in Science., Hence, it is our duty and responsibility to enrich and enhance the students’ interest, in science. You all will of course always actively pursue the objective of developing, their creativity and imbuing them with a scientific temper., You can use ‘Let’s recall’ to review the previous knowledge required for a lesson and, ‘Can you tell?’ to introduce a topic by eliciting all the knowledge that the students, already have about it from their own reading or experience. You may of course use, any of your own activities or questions for this purpose. Activities given under ‘Try, this’ and ‘Let’s try this’ help to explain the content of the lesson. The former are for, students to do themselves and the latter are those that you are expected to demonstrate., ‘Use your brain power!’ is meant for application of previous knowledge as well as, the new lesson, and ‘Always remember’ gives important suggestions/information or, values. ‘Research’, ‘Find out’, ‘Do you know?’, ‘An introduction to scientists’ and, ‘Institutes at work’ are meant to give some information about the world outside the, textbook and to develop the habit of doing independent reference work to obtain, additional information., This textbook is not meant for reading and explaining in the classroom but guiding, students to learn the methods of gaining knowledge by carrying out the given, activities. An informal atmosphere in the classroom is required to achieve the aims, of this textbook. All students should be encouraged to participate in discussions,, experiments and activities. Special efforts should be made to organise presentations, or report-reading in the class based on students’ activities and projects, besides, observing of Science Day and other relevant occasions/ days., The science and technology content of the textbook has been complemented with, Information Communication Technology. These activities are to be conducted under, your guidance along with the learning of various new scientific concepts., , Front and back covers : Pictures of various activities, experiments and concepts in the book., DISCLAIMER Note : All attempts have been made to contact copy righters (©) but we have not heard from them., We will be pleased to acknowledge the copy right holder (s) in our next edition if we learn from them.

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Competency Statements Standard IX, The living world, 1. To distinguish between the life processes of, plants and animals., 2. To use the knowledge about chemical control, in living organisms and based on that to, understand/ explain events in day to day life., 3. To distinguish between the different types of, tissue based on their exact structure., 4. To explain the importance/use of microorganisms in the production of antibiotics., 5. To explain the cause and effect relationship, between micro-organisms and the various life, processes of living organisms., 6. To explain the various diseases caused by, harmful micro-organisms and their remedies, and to be able to take care of one’s own health, and that of society., 7. To classify plants scientifically., 8. To draw a diagram of the excretory system, and nervous system of humans correctly and, explain their importance in our life., 9. To explain the importance of the hormones, secreted by the endocrine glands in the physical, development of the body and to explain their, causal relationship with problems like overexcitability and over-emotionality., , Diet and nutrition, 1. To explain what is tissue culture and its use, in agriculture and related occupations and to, give information about processes involved in, it., 2. To explain convincingly the importance, of agriculture-related occupations for, development of society., 3. To analyse the inter-relationship between the, food chain and the energy pyramid., 4. To find out the reasons for the changes in the, various cycles in nature., 5. To analyse the information about the factors, that endanger individual and social health, and suggest the remedies., 6. To change one’s lifestyle by taking into, account the effects of the various diseases, and disorders., , Energy, 1. To explain the inter-relationship between, work and energy and to identify the type, of work done in everyday instances., 2. To explain the logic involved in examples, of work, energy and power from everyday, life, and to solve numerical problems., 3. To explain the importance of various, sound-related concepts in everyday life, and solve various related problems., 4. To draw a diagram of a SONAR station, and explain it., 5. To explain the sound-related functions of, the human ear with the help of a diagram., 6. To identify the different types of mirrors,, to give a scientific explanation of the, images formed by them and to draw the, related ray diagrams., 7. To find the number of multiple images by, experiment., 8. To find out the scientific reasons for the, use of the different types of mirrors in our, daily life., Substances, 1. To describe the form structure and shape, of the substances of the universe and, explain the science behind it., 2. To verify the laws of chemical, combination, conservation of mass, and constant proportions and to make, inferences based on them., 3. To state the meaning of the concepts of, molecular mass and mole, to recognise, and write some molecular formulae as, also to explain them., 4. To classify substances of everyday use, with the help of indicators and to explain, their uses on the basis of experiments., 5. To verify by experiments the effects, of acids and alkalis on metals and, non-metals, 6. To eradicate superstitions and rigid, customs prevailing in society with the, help of relationship between indicators,, acids and bases., 7. To produce natural indicators., 8. To demonstrate the effectiveness of the, chemical substances.

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Natural resources and disaster management, 1. To explain the application/ relevance of, modern science and technology in the, work of the meteorological department., 2. To classify garbage generated in the house, and in the surroundings., 3. To produce manure from garbage or reuse, the waste materials., 4. To undertake activities related to, cleanliness of surroundings and motivate, others to do the same., 5. To compile information about how the, disaster management systems function, and make a presentation based on it. Thus, to be able to overcome crisis situations in, one’s own life., , Motion, Force and Machines, 1. To write equations of motion and use them to solve, numerical problems., 2. To obtain formulae by drawing graphs involving, quantities such as displacement, distance, time and, velocity., 3. To verify the cause and effect relationships, between motion and laws of motion as seen in, various events of everyday life., The Universe, 1. To use the telescope for sky watching., 2. To explain the contribution of astronomy and, modern technology to human progress., 3. To distinguish between the different types of, telescopes., , Information Communication Technology (ICT), 1. To state the fundamental changes that computer technology has brought about in society and the, fields of economics, science, industry, etc., 2. To use the computer to search for information in order to solve various problems., 3. To use the computer to explain to scientific concepts., 4. To identify problems arising in using computer software and to resolve them., 5. To use different ways of processing the information obtained by using the computer., , Contents, S.No. Name of Lesson , 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., , Page No., , Laws of Motion......................................................................................................... 1, Work and Energy..................................................................................................... 18, Current Electricity................................................................................................... 30, Measurement of Matter........................................................................................... 46, Acids, Bases and Salts............................................................................................ 58, Classification of Plants........................................................................................... 75, Energy Flow in an Ecosystem................................................................................. 81, Useful and Harmful Microbes................................................................................. 88, Environmental Management................................................................................... 96, Information Communication Technology (ICT) ....................................................... 108, Reflection of Light................................................................................................. 115, Study of Sound...................................................................................................... 128, Carbon : An important element............................................................................. 138, Substances in Common Use.................................................................................. 150, Life Processes in Living Organisms...................................................................... 163, Heredity and Variation.......................................................................................... 179, Introduction to Biotechnology............................................................................... 194, Observing Space : Telescopes .............................................................................. 209

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1. 1., Laws, Motion, गतीचेofनियम, Ø Motion , Ø Acceleration, , Distance and displacement, Ø Newton’s laws of motion and related equations., Ø, , Motion of an object, Can you tell?, , In which of the following examples can you sense motion?, How will you explain presence and absence of motion?, , 1. The flight of a bird , 2. A stationary train, 3. Leaves flying through air 4. A stone lying on a hill, We see the motion of several objects every day. Sometimes we cannot see the, motion of an object directly, as in the case of a breeze. Can you list other examples of, motion, besides those given here?, Think about it., 1. You are travelling in a bus. Is the person sitting next to you in motion?, 2. What do you take into consideration to decide if an object is moving or not?, You have learnt that motion is a relative concept. If the position of an object is, changing with respect to its surroundings, then it is said to be in motion. Otherwise, it is, said to be at rest., Displacement and distance, , A, B, , Let’s try this, , (a), , School, , 13, , 00, , m, , 1. Measure the distance between points, A and B in different ways as shown in, figure 1.1(a), 2. Now measure the distance along the, dotted line. Which distance is correct, according to you and why?, , Sheetal and, Prashant’s house, , (b), , Think about it., , 1200, m, , Path B, , 500 m, Path A, Sangeeta’s house, , 1.1 Location of the school and houses, , A. Sheetal first went to her friend Sangeeta’s house on her way to school (see figure 1.1b)., B. Prashant went straight from home to school. Both are walking with the same speed., Who will take less time to reach the school and why?, In the above example, is there a difference between the actual distance and the, distance travelled? What is it?, , 1

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‘Distance’ is the length of the actual path travelled by an object in motion while, going from one point to another, whereas displacement is the minimum distance between, the starting and finishing points., 1. Every morning, Swaralee walks round the edge of a, circular field having a radius of 100 m. As shown in, figure 1.2 (a), if she starts from the point A and takes, one round, how much distance has she walked and, what is her displacement?, , Use your brain power!, (a), , A, , ., , 2. If a car, starting from point P, goes to point Q (see, figure 1.2 b) and then returns to point P, how much, distance has it travelled and what is its displacement?, , ®, ®, , (b), 1.2 Distance and displacement, , 360 metres, , P, , Q, , Even if the displacement of an object is zero, the actual distance traversed by it may, not be zero., Speed and velocity, Can you recall?, , Speed =, , 1. What are vectors and scalars?, 2. Which of the quantities distance, speed, velocity, time and, displacement are scalars and which are vectors?, , Total distance travelled, Time required, , Always remember, 1. The units of speed and velocity are, the same. In the SI system, the unit, is m/s while in the CGS system, it, is cm/s., , The distance travelled in one direction, by an object in unit time is called its, velocity. Here, unit time can be one second,, one minute, one hour, etc. If large units are, used, one year can also be used as a unit of, time., The displacement that occurs in unit, time is called velocity., , Velocity =, , 2. Speed is related to distance while, velocity is related to the, displacement., 3. If the motion is along a straight, line, the values of speed and, velocity are the same, otherwise, they can be different., , Displacement, , Velocity is the displacement that, occurs in unit time., , Time, , 2

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In the first example (on page 1), the straight line distance between the houses of, Sheetal and Sangeeta is 500 m and that between Sangeeta’s house and school is 1200 m., Also, the straight line distance between Sheetal’s house and school is 1300 m. Suppose, Sheetal takes 5 minutes to reach Sangeeta’s house and then 24 minutes to reach school, from there, Then,, 500 m, Distance, = 100 m/minute, Sheetal’s speed along path A =, =, 5 minute, Time, Sheetal’s speed along path B =, , Distance, Time, , =, , 1200 m, 24 minute, , Sheetal’s average speed = Total distance, Total time, Displacement, 1300 m, Sheetal’s velocity =, =, Time, 29 minute, , = 50 m/minute, , 1700 m, = 58.6 m/minute, 29 minute, , Sheetal’s velocity = 44.83 m/minute, Effect of speed and direction on velocity, Sachin is travelling on a motorbike. Explain what, will happen in the following events during Sachin’s ride, (see figure 1.3)., 1. What will be the effect on the velocity of the, motorcycle if its speed increases or decreases, but its, direction remains unchanged?, 2. In case of a turning on the road, will the velocity and, speed be same?, If Sachin changes the direction of the motorcycle,, keeping its speed constant, what will be the effect on, the velocity?, 3. If, on a turning, Sachin changes the direction as well, as the speed of the motorcycle, what will be the effect, on its velocity?, It is clear from the above that velocity depends on, speed as well as direction and that velocity changes, by, 1. changing the speed while keeping the direction same, 2. changing the direction while keeping the speed same, 3. changing the speed as well as the direction., 1.3 Effect on velocity, , Always remember, , The first scientist to measure speed as the distance /time was Galileo. The speed, of sound in dry air is 343.2 m/s while the speed of light is about 3 × 108 m/s. The, speed of revolution of the earth around the sun is about 29770 m/s., , 3

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Uniform and non-uniform linear motion, Amar, Akbar and Anthony are travelling in different cars with different velocities., The distances covered by them during different time intervals are given in the following, table., Time in the, clock, , Distance covered by, Amar in km, , Distance covered by, Akbar in km, , Distance covered by, Anthony in km, , 5.00, 5.30, 6.00, 6.30, 7.00, , 0, 20, 40, 60, 80, , 0, 18, 36, 42, 70, , 0, 14, 28, 42, 56, , 7.30, , 100, , 95, , 70, , 8.00, , 120, , 120, , 84, , Use your brain power !, , 1. What is the time interval between the notings of distances made, by Amar, Akbar and Anthony?, 2. Who has covered equal distances in equal time intervals?, 3. Are all the distances covered by Akbar in the fixed time intervals, the same?, 4. Considering the distances covered by Amar, Akbar and Anthony, in fixed time intervals, what can you say about their speeds?, , If an object covers, unequal distances, in, equal, time, intervals, it is said, to be moving with, non-uniform speed., For example, the, motion of a vehicle, being, driven, througth, heavy, , If an object covers equal distances in equal time intervals, it, is said to be moving with uniform speed., traffic., Acceleration, , Let’s try this., , Channel, Ball, , 1.4 Change in velocity, , 1. Take a 1m long plastic tube and cut it lengthwise, into two halves., 2. Take one of the channel shaped pieces. Place, one of its ends on the ground and hold the other, at some height from the ground as shown in, figure 1.4., 3. Take a small ball and release it from the upper, end of the channel., 4. Observe the velocity of the ball as it rolls down, along the channel., 5. Is its velocity the same at all points?, 6. Observe how the velocity changes as it moves, from the top, through the middle and to the, bottom., , 4

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You must have all played on a slide in a park. You, know that while sliding down, the velocity is less at the top,, it increases in the middle and becomes zero towards the, end. The rate of change of velocity is called acceleration, Acceleration =, , Change in velocity, Time., , If the initial velocity is ‘u’ and in time ‘t’ it changes to, the final velocity ‘v’,, , Use your brain power!, 1. If the velocity, changes by equal, amounts in equal time, intervals, the object is, said to be in uniform, acceleration., 2., If the velocity, changes by unequal, amounts in equal time, intervals, the object is, say to be non-uniform, acceleration., , Final velocity – Initial velocity, (v-u), \a=, Time, t, If the velocity of an object changes during a certain time, period, then it is said to have accelerated motion. An object in, motion can have two types of acceleration., 1. When an object is at rest in the beginning of its motion,, what is its initial velocity?, 2. When an object comes to rest at the end of its motion, what is its final velocity?, Positive, negative and zero acceleration, An object can have positive or negative acceleration. When the velocity of an object, increases, the acceleration is positive. In this case, the acceleration is in the direction of, velocity. When the velocity of an object decreases with time, it has negative acceleration., Negative acceleration is also called deceleration. Its direction is opposite to the direction, of velocity. If the velocity of the object does not change with time, it has zero acceleration., Distance-time graph for uniform motion, The following table shows the distances covered by a car in fixed time intervals., Draw a graph of distance against time taking ‘time’ along the X-axis and ‘distance’ along, the Y-axis in figure 1.5., Y, Scale : X axis 1 cm =, Y axis 1 cm =, Time Distance, 140, (sec(metres), 120, onds), , 0, 10, 20, 30, 40, 50, 60, 70, , 0, 15, 30, 45, 60, 75, 90, 105, , Distance (metres), , Acceleration = a =, , 100, 80, 60, 40, 20, 0, , 10, , 20, , 1.5 Distance - time graph, , 5, , 30, , 40, , 50, , Time (seconds), , 60, , 70, , 80, , X

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An object in uniform motion, covers equal distances in equal time, intervals. Thus, the graph between, distance and time is a straight line., , Use your brain power !, In the distance-time graph above, what, does the slope of the straight line indicate?, , Distance-time graph for non-uniform motion, The following table shows the distances covered by a bus in equal time intervals, Draw a graph of distance against time taking the time along the X-axis and distance, along the Y-axis in figure 1.6. Does the graph show a direct proportionality between, distance and time?, Time, Distance, (second) (metre), , 0, 5, 10, 15, 20, 25, 30, 35, , 0, 7, 12, 20, 30, 41, 50, 58, , 1.6 Distance - time graph, , Here, the distance changes non-uniformly with time. Thus, the bus is having non-uniform motion., , Velocity-time, graph, for, uniform velocity, A train is moving with a, uniform velocity of 60 km/hour, for 5 hours. The velocity-time, graph for this uniform motion is, shown in figure 1.7., 1. With the help of the graph, how, will you determine the distance, covered by the train between 2, and 4 hours?, 2. Is there a relation between the, distance covered by the train, between 2 and 4 hours and the, area of a particular quadrangle, in the graph? What is the, acceleration of the train?, , What difference do you see in the distance-time, graphs for uniform and non-uniform motion?, Y, , 70, , A, , 60, Velocity (km/hr), , Use your brain power !, , Scale : X axis 1 cm = 1 hr, Y axis 1 cm = 10 km/hr, , B, , 50, 40, 30, 20, 10, C t1, , 1, , 0, , 2, , D t2, , 3, , 4, , 5, , Time (hours), 1.7 Velocity - time graph, , 6, , 6, , X

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Velocity-time graph for uniform acceleration, The changes in the velocity of a car in specific time intervals are given in the following, Y, table., Time Velocity, (seconds) (m/s), , 0, 8, 16, 24, 32, 40, 48, 56, , 48, Velocity (m/s), , 0, 5, 10, 15, 20, 25, 30, 35, , 56, , Scale : X axis 1 cm = 5 second, Y axis 1 cm = 8 m/second, , 40, , B, , 32, 24, 16, , A, , E, , 8, 0, , D, 5 10, 1.8, , 15, , C, 20 25, , 30, , 35, , 40, , X, , Time (seconds), Velocity - time graph, , The velocity-time graph in figure 1.8 shows that,, 1. The velocity changes by equal amounts in equal time intervals. Thus, this is uniform, acceleration in accelerated motion. How much does the velocity change every 5 minutes?, 2. For all uniformly accelerated motions, the velocity-time graph is a straight line., 3. For non-uniformly accelerated motions, the velocity-time graph may have any shape, depending on how the acceleration changes with time., From the graph in figure 1.8, we can determine the distance covered by the car between, the 10th and the 20th seconds as we did in the case of the train in the previous example. The, difference is that the velocity of the car is not constant (unlike that of the train) but is, continuously changing because of uniform acceleration. In such a case, we have to use the, average velocity of the car in the given time interval to determine the distance covered in, that interval., 32+16 = 24 m/s, From the graph, the average velocity of the car =, 2, Multiplying this by the time interval, i.e. 10 seconds gives us the distance covered by, Distance covered = 24 m/s x 10 s = 240 m, the car., Check that, similar to the example of the train, the distance covered is given by the, area of quadrangle ABCD., A(, , ABCD ) = A (, , AECD ) + A (, , ABE ), , Equations of motion using graphical method, Newton studied motion of an object and gave a set of three equations of motion., These relate the displacement, velocity, acceleration and time of an object moving along, a straight line., , 7

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Suppose an object is in motion along a straight line with initial velocity ‘u’. It attains, a final velocity ‘v’ in time ‘t’ due to acceleration ‘a’ its desplacement is ‘s’. The three, equations of motion can be written as, , v = u + at This is the relation between velocity and time., s = ut +, , 1 2, at This is the relation between displacement and time., 2, , v2 = u2 + 2as This is the relation between displacement and velocity., Let us try to obtain these equations by the graphical method., Equation describing the relation between velocity and time, Figure 1.9 shows the change in velocity with time of a uniformly accelerated object., The object starts from the point D in the graph with velocity u. Its velocity keeps increasing, and after time t, it reaches the point B on the graph., The initial velocity of the object = u = OD, The final velocity of the object = v = OC, Time = t = OE, Change in velocity, Acceleration (a) =, Time, , =, , (Final velocity – Initial velocity), Time, , (OC - OD), t, , \ CD = at, , u, , …… (i) (OC - OD = CD), , Draw a line parallel to Y axis passing through, B. This will cross the X axis in E. Draw a line, parallel to X-axis passing through D. This will, cross the line BE at A., From the graph.... BE = AB + AE, , \ v = CD + OD .....(AB = CD and, \ v = at + u ............(from i ), \ v = u + at, , B, C, , Velocity, , =, , v, , A, , D, , O, , Time, , 1.9, , t, E, , Velocity - time graph, , AE = OD), , This is the first equation of motion., Equation describing the relation between displacement and time, Let us suppose that an object in uniform acceleration ‘a’ and it has covered the, distance ‘s’ within time ‘t’. From the graph in figure 1.9, the distance covered by the object, during time ‘t’ is given by the area of quadrangle DOEB., , \ s = area of quadrangle DOEB, = area (rectangle DOEA) + area of triangle (DAB), , \ s = (AE × OE ) + (, , 1, × [AB × DA]), 2, , 8

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But, AE = u, OE = t and (OE = DA = t), AB = at ---( AB = CD ) --- from (i), , \s=u×t+, , 1, × at × t, 2, , \ Newton’s second equation of motion is s = ut +, , 1 2, at, 2, , Equation describing the relation between displacement and velocity, We have seen that from the graph in figure 1.9 we can determine the distance covered, by the object in time t from the area of the quadrangle DOEB. DOEB is a trapezium. So, we can use the formula for its area., , \ s = area of trapezium DOEB, \ s = 1 × sum of lengths of parallel sides × distance between the parallel sides, , 2, \ s = 1 × (OD + BE ) × OE But, OD = u, BE = v and OE = t, 2, 1, \ s = 2 × ( u + v) × t ------ (ii), (v-u), But, a =, t, , Always remember, , (v-u), a, , \ t=, , \ s=, , ---------------(iii), , 1, (v-u), × (u + v)×, 2, a, , (v+u) ( v-u), 2a, \ 2 as =(v+u) ( v-u) = v2-u2, s=, \ , , The velocity of an accelerated, object changes with time. Change, in the velocity can be due to a, change in direction or magnitude, of the velocity or both., , \ v2= u2 + 2as, this is Newton’s third equation of motion., Uniform circular motion, Let’s try this, , Observe the tip of the second hand of a clock. What can you, say about its velocity and speed?, , The speed of the tip of a clock is constant, but the direction of its displacement and, therefore, its velocity is constantly changing. As the tip is moving along a circular path,, its motion is called uniform circular motion. Can you give more examples of such motion?, , 9

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Try out and think about it, 1. Draw a rectangular path as shown figure 1.10, 2. Place the tip of your pencil on the middle of any side of, the square path and trace the path., 3. Note how many times you have to change the direction, while tracing the complete path., 4. Now repeat this action for a pentagonal, hexagonal,, octagonal path and note the number of times you have to, change direction., 5. If you increase the number of sides of the polygon and, make it infinite, how many times will you have to change, the direction? What will be the shape of the path?, This shows that as we increase the number of sides, we, have to keep changing direction more and more times., And when we increase the number of sides to infinity, the, polygon becomes a circle., When an object is moving with a constant, speed along a circular path, the change in, velocity is only due to the change in direction., Hence, it is accelerated motion. When an object, moves with constant speed along a circular, path, the motion is called uniform circular, motion, e.g. the motion of a stone in a sling or, that of any point on a bicycle wheel when they, are in uniform motion., , Research, , 1.10 Changes in direction, , If an object, moving along a circular, path of radius ‘r’, takes time ‘t’ to, come back to its starting position,, its speed can be determined using, the formula given below :, Speed = Circumference, Time, , v=, , 2 pr, t, , r =radius of the circle, , Find out more examples of circular motion in day to day life., , Determining the direction of velocity in uniform circular motion., Let’s try this, , Take a circular disc and put a five rupee coin at a point, along its edge., , Make it move around its axis by, putting a pin through it. When the, disc is moved at higher speed, the, coin will be thrown off as shown in, figure 1.11. Note the direction in, which it is thrown off. Repeat the, action placing the coin at different, points along the edge of the circle and, observe the direction in which the, coin is thrown off., , Coin, , Disc, , 1.11 The coin and the disc, , 10

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The coin will be thrown off in the direction of the tangent which is perpendicular to, the radius of disc. Thus, the direction in which it gets thrown off depends on its position at, the moment of getting thrown off. It means that, as the coin moves along a circular path, the direction of its motion is changing at every point., Solved examples, Example 1: An athlete is running on a circular track. He runs a distance of 400 m in 25 s, before returning to his original position. What is his average speed and velocity?, Given : Total distance travelled = 400 m, Total displacement = 0, as he returns to his original position., Total time = 25 seconds., Average speed = ?, Average velocity = ?, Average speed =, , Total distance covered, 400, =, Total time taken, 25, , Average velocity =, , Total displacement, Total time taken, , = 16 m/s, , 0, , = 25 = 0 m/s, , Example 2: An aeroplane taxies on the runway for 30 s with an acceleration of 3.2 m/s2, before taking off. How much distance would it have covered on the runway?, Given : a= 3.2 m/s2, t = 30 s, u = o , s = ?, , 1, 2, , s = ut + at2 = 0 × 30 +, , 1, × 3.2 × 302 = 1440 m., 2, , Example 3: A kangaroo can jump 2.5 m, vertically. What must be the initial velocity, of the kangaroo?, Given :, , Example 4 : A motorboat starts from rest, and moves with uniform acceleration. If it, attains the velocity of 15 m/s in 5 s,, calculate the acceleration and the distance, , a = 9.8 m/s2, s = 2.5 m, v=0, u=?, v2= u2 + 2as, (0)2 = u2 + 2 × (-9.8) (2.5) Negative sign, , travelled in that time., Given :, Initial velocity, u = 0,, final velocity, v = 15 m/s, time, t = 5 s., , is used as the acceleration is in the direction opposite to that of velocity., , 0 = u2 - 49, u2 = 49, u = 7 m/s, , Acceleration = a = ?, From the first equation of motion, a =, , 11, , v-u, 15-0, 2, =, = 3 m/s, t, 5

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From the second equation of motion, the distance covered will be, , 1 2, at, 2, 1, s = 0 × 5 + 3 × 52, 2, = 0 + 75 = 37.5 m, 2, , s = ut +, , Newton’s laws of motion, What could be the reason for the following?, 1. A static object does not move without the application of a force., 2. The force which is sufficient to lift a book from a table is not sufficient to lift the table., 3. Fruits on a tree fall down when its branches are shaken., 4. An electric fan keeps on rotating for some time even after it is switched off., If we look for reasons for the above, we realize that objects have some inertia. We, have learnt that inertia is related to the mass of the object. Newton’s first law of motion, describes this very property and is therefore also called the law of inertia., Newton’s first law of motion, Let’s try this, , Fill a glass with sand. Keep a piece of cardboard on it., Keep a five rupee coin on the cardboard. Now strike the cardboard hard using your fingers. Observe what happens., , Balanced and unbalanced force, You must have played tug-of-war. So long as the forces applied by both the sides are, equal, i.e. balanced, the centre of the rope is static in spite of the applied forces. On the, other hand, when the applied forces become unequal, i.e. unbalanced, a net force gets, applied in the direction of the greater force and the centre of the rope shifts in that direction., ‘An object continues to remain at rest or in a state of uniform motion along a, straight line unless an external unbalanced force acts on it.’, When an object is at rest or in uniform motion along a straight line, it does not mean that, no force is acting on it. Actually there are a number of forces acting on it, but they cancel, one another so that the net force is zero. Newton’s first law explains the phenomenon of, inertia, i.e. the inability of an object to change its state of motion on its own. It also, explains the unbalanced forces which cause a change in the state of an object at rest or in, uniform motion., All instances of inertia are examples of Newton’s first law of Motion., , 12

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Newton’s second law of motion, A. 1. Ask your friend to drop one plastic and one rubber, Let’s try this, ball from the same height., 2. You catch the balls. Which ball was easier to catch, and why?, B. 1. Ask your friend to throw a ball towards you at slow speed. Try to catch it., 2. Now ask your friend to throw the same ball at high speed towards you. Try to catch, it. Which ball could you catch with greater ease? Why?, The effect of one object, striking another object depends, both on the mass of the former, object and its velocity. This, means that the effect of the force, depends on a property related to, both mass and velocity of the, striking object. This property, was termed ‘momentum’ by, Newton., , Momentum has magnitude as well as, direction. Its direction is the same as that of, velocity. In SI system, the unit of momentum is, kg m/s, while in CGS system, it is g cm/s., If an unbalanced force applied on an object causes, a change in the velocity of the object, then it also, causes a change in its momentum. The force, necessary to cause a change in the momentum of, an object depends upon the rate of change of, momentum., , Momentum (P) : Momentum is the product of mass and velocity of an object. P = m v., Momentum is a vector quantity., ‘The rate of change of momentum is proportional to the applied force and the, change of momentum occurs in the direction of the force.’, Suppose an object of mass m has an initial velocity u. When a force F is applied in, the direction of its velocity for time t, its velocity becomes v., , \ The initial momentum of the object = mu,, Its final momentum after time t = mv, , \ Rate of change of momentum =, , Change in momentum, Time, , \ Rate of change of momentum =, , mv- mu, t, , = m (v- u) = ma, t, , According to Newton’s second law of motion, the rate of change of momentum is, proportional to the applied force., , \ ma a F, \ F = k ma (k = Constant of proportionality and its value is 1)., F= m×a, , 13

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Consider two objects having different, masses which are initially at rest. The, initial momentum for both is zero. Suppose, a force ‘F’ acts for time ‘t’ on both objects., The lighter object starts moving faster than, the heavier object. However, from the, above formula, we know that the rate of, change of momentum i.e. ‘F’ in both, objects is same and the total change in their, momentum will also be same i.e. ‘Ft’., Thus, if the same force is applied on, different objects, the change in momentum, is the same., Use your brain power !, , In SI system, the unit of force is, newton., Newton (N) : The force necessary to cause, an acceleration of 1 m/s2 in an object of, mass 1 kg is called 1 newton., 1 N = 1 kg × 1 m/s2, In CGS system the unit of force is a dyne., Dyne: The force necessary to cause an, acceleration of 1 cm/s2 in an object of, mass 1 gm is called 1 dyne., 1 dyne = 1 g × 1 cm/s2, , Why is there a thick bed of sand for a high jumper, to fall on after his jump?, , Newton’s third law of motion, Let’s try this, , 1. Take a plastic boat and make a hole at its rear end., 2. Inflate a balloon and fix it on the hole in the boat. Release, the boat in water. What happens to the boat as the air in the, balloon escapes slowly? Why?, , We have learnt about force and its effect on an object through Newton’s first and, second laws of motion., ‘However, in nature force cannot act alone.’ Force is a reciprocal action between two, objects. Forces are always applied in pairs. When one object applies a force on another, object, the latter object also simultaneously applies a force on the former object. The, forces between two objects are always equal and opposite. This idea is expressed in, Newton’s third law of motion. The force applied by the first object is called action force, while the force applied by the second object on the first is called reaction force., ‘Every action force has an equal and opposite reaction force which acts simultaneously.’, , 1. Action and reaction are terms that, express force., 2. These forces act in pairs. One force, cannot exist by itself., 3. Action and reaction forces act, simultaneously., 4. Action and reaction forces act on, different objects. They do not act, on the same object and hence, cannot cancel each other’s effect., , Use your brain power !, 1. While hitting a ball with a bat, the speed, of the bat decreases., 2. A gun recoils i.e. moves backwards, when a bullet is fired., 3. Mechanism of firing of a rocket., How will you explain these with the, help of Newton’s third law of motion?, , 14

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Law of conservation of momentum, Suppose an object A has mass m1 and its initial velocity is u1. An object B has mass m2 and, initial velocity u2., According to the formula for momentum, the initial momentum of A is m1 u1 and that of B, is m2u2 ., Suppose these two objects collide. Let the force on A due to B be F1. This force will cause, acceleration in A and its velocity will become v1., , \ Momentum of A after collision = m1 v1, , According to Newton’s third law of motion, A also exerts an equal force on B but in the, opposite direction. This will cause a change in the momentum of B. If its velocity after, collision is v2,, The momentum of B after collision = m2v2. If F2 is the force that acts on object B,, , F2 = -F1, \, \ m2 a2 = - m1 a1………… F= ma, , \ m2 ×, , (v -u ), (v2-u2), = - m1 × 1 1 ……… \ a = (v-u), t, t, t, , \ m2 (v2 - u2 )= - m1 (v1-u1), \ m2 v2 - m2 u2 = - m1 v1+ m1 u1, , \ (m2 v2 + m1 v1 )= (m1 u1+m2 u2), , The magnitude of total final momentum = the magnitude of total initial momentum., Thus, if no external force is acting on two objects, then their total initial momentum is, equal to their total final momentum. This statement is true for any number of objects., ‘When no external force acts on two interacting objects, their total momentum, remains constant. It does not change.’, This is a corollary to Newton’s third law of motion. The momentum is unchanged, after the collision. The momentum gets redistributed between the colliding objects. The, momentum of one of the objects decreases while that of the other increases. Thus, we can, also state this corollary as follows., ‘When two objects collide, the total momentum before collision is equal to the, total momentum after collision.’, In order to understand this principle, let us consider the example of a bullet fired from, a gun. When a bullet of mass m1 is fired from a gun of mass m2, its velocity becomes v1,, and its momentum becomes m1 v1. Before firing the bullet, both the gun and the bullet are, at rest and hence the total initial momentum is zero. According to the above law, the total, final momentum also has to be zero. Thus, the forward moving bullet causes the gun to, move backward after firing. This backward motion of the gun is called its recoil. The, velocity of recoil, v2 , is such that,, , m1 v1 + m2 v2 = 0 or v2 = -, , m1, m2 × v1, , 15

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As the mass of the gun is much higher than the mass of the bullet, the velocity of the, gun is much smaller than the velocity of the bullet. The magnitude of the momentum of, the bullet and that of the gun are equal and their directions are opposite. Thus, the total, momentum is constant. Total momentum is also constant during the launch of a rocket., Solved examples, Example 1: The mass of a cannon is 500 kg and it recoils with a speed of 0.25 m/s. What, is the momentum of the cannon?, Given : mass of the cannon = 500 kg, recoil speed = 0.25 m/s, Momentum = m × v = 500 x 0.25 = 125 kg m/s, , Momentum = ?, , Example 2: 2 balls have masses of 50 gm and 100 gm respectively and they are moving, along the same line in the same direction with velocities of 3 m/s and 1.5 m/s respectively., They collide with each other and after the collision, the first ball moves with a velocity of, 2.5 m/s. Calculate the velocity of the other ball after collision., Given :, The mass of first ball = m1 = 50 g = 0.05 kg, mass of the second ball = m2= 100 g = 0.1 kg, Initial velocity of the first ball = u1 = 3 m/s, Initial velocity of the second ball = u2 = 1.5 m/s, Final velocity of the first ball = v1 = 2.5 m/s ,Final velocity of the second ball = v2 = ?, According to the law of conservation of momentum, total initial momentum = Total final, momentum., , m1u1 + m2u2 = m1v1 + m2v2, (0.05 × 3) + (0.1 × 1.5) = (0.05 × 2.5) + (0.1 × v2), \ (0.15)+(0.15) = 0.125 + 0.1v2, \ 0.3 = 0.125 + 0.1 v2, 0.175, \ 0.1v2 = 0.3 - 0.125 \v2 =, = 1.75 m/s, 0.1, , Exercises, 1. Match the first column with appropriate entries in the second and third columns, and remake the table., S. No., , 1, 2, 3, , Column 1, Column 2, Column 3, Negative The velocity of the obA car, initially at rest, acceleration ject remains constant, reaches a velocity of 50 km/hr in 10 seconds, Positive, The velocity of, A vehicle is moving with a, acceleration the object decreases, velocity of 25 m/s, Zero, The velocity of the, A vehicle moving with the velocity of, acceleration, object increases, 10 m/s, stops after 5 seconds., , 2. Clarify the differences, A. Distance and displacement, B. Uniform and non-uniform motion., , 16

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3. Complete the following table., , u (m/s), 2, -, , a (m/s2), 4, 5, , t (sec), 3, 2, , u (m/s), , a (m/s2), , t (sec), , 5, 7, , 12, -, , 3, 4, , u (m/s), 4, -, , a (m/s2), 3, 5, , s (m), 8.4, , v = u + at (m/s), 20, , s = ut +, , 1 2, at (m), 2, 92, , v 2= u2 + 2as (m/s)2, 8, 10, , 7. Solve the following examples., a) An object moves 18 m in the first, 3 s, 22 m in the next 3 s and 14 m in, the last 3 s. What is its average, speed? , (Ans: 6 m/s), b) An object of mass 16 kg is moving, with an acceleration of 3 m/s2 ., Calculate the applied force. If the, same force is applied on an object of, mass 24 kg, how much will be the, acceleration? (Ans: 48 N, 2 m/s2), c) A bullet having a mass of 10 g and, moving with a speed of 1.5 m/s,, penetrates a thick wooden plank of, mass 900 g. The plank was initially, at rest. The bullet gets embedded in, the plank and both move together., Determine their velocity., , (Ans: 0.15 m/s), d) A person swims 100 m in the first, 40 s, 80 m in the next 40 s and 45 m, in the last 20 s. What is the average, speed?, (Ans: 2.25 m/s2), , 4. Complete the sentences and explain, them., a. The minimum distance between, the start and finish points of the, motion of an object is called the, ……….. of the object., b. Deceleration is -------- acceleration, c. When an object is in uniform, circular motion, its ………, changes at every point., d. During collision ......….. remains, constant., e. The working of a rocket depends, on Newton’s ….…. law of motion., 5. Give scientific reasons., a. When an object falls freely to the, ground, its acceleration is uniform., b. Even though the magnitudes of, action force and reaction force are, equal and their directions are, opposite, their effects do not get, cancelled., c. It is easier to stop a tennis ball as, compared to a cricket ball, when, both are travelling with the same, velocity., d. The velocity of an object at rest is, considered to be uniform., 6. Take 5 examples from, your, surroundings and give explanation, based on Newtons laws of motion., , Project:, Obtain, information, about, commonly used gadgets or devices, which are based on the principles, of Newton’s laws of motion., , ²²², , 17

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2. Work, and, Energy, 1. गतीचे, नियम, Ø, , Work , , Ø, , Law of conservation of energy, , Ø, , Energy , , Ø, , Mechanical energy, , Ø, , Free fall, , Observe, , 2.1 Various activities, , Can you tell?, , 1. In which of the pictures above has work been done?, 2. From scientific point of view, when do we say that no, work was done?, , Generally, any mental or physical activity is referred to as work. When we walk or, run, the energy in our body is used to do the necessary work. We say that a girl who is, studying is working or performing work. But that is mental work., In physics, we deal with physical work. Work has a special meaning in physics., ‘Work is said to be done when a force applied on an object causes displacement, of the object.’, You have already learnt that the work done by a force acting on an object is the, product of the magnitude of the force and the displacement of the object in the direction of, the force. Thus, Work = force × displacement, Use your brain power !, What are different types of, You have learnt how to, forces and their examples?, calculate the work done on an, object when the displacement, Minakshee wants to displace a wooden, is in the direction of the applied, block from point A to point B along the surface, force. But if the displacement, of a table as shown in figure 2.2A. She has used, is not in the direction of the, force F for the purpose. Has all the energy she, applied force, how do we, spent been used to produce acceleration in the, calculate the amount of work, block? Which forces have been overcome using, done?, that energy?, Can you recall?, , 18

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B, , Observe and discuss., , A, , B, , A, , C, 2.2 Displacement of an object, , You must have seen the events depicted in the pictures B and C above. When a child, pulls a toy with the help of a string, the direction of the force is different from that of, displacement. Similarly, when a large vehicle tows a small one, the directions of force and, the displacements are different. In both these cases, the direction of force makes an angle, with the direction of displacement. Let us see how to calculate work done in such cases., When a child pulls a toy cart, force is applied along the direction of the string while, the cart is pulled along the horizontal surface. In this case, in order to calculate the amount, of work done, we have to convert the applied force into the force acting along the direction, of displacement., Let F be the applied force and F1 be its component in the direction of displacement., Let s be the displacement. The amount of work done is given by, , W = F1.s ................................. (1), , The force F is applied in the direction of the string i. e. at an angle with the horizontal., Let q be the angle that the string makes with the horizontal. We can determine the component, F1, of this force F, which acts in the horizontal direction by means of trigonometry., (see figure2.3), F, cos q = base / hypotenuse, , cos q = F1 / F, F1 = F cos q, , Thus, the work done by F1 is, , W = F cos q s, W = F s cos q, , )q, F1, , Enter your conclusions about the work, done for the specific values of q in the, following table., Conclusion, , 2.3 Force used for the displacement, , q, 00, 900, 1800, , cos q, 1, 0, -1, , W = F s cos q, W=Fs, 0, W = -F s, , 19

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Unit of work, Work = Force × Displacement, In SI system, the unit of force is newton (N) and the unit of displacement is metre, (m). Thus, the unit of force is newton-metre. This is called joule., 1 Joule : If a force of 1 newton displaces an object through 1 metre in the direction, of the force, the amount of work done on the object is 1 joule., \ 1 joule = 1 newton ´ 1 metre, 1J=1N ´1m, In CGS system, the unit of force is dyne and that of displacement is centimeter, (cm). Thus, the unit of work done is dyne-centimetre. This is called an erg., 1 erg : If a force of 1 dyne displaces an object through 1 centimetre in the direction, of the force, the amount of work done is 1 erg., 1 erg = 1 dyne ´ 1 cm, Relationship between joule and erg, We know that, 1 newton = 105 dyne and 1 m = 102 cm, Work = force ´ displacement, 1 joule = 1 newton ´ 1 m, 1 joule = 105 dyne ´ 102 cm, = 107 dyne cm, 1 joule = 107 erg, Positive, negative and zero work, Think before you answer, , Discuss the directions of force and of, displacement in each of the following cases., , 1. Pushing a stalled vehicle, 2. Catching the ball which your friend has thrown towards you., 3. Tying a stone to one end of a string and swinging it round and round by the other, end of the string., 4. Walking up and down a staircase; climbing a tree., 5. Stopping a moving car by applying brakes., You will notice that in some of the above examples, the direction of the force and, displacement are the same. In some other cases, these directions are opposite to each, other, while in some cases, they are perpendicular to each other. In these cases, the work, done by the force is as follows., 1. When the force and the displacement are in the same direction (q = 00 ), the work done by, the force is positive., 2. When the force and the displacement are in opposite directions (q = 1800), the work done, by the force is negative., 3. When the applied force does not cause any displacement or when the force and the, displacement are perpendicular to each other (q =900), the work done by the force is zero., , 20

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Try this, Take a plastic cup and make a hole in the Figure A, centre of its bottom. Take a long thread, double it, and pass it through the hole. Tie a thick enough, knot at the end so that the knot will not pass, through the hole, taking care that the two loose, ends are below the bottom of the cup. Tie a nut, each to the two ends as shown in figure 2.4. Now, do the following., As shown in figure ‘A’, put the cup on a table,, keep one of the nuts in the cup and let the thread, carrying the other nut hang down along the side Figure B, of the table. What happens?, As shown in figure ‘B’, when the cup is, sliding along the table, stop it by putting a ruler in, its path., As shown in figure ‘C’, keep the cup at the, centre of the table and leave the two nuts hanging, on opposite sides of the table., Questions:, 1. Figure A - Why does the cup get pulled?, 2. Figure B - What is the relation between the, displacement of the cup and the force applied, through the ruler?, 3. In figure C - Why doesn’t the cup get displaced?, 4. What is the type of work done in figures A, B, and C?, In the three actions above, what is the, relationship between the applied force and the, displacement?, , Figure C, , Cup, , thread, nut, Cup, , thread, nut, , Cup, , thread, nut, , nut, , 2.4 Positive, negative and zero work, , Suppose an artificial satellite is moving around the earth in a circular orbit. As, the gravitational force acting on the satellite (along the radius of the circle) and its, displacement (along the tangent to the circle) are perpendicular to each other, the, work done by the gravitational force is zero, Institutes at work, The National Physical Laboratory, New Delhi, was conceptualized in 1943. It, functions under the Council of Scientific and Industrial Research. Its conducts basic, research in the various branches of physics and helps various industries and institutes, engaged in developmental work. Its main objective is to establish national standards of, various physical quantities., , 21

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Solved examples, Example 2 : Pravin has applied a force of, Example 1: Calculate the work done to, 100 N on an object, at an angle of 600 to, take an object of mass 20 kg to a height of, the horizontal. The object gets displaced in, 10 m., the horizontal direction and 400 J work is, (g = 9.8 m/s2), done. What is the displacement of the, Given: m = 20 kg; s = 10 m, object?, 2, , g = 9.8 m/s, \ F = m.g, = 20 ´ (-9.8), , (cos 600 = 1 ), Given :, , 2, , q = 600 , F = 100 N, W = 400 J , s = ?, W = F s Cos q, 400 = 100 ´ s ´ 12, , (The negative sign is taken because, the displacement is opposite to the direction, of the force.), , F = -196 N, \W=Fs, = -196 ´ 10, W = -1960 J, , 400 = 1 ´ s, 100, 2, , (The negative sign appears because, 4´2=s, \ s = 8 m , the direction of force is opposite to the, direction of displacement so that the work, The object will be displaced through 8 m., done is negative.), Energy, Why does it happen?, 1. If a pot having a plant is kept in the dark, the plant languishes., 2. On increasing the volume of a music system or TV beyond a limit, the vessels in the, house start vibrating., 3. Collecting sunlight on a paper with the help of a convex lens burns the paper., The capacity of a body to perform work is called its energy. The units of work and, energy are the same. The unit in SI system is joule while that in cgs system is erg., You have learnt that energy exists in various forms like mechanical, heat, light, sound,, electro-magnetic, chemical, nuclear and solar. In this chapter, we are going to study two, forms of mechanical energy, namely, potential energy and kinetic energy., Kinetic energy, What will happen in the following cases?, 1. A fast cricket ball strikes the stumps., 2. The striker hits a coin on the carom board., 3. One marble strikes another in a game of marbles., From the above examples we understand that when a moving object strikes a stationary, object, the stationary object moves. Thus, the moving object has some energy, part or all, of which it shares with the stationary object, thereby setting it in motion. ‘The energy, which an object has because of its motion is called its kinetic energy’. The work done by, a force to displace a stationary object through a distance s is the kinetic energy gained by, the object., Kinetic energy = work done on the object, , \ K.E. = F × s, , 22

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Expression for kinetic energy :, Suppose a stationary object of mass m moves because of an applied force. Let u be its, initial velocity (here u = 0). Let the applied force be F. This generates an acceleration a in, the object, and, after time t, the velocity of the object becomes equal to v. The displacement, during this time is s. The work done on the object, W = F . s, , W=F×s, , According to Newton’s second law of motion,, F = ma -------- (1) Similarly, using Newton’s second equation of motion, s = ut + 1 at2, However, as initial velocity is zero, u = 0., , 2, , s=0+, s=, , 1 at2, 2, , 1 at2 ------(2), 2, , \ W = ma ´ 1 at2 ------ using equations (1) and (2), 2, W = 12 m(at)2 -------(3), Using Newton’s first equation of motion .............., , v = u + at, \ v = 0 + at, \ v = at, \ v2 = (at)2 ------(4), \ W = 1 mv2 ------- using equations (3) and (4), , 2, , The kinetic energy gained by an object is the amount of work done on the object., , \ K. E. = W, \ K. E. = 12 mv2, Example : A stone having a mass of 250 gm is falling from a height. How much kinetic, energy does it have at the moment when its velocity is 2 m/s?, m = 250 g , m = 0.25 kg , Given :, , v = 2 m/s, K.E . = 12 mv2 = 12 × 0.25 × (2)2 = 0.5 J, , Use your brain power !, , The mass of a moving body is doubled, how, many times will the kinetic energy increase?, , 23

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Potential energy, 1. An arrow is released from a stretched bow., 2. Water kept at a height flows through a pipe into the tap below., Try this, 3. A compressed spring is released., Which words describe the state of the object in the above examples? Where did the, energy required to cause the motion of objects come from?, If the objects were not brought in those states, would they have moved?, ‘The energy stored in an object because of its specific state or position is called, its potential energy.’, 1.Hold a chalk at a height of 5 cm from the floor and release it., 2. Now stand up straight and then release the chalk., 3. Is there a difference in the results of the two activities? If so, why?, Expression for potential energy, To carry an object of mass ‘m’ to a height ‘h’ above the earth’s surface, a force equal, to ‘mg’ has to be used against the direction of the gravitational force. The amount of, work done can be calculated as follows., Work = force x displacement, , W = mg × h, \ W = mgh, \ The amount of potential energy stored in the object because of its displacement, P.E. = mgh (W = P.E.), \ Displacement to height h causes energy equal to mgh to be stored in the object., Example : 500 kg water is stored in the overhead tank of a 10 m high building. Calculate, the amount of potential energy stored in the water., Given :, , h = 10 m, m = 500 kg g = 9.8 m/s2, \ P.E. = mgh, = 10 × 9.8 ×500, P.E. = 49000 J, Ajay and Atul have been asked to, determine the potential energy of a ball of, mass m kept on a table as shown in the, figure. What answers will they get? Will, they be different? What do you conclude, from this?, Potential energy is relative. The, heights of the ball with respect to Ajay, and Atul are different. So the potential, energy with respect to them will be, different., , Atul, Ajay, , h2, h1, , 24

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Transformation of energy, Can you tell?, , Which are the different forms of energy? Which type of, energy is used in each of the following processes?, , 1. A stretched piece of rubber 2. Fast moving car 3. The whistling of a cooker due to, steam 4. The crackers exploded in Diwali 5. A fan running on electricity 6. Drawing out, pieces of iron from garbage, using a magnet 7. Breaking of a glass window pane because, of a loud noise., Energy can be transformed from one type to another. For example, the exploding, firecrackers convert the chemical energy stored in them into light, sound and heat energy., Engine/Fan, , am, , cl, , tri, , ec, , El, , Heat energy, , Thermo-couple, Lo, ud, sp, ea, ke, M, r, ic, ro, ph, on, e, Sound, energy, Secondary cell, , ®, ®, , p, , cc, , tri, , -el, , ®, oto, , ph, , ll /, ce, lar, So, , Light, energy, , ®, , Generator, , ®, ®, ®, ®, , Electrical, energy, , ell, , ®, ®, ec, , Mechanical, energy, , Heater, , Primary cell, , Chemical, energy, , 2.5 Tranformation of energy, , Observe the above diagram (figure 2.5) and discuss how tranformation of energy, takes place, giving example of each., Law of conservation of energy, ‘Energy can neither be created nor destroyed. It can be converted from one form, into another. Thus, the total amount of energy in the universe remains constant’., Try this, , Make two pendulums of the same length with the help of thread, and two nuts. Tie another thread in the horizontal position., , Tie the two pendulums to this horizontal thread, in such a way that they will not hit each other while, swinging. Now swing one of the pendulums and, observe. What do you see?, You will see that as the speed of oscillation of the, pendulum slowly decreases, the second pendulum, which was initially stationary, begins to swing. Thus,, one pendulum transfers its energy to the other., , 25, , thread, thread, , nut, , 2.6, , thread, , nut, , Coupled oscillators

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Free fall, If we release an object from a height, it gets pulled towards the earth because of the, gravitational force. An object falling solely under the influence of gravitational force is, said to be in free fall or to be falling freely. Let us look at the kinetic and potential energies, of an object of mass m, falling freely from height h, when the object is at different, heights, A, As shown in the figure, the point A is at a height h, from the ground. Let the point B be at a distance x,, vertically below A. Let the point C be on the ground, directly below A and B. Let us calculate the energies of, the object at A, B and C., x, 1. When the object is stationary at A, its initial velocity, is u = 0, , \ K.E. = 1 mass x velocity2, , 2, = 1 mu2, 2, , K.E. = 0, P.E. = mgh, \ Total energy = K.E. + P.E., = 0 + mgh, Total Energy = mgh.--- (1), , h-x, , C, , 2. Let the velocity of the object be vB when, it reaches point B, having fallen through a, distance x., u = 0, s = x, a = g, , 2.7, , Free fall, , 3. Let the velocity of the object be vC when, it reaches the ground, near point C., , u = 0, s = h, a = g, v2 = u2 + 2as, vc2 = 0 + 2gh, \ K.E. = 1 mvC2 = 1 m(2gh), , v = u + 2as, 2, , h, , B, , 2, , vB2 = 0 + 2gx, vB2 = 2gx, , 2, , \ K.E. = 12 mvB2 = 12 m(2gx), , 2, , K.E. = mgh, , K.E. = mgx, , The height of the object from the, ground at point C is, h=0, , Height of the object when at B = h-x, , \ P.E. = mg (h-x), P.E. = mgh - mgx, \ Total Energy T.E. = K.E. + P.E., = mgx + mgh - mgx, \ T.E. = mgh -------(2), , \ P.E. = mgh = 0, \ T.E. = K.E. + P.E, T.E. = mgh ------(3), , From equations (1), (2) and (3) we see, that the total energy of the object is the, same at the three points A, B and C., , 26

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Thus, every object has potential energy when it is at a height above the ground and it, keeps getting converted to kinetic energy as the object falls towards the ground. On, reaching the ground (point C), all the potential energy gets converted to kinetic energy., But at any point during the fall the total energy remains constant., i.e., T.E. = P.E. + K.E., T.E. at A = mgh + 0 = mgh, T.E. at B = mgx + mg (h - x) = mgh, T.E. at C = 0 + mgh = mgh, Power, Think before you answer 1. Can your father climb stairs as fast as you can?, 2. Will you fill the overhead water tank with the help of a bucket or an electric motor?, 3. Suppose Rajashree, Yash and Ranjeet have to reach the top of a small hill. Rajashree, went by car, Yash went cycling while Ranjeet went walking. If all of them choose the, same path, who will reach first and who will reach last?, In the above examples, the work done is the same in each example but the time taken, to perform the work is different for each person or each method. The fast or slow rate of, the work done is expressed in terms of power. ‘Power is the rate at which work is done.’, If W amount of work is done in time t then,, Power =, , Work, Time, , An introduction to scientists, , W, P=, t, , In SI system the unit of work is J, so the unit of, power is, J/s. This is called watt, 1 watt = 1 joule / 1 second, In the industrial sector the unit used to measure, power is called ‘horse power.’, 1 horse power = 746 watt., The unit of energy for commercial use is kilo watt, hour., 1000 joule work performed in 1 second is 1, kilowatt power., , 1 kW h, , , 1 kW h, , = 1 kW ´ 1hr, = 1000 W ´ 3600 s, = 3600000 J, = 3.6 ´ 106 J, , Electricity used for domestic purposes is measured, in units of kilowatt hour., , 1 kW h = 1 unit, , 27, , The steam engine was, invented in 1781 by the, Scottish scientist James, Watt (1736 – 1819). This, invention brought about an, industrial revolution. The, unit of power is called Watt, in his honour. James Watt, was the first to use the term, ‘horse-power’.

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Solved problems, Example 1 : Swaralee takes 20 s to carry, Example 2 : A 25 W electric bulb is used, a bag weighing 20 kg to a height of 5 m., for 10 hours every day. How much electricHow much power has she used?, ity does it consume each day?, Given : m = 20 kg, h = 5 m, t = 40 s, \ The force which has to be applied Given :, P = 25, W = 0.025 kW, by Swaralee,, , \ Energy consumed = power ´ time, = 0.025 ´ 10, Energy = 0.25 kW hr, , F = mg = 20 ´ 9.8, F = 196 N, , Work done by Swaralee to carry the, bag to a height of 5 m,, , W = F s = 196 ´ 5 = 980 J, Work, \ power = (P) = t, , , , Websites for more information :, , 980, =, 40, , www.physicscatalyst.com, www.tryscience.org, , P = 24.5 W, , Exercises, 1. Write detailed answers?, a. Explain the difference between, potential energy and kinetic energy., b. Derive the formula for the kinetic, energy of an object of mass m,, moving with velocity v., c. Prove that the kinetic energy of a, freely falling object on reaching, the ground is nothing but the, transformation of its initial potential, energy., d. Determine the amount of work, done when an object is displaced at, an angle of 300 with respect to the, direction of the applied force., e. If an object has 0 momentum, does, it have kinetic energy? Explain your, answer., f. Why is the work done on an object, moving with uniform circular, motion zero?, 2. Choose one or more correct alternatives., , a. For work to be performed, energy, must be …., (i) transferred from one place to, another (ii) concentrated, (iii) transformed from one type to, another (iv) destroyed, b. Joule is the unit of …, (i) force (ii) work (iii) power, (iv) energy, c. Which of the forces involved in, dragging a heavy object on a, smooth, horizontal surface, have, the same magnitude?, (i) the horizontal applied force (ii), gravitational force (iii) reaction, force in vertical direction (iv) force, of friction, d. Power is a measure of the ...…., (i) the rapidity with which work is, done (ii) amount of energy required, to perform the work (iii) The, slowness with which work is, performed (iv) length of time, , 28

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e. While dragging or lifting an object,, negative work is done by, (i) the applied force (ii) gravitational, force, (iii), frictional, force, (iv) reaction force, 3. Rewrite the following sentences, using proper alternative., a. The potential energy of your body is, least when you are ….., (i) sitting on a chair (ii) sitting on, the ground (iii) sleeping on the, ground (iv) standing on the ground, b. The total energy of an object falling, freely towards the ground …, (i) decreases (ii) remains unchanged, (iii) increases (iv) increases in the, beginning and then decreases, c. If we increase the velocity of a car, moving on a flat surface to four, times its original speed, its potential, energy …., (i) will be twice its original energy, (ii) will not change (iii) will be 4, times its original energy (iv) will be, 16 times its original energy., d. The work done on an object does, not depend on …., (i), displacement (ii) applied, force (iii) initial velocity of the, object (iv) the angle between force, and displacement., 4. Study the following activity and, answer the questions., 1. Take two aluminium channels of, different lengths., 2. Place the lower ends of the channels, on the floor and hold their upper, ends at the same height., 3. Now take two balls of the same size, and weight and release them from, the top end of the channels. They, will roll down and cover the same, distance., , Questions, 1. At the moment of releasing the, balls, which energy do the balls, have?, 2. As the balls roll down which energy, is converted into which other form, of energy?, 3. Why do the balls cover the same, distance on rolling down?, 4. What is the form of the eventual, total energy of the balls?, 5. Which law related to energy does, the above activity demonstrate ?, Explain., 5. Solve the following examples., a. An electric pump has 2 kW power., How much water will the pump lift, every minute to a height of 10 m?, (Ans : 1224.5 kg), b. If a 1200 W electric iron is used, daily for 30 minutes, how much, total electricity is consumed in the, month of April?, (Ans :18 Unit), c. If the energy of a ball falling from a, height of 10 metres is reduced by, 40%, how high will it rebound?, , (Ans : 6 m), d. The velocity of a car increase from, 54 km/hr to 72 km/hr. How much is, the work done if the mass of the car, is 1500 kg ?, , (Ans. : 131250 J), e. Ravi applied a force of 10 N and, moved a book 30 cm in the direction, of the force. How much was the, work done by Ravi?, (Ans: 3 J), Project :, Study the various instances of, trasnformation of energy you see, around you and discuss them in, class., , 29, , ²²²

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3. Current, 1. गतीचे Electricity, नियम, Potential and potential difference Ø Conductors and insulators, (bad conductors) Ø Electrical resistance and Ohm’s Law, Ø Connection of resistors and effective resistance, , Ø, , All around us, Electricity is of utmost importance in the modern world. We depend on it for almost, everything in our day to day life. In order to avoid the inconvenience faced due to failure, of power supply, hospitals, banks, offices and private institutions make alternative, arrangements with the help of generators. Electricity is used for running electric furnaces,, electric motors and several other instruments used in industries., Domestic appliances like the fridge, electric oven, mixer, fans, washing machines,, vacuum cleaner, rotimaker, etc. have helped us by saving time and labour. All these, devices cannot be run without electricity., Not only human beings but some animals also use electricity. For example, fishes, such as eels use electricity to catch their prey and also for self-defence. The lightning that, strikes the earth is an excellent example of natural flow of electricity. What if we could, collect and store this electricity!, Can you recall?, , You must have seen a waterfall. Which way does the water, flow?, , For the generation of electricity, water is released from a dam at a higher level and, because of gravity, it falls to a lower level. Thus, as we know, the direction of flow of, water between two points depends on the level of the two points., Potential and potential difference, Try this, , Equipment : Two plastic bottles, rubber tube, clamp, water., Procedure : Set up the experiment as shown in figure 3.1. Then, remove the clamp from the rubber tube. Note your observations., Answer the following questions., 1. What happens when the clamp is, removed?, 2. Does the water stop flowing? Why?, 3. What will you do to keep the water, flowing for a longer duration?, , Clamp, , Just like water, the flow of electric, charge between two points depends on, a kind of electric level at those points., This level is called electric potential., , 3.1 Level of water and direction of flow, , 30

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A positive charge flows from a point of higher potential to a point of lower potential., We have seen earlier that electricity flows due to the conduction of negatively charged, electrons. Electrons flow from the point of lower potential to a point of higher potential. A, lightning strike is the flow of electrons from point of lower (negative) potential on the, clouds to the point of higher (zero) potential on the earth. We shall study the definition of, electric potential in higher standards., The difference between the values of potentials at two points A and B is called the, potential difference between them., Low electric potential, High electric potential, In the figure 3.2, conductor A is, at a higher potential than conductor, Conducting wire, B, A, B. When these two are connected by, a conducting wire, a potential, Negatively, Positively charged, charged, difference is created between its, conductor, conductor, two ends and electrons will flow, from B to A through the wire. This, flow will continue until the two Stand with insulating, Stand with insulating, conductors, A and B have the same covering, covering, potential, i.e. until their potential, difference becomes zero. Only then, 3.2 Potential difference and flow of electricity, will the flow of electrons stop., Work has to be done against the electric field to take a positive charge from a point of, lower potential to a point of higher potential., Potential difference of a cell, The difference in potential between the positive and negative terminals of a cell is the, potential difference of that cell. This potential difference is caused by chemical reactions, occurring inside the cell. The potential difference sets the electrons in motion and results, in the flow of electricity through a conducting wire connected to the two ends of the cell., The amount of work done to carry a unit positive charge from point A to point B is, called the electric potential difference between the two points., , Potential difference between two points =, , The unit of potential difference in SI system is volt., Electrons Weakly attached outermost electrons, , Single atom, , Ê, , Nucleus, , 1J, 1C, , Ê, , 1V=, , Work, W, ,V=, Total charge transferred, Q, , Ê, , Ê, , Free electrons move freely, from atom to atom, , Atoms in a conducting solid, , 3.3 Free electrons, , 31

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An introduction to scientists, The Italian scientist Alessandro, Volta constructed the first electric cell., The unit of potential difference is, named ‘volt’ in his honour., Volta’s simple electric cell, , Do you know?, Very small values of potential difference, are expressed in the following units., 1. 1mV (millivolt) = 10-3 V, 2. 1mV (microvolt) = 10-6 V, , Large values of potential difference are, expressed in the following units., 1. 1kV (kilovolt) = 103 V, 2. 1MV (megavolt) = 106 V, , Free electrons : Every atom of a metallic conductor has one or more outermost electrons, which are very weakly bound to the nucleus. These are called free electrons., As shown in figure 3.3, these electrons can easily move from one part of a conductor to its, other parts. The negative charge of the electrons also gets transferred as a result of this, motion. The free electrons in a conductor are the carriers of negative charge., Current flowing through a wire, As shown in the figure 3.4 A, if a, conducting wire is not connected, to a cell, its free electrons move, randomly in all directions in the, space between the atoms. When, we connect the ends of the wire to, the two terminals of a cell, electric, force acts on the electrons. Being, negatively charged, they start, moving from the negative (lower, potential) to the positive (higher, potential) terminal of the cell, as, shown in figure 3.4 B. Due to the, flow of these electrons, current, starts to flow through the wire., This motion of electrons is, irregular but there is a definite,, non-zero value to their average, velocity., , Electrons, , Metal wire, , ®, , A. Random motion of electrons in the wire, , ®, , Direction of flow of electrons, , +, , Direction of conventional electric current, , +, , -, , ®, , Electric cell, , B. Motion of electrons after applying a potential, difference to the two ends of the wire, 3.4 Motion of free electrons, , 32

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Electric current, An electric current is the flow of electrons through, a conductor. Quantitatively, current (I) is defined as, the charge passing through a conductor in unit time., If charge Q is flowing through cross-section of a, conductor in time t then the, current = I =, , Q, t, , Even though, electrons, move from negative end to, positive end, conventionally, the, direction of current flow is taken, to be opposite of the direction of, flow of electrons i.e. from the, +ve end to the –ve end of a cell., , The unit of charge in SI units is Coulomb (C). Current is expressed in Ampere (A)., The charge of one electron is 1.6 x10-19 C., Ampere : One ampere current is said to flow in a conductor if one Coulomb charge flows, through it every second., , 1A =, , 1C, 1s, , Do you know?, Very small values of current are expressed in the, following units., 1. 1mA (mili ampere ) = 10-3 A, 2. 1mA (micro ampere) = 10-6 A, The French mathematician and scientist, Ampere,, conducted a number of experiments on electricity. Today,, we can measure the current flowing in a conductor only, because of his work. The unit of current is called ampere, in recognition of his work., Using ICT, , Example : A current of 0.4 A flows through, a conductor for 5 minutes. How much, charge would have passed through the conductor?, Given : I = 0.4 A, , Study current electricity and other, scientific concepts with the help of, simulation technology ., Website :, www.phet.colorado.edu, www.edumedia-sciences.com, Find some more websites like the ones, mentioned above and share them with, others., , t = 5 min = 5 ´ 60 s =300 s, Formula, Q=I´t, Q = 0.4 A ´ 300 s, Q = 120 C., \ Charge passing through the conductor, , = 120 C, , 33

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Resistance and Ohm’s Law, Ohm’s law, The relationship between the current flowing through a wire (I) and the potential, difference across its ends (V) can be obtained from the law that was given by the German, scientist George Simon Ohm., If the physical state of a conductor remains constant, the current (I) flowing through, it is directly proportional to the potential difference (V) between its two ends., , IaV, I = kV ( k = constant of proportionality), I´ 1=V ( 1, , k, , k, , = R = Resistance of the conductor ), , I ´ R = V Hence V = IR or R=, This is known as Ohm’s law., , V, I, , Physical state of a, conductor means its, length, area of crosssection, temperature, and the material it is, made up of., , We can obtain the SI unit of resistance from the above formula, Potential difference, and current are measured in Volts and Amperes respectively. The unit of resistance is, called Ohm. It is indicated by the symbol W., , \, , 1 Volt, 1 Ampere, , = 1 Ohm (W), , Resistance of one Ohm : If one Ampere current flows through a conductor when, one Volt potential difference is applied between its ends, then the resistance of the, conductor is one Ohm., Resistance and resistivity of a conductor, As shown in figure 3.4, there are a large number, of free electrons in a conductor. They are constantly, in random motion. When a potential difference is, applied between the two ends of the conductor, these, electrons start moving from the end at lower, potential to the end at higher potential. This, directional motion of the electrons causes the flow, of current. Moving electrons strike the atoms and, ions which lie along their path. Such collisions, cause hindrance to the flow of electrons and oppose, the current. This hindrance is called the resistance, of the conductor., Resistivity : At a given temperature, the resistance, (R) of a conductor depends on its length (L), area of, cross-section (A) and the material it is made of., , 34, , German physicist, George, Simon Ohm established a law, for measuring the resistance of, a conductor. In his honour, the, unit of resistance is called the, Ohm.

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If the resistance of a, conductor is R, then, , RaL, Also, R a, , \ Ra, , 1, A, , Think about it, How will you prove that the unit of resistivity, is W m ?, Resistivity of some materials, Copper - 1.7 ´ 10-8 W m, Nichrome - 1.1 ´ 10-6 W m, Diamond - 1.62 ´ 1013 to 1.62 ´ 1018 W m, , L, , A, , L, R=r A, , ρ is the constant of proportionality and is called the resistivity of the material. The, unit of resistivity in SI units is Ohm metre (Wm). Resistivity is a specific property of a, material and different materials have different resistivity, , Electric circuit, A continuous path of an electric, current through conducting wires, connected to the two ends of a cell and, other resistances is called an electric, circuit. A circuit is depicted by a figure., This figure shows how different, components are to be connected in the, circuit, by using special symbols for, each of the components. Such a figure, is called an electric circuit diagram., , Voltmeter, (in parallel with the, resistance), , Ammeter (connected, in series), Resistance, Electric cell, , ., , ( ), Conducting wire, 3.5 Electrical circuit, , In the circuit in figure 3.5, an ammeter is used to measure current and a voltmeter to, measure the potential difference between the two ends of a resistor. As the voltmeter has, a very high resistance, only very small current flows through it., , Observe, , Piece of rubber, , 1. Point out the mistakes in the figure above., 2. Why are the bulbs in Figures B, C and D below not lighting up ?, , A, , B, , C , 35, , D , , E

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Symbols for components of an electric circuit and their uses, Component, Electric cell, , Picture, , Symbol, , Battery (collection, of a number of, cells), Open tap key or, plug key, , Use, To apply a potential, difference between two, ends of a conductor, To apply a larger potential, difference between two, ends of a conductor, To stop the flow of current, flowing in a circuit by, disconnecting two ends of, a wire, To start the flow of current, in a circuit by connecting, two ends of a wires., To connect various, components in the circuit., To show wires which cross, but are not connected, , ( ), , Closed tap key or, plug key, , ., , ( ), , Connecting, (conducting) wires, Crossing wires, Light bulb, , To test the flow of electricity : Lighted : current is, flowing; unlighted :, current is not flowing, To control the flow of, current in the circuit, , Resistance, , Variable resistance, , To change the resistance, as required and thereby, control the current, , Ammeter, , +, , Voltmeter, , +, , -, , Material: copper and aluminium, wires, glass rod, rubber, Method : Make connections as shown in figure 3.6., First connect a copper wire between points A and B and, measure the current in the circuit. Then, in place of the, copper wire, connect aluminium wire, glass rod, rubber,, etc, one at a time and measure the current each time., Compare the values of the current in different cases., , To measure the current, flowing in the circuit, , To measure the potential, difference between two, points in the circuit, , Try this, , 36, , 3.6 Electric Circuit

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Conductors and insulators, We have learnt about the resistance to an electric current. We can divide substances, into conductors and insulators (bad conductors)., Conductors : Those substances which have very low resistance are called conductors., Current can flow easily through such materials., Insulators : Those substances which have extremely high resistance and through which, current cannot flow are called insulators., 1. Why are some substances conductors while others are insulators?, 2. Why can our body conduct electricity?, Make a list of conductors and insulators you see around you., Experimental proof of Ohm’s law :, Try this, , Material : 4 cells of 1.5 V each, ammeter, voltmeter, conducting, wires, nichrome wire, plug key., , Procedure :, 1. Set up the circuit as shown in figure 3.7., 2. Use the nichrome wire XY as the, resistance., 3. Connect one of the 4 cells as shown in, figure 3.7 (a.) Take readings of ammeter, and voltmeter and enter them in the, table below., 4. Now add the rest of the cells one by one, as shown in figures 3.7 (b, c and d)., Enter the readings in the table for each, case., V, 5. Determine the values of, for each, I, case., 6. Draw a graph between current and, potential difference and study it., , a b c d, , X, , R, , K, , Y, , 3.7 Verification of Ohm’s Law, , Observation chart, No., , Number of, cells used, , Current (I), (mA), , Current (I), (A), , 1., 2., 3., 4., , 37, , Potential, difference, (Volts), , V / I = R in (Ω)

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Solved examples : Ohm’s law and resistivity, Example 1 : The resistance of the filament, Example 3 : A current of 0.24 A flows, in a light bulb is 1000 W. If the bulb is fed, through a conductor when a potential, by a current from a source of potential, difference of 24 V is applied between its, difference 230 V, how much current will, two ends. What is its resistance?, flow through it?, Given : V = 24 V, I = 0.24 A, R = 1000 W, Given :, , , , V = 230 V, , Formula, , I= R, , \I=, , Formula, , V, , \I=, , 230 V, = 0.23 A., 1000 W, , V, I, , R=, , 24 V, 0.24 A, , R = 100 W, , The resistance of the conductor is, , 100 W., , \ The current flowing through the filament, of the bulb = 0.23 A., Example 2 : The length of a conducting, wire is 50 cm and its radius is 0.5 mm. If its, resistance is 30 W, what is the resistivity of, its material?, Given : L = 50 cm = 50 ´ 10-2 m, , Example 4 : Determine the current that, will flow when a potential difference of, 33 V is applied between two ends of an, appliance having a resistance of 110 W. If, the same current is to flow through an, appliance having a resistance of 500 W,, how much potential difference should be, applied across its two ends?, Given : V = 33 V and R = 110 W, In the first case,, , r = 0.5 mm = 0.5 ´ 10-3m, = 5 ´ 10-4 m and R = 30 W, Resistivity r = RA, L, and A = pr2, , pr2, \r=R, L, 30 ´ 3.14 ´ (5 ´ 10-4)2, =, 50 ´ 10-2, , V, , I= R, =, \ I = 0.3 A, , 33, 110, , Current flowing through the appliance, = 0.3 A, , 30 ´ 3.14 ´ 25 ´ 10-8, =, 50 ´ 10-2, , In the second case,, , I = 0.3 A, R = 500 W, V = IR = 0.3 ´ 500 V = 150 V., , = 47.1 ´ 10-6 W m, = 4.71 ´ 10-5 W m, , The required potential difference between, its two ends = 150 V, , \ Resistivity of the wire 4.71 ´ 10-5 W m, Using ICT, , Using the internet find out about the different softwares used to solve mathematical, problems and use them to solve problems given in this and other chapters., , 38

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Example 5 : Determine the resistance of a copper wire having a length of 1 km and, diameter of 0.5 mm, Given : r = Resistivity of copper = 1.7 ´ 10-8 W m, Converting all measures into metres., , L = 1 km = 1000 m = 103 m, d = 0.5 mm = 0.5 ´ 10-3 m, , If r is the radius of the wire then, its area of cross-section, , A = pr2, , 2, , d, \ A=p´, 2, p, =, (0.5 ´ 10-3)2 m2 = 0.2 ´ 10-6 m2, 4, 1.7 ´ 10-8 W m ´ (103m), L, 0.2 ´ 10-6m2, R=r A =, = 85 W, , System of resistors and effective resistance, A resistor is a two ended component having a given amount of resistance between its, two ends. In several electrical devices, a number of resistors are connected together in, different ways. Ohm’s law is applicable to all such connected resistors., Resistors in series, Study figure 3.8., You can see that the ends of the three, resistors are connected so that they follow, one after the other in a single line. These, resistors are said to be connected in ‘series.’, In such an arrangement, the same current, flows through each resistor. The value of, current is I and the potential difference, between C and D is V., The three resistors, R1, R2 and R3 are, connected in series in the circuit. If V1, V2 ,, V3 are potential differences of every resistor, R1, R2 and R3 respectively, then, , C, , R1, , R2, , R3, , K, , E, , D, , 3.8 Resistors in series, , V = V1+ V2 + V3 --------(1), , If RS (S for series) is the effective resistance, between C and D, then, according to Ohm’s, law,, , I RS = I R1+ I R2 + I R3, RS = R1+ R2 + R3, , V = I RS, V1 = I R1, V2 = I R2 and V3 = I R3 . Substituting, , If n resistors are connected in series then,, , all these in equation (1) we get,, , Rs = R1+ R2 + R3+-------+ Rn, , 39

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If resistors are connected in series,, 1. The same current flows through each, resistor., 2. The effective resistance of the, resistors is equal to the sum of their, individual resistances., 3. The potential difference between the, two extremes of the arrangement is, equal to the sum of the potential, differences, across, individual, resistors., 4. The effective resistance is larger than, each of the individual resistances., 5. This arrangement is used to increase, the resistance in a circuit., , Do you know?, When resistors are connected in, series, they are connected one after, another. If any one of them does not, function, the circuit breaks and there is, no flow of electricity. If two bulbs are, connected in series, they will both give, less light than if they had been, connected individually. If three bulbs, are connected in series, their light, output will decrease further., Think about it : What is the reason, behind this?, , Solved examples for resistors in series, Example 1 : Three resistors having resistances of 15 W, 3 W and 4 W are connected in, series. What is the effective resistance in the circuit?, Given : R1 = 15 W, R2 = 3 W, R3 = 4 W, Effective resistance Rs = R1+ R2 + R3 = 15 + 3 + 4 = 22 W, \ The effective resistance in the circuit = 22 W, Example 2 : Two resistors having resistances of 16 W and 14 W are connected in series., If a potential difference of 18 V is applied across them, calculate the current flowing, through the circuit and the potential difference across the end of each individual resistor., Given : R1 = 16 W and R2 = 14 W, , Rs = 14 W + 16 W = 30 W, , Let the current flowing through the circuit be I and the potential differences across the end, 16 W, and 14 W be V1 and V2 respectively., , V=IR, V, , V = V1 + V2 = 18 V, 18 V, , I= R, =, 30 W, \ I = 0.6 A., V1= I R1, V1= 0.6 ´ 16 = 9.6 V, V2= I R2 = 0.6 ´ 14 = 8.4 V, \ The current flowing in the circuit is 0.6 A and the potential differences across the end, , of the resistances 16 W and 14 W are 9.6 V and 8.4 V respectively., , 40

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Do you know?, The resistance of some conductors becomes nearly zero if their temperature is, decreased upto a certain value close to 0 Kelvin (K). Such conductors are called super, conductors., Some conductors do not obey Ohm’s law. Such conductors are called non-ohmic, conductors., Resistors in parallel, Resistors are said to be connected in, parallel when their ends are connected at, both sides as shown in figure 3.9. The, figure shows three resistors R1, R2 and R3, connected in parallel between points C and, D. V is the potential difference between C, and D. Let I1, I2 and I3 be the currents, flowing through R1, R2, and R3 respectively., Then, the total current flowing, through the circuit is, , R1, , C, , D, , R2, R3, , K, , E, , 3.9 Resistors in parallel, , I = I1+ I2+ I3-------(1), , Let Rp (p for parallel) be the effective resistance between C and D. According to, Ohm’s law,, , I=, , V, RP, , V, RP, , =, , V, V, V, , I2 =, , I3 =, R1, R2, R3, Substituting these in equation (1), Similarly I1 =, , V V, + +, R1 R2, 1 1, 1, =, + +, \, R1 R2, RP, , V, R3, 1, R3, , If n resistors are connected in parallel,, , 1, 1, 1, 1, 1, =, +, +, +........+, R1, R2, Rn, RP, R3, Even if any one of the several bulbs connected in parallel becomes non-functional, because of some damage to its filament, the circuit does not break as the current flows, through the other paths, and the rest of the bulbs light up., When several bulbs are connected in parallel, they emit the same amount of light, as when they are connected individually in the circuit, while bulbs connected in series, emit less light than when connected individually., , 41

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If a number of resistors are connected in parallel,, 1. The inverse of the effective resistance is equal to the sum of the inverses of individual, resistances., 2. The current flowing through an individual resistor is proportional to the inverse of its, resistance and the total current flowing through the circuit is the sum of the currents, flowing through individual resistors., 3. The potential difference across the end of all resistors is the same., 4. The effective resistance of resistors connected in parallel is less than the least, resistance of individual resistors., 5. This arrangement is used to reduce the resistance in a circuit., Solved examples of resistors in parallel, Example 1: Resistors having resistances of 15 W, 20 W and 10 W are connected in, parallel. What is the effective resistance in the circuit?, Given : R1= 15 W, R2 = 20 W and R3 = 10 W, , 1, 1, 1, 1, =, +, +, RP R1, R2 R3, 1, 1, 1, 1, =, +, +, RP 15, 20 10, 60, RP =, = 4.615 W, 13, , 13, = 4+3+6 =, 60, 60, , \ Effective resistance in the circuit = 4.615 W, less than the least of the three, 10 W., Example 2 : Three resistors having resistances of 5 W, 10 W and 30 W are connected in, parallel and a potential difference of 12 V is applied across them. Obtain the current, flowing through the circuit and through individual resistors. What is the effective resistance, in the circuit?, Given : R1= 5 W, R2 = 10 W and R3 = 30 W, V = 12 V, , V, , I1 = R, 1, V, , I2 = R, 2, V, , I3 = R, 3, , 12, = 2.4 A, 5, 12, =, = 1.2 A, 10, 12, =, = 0.4 A, 30, =, , I = I1 + I2 + I3 = 2.4 + 1.2 + 0.4 = 4.0 A, , 1 1, 1, 1, 1+ 1 + 1, 6 +3 + 1 10 1, =, =, +, +, =, = 30 = 3, RP R1 R2 R3, 5 10 30, 30, , Effective resistance in the circuit = 3 W and the current flowing through the resistances 5, W, 10 W and 30 W is 2.4 A, 1.2 A and 0.4 A respectively. The total current flowing through, the circuit is 4 A., , 42

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Domestic electrical connections, The electricity in our homes is brought through the main conducting cable either, from the electric pole or from underground cables. Usually, there are three wires in the, cable. One is called the live wire which brings in the current. It has a red or brown, insulation. The other wire is called neutral wire through which the current returns. It is, blue or black. In India, the voltage difference between the live and neutral wires is, about 220V. Both these wires are connected to the electric meter through a fuse. Through, a main switch, they are connected to all the conducting wires inside the home so as to, provide electricity to every room. In each separate circuit, various electrical appliances, are connected between the live and neutral wires. The different appliances are connected, in parallel and the potential difference across every appliance is the same. The third, wire is called the earth wire and is of yellow or green colour. This is connected to a, metal plate buried deep underground near the house and is for safety purposes., , Fuse wire : Fuse wire is used to protect domestic, appliances. It is made of a mixture of substances and, has a specific melting point. It is connected in series to, the electric appliances. If for some reason, the current in, the circuit increases excessively, the fuse wire gets, heated up and melts. The circuit gets broken and the, flow of current stops, thus protecting the appliance. This, wire is fitted in a groove in a body of porcelain - like, non-conducting material. For domestic use, fuse wires, with upper limits of 1 A, 2 A, 3 A, 4 A, 5 A and 10 A are, used., , Cartridge fuse, , Ceramic fuse, , Precautions to be taken while using electricity, 1. Electric switches and sockets should be fitted at a height at which small children, cannot reach and put pins or nails inside. Pull a plug. Plug wires should not be, pulled while removing a plug from its socket., 2. Before cleaning an electrical appliance it should be switched off and its plug, removed from the socket., 3. One’s hands should be dry while handling an electrical appliance, and, as far as, possible, one should use footwear with rubber soles. As rubber is an insulator, it, prevents the current from flowing through our body, thereby protecting it., 4. If a person gets an electric shock, you should not touch that person. You should, switch off the main switch and if the switch is too far or you do not know where it, is located, then you should remove the plug from the socket if possible. If not, then, you should use a wooden pole to push the person away from the electric wire., , 43

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Exercises, 1. The accompanying figure shows, some electrical appliances connected, in a circuit in a house. Answer the, following questions., A. By which method are the appliances, connected?, B. What must be the potential, difference, across, individual, appliances?, C. Will the current passing through, each appliance be the same? Justify, your answer., D. Why are the domestic appliances, connected in this way?, E. If the T.V. stops working, will the, other appliances also stop working?, Explain your answer., , C. What will be the effective resistance, in the above circuit?, , 4. The following table shows current in, Amperes and potential difference in, Volts., , 2. The following figure shows the symbols, for components used in the, accompanying electrical circuit., Place them at proper places and, complete the circuit., , Which law can you prove with the help, of the above circuit?, 3. Umesh has two bulbs having, resistances of 15 W and 30 W. He, wants to connect them in a circuit,, but if he connects them one at a time, the filament gets burnt. Answer the, following., A. Which method should he use to, connect the bulbs?, B. What are the characteristics of this, way of connecting the bulbs, depending on the answer of question, A above?, , a. Find the average resistance., b. What will be the nature of the graph, between the current and potential, difference? (Do not draw a graph.), c. Which law will the graph prove?, Explain the law., , 5., , V (Volts), , I (Amp), , 4, 5, 6, , 9, 11.25, 13.5, , Match the pairs, ‘A’ Group, ‘B’ Group, 1. Free electrons, , a. V/ R, , 2. Current, , , , b. Increases the , resistance in the , circuit, , 3. Resistivity, , c. Weakly attached, , 4. Resistances in, series, , 44, , d. VA/LI

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6. The resistance of a conductor of, , 9. Solve the following problems., A. The resistance of a 1m long, nichrome wire is 6 W. If we reduce, the length of the wire to 70 cm., what will its resistance be?, (Answer : 4.2 W), B. When two resistors are connected, in series, their effective resistance, is 80 W. When they are connected, in parallel, their effective resistance, is 20 W. What are the values of the, two resistances? , (Answer : 40 W , 40 W), C. If a charge of 420 C flows through, a conducting wire in 5 minutes, what is the value of the current?, (Answer : 1.4 A), Project :, Ask an electrician to explain to you, the electrical wiring in your house, and other related important points., Take care to understand them well,, and explain them to others also., , length x is r. If its area of crosssection is a, what is its resistivity?, What is its unit?, , 7. Resistances R1, R2, R3 and R4 are, connected as shown in the figure. S1, and S2 are two keys. Discuss the, current flowing in the circuit in the, following cases., , C, , R1, , D, , F, , HH, , S1, , B, , R2, , AA, , RR3, 3, , E, , + -, , R, R4 4, , S2, , GG, , II, , a. Both S1 and S2 are closed., b. Both S1 and S2 are open., c. S1 is closed but S2 is open., 8. Three resistances x1, x2 and x3 are, connected in a circuit in different, ways. x is the effective resistance., The properties observed for these, different ways of connecting x1, x2, and x3 are given below. Write the, way in which they are connected in, each case. (I-current, V-potential, difference, x-effective resistance), , ²²², , a. Current I flows through x1, x2 and x3, b. x is larger than x1, x2 and x3, c. x is smaller than x1, x2 and x3, d. The potential difference across x1, x2, and x3 is the same, e. x = x1 + x2 + x3, f. x =, , 1, 1 + 1 +1, x1 x2 x3, , 45

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4. Measurement of Matter, Ø, Ø, , Laws of chemical combination Ø Atom - shape, mass, valency, Molecular mass and the concept of mole Ø Radicals, , 1. What is the Dalton’s atomic theory ?, 2. How are the compounds formed ?, Can you recall?, 3. What are the molecular formulae of common salt, slaked, lime, water, lime, limestone ?, In the previous standard we have learnt that compounds are formed by chemical, combination of elements. We have also learnt that an important principle of Dalton’s, atomic theory is that molecules of a compound are formed by joining atoms of different, elements to each other., Laws of chemical combination, The composition of a substance changes during a chemical change. The fundamental, experiments in this regard were performed by scientists in the 18th and 19th century. While, doing this, they measured accurately, the substances used and formed and discovered, the laws of chemical combination. Scientists could then write the molecular formulae, of various compounds on the basis of Dalton’s atomic theory and the laws of chemical, combination. Here we shall verify the laws of chemical combination by means of known, molecular formulae., Try this, , Apparatus : Conical flask, test tubes, balance, etc., Chemicals : Calcium chloride (CaCl2), sodium sulphate (Na2SO4),, calcium oxide (CaO), Water (H2O), , Activity 1, — Take 56 g calcium oxide in a large, conical flask and put 18 g water in it., — Observe what happens., — Measure the mass of the substance, formed., — What similarity do you find? Write, your inference., , -------------------------------------------------------------------------------------------------, , Activity 2, — Take a solution of calcium chloride in a, conical flask and a solution of sodium, sulphate in a test tube., — Tie a thread to the test tube and insert it, in the conical flask., — Seal the conical flask with an airtight, rubber cork., — Weigh mass of the conical flask using a, balance., — Now tilt the conical flask so that the, solution in the test tube gets poured in, the conical flask., — Now weigh mass of the conical flask, again., — Which changes did you notice? Was, there any change in the mass?, , 46

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Solution of, Calcium Chloride, (CaCl2), , Solution of, sodium, sulphate (Na2SO4), , White precipitate, of CaSO4 in NaCl, solution., , 4.1 Verification of law of the chemical combination, , Law of conservation of matter, In the above activities, the mass of the original matter and the mass of the matter, newly formed as a result of the chemical change are equal. In 1785, the French Scientist, Antoine Lavoisier inferred from his research that ‘there is no rise or drop in the mass of the, matter during a chemical reaction.’ In a chemical reaction the total mass of the reactants, is same as the total mass of the products formed due to the chemical reactions and this is, called the law of conservation of matter., Law of constant proportion, In 1794 the French scientist, J. L. Proust stated the law of constant, proportions as “The proportion by mass, of the constituent elements in the different, samples of a compound is fixed,” e.g.,, the proportion by mass of hydrogen and, oxygen in water is obtained from any, source 1:8. This means that 9 g water, is formed by chemical combination of 1, g hydrogen and 8 g oxygen. Similarly,, the proportion by mass of carbon and, oxygen in carbon dioxide obtained from, any source is 3:8. This means that in 44 g, of carbondioxide there is 12 g of carbon, and 32 g of oxygen so that the proportion, by mass of carbon and oxygen is 3:8., , An introduction to scientists, Antoine Lavoisier (1743-94), French scientist, father of modern, chemistry, substantial contribution in the fields, of chemistry, biology and economics., •• Nomenclature of oxygen and hydrogen., •• Showed that matter combines with oxygen, ••, , ••, ••, ••, , ••, , ••, Proust, , Lavoisier, , during combustion., Was the first to use accurate weighing, techniques to weigh mass of reactants and, products in a chemical reaction., Discovered that water is made up of, hydrogen and oxygen., First writer of the law of conservation of, mass, in a chemical reaction., Assigned systematic names to the, compounds, e.g. sulphuric acid, copper, sulphate, sulphite., Authored the first book on modern, chemistry- ‘Elementary Treatise on, Chemistry in 1789.’, Studied the elements such as oxygen,, hydrogen, nitrogen, phosphorus, mercury,, zinc and sulphur., , 47

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Verification of the law of constant proportion, Many compounds can be made by different methods. For example, two samples of the, compound copper oxide, CuO, were obtained, one by decomposition of copper carbonate,, CuCO3, and another by decomposition of copper nitrate, Cu(NO3)2. From each of these samples,, a mass of 8g of copper oxide was taken and each was treated independently with hydrogen, gas. Both gave 6.4 g copper and 1.8 g water. Let us see how does this is a verify of the law of, constant proportion., The reaction of copper oxide with hydrogen yielded two known substances, namely, the, compound water and the element copper. It is known that, in the compound water, H2O, the, elements H and O are in the proportion 1:8 by mass. This means that in 9g water there are 8g of, the element oxygen. Therefore, 1.8g water contains (8x1.8/9 = 1.6)g oxygen. This oxygen has, come from 8g copper oxide. It means that 8g of both the samples of copper oxide contained 6.4g, copper and 1.6g oxygen; and the proportion by mass of copper and oxygen in it is 6.4:1.6, that, is, 4:1. Thus, the experiment showed that the proportion by mass of the constituent elements in, different samples of a compound is constant., Now let us see what the expected proportion by mass of the constituent elements of copper, oxide would be from its known molecular formula CuO. To find out this, we need to use, the known atomic masses of the elements. The atomic masses of Cu and O are 63.5 and 16, respectively. This means that the proportion by mass of the constituent elements Cu and O in, the compound CuO is 63.5 : 16 which is 3.968:1, or approximately 4:1., The experimental value of proportion by mass of the constituent elements matched with, the expected proportion calculated from the molecular formula. Thus, the law of constant, proportion is verified., , Atom : size, mass and valency, 1. From which experiments was it discovered that atoms have an, internal structure? When?, Can you recall?, 2.What are the two parts of an atom? What are they made up of?, We have learnt that at the centre of an atom is the nucleus and that there are moving, electrons in the extra-nuclear part. The electrons are negatively charged elementary, particles while the elementary particles that make up the nucleus are positively charged, protons and electrically neutral neutrons., The size of an atom is determined by its radius. The, atomic radius of an isolated atom is the distance between the, nucleus of an atom and its outermost orbit. Atomic radius is, expressed in nanometres., Approximate size of atom and Molecule, Atomic radius (in metres), , 1, m = 1nm, 109, 1m = 109 nm., , 10-10, 10-9, 10-8, , Example, Hydrogen atom, Water molecule, Haemoglobin, molecule, , 48, , 4.2 Field ion microscope image of, iridium atoms (every spot in this, image is an atom)

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Atoms, are, very, tiny., Modern, instruments, like, electron, microscope,, field ion microscope, scanning, tunneling, microscope, enlarged images of the atom., Look at the image of an atom, fig. 4.2 obtained with a field, ion microscope., , The atomic size depends on the number of electron, orbits in the atom. The greater the number of orbits the, larger the size. For example, an atom of K is bigger than, an atom of Na. If two atoms have the same outermost, orbit, then the atom having the larger number of, electrons in the outermost orbit is smaller than the one, having fewer electrons in the same outermost orbit. For, example an atom of Mg is smaller than an atom of Na., , The mass of an atom, The mass of an atom is concentrated in its nucleus and it is due to the protons (p), and neutrons (n) in it. The total number (of protons and neutrons) in the atomic nucleus is, called the atomic mass number. Protons and neutrons are together called nucleons., An atom is very tiny. Then how do we determine its mass? Scientists too, faced this, question. It was not possible for scientists of the 19th century to measure atomic mass, accurately. Therefore, the concept of ‘relative mass of an atom’ was put forth. A reference, atom was required for expressing the relative mass of an atom. The hydrogen atom being, the lightest was initially chosen as the reference atom. The relative mass of a hydrogen, atom which has only one proton in its nucleus was accepted as one (1). Therefore, the, magnitude of the relative atomic masses of various atoms became equal to their atomic, mass number (p+n)., Let us see how to express the relative mass of a nitrogen atom, having accepted the, relative atomic mass of hydrogen as 1., The mass of one nitrogen atom is fourteen (14) times that of a hydrogen atom. Therefore,, the relative mass of a nitrogen atom is 14. This is how the relative atomic masses of various, elements were determined. On this scale, the relative atomic masses of many elements came, out to be fractional. Therefore, in the course of time, some other atoms were chosen as, reference atoms. Finally in 1961, the carbon atom was selected as the reference atom. In this, scale, the relative mass a carbon atom was accepted as 12. The relative atomic mass of one, hydrogen atom compared to the carbon atom becomes 12 x 1/12, that is 1. The mass of one, proton and of one neutron on the scale of relative atomic masses is approximately one., Research, Element, , The relative atomic masses of some elements in the chart below are, given. You have to find the relative atomic masses of the others., Atomic mass, , Element, , Hydrogen, , 1, , Oxygen, , Helium, Lithium, Beryllium, Boron, Carbon, Nitrogen, , 4, 7, 9, 11, 12, 14, , Fluorine, Neon, Sodium, Magnesium, Aluminium, Silicon, , Atomic mass, , 49, , Element, , Atomic mass, , -, , Phosphorus, , -, , 19, 20, 24, 28, , Sulphur, Chlorine, Argon, Potassium, Calcium, , 32, 35.5, 40

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Today, we have highly accurate methods for measuring the mass of an atom directly., Hence, instead of relative mass, Unified Mass has now been accepted as the unit of atomic, mass. It is called Dalton. Its symbol is ‘u’. 1u = 1.66053904 ´ 10-27 kg, Chemical symbols of elements, 1. How is an element represented in Chemistry?, Can you tell? 2. Write down the symbols of the elements you know., 3. Write down the symbols for the following elements : antimony,, iron, gold, silver, mercury, lead, sodium., Dalton used certain signs to represent elements. For example € for hydrogen, © for, copper. Today we use the symbols determined by IUPAC (International Union of Pure, and Applied Chemistry). These are official names and symbols and are used all over the, world. The current method of choosing chemical symbols is based on the method invented, by Berzelius. According to this method the symbol of an element is either the first letter or, the first and second/another specific letter in its name. Of the two letters, the first is written, as capital letter and the second is small., Molecules of elements and compounds, Atoms of some elements such as helium, neon have independent existence. It means, that these elements are in a mono-atomic molecular state. Sometimes, two or more atoms, of an element combine to form molecules of that element. Such elements are in a polyatomic molecular state. For example, the elements oxygen, nitrogen are in a diatomic, molecular state as O2, N2 respectively. When atoms of different elements combine with, each other, the molecules of compounds are formed. In other words, compounds are formed, by chemical attraction between different elements., Make a list and discuss, , Make a list of elements that exist in mono-atomic and, diatomic molecular states., , Molecular mass and the concept of mole, Molecular mass, The molecular mass of a substance is the sum of the atomic masses of all the atoms in, a single molecule of that substance. Like atomic mass, molecular mass is also expressed, in the unit Dalton (u)., How to deduce the molecular mass of H2O ?, Atomic mass, u, , Number of, atoms in the, molecule, , Atomic mass ´, number of, atoms, , Mass of the, constituents, u, , Hydrogen, , 1, , 2, , 1´2, , 2, , Oxygen, , 16, , 1, , 16 ´ 1, , 16, , Molecule Constituent, elements, , H2O, , Molecular mass = sum of constituent atomic masses, (Molecular mass of H2O) = (Atomic mass of H) ´ 2 + (Atomic mass, of O) ´ 1, , 50, , Molecular, Mass, 18

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Following are atomic masses of a few elements in, Dalton, and the molecular formulae of some compounds., Use your brain power !, Deduce the molecular masses of those compounds., Atomic masses à H(1), O(16), N(14), C(12), K(39), S(32) Ca(40), Na(23), Cl(35.5),, , Mg(24), Al(27), Molecular formulae àNaCl, MgCl2, KNO3, H2O2, AlCl3, Ca(OH)2 , MgO, H2SO4,, HNO3, NaOH, , Mole, , 1. Weigh mass of single grains of tur dal, masoor dal and chana dal, on a balance. What was your experience?, Try this, 2. Weigh mass of 10g of Tur dal, Masoor dal and Chana dal each and, count the number of dal grains of each kind in the weighed portions. Is the number the, same for all or different?, 3. Draw a line sketch on a paper. Paint it by placing/pasting the dal grains in the, sequence Tur, Masoor and Bengal gram. You will need equal number of dalgrains of the three kinds. Count that number and also find out how many dozens, of the respective dal-grains were required. Therefrom deduce the number of grams, of tur dal, masoor dal and chana dal required for painting the picture., 4. What inference will you draw about the mass of an equal number of its different, dal grains and the number of its dal grains in equal mass of different dals?, How much of wheat, jowar and bajra seed is required for, Think about it sowing one acre of land? Can these masses be correlated to the, number of grains of the respective cereals they contain?, 1. Is it possible to weigh mass of one molecule using a weighing, balance?, 2. Will the number of molecules be the same in equal quantities of different substances?, 3. If we want equal number of molecules of different substances, will it work to take equal, masses of those substances?, When elements and compounds take part in chemical reactions, it is their atoms and, molecules that react with each other, and therefore it is necessary to know the numbers, of their atoms and molecules. However, while carrying out a chemical reaction it, is, convenient to measure out quantities that can be handled instead of counting the numbers, of atoms and molecules. The concept of ‘mole’ is useful for this purpose., A mole is that quantity of a substance whose mass in grams is equal in magnitude to, the molecular mass of that substance in Daltons. Thus, the molecular mass of oxygen is, 32u, and therefore 32g oxygen is 1mole of oxygen. The molecular mass of water is 18u., Therefore, 18g of water make 1 mole of water., Can you tell?, , 1 mole of a compound is, the mass of that subtance in, grams equal in magnitude to, its molecular mass. The SI, unit is mol., , Number of moles, Mass of substance in grams, of a substances (n) =, Molecular mass of substance, , 51

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Avogadro’s number, The number of molecules in one mole of any substance is constant. The Italian, scientist Avogadro did fundamental work in this context. Therefore this number is called, Avogadro’s number and is denoted by the symbol NA. Later scientists demonstrated, experimentally that the value of Avogadro’s number is 6.022 x 1023. A mole of any, substance stands for 6.022 x 1023 molecules. Just as a dozen has 12 items, a century has, 100 or a gross has 144, a mole means 6.022 x 1023. For example, a mole of water, that is,, 18g of water contains 6.022 x 1023 molecules of water., , How many molecules are there in 66 g of CO2?, Method : molecular mass of CO2 is 44., Number of moles in the given CO2 (n) =, , Mass of CO2 in grams, Molecular mass of CO2, , =, , 66, 44, , . ं. n = 1.5 mol, . ं. 1 mol of CO2 contains 6.022 x 1023 molecules., . ं. 1.5 mol CO2 contains 1.5 x 6.022x1023 molecules = 9.033 x 1023 molecules, , 1 dozen bananas, are 12 bananas, , 144 notebooks make, 1 gross of note books, , 1 mole common salt =, 6.022 x 1023 molecules, , 58.5 g, 1 mole water = 6.022 x 1023 molecules, 4.3 One mole (Avogadro number), , Always remember, , Use your brain power !, , 1. How many molecules of water, are there in 36g water?, , 2. How many molecules of, H2SO4 are there in a 49g, sample?, , 1. The number of molecules in a given quantity, of a substance is determined by its molecular, mass., 2. The number of molecules in equal masses of, different substances are different., 3. One mole quantities of different substances, have different masses measured in grams., , 52

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Valency, Can you recall?, , 1. Determine the valencies of H, Cl, O and Na from the, molecular formulae H2, HCl, H2O and NaCl., 2. What is the type of chemical bond in NaCl and MgCl2?, , The capacity of an element to combine is called its valency. The valency of an element, is indicated by a specific number. It is the number of chemical bonds formed by one atom, of that element with other atoms. In the 18th and 19th century, the laws of chemical, combination were used to find out the valencies of elements. In 20th century, the relationship, of the valency of an element with its electronic configuration was recognised., Sodium atom (Na) Electron configuration (2,8,1), Chlorine atom (Cl) Electron configuration (2,8,7), , -1e+1e, , Na+ + Cl-, , -, , Sodium ion Na+ (2,8), Chloride ion Cl- (2,8,8), NaCl (sodium chloride), , A sodium atom gives away one electron and a cation of sodium is formed, hence, the, valency of sodium is one. A chlorine atom takes up one electron and forms an anion of, chlorine (chloride) and thus, the valency of chlorine is 1. After the give and take of electrons, is over, the electronic configuration of both the resulting ions has a complete octet. Due to, the attraction between the unit opposite charges on the two ions, one chemical bond is, formed between Na+ and Cl- and the compound NaCl is formed., Thus, a sodium atom has the capacity to give, away one electron while a chlorine atom has the, capacity to take up one electron. This means that the, valency of both the elements sodium and chlorine is, 1. From this the electronic definition of valency is as, follows : “The number of electrons that an atom of, an element gives away or takes up while forming an, ionic bond, is called the valency of that element.”, , Use your brain power !, The number of, electrons that are, given away or, taken up is always, a whole number., Therefore, valency, is always a whole, number., , Science capsule, Positively charged ions are, called cations while negatively, charged ions are called anions., For example, MgCl2 contains, Mg++ and Cl- as cation and, anion respectively., The electrons present in the, outermost orbit of an atom are, called valence electrons., , How will the compounds, MgCl2 and CaO be, formed their elements?, , The National Chemical Laboratory (NCL), a unit of the CSIR,, was established in 1950. Its objectives are to conduct research, in the various branches of chemistry, to aid industry and to, develop new technology with a view to making profitable use, of the country's natural resources. The Laboratory conducts, research in fields such as biotechnology, nanotechnology,, catalysis, drugs, instrumentation, agro chemicals, plant tissue, culture and polymer science., , 53

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Complete the following chart., , Variable valency, , Element, , Atomic, number, , Electron, configuration, , Valence Valeneleccy, trons, , Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon, , 1, 2, ……, 4, 5, ……., , 1, 2, 2,1, ……., 2,3, 2,4, , 1, 2, ….., ……., ……, 4, , 1, 0, ……, 2, ……., ……., , Nitrogen, Oxygen, Fluorine, Neon, Sodium, Magnesium, Aluminium, Silicon, , 7, ….., 9, 10, ……, 12, 13, 14, , …….., 2,6, ……, ………., 2,8,1, ……, 2,8,3, ……, , …….., 6, 7, ……, 1, 2, ……, 4, , 3, …….., ……., …….., 1, ……, ……, ……., , Under different conditions, the atoms of some elements give, away or take up different, numbers of electrons. In such, cases those elements exhibit, more than one valency. This, property of elements is called, variable valency., , Always remember, Iron (Fe) exhibits the, variable valencies 2 and 3., Therefore iron forms two, compounds with chlorine, FeCl2 and FeCl3., , Some elements that exhibit variable valency, Element, , Symbol, , Valency, , Ion, , Nomenclature, , Copper, , Cu, , 1 and 2, , Mercury, , Hg, , 1 and 2, , Cu, Cu2+, Hg+, Hg2+, , Cuprous, Cupric, Mercurous, Mercuric, , Fe2+, Fe3+, , Ferrous, Ferric, , Iron, , Fe, , 2 and 3, , +, , Research, 1. Find out some more, elements which have, variable valency., 2. Find out the compounds, of the above elements, which have variable, valency., , Radicals, Complete the table., Base, , NaOH, KOH, Ca(OH)2, , Cation, , Write down the cations and anions obtained from the, compounds in the following chart., Anion, , Acid, , HCl, HBr, HNO3, , 54, , Cation, , Anion

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Compounds with ionic bonds have two constituents. These are cations (positively, charged ions) and anions (negatively charged ion).They take part independently in, chemical reaction and are therefore, called radicals. It is seen from the above chart that, different bases such as NaOH, KOH are formed when various cationic radicals are paired, with the different anionic radical, hydroxide. Hence the cationic radicals are also called, basic radicals. Different bases are distinguished from each other by the basic radicals in, them. On the other hand, different acids, such as HCl, HBr are formed when different, anionic radicals are paired with the cationic radical H+. Therefore, the anionic radicals are, called acidic radicals. The difference in the composition of various acids becomes clear, from the acidic radicals present in them., Which are the basic radicals and which are the acidic, Can you tell? radicals among the following?, Ag+, Cu2+, Cl-, I-, SO42-, Fe3+, Ca2+, NO3-, S2-, NH4+, K+, MnO4-, Na+, Generally, basic radicals are formed by removal of electrons from the atoms of metals,, such as Na+, Cu2+. But there are some exceptions, such as NH4+. Similarly, the acidic, radicals are formed by adding electrons to the atoms of non-metals, such as Cl-, S2-. But, there are some exceptions like MnO4-., Classify the following radicals into two types. While, Use your brain power ! doing this use a criterion other than the sign of the, electronic charge on them., Ag+, Mg2+, Cl-, SO42-, Fe2+, ClO3-, NH4+, Br-, NO3Monoatomic radicals such as Na+, Cu+, Cl- are called simple radicals. When a radical, is a group of atoms carrying charge, such as SO42-, NH4+, it is called composite radical., The magnitude of charge on any radical is its valency., Chemical formulae of compounds : 'A' recapitulation., The characteristic of a compound formed by ionic bonds is that its molecule has two, parts. These are a cation and an anion, that is, a basic radical and an acidic radical. These, two parts are oppositely charged. The force of attraction between them constitutes the, ionic bond. The name of an ionic compound contains two words. The first word is the, name of the cation and the second is the name of the anion. For example, the formula of a, compound such as sodium chloride is written by writing the symbol of the cation on the, left and adjoined to it on the right is the symbol of the anion. The charges are not shown, though the number of the ions is written as a subscript on the right of the symbol of the ion., In the case of composite radical the number is written as subscript outside the bracket, enclosing its symbol. This number is obtained easily by the method of cross multiplication, of the valencies. The steps for writing a chemical formula are shown on the next page., Using ICT, To study ‘Measurement of Matter’ further, and for additional information, visit the, websites given alongside., Prepare a spreadsheet showing the atomic, mass of elements, molecular masses, electronic, configurations and valencies., , 55, , Website for more information, www.organic.chemistry.org, www. masterorganicchemistry.com, www. rsc.org.learnchemistry

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Using the chart of ions/radicals and the crossUse your brain power ! multiplication method, write the chemical formulae of, the following compounds : Calcium carbonate, Sodium, bicarbonate, Silver chloride, Calcium hydroxide, Magnesium oxide, Ammonium, phosphate, Cuprous bromide, Copper sulphate, Potassium nitrate, Sodium dichromate., , Exercises, 1. Give examples., a. Positive radicals, b. Basic radicals, c. Composite radicals, d. Metals with variable valency, e. Bivalent acidic radicals, f. Trivalent basic radicals, 2. Write symbols of the following, elements and the radicals obtained, from them, and indicate the charge, on the radicals., Mercury, potassium, nitrogen, copper,, sulphur, carbon, chlorine, oxygen, 3. Write the steps in deducing the, chemical formulae of the following, compounds., Sodium sulphate, potassium nitrate,, ferric phosphate, calcium oxide,, aluminium hydroxide, 4. Write answers to the following, questions and explain your answers., a. Explain the monovalency of the, element sodium., b. M is a bivalent metal. Write down, the steps to find the chemical, formulae of its compounds formed, with the radicals : sulphate and, phosphate, c. Explain the need for a reference, atom for atomic mass. Give some, information about two reference, atoms., d. What is meant by Unified Atomic, Mass?, e. Explain with examples what is, meant by a 'mole' of a substance., , 5. Write the names of the following, compounds and deduce their, molecular masses., , Na2SO4, K2CO3, CO2, MgCl2, NaOH,, AlPO4, NaHCO3, , 6. Two samples ‘m’ and ‘n’ of slaked, lime were obtained from two, different reactions. The details, about their composition are as, follows:, ‘sample m’ mass : 7g, Mass of constituent oxygen : 2g, Mass of constituent calcium : 5g, ‘sample n’ mass : 1.4g, Mass of constituent oxygen : 0.4g, Mass of constituent calcium : 1.0g, Which law of chemical combination, does this prove? Explain., 7. Deduce the number of molecules of, the following compounds in the given, quantities., 32g oxygen, 90g water, 8.8g carbon di, oxide, 7.1g chlorine., 8. If 0.2 mol of the following substances, are required how many grams of, those substances should be taken?, Sodium chloride, magnesium oxide,, calcium carbonate, Project :, Prepare models of various radicals, using cardboard, small circular, magnets and araldite. From these, make models of molecules of, various compounds., , ²²², , 57

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5. Acids, 1., Bases, गतीचेand, नियमSalts, Ø, Ø, , Arrhenius theory of acids and bases Ø Concentration of an acid or a base, pH of a solution Ø pH of an acid and a base Ø Salts, , How are the following substances classified into three groups, with the help of litmus? Lemon, tamarind, baking soda, buttermilk,, Can you recall?, vinegar, orange, milk, lime, tomato, milk of magnesia, water,, alum., We have seen earlier that some foodstuffs are sour to taste while some others are, bitter and slippery or soapy to touch. When these substances are studied scientifically, it, is found that they contain acidic and basic substances respectively. We have also learnt, about an easy and safe method of using an indicator like litmus to detect acids and bases., How are acids and alkalies detected with the help of litmus paper?, We shall now learn more about acids and bases. But let us first recapitulate on the, constituents of molecules of compounds., Fill in the columns in the part ‘A’ of the following table., , Name of the, Molecular, formula, compound, Hydrochloric acid HCl, HNO3, , A, , B, , Basic radical, , Acidic radical, , Type of the, compound, , H+, , Cl-, , Acid, , HBr, H2SO4, H3BO3, NaOH, KOH, Ca(OH)2, NH4OH, NaCl, Ca(NO3)2, K2SO4, CaCl2, (NH4)2SO4, Some compounds are seen to have H + as the basic radical in their molecules. These, are all acids. Some compounds are seen to have OH - as the acidic radical in their molecules., All these compounds are bases. These ionic compounds having basic radicals other than, H + and acidic radicals other than OH - are called salts., , 58

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Now complete part ‘B’ of the table on page 58. It will be clear that there are three, types of ionic compounds and these are acids, bases and salts., Ionic compounds : A recapitulation, The molecule of an ionic compound has two constituents, namely, cation (postive ion/, basic radical) and anion (negative ion /acidic radical). There is a force of attraction, between these ions as they are oppositely charged, and that is called the ionic bond. The, force of attraction between one positive charge on a cation and one negative charge on an, anion makes one ionic bond., 1 electron, outgoing, , -e-, , Na+ (2,8), , Na (2,8,1), , 1 electron, incoming, , +eCl (2,8,7), , Na, , Cl- (2,8,8), , Cl, , NaCl with an ionic bond, , While, studying, static, electricity we have learnt that, there is a natural tendency of any, body to change from an, electrically charged state into an, electrically neutral state. Why,, then, is an electrically charged, ion formed from an electrically, balanced, that is, neutral atom ?, The explanation lies in the, electronic configuration of atoms., Figure 5.1 shows how the sodium, and chlorine atoms form the Na+, and Cl and as a result, how the, NaCl salt is formed., , 5.1 Formation of the compound NaCl, Electronic configuration, , The outermost shell of a sodium and a chlorine atoms is not a complete octet. However, outermost shells in both the Na+ and Cl ions are complete octet., An electronic configuration with a complete octet indicates a stable state. Further, an, ionic bond is formed between the oppositely charged Na+ and Cl ions and therefore an, ionic compound NaCl having very high stability is formed., Dissociation of ionic compounds, Can you recall?, , What are the resulting mixtures formed by mixing the following, substances?, , 1. Water and salt, 2. Water and sugar, 3. Water and sand, 4. Water and sawdust, An ionic compound forms an aqueous solution on dissolving in water. In the solid, state, the oppositely charged ions in the ionic compound are sitting side by side. When an, ionic compound begins to dissolve in water, the water molecules penetrate in between the, ions of the compound and separate them from each other. That is to say, an ionic compound, dissociates during formation of an aqueous solution. (See figure 5.2), , 59

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Each of the dissociated ions in the aqueous solution is surrounded by water molecules., This state is indicated by writing (aq), meaning aqueous, on the right of the symbol of the, ion., Salt in solid state before, dissolving, , Aqueous solution, of salt, , Water, , Sodium, Chloride Na, , NaCl(s), , Water, , (dissociation), , Na+(aq) + Cl-(aq), , 5.2 Dissociation of salt in aqueous solution, , Arrhenius theory of acids and bases, The Swedish scientist Arrhenius put forth a theory of Acids and Bases in the year, 1887. This theory gives definitions of acids and bases as follows :, Acid : An acid is a substance which on dissolving in water gives rise to H+ ion as the only, cation. For example, HCl, H2SO4, H2CO3., water, HCl (g) (dissociation) H+(aq) + Cl-(aq), water, , H2SO4 (l) (dissociation) H+(aq) + HSO4-(aq), HSO4-(aq), , (dissociation), , H+(aq) + SO42-(aq), , Use your brain power !, 1. What are the names of the following compounds?, NH3, Na2O, CaO., 2. When the above compounds are mixed with water they combine with water., Complete the following table by showing the ions formed by their combination, with water., 3. Into which type will you classify the above compounds-acid, base or salt ?, , NH3 (g) + H2O(l), , NH4+ (aq) + OH-(aq), , Na2O(s) + .........., , 2 Na+(aq) +.............., , CaO(s) + H2O(l), , ........... + ............., 60

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Base : A base is a substance which on dissolving in water gives rise to the OH- ion as the, only anion. For example, NaOH, Ca(OH)2., water, , NaOH (s) (dissociation) Na+(aq) + OH-(aq), Ca(OH)2 (s), , water, (dissociation), , Ca2+(aq) + 2OH-(aq), , Classification of acids and bases, 1. Strong and weak acids, bases and alkali, 1. Acids and bases are classified as strong and weak on the basis of the extent to, which they dissociate in their aqueous solutions., Strong acid : On dissolving in water, a strong acid dissociates almost completely and the, resulting aqueous solution contains mainly H+ ions and the concerned acidic radical. For, example, HCl, HBr, HNO3 , H2SO4., Weak acid : On dissolving in water a weak acid does not dissociate completely. The, resulting aqueous solution contains H+ ion and the concerned acidic radical in small, proportion along with large proportion of the undissociated molecules of the acid. For, example, CH3COOH (Acetic Acid), CO2., Strong base : On dissolving in water, a strong base dissociates almost completely and the, resulting aqueous solution contains mainly OH- ions and the concerned basic radicals., For example, NaOH, KOH, Ca(OH)2, Na2O., Weak base : On dissolving in water a weak base does not dissociate completely. The, resulting aqueous solution contains a small proportion of OH- ions and the concerned, basic radical along with a large proportion of undissociated molecules of the base. For, example, NH3., Alkali : The bases which are highly soluble in water are called alkali. For example, NaOH,, KOH, NH3. Here, NaOH and KOH are strong bases while NH3 is a weak base., 2. Basicity and acidity, Complete the following table., Acid : Number of H+ obtained from one molecule., HCl, , HNO3, , H2SO4, , H2CO3, , H3BO3, , H3PO4, , CH3COOH, , Fe(OH)3, , NH4OH, , Base : Number of OH- ions obtained from one molecule, NaOH, , KOH, , Ca(OH)2, , Ba(OH)2, , Al (OH)3, , Acids and bases are also classified according to their basicity and acidity respectively., , 61

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Basicity of acids : The number of H+ ions obtainable by the dissociation of one molecule, of an acid is called its basicity., Acidity of bases : The number of OH- ions obtainable by the dissociation of one molecule, of a base is called its acidity., 1. Refer to the table on page no. 61 and give examples, Use your brain power !, of monobasic, dibasic and tribasic acids., 2. Refer to the table on page no. 61 and give the three, types of bases and their examples., Concentration of acid and base, Try this, A, , B, , 5.3 Solution of lemon juice, , Cut a lemon into two equal parts. Take the juice, of each part into two separate beakers. Pour 10ml of, drinking water in one beaker and 20ml in the second., Stir the solutions in both the beakers and taste them., Is there any difference in the tastes of the solutions, in the two beakers? What is it?, In the above activity, the sour taste of the, solutions is because of the solute, lemon juice, in, them. The quantity of the lemon juice is the same in, both the solutions. Yet their taste is different. The, solution in the first beaker is more sour than the one, in the second. Why is it so?, , Although the quantity of the solute is the same in both the solutions, the quantity of, the solvent is different. Ratio of the quantity of the solute to the quantity of the resulting, solution is different. This ratio is larger for the soultion in the first beaker and, therefore,, that solution tastes more sour. On the other hand, the proportion of the lemon juice to the, total solution in the second beaker is smaller and the taste is less sour., The taste of foodstuff depends upon the nature of the taste-giving ingredient and its, proportion in the foodstuff. Similarly, all the properties of a solution depend on the nature, of the solute and solvent and also on the proportion of the solute in the solution. The, proportion of a solute in a solution is called the concentration of the solute in the solution., When the concentration of a solute in its solution is high, it is a concentrated solution,, while the solution is called a dilute solution when the concentration of the solute is low., Several units are used to express the concentration of a solution. Two of these units, are used more frequently. The first unit is the mass of solute in grams dissolved in one litre, of the solution. (grams per litre, g/L). The second unit is the number of moles of the solute, dissolved in one litre of the solution. This is also called the molarity (M) of the solution., The molarity of a solute is indicated by writing its molecular formula inside a square, bracket. For example ‘[NaCl] = 1’ means the molarity of this solution of common salt is, 1M (1 Molar)., , 62

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Complete the following table of the concentration of various aqueous solutions., Solute, , A, Name, , B, , Quantity of solute, , C, , Molecu- Molecular, lar mass, formula (u), , Sodium NaCl, Chloride, , 58.5 u, , D, , Volume of, solution, , E= D, C, , F, , Concentration of, the solution, , G=, , D, F, , Gram (g), , Mole, (mol), , Litre (L), , Gram/, litre, (g/L), , 117 g, , 2 mol, , 2L, , 58.5 g/L, , H =, , E, F, , Molarity, (M), mole/litre, (mol/L), 1M, , ....., , HCl, , ......, , 3.65 g, , ......., , 1L, , ......, , ......., , ....., , NaOH, , ......, , ......, , 1.5 mol, , 2L, , ......, , ......., , pH of solution, We have seen that acids and bases dissociate to a smaller or larger extent on dissolving, in water forming H+ and OH- ions respectively. H+ and OH- ions are found in different, proportions in all natural aqueous solutions, and that determines the properties of those, solutions., For example, the proportion of H+, pH of some common aqueous solutions, and OH- ions divides soil into the, Solution, pH, acidic, neutral and basic types. It is, 0.0, necessary for blood, cell sap, etc. to Strong acids 1M HCl, +, have H and OH ions in certain, Gastric juice, 1.0, definite proportions for their proper, Lemon juice, 2.5, functioning. Fermentation carried out, Vinegar, 3.0, other biochemical processes with the, Tomato juice, 4.1, help of micro-organisms, and also, Black coffee, 5.0, many chemical processes require the, Acid rain, 5.6, proportion of H+ and OH- ions to be, maintained within certain limits. Pure, Weak acids Urine, 6.0, water also undergoes dissociation to a, Neutral, Rain, milk, 6.5, very small extent and gives rise to H+, weak bases Pure water, sugar solution, 7.0, and OH- ions in equal proportion., Blood, 7.4, dissociation +, H2O, H + OHDue to this property of water to, undergo dissociation, there exist both, H+ and OH- ions in any aqueous, solution. However, their concentration, may be different., , Solution of baking soda, Toothpaste, Milk of magnesia, Limewater, Strong bases 1 M NaOH, , 63, , 8.5, 9.5, 10.5, 11.0, 14.0

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The concentration of H+ ions formed by dissociation of water is 1 x 10-7 mol/L, at 250C. At the same temperature, the concentration of H+ ions in 1M solution of, HCl is 1 x 100 mol/L, on the other hand in a 1M NaOH solution, the concentration, of H+ ions is 1 x 10-14 mol/L. Thus, we see that in common aqueous solutions, the, range of H+ ion concentration is very wide from 100 to 10-14 mol/L. In 1909, the, Danish scientist Sorensen introduced a convenient new scale of expressing H+ ion, concentration which is found to be very useful in chemical and biochemical, processes. It is the pH scale (pH : power of hydrogen) The pH scale extends from, 0 to 14. According to this scale pure water has a pH of 7 which means that pure, water has ‘[H+] = 1 x 10-7 mol/L.’ pH 7 indicates a neutral solution. This pH is, the midpoint of the scale. The pH of an acidic solution is less than 7 and that of, a basic solution is greater than 7. The table (See page no. 63) gives the pH values, of some common solutions., By which other method could we find out the pH of a solution?, Universal indicators, What are the colours of the following natural and, Can you recall? synthetic indicators in acidic and basic solutions ?, Litmus, turmeric, jamun, methyl orange, phenolphthalein ?, We know that some natural and synthetic dyes show two different colours in acidic, and basic solutions, and such dyes are used as acid-base indicators. In the pH scale, the, pH of solutions varies from 0 to 14 in accordance with the strength of the acid or base. To, show these variations in pH, a universal indicator is used. A universal indicator shows, different colours at different values of pH., Neutral, Acid, , Basic, , 5.4 Measurement of pH : universal indicator and pH meter, , A universal indicator is made by mixing several synthetic indicators in specific, proportions. The pH of a solution can be determined by means of a universal, indicator solution or the pH paper made from it. However, the most accurate method, of measuring the pH of a solution is to use an electrical instrument called pH, meter. In this method, pH is measured by dipping electrodes into the solution., , 64

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Reactions of acids and bases, 1. Neutralization, Try this, Do this : Take 10ml dilute HCl in a beaker. Use a, glass, rod to put a drop of this solution on a pH paper, Glass rod, pH indicator strip and record the pH of the solution., Add to it a few drops of dilute NaOH solution by, Dilute HCl, means of a dropper and stir the solution with the glass, rod. Measure the pH of the resulting solution by, putting a drop of this solution on another pH paper. In, pH Indicator, this manner, go on adding dilute NaOH drop by drop, strip, and recording the pH. What do you find? Stop adding, 5.5 Neutralization, NaOH when a green colour appears on the pH paper,, that is when the pH of the solution becomes 7., The neutralization reaction : Why does the pH increase as NaOH solution is added drop, by drop to the HCl solution? The answer lies in the process of dissociation. Both HCl and, NaOH dissociate in their aqueous solutions. Addition of NaOH solution to HCl solution is, like adding a large concentration of OH- ions to a large concentration of H+ ions. However, water dissociates into H+ and OH- ions to a very small extent. Therefore, on mixing, the, excess OH- ions combine with the excess H+ ions to form H2O molecules which mix with, the solvent water. This change can be represented by the ionic equation shown as follows., Na+ + Cl- + H2O, H+ + Cl- + Na+ + OHIt can be seen from the above equation that the Na+ and Cl- ions are on both the sides., Therefore the net ionic reaction is, H+ + OHHO, 2, , As the NaOH solution is added drop by drop to the HCl solution, the concentration of, H goes on decreasing due to combination with added OH- ions, and that is how the pH, goes on increasing., When enough NaOH is added to HCl, the resulting aqueous solution contains only, +, Na and Cl- ions, that is, NaCl, a salt, and the solvent water. The only source of H+ and, OH- ions in this solution is dissociation of water. Therefore, this reaction is called the, neutralization reaction. The neutralization reaction is also represented by the following, simple equation., NaCl + H2O, HCl + NaOH, Acid base, Salt Water, +, , Complete the following table of neutralization reactions and also write down the, names of the acids, bases and salts in it., Acid, , +, , base, , Salt, , +, , Water, , HNO3, , +, , .........., , KNO3 + H2O, , ...............+ 2 NH4OH, , (NH4)2 SO4 + ..........., , ..............+ KOH, , KBr +, , 65

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Use your brain power !, , Always remember, , What would be the definition of an, acid and a base with reference to the, neutralization reaction ?, , In the neutralization reaction, an, acid reacts with a base to form a salt, and water., , 2. Reaction of acids with metals, The reaction of acids with metals is determined, by the strength and the concentration of the acid, and also by the reactivity of the metal and the, temperature. It is easy to bring about the reaction, of a dilute solution of strong acids with moderately, reactive metals at normal temperature., , Burning of H2 with an explostion, Cork, , Test tube, Bubbles of H2, , Try this, Activity : Take a big test tube. Choose a rubber, stopper in which a gas tube can be fitted. Take, a few pieces of magnesuim ribbon in the test tube, and add some dilute HCl to it. Take a lighted, candle near the end of the gas tube and observe., What did you observe ?, , Dilute HCl, Mg ribbon, 5.6 Reaction of a dilute solution, of a strong acid with a metal, , Magnesium metal reacts with dilute hydrochloric acid and an inflammable gas,, hydrogen, is formed. During this reaction, the reactive metal displaces hydrogen from the, acid to release hydrogen gas. At the same time, the metal is converted into basic radical, which combines with the acidic radical from the acid to form the salt., Complete the following reactions., , Metal + Dilute acid, , Mg(s) + 2HCl (aq), , Zn (s) + .......... (aq), , ........(s) + ....... (aq), , Salt + Hydrogen, MgCl2 (aq) + H2 (g), ZnSO4 (aq) + ......., Cu (NO3)2 (aq) + H2 (g), , 3. Reaction of acids with oxides of metals, Try this, , Take some water in a test tube and add a little red oxide, (the primer used before painting iron articles) to it. Now add, a small quantity of dilute HCl to it, shake the test tube and, observe., 1. Does the red oxide dissolve in water?, 2. What change takes place in the particles of red oxide on, adding dilute HCl ?, , 66

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The chemical formula of red oxide is Fe2O3. The water-insoluble red oxide reacts with, HCl to produce a water soluble salt FeCl3. This gives a yellowish colour to the water. The, following chemical equation can be written for this chemical change., , Fe2O3 (s) + 6HCl (aq), Complete the following., Metal oxide + dilute acid, , 2FeCl3 (aq) + 3H2O (l), Salt + Water, , CaO (s) + 2 HCl (aq), , MgO (s) + ................., ZnO (s) + 2 HCl (aq), Al2O3 (s) + 6 HF(l), , ......... + ........, MgCl2 (aq) + H2O (l), ..............+................, ...............+................., , 1. What type of compound is a metal oxide, with reference to neutralization reaction?, 2. Explain the statement ‘Metal oxides are basic in nature.’, 4. Reaction of bases with oxides of non-metals, Try this, , Bases react with oxides of non-metals to form a salt and water., Hence, oxides of non-metals are said to be acidic in nature. Sometimes, the oxides of non-metals themselves are said to be examples of acids., Complete the following reactions., , Oxide of non-metal + base, , CO2 (g) + 2 NaOH (aq) , ...........+ 2 KOH (aq) , SO3 (g) + ............. , , salt + water, , Na2CO3 (aq) + H2O (l), K2CO3 (aq) + H2O (l), Na2SO4 (aq) + H2O (l), , Zinc oxide reacts with sodium hydroxide to form sodium zincate (Na2ZnO2) and, water. Similarly, aluminium oxide reacts with sodium hydroxide to form sodium aluminate, (NaAlO2) and water., , Use your brain power !, , 1. Write down chemical equations for both these, reactions., 2. Can we call Al2O3 and ZnO acidic oxides on the, basis of these reactions?, 3. Define ‘amphoteric oxides’ and give two examples., , 5. Reaction of acids with carbonates and bicarbonates of metals, Try this, , Activity : Fit a bent tube in a rubber cork. Take some lime water in, a test tube and keep it handy. Take some baking soda in another test, tube and add some lemon juice to it. Immediately fit the bent tube, over it. Insert its other end into the lime water. Note down your, observations of both the test tubes. Repeat the procedure using, washing soda, vinegar and dilute HCl properly. What do you see ?, , 67

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In this activity, when limewater comes in contact with the gas released in the form of, an effervescence, it turns milky. This is a chemical test for carbon dioxide gas. When lime, water turns milky, we infer that the effervescence is of carbon dioxide gas. This gas is, produced on reaction of acids with carbonate and bicarbonate salts of metals. A precipitate, of CaCO3 is produced on its reaction with the limewater Ca(OH)2. This reaction can be, represented by the following chemical equation., Ca(OH)2 (aq) + CO2 (g), CaCO3 (s) +H2O(l), Complete the reactions in the following table., Carbonate salt of metal + dilute acid, , Another salt of metal + Carbon dioxide, , Na2CO3 (s) + 2 HCl (aq), , 2 NaCl (aq) + CO2 (g) + H2O (l), , Na2CO3 (s) + ..................., , Na2SO4 (aq) + CO2 (g) + .................., , CaCO3 (s) + 2 HNO3 (aq), , .................. + .................. + .................., , K2CO3 (s) + H2SO4 (aq), , .................. + .................. + .................., , Bicarbonate salt of metal + dilute acid, , Another salt of metal + carbon dioxide + water, , 1. NaHCO3 (s) + HCl (aq), , NaCl (aq) + CO2 (g) + H2O (l), , 2. KHCO3 (s) + HNO3 (aq), , .................. + .................. + .................., , 3. NaHCO3 (s) + .............., , CH3COONa (aq)+ ............ + .................., , Salts, Types of salts : acidic, basic and neutral salts, Try this, , Activity : Prepare 10 ml aqueous solutions from 1gm each of sodium, chloride, ammonium chloride and sodium bicarbonate. Measure pH, of each solution by means of pH paper. Are the values the same for all, three ? Classify the salts based on the pH values., , We have seen that salts are formed by the reaction between acids and bases. Though, this reaction is called a neutralization reaction, the resulting salts are not always neutral., A neutral salt is formed by neutralization of a strong acid by a strong base. The aqueous, solution of a neutral salt has pH equal to 7., An acidic salt is formed by the neutralization reaction between a strong acid and a, weak base. The pH of the aqueous solution of an acidic salt is less than 7. On the contrary,, a basic salt is formed by a neutralization reaction between a weak acid and a strong base., The pH of an aqueous solution of such a basic salt is greater than 7., Classify the following salts into the types acidic, basic and neutral. Sodium sulphate,, potassium chloride, ammonium nitrate, sodium carbonate, sodium acetate, sodium, chloride., , 68

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Activity : Take some crystals of blue vitriol in, two test tubes., Add some water in one test tube and shake it., Try this, What did you see?, What is the colour of the solution formed?, Drops of water, Copper, Heat the other test tube on low flame of a, sulphate, burner. What did you see?, (Blue), What change did occur in the colour of blue, on giving heat to, vitriol?, copper sulphate, Copper, What did you see in the upper part of the test, sulphate, tube?, (White), When the second test tube cools down add, some water in it and shake. What is the colour, of the resulting solution? What inference can, 5.7 Properties of water of crystallisation, be drawn from this observation?, On heating, the crystalline structure of, Heat, blue vitriol broke down to form a colourless, CuSO4. 5 H2O ® CuSO4 + 5 H2O, powder and water came out. This water was, (White), (Blue), part of the crystal structure of blue vitriol. It, is called water of crystallisation. On adding water to the white powder a solution was, formed which had the same colour as the solution in the first test tube. From this we come, to know that no chemical change has occurred in the crystals of blue vitriol due to heating., Losing water on heating blue vitriol, breaking down of the crystal structure, losing blue, colour and regaining blue colour on adding water are all physical changes., Water of crystallisaton, , Repeat the above activity for Ferrous sulphate, sodium carbonate and write chemical, equations. Take 'x' as a coefficient for H2O., Try this, , Apparatus : Evaporating dish, Bunsen burner, tripod stand, wire gauze, etc., , Chemicals : Alum., Procedure : Take a small stone of alum in the evaporating dish. Keep the dish on the tripod stand, and heat it with the help of burner., What did you see in the dish? What is meant by puffed alum?, Ionic compounds are crystalline in nature. These crystals are formed as a result of, definite arrangement of ions. In the crystals of some compounds water molecules are also, included in this arrangement. That is the water of crystallisation. The water of crystallisation, is present in a definite proportion of the chemical formula of the compound. It is indicated, in the chemical formula as shown below., 1. Crystalline blue vitriol- CuSO4.5H2O 1. Crystalline substances contain water of, crystallisation., 2. Crystalline ferrous sulphate, 2.The molecules of water of crystallisation are, (Green vitriol) - FeSO4.7H2O, part of the internal arrangement of the crystal., 3. Crystalline washing soda -Na2CO3.10H2O 3. On heating or just by keeping, the water of, crystallisation is lost and the crystalline shape, 4. Crystalline alum -K2SO4.Al2(SO4)3.24 H2O, of that part is lost., , 69

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Ionic compounds and electrical, conductivity, , Activity : Prepare a solution of 1g sodium, chloride in 50ml water. Take two electrical, wires. Connect one wire to the positive terminal, Bulb, Try this, of a 6V battery. While connecting the other, wire to the negative terminal of the battery,, Switch, include one switch and one holder with an, electric bulb. Remove the insulating cladding, from 3cm portion of the other free ends of the, two wires. Take the salt solution in a 100ml, Support, capacity beaker and immerse the uncovered, ends of the two wires in it keeping the wire, Beaker, erect with the help of a support. Switch on the, current. Note whether the bulb glows. Repeat, Battery, the same procedure using solutions of 1g, copper sulphate, 1g glucose, 1g urea, 5ml dilute, Solution of sodium chloride H2SO4 and 5ml dilute NaOH each in 50ml, water. Record your observations in a table., Bare electric wire, (Do not forget to clean the beaker and, uncovered part of the wires with water,, 5.8 Testing the electrical conductivity, every time you change the solution.), of a solution, , 1. With which solutions did the bulb glow?, 2. Which solutions are electrical conductors?, The bulb glows only when electric current passes through it. And this can, happen only when the electric circuit is complete. In the above activity, the circuit, is found to be complete when the aqueous solutions of NaCl, CuSO4, H2SO4 and, NaOH are used. It means that these solutions are conductors of electricity., Electrons conduct electricity through electrical wires; and ions conduct electricity, through a liquid or a solution. Electrons leave the battery at the negative terminal,, complete the electric circuit and enter the battery at the positive terminal. When, there is a liquid or a solution in the circuit, two rods, wires or plates are immersed, in it. These are called electrodes. Electrodes are usually made of a conducting solid., The electrode connected to the negative terminal of a battery by means of a, conducting wire is called a cathode and the electrode connected to the positive, terminal of a battery is called an anode., Why does the electric circuit get completed on immersing the electrodes in certain, liquids or solutions? In order to understand this phenomenon, let us look more closely, at the solutions in the above activity, which were found to be electrical conductors., Dissociation of ions and electrical conductivity, In the above activity it was found that the aqueous solutions of the compounds, NaCl, CuSO4, H2SO4 and NaOH are electricity conductors. Out of these NaCl and, CuSO4 are salts, H2SO4 is a strong acid and NaOH is a strong base. We have seen, that salts, strong acids and strong bases dissociate almost completely in their aqueous, solutions. Therefore, the aqueous solutions of all these three contain large numbers, of cations and anions., Use your brain power !, , 70

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A characteristic of the liquid state is the, mobility of its particles. Due to this mobility, the, positively charged cations in the solution are, attracted towards the negative electrode or cathode, and move towards the cathode; on the other hand,, the negatively charged anions move in the, direction of the anode. The movement of ions in, the solution towards the respective electrodes, amounts to the conduction of electricity through, the solution. From this, you will understand that, 5.9 Dissociation of ions, those liquids or solutions which contain a large, number of dissociated ions conduct electricity., Electrolysis, Try this, Procedure : Take a solution of 1g copper, sulphate in 50ml water in a 100ml capacity, Key / Switch, beaker. Use a thick plate of copper as, anode and a carbon rod as cathode., eArrange the apparatus as shown in the, figure and pass an electric current though, the circuit for some time. Do you see any, Cu, C, changes ?, eIn the above activity copper appears to, have deposited on the portion of the cathode, immersed in the solution. How did this, happen? When an electric current started, flowing through the circuit, the cations, that, Solution of CuSO4 is, Cu++ ions in the solution got attracted, towards the cathode. Cu atoms are formed, 5.10 Electrolysis, when electrons coming out from the cathode, combine with the Cu++ ions. A deposit of the, copper appeared on the cathode. Even though, ++, the Cu ions in the solution were used up in this manner, the colour of the solution remained, the same. Because, while electric current was on, electrons were removed from the Cu, atoms of the anode and sent to the battery through the electric wire. The Cu++ ions formed, in this manner, entered the solution. In this way decomposition of the solute in the solution, took place due to the electric current. This is called electrolysis. There are two parts in the, electrolysis process. These are the cathode reaction and the anode reaction. The two parts, of the electrolysis process that take place in the above activity are shown below., Cathode reaction Cu2+(aq)+ 2eAnode reaction, , Cu (s), , Cu(s), Cu2+(aq) + 2e-, , , , 71

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Always remember, , Use your brain power !, , 1. It is necessary for the liquid/solution to have a, large number of dissociated ions for electrolysis, to take place. Therefore, substances which, undergo dissociation to great extent in the, liquid state or a solution are called strong, electrolytes. Salts, strong acids and strong, bases are strong electrolytes. Their solutions, have high electrical conductivity. In other, words strong electrolytes are good conductors, of electricity in their liquid or solution state., Weak acids and weak bases are weak, electrolytes., 2. An assembly that consists of a container, electrolyte and the electrodes dipped in it, is, called an electrolytic cell., , 1. In the above activity, if, , electric current passesd, through the electrolytic, cell for a long time, what, change would be seen at, the anode?, 2. Would water be a good, conductor of electricity?, , Website for more information, , www.chemicalformula.org, , If pure water is used in an electrolytic cell, current does not flow even on putting on, the switch. From this we learn that pure water is a bad conductor of electricity. And we, have already seen the reason behind this. The concentration of H+ and OH- ions formed, by dissociation of water is very low, only 1 x 10-7 mol/L for each ion. However, the, electrical conductivity of water increases on mixing a small amount of salt or a strong, acid/base in it due to their dissociation and electrolysis of water takes place., Electrolysis of water, Try this, Test tube, , Beaker, , +, , Battery, , Activity : Dissolve 2g salt in 500ml pure water., Take 250 ml of this solution in a 500ml capacity, beaker. Connect two electrical wires to the, positive and negative terminals of a power, supply. Remove the insulating cladding from, about 2cm portions at the other ends of the, wires. These are the two electrodes. Fill two, test tubes upto the brim with the prepared dilute, salt solution. Invert them on the electrodes, without allowing any air to enter. Start the, electric current under 6V potential difference, form the power supply. Observe what happens, in the test tubes after some time., , 5.11 Electrolysis of water, , 1. Did you see the gas bubbles forming near the electrodes in the test tubes?, 2. Are these gases heavier or lighter than water?, 3. Are the volumes of the gases collected over the solution in the two test tubes the same, or different?, , 72

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It is found in the above activity that the volume of the gas formed near the cathode is, double that of the gas formed near the anode. Scientists have shown that hydrogen gas is, formed near the cathode and oxygen gas near the anode. From this, it is clear that, electrolysis of water has taken place and its constituent elements have been released. The, concerned electrode reactions are as follows., , Cathode reaction 2H2O (l) + 2eH2(g) + 2OH-(aq), , Anode reaction 2H2O (l), O2 (g) + 4H +(aq)+ 4e1. Test the solutions in the two test tubes with litmus paper, what do you see ?, 2. Repeat the activity by using dilute H2SO4 as well as dilute NaOH as the electrolyte., Research, , There are many applications of electrolysis of electrolytes., Collect information about them., , Exercises, 1. Identify the odd one out and justify., (a) Chloride, nitrate, hydride,, ammonium, (b) Hydrogen, chloride,, sodium, hydroxide, calcium oxide, ammonia, (c) Acetic acid, carbonic acid,, hydrochloric acid, nitric acid, (d) Ammonium chloride, sodium, chloride, potassium nitrate, sodium, sulphate, (e) Sodium nitrate, sodium carbonate,, sodium sulphate, sodium chloride, (f) Calcium oxide, magnesium oxide,, zinc oxide, sodium oxide., (g) Crystalline blue vitriol, crystalline, common salt, crystalline ferrous, sulphate,, crystalline, sodium, carbonate., (h) Sodium, chloride,, potassium, hydroxide, acetic acid, sodium, acetate., 2. Write down the changes that will be, seen in each instance and explain the, reason behind it., (a) 50ml water is added to 50ml, solution of copper sulphate., (b) Two drops of the indicator, phenlphthalein were added to 10ml, , solution of sodium hydroxide., (c) Two or three filings of copper were, added to 10ml dilute nitric acid and, stirred., (d) A litmus paper was dropped into, 2ml dilute HCl. Then 2ml, concentrated NaOH was added to it, and stirred., (e) Magnesium oxide was added to, dilute HCl and magnesium oxide, was a added to dilute NaOH., (f) Zinc oxide was added to dilute HCl, and zinc oxide was added to dilute, NaOH., (g) Dilute HCl was added to limestone., (h) Pieces of blue vitriol were heated in, a test tube. On cooling, water was, added to it., (i) Dilute H2SO4 was taken in an, electrolytic cell and electric current, was passed through it., 3. Classify the following oxides into, three types and name the types., CaO, MgO, CO2, SO3, Na2O, ZnO,, Al2O3, Fe2O3, , 4. Explain by drawing a figure of the, electronic configuration., a. Formation of sodium chloride from, , 73

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sodium and chlorine., b. Formation of a magnesium chloride, from magnesium and chlorine., , 9. State the differences., a. Acids and bases, b. Cation and anion, c. Negative electrode and positive, electrode., , 5. Show the dissociation of the following, , compounds on dissolving in water,, with the help of chemical equation, and write whether the proportion of, dissociation is small or large., Hydrochloric acid, Sodium chloride,, Potassium hydroxide, Ammonia,, Acetic acid, Magnesium chloride,, Copper sulphate., , 10. Classify aqueous solutions of the, , following substances according to, their pH into three groups : 7, more, than 7, less than 7., , Common salt, sodium acetate,, hydrochloric acid, carbon dioxide,, potassium bromide, calcium hydoxide,, ammonium chloride, vinegar, sodium, carbonate, ammonia, sulphur dioxide., , 6. Write down the concentration of, , each of the following solutions in g/L, and mol/L., a. 7.3g HCl in 100ml solution, b. 2g NaOH in 50ml solution, c. 3g CH3COOH in 100ml solution, d. 4.9g H2SO4 in 200ml solution, , Project :, 1. Collect, information, about, electroplating. Make a list of articles, in day-to-day life, where this technique, is used., , 7. Answer the following questions., , a. Classify the acids according to, their basicity and give one example, of each type., b. What is meant by neutralization?, Give two examples from everyday, life of the neutralization reaction., c. Explain what is meant by, electrolysis of water. Write the, electrode reactions and explain, them., 8. Write the chemical equations for the, following activities., (a) NaOH solution was added to HCl, solution., (b) Zinc dust was added to dilute, H2SO4., (c) Dilute nitric acid was added to, calcium oxide., (e) Carbon dioxide gas was passed, through KOH solution., (f) Dilute HCl was poured on baking, soda., , 2. Obtain a sample of rainwater. Add to it, a few drops of universal indicator., Meausre its pH. Describe the nature of, the sample of rainwater and write the, effect if it has on the living world., , ²²², , 74

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6.1.Classification, गतीचे नियम of plants, Kingdom Plantae, Ø Sub-kingdom: Gymnosperms, Ø Sub-kingdom: Angiosperms, , Ø, , Living Organisms, , Can you recall?, , How have living organisms been, classified?, Prokaryotic, Eukaryotic, You have already studied the, kingdoms Monera, Protista and Fungi Monera, of the ‘Five Kingdom’ classification, Unicellular, Multicellular, system proposed by Robert Whittaker, (1969) for the study of living, Protista, organisms., Without, cell, wall, What are the hidden secrets of the, With cell, wall, Kingdom plantae which impart this, green freshness to our surroundings?, (Animalia), Just how much diversity is there in, Heterotrophs, Autotrophs, (Fungi), (Plantae), this Kingdom? Let us see!, Kingdom plantae, Which are the special cell organelles that differentiate plant, cells from animal cells?, The group of autotrophic living organisms having eukaryotic cells with cell walls, is the group of plants. Plants have become autotrophic as they can perform photosynthesis, with the help of chlorophyll. Living organisms of kingdom plantae are the main source of, food for all other living organisms., Basis for classification :, The presence or absence of organs is the first criterion for classification of plants., The presence or absence of separate conducting tissues for conduction of water and food, is the next consideration for classification. Do the plants bear, An introduction, seeds? If they do then, whether the seeds are enclosed in a, to scientists, fruit or not is also an important criterion for classification., Finally, plants are grouped depending upon the number of, In 1883, Eichler, a, cotyledons in the seeds., botanist, classified the, At the higher levels of plant classification, different, Kingdom Plantae into, characteristics are considered for classification, e.g., two subkingdoms. As a, depending upon the absence or presence of flowers, fruits and, result, two subkingdoms,, seeds, plants are classified as cryptogams or phanerogams., cryptogams, and, Depending upon whether seeds are enclosed within a fruit or, phanerogams, were, not, phanerogams are classified as gymnosperms and, considered for plant, angiosperms. Angiosperms are further classified as monocots, classification., or dicots depending upon the number of cotyledons in seeds., Can you tell?, , 75

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Cryptogams, Search for a pond with greenish water. Collect some of the, green fibres from the water. Put the fibres in a Petri dish and wash, Observe, them clean with water. Put one of the fibres in a drop of water on a, glass slide and spread it out straight., Put a cover-slip over the slide and observe under a compound microscope. Do you, see the spirally arranged green thread-like chloroplasts in the cells in that straight fibre?, This plant is known as Spirogyra., Division I - Thallophyta, These plants grow mainly in water. This group of plants, which do not have specific, parts like root-stem-leaves-flowers but are autotrophic due to the presence of chlorophyll,, is called algae. Algae show great diversity. They may be unicellular or multicellular, and, microscopic or large. Examples of algae are Spirogyra, Ulothrix, Ulva, Sargassum, etc., Some of these are found in fresh water while some are found in saline water. These plants, usually have a soft and fibre-like body. Various types of fungi like yeasts and moulds, which do not have chlorophyll are also included in this group., Cell wall, , Ulva, , Chara, , Spiral, chloroplasts, , Nucleus, , Pyrenoid, , Spirogyra, , 6.1 Plants of the Thallophyta division., , Division II - Bryophyta, You may have seen a lush green soft carpet on old, Observe and discuss. walls, bricks and rocks in the rainy season. Scrape it gently, with a small ruler, observe it under a magnifying lens and, discuss., This group of plants is called the ‘amphibians’ of the plant kingdom because they grow, in moist soil but need water for reproduction. These plants are thalloid, multicellular and, autotrophic. They reproduce by spore formation.The structure of the plant body of bryophytes, is flat, ribbon-like long, without true roots, stem and leaves. Instead, they have stem-like or, leaf-like parts and root-like rhizoids. They do not have specific tissues for conduction of food, and water. Examples are Moss (Funaria), Marchantia, Anthoceros, Riccia, etc., , 76

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Capsule, , Capsule, , Capsule, Stalk, , Stalk, , Leaf - like parts, Leaf - like, parts, Rhizoids, Funaria, , Marchantia, , Rhizoids, , Leaf - like parts, Anthoceros, , 6.2 Plants of the bryophyta division, , Observe and discuss., Leaflets, , You may have seen ferns among the, ornamental plants in a garden. Take a leaf of, a fully grown fern and observe it carefully., Division III- Pteridophyta, Plants from this group have welldeveloped roots, stem and leaves and, separate tissues for conduction of food and, water. But, they do not bear flowers and, fruits. They reproduce with the help of spores, formed along the back or posterior surface of, their leaves. Examples are ferns like, Nephrolepis, Marsilea, Pteris, Adiantum,, Equisetum, Selaginella, Lycopodium, etc., These plants reproduce asexually by, spore-formation and sexually by zygote, formation. They have a well-developed, conducting system., , Sporangia in sori, on leaflet, , Ferns, , Selaginella, , Lycopodium, , roots, , Use your brain power !, What is the similarity between the plants, of the groups Thallophyta, Bryophyta and, Pteridophyta irrespective of differences in, their body structure?, , 6.3 Plants of the pteridophyta division, , 77

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All these plants reproduce by spore formation. They are called cryptogams as their, reproductive organs cannot be seen. (cryptos: hidden, gams: reproductive organs)., Phanerogams, Plants which have special structures for reproduction and produce seeds are called, phanerogams. In these plants, after the process of reproduction, seeds are formed which, contain the embryo and stored food. During germination of the seed, the stored food is used, for the initial growth of the embryo. Depending upon whether seeds are enclosed in a fruit or, not, phanerogams are classified into gymnosperms and angiosperms., Division I - (Gymnosperms), Observe, Observe all garden plants like Cycas,, Christmas tree, Hibiscus, lily, etc. and compare, them. Note the similarities and differences among, them. Which differences did you notice between, gymnosperms and angiosperms?, , Cycas, , Gymnosperms are mostly evergreen,, perennial and woody. Their stems are without, branches. The leaves form a crown. These plants, bear male and female flowers on different, sporophylls of the same plant. Seeds of these, plants do not have natural coverings, i.e. these, plants do not form fruits and are therefore called, gymnosperms. (gymnos: naked, sperms: seeds)., Examples Cycas, Picea (Christmas tree),, Thuja (Morpankhi), Pinus (Deodar), etc., , 6.4 Gymnosperms, , Division II- Angiosperms, Try this, , Soak the seeds of corn, beans, groundnut, tamarind, mango,, wheat, etc. in water for 8 to 10 hrs. After they are soaked, check each, seed to see whether it divides into two equal halves or not and, categorize them accordingly., , The flowers these plants bear are their reproductive organs. Flowers develop into, fruits and seeds are formed within fruits. Thus, these seeds are covered; hence, they are, called angiosperms (angios: cover, sperms: seeds)., The plants whose seeds can be divided into two equal halves or dicotyledons are, called dicotyledonous plants and those whose seeds cannot be divided into equal parts are, called monocotyledonous plants., , 78

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Observe and verify, , Seed, Root, Stem, , Leaf, , Dicotyledonous plants, Two cotyledons, , Monocotyledonous, Single cotyledon, , Well developed, primary root Fibrous roots, (Tap root), Strong, hard. Ex. Banyan tree Hollow, Ex. Bamboo, False, Ex. Banana, Disc-like, Ex. Onion., Reticulate venation, Parallel venation, , Flower Flowers with 4 or 5 parts or Flowers with 3 parts or in multiples of three, in their multiples (tetramerous (trimerous)., or pentamerous), , 6.4 Mustard and Maize, , Kingdom: Plantae, , Cryptogams, , Phanerogams, Gymnosperms, , Thallophyta, , Bryophyta, , Angiosperms, , Pteridophyta, Dicotyledons, , 79, , Monocotyledons

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Using ICT:, 1. Sketch the diagrams of the plants mentioned in the lesson with the help of the, drawing software in the computer., 2. Using those sketches, prepare a power point presentation about plant classification, and present it in the class., , Exercises, 1. Match the proper terms from columns A and C with the description in column B., ‘A’, Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, Angiosperms, , ‘B’, Seeds are formed in fruits., No natural covering on seeds., These plants mainly grow in water., These plants need water for reproduction., Tissues are present for conduction of water and food, , ‘C’, Fern, Cycas, Tamarind, Moss, Algae, , e. Write the characteristics of the, plants belonging to division, Bryophyta., 4. Sketch and label the figures of the, following plants and explain them, into brief., Marchantia, Funaria, Fern, Spirogyra., 5. Collect a monocot and dicot plant, available in your area. Observe the, plants carefully and describe them in, scientific language., 6. Which criteria are used for the, classification of plants? Explain with, reasons., Project :, a. Collect more information about, plant classification from the, internet, prepare a talk of about, 5 to 7 minutes on that topic and, present it in school during assembly., b. Prepare an album of moncot and, dicot seeds and display it in the, classroom., c. Collect photographs of 5 plants, each of the Thallophyta, Bryophyta, and Pteridophyta divisions and, write a description of each., , 2. Complete the sentences by filling in, the blanks and explain those, statements., (angiosperms, gymnosperms, spore,, bryophyta, thallophyta, zygote), a. .................... plants have soft and, fibre-like body., b. ...................., is, called, the, ‘amphibian’ of the plant kingdom., c. In, pteridophytes,, asexual, reproduction occurs by ...................., formation and sexual reproduction, occurs by ....................formation., d. Male and female flowers of, ....................are borne on different, sporophylls of the same plant., 3. Answer the following questions in, your own words., a. Write, the, charateristics, of, subkingdom Phanerogams., b. Distinguish between monocots and, dicots., c. Write a paragraph in your own, words about the ornamental plants, called ferns., d. Sketch, label and describe the, Spirogyra., , 80, , ²²²

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7. Energy, Flow, in an Ecosystem, 1. गतीचे, नियम, Ø, Ø, , Food chain and food web Ø The energy pyramid, Bio-geo-chemical cycle : Carbon, oxygen and nitrogen cycles, , Looking back, , 1. What is meant by ‘ecosystem’?, 2. Which are the different types of ecosystems?, 3. How do interactions take place between biotic and abiotic, factors of an ecosystem?, , Energy flow in an ecosystem, We have already learnt the classification of living organisms according to the mode, of nutrition into producers, consumers, saprotrophs (saprophytes) and decomposers., Consider the various trophic levels of the ecosystem around you as given below., Primary consumers, (herbivores), , Ex. Grasshopper,, squirrel, elephant,, etc. They are directly, dependent on, autotrophs, (producers)., , Apex or top consumers, (carnivores), , Secondary, consumers, (carnivores), , Ex. Tiger, lion, etc., These consumers use, herbivores and carnivores as their food. No, other animals feed on, top consumers., , Ex. Frog, owl, fox,, etc., These consumers, use herbivores as, their food., , Omnivores, (mixed, consumers), , Ex. Humans,, bear, etc. Feed, on herbivores,, carnivores and, producers., , Food chain and food web, Observe, , Observe figure 7.1 and explain the relationship between the components., , Construct four chains like the one, shown in figure 7.1., Interactions go on continuously, between producers, consumers and, saprophytes. There is a definite, sequence in these interactions which is, called the food chain. Each chain, consists of four, five or more links. An, ecosystem consists of many food chains, that are interconnected at various, levels. Thus a food web is formed., 7.1 Food chain, , Use your brain power !, , Explain the food chains of various ecosystems which, you have studied last year., , 81

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An organism may be the prey for many other organisms. For example, an insect feeds, upon leaves of various plants but the same insect is the prey for different animals like frog,, wall lizard, birds, etc. If this is to be shown in a figure, it will form an intricate web instead, of a linear food chain. Such an intricate network is called a ‘Food Web’. Generally, foodwebs are found everywhere in nature., Use your brain power !, Make a list of the various, consumers of the ecosystems, around you and classify them, according to mode of nutrition., Pictures, of, various, organisms are given in fig. 7.2., Construct a foodweb from those, pictures., 1. Is the number of consumers, in a food web fixed?, 2. What will be the effect on an, ecosystem if only one type of, organism in it forms the food, for, several, different, 7.2 Various living organisans, consumers in that ecosystem?, 3. Why, is, balance, or, equilibrium necessary in a, foodweb?, Make some interesting observations while having a meal at, home. Identify the trophic level of the various food items in your dish., Research Identify your own level in the chain., The energy pyramid, Trophic level, Omnivores, 3rd Trophic level, Each level in the food chain is, called a trophic level. A trophic level, Carnivores, 2nd Trophic level, is the step at which the organism, 1st Trophic level, Herbivores, obtains its food in the chain. The, amount of matter and energy gradually, Producers, decreases from producers at lowest All producers in the ecosystem (Plants), level to top consumers at the highest, 7.3 Trophic levels, level., An introduction to scientists, Lindeman, In 1942 studied the food chain and energy flow through it. Charles Elton,, a British scientist first proposed the concept of the Ecological Pyramid in 1927 after his, study of the Tundra Ecosystem of the Beer islands in England. Hence, this pyramid is, also called the Eltonian Pyramid., , 82

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Think about it, , Use your brain power !, , What happens to the energy during, its transfer from producers to apex, consumers? Does it remain trapped in, the apex consumer? Does it remain in, the body of apex consumer till its, death?, , What would happen if the energy, remains trapped in the body of apex, consumers even after their death? What, will happen if there were no decomposers, like microbes and fungi in nature?, , Figure 7.4 shows the energy transfer that takes place at each trophic level. There are, different levels of energy exchange in the food chain. The initial quantity of energy goes, on decreasing at every level of energy exchange. Similarly, the number of organisms also, decreases from the lowest level to the highest level. This pattern of energy exchange in an, ecosystem is called a ‘Pyramid of energy’., After the death of apex consumers,, their energy becomes available to the, 10 kcal, decomposers. Fungi and other microHumans, -organisms decompose the bodies of dead, 100 kcal, Fishes, animals. They are called decomposers. In, 1000 kcal, the process of obtaining food from the, Zooplanktons, remains of organisms, decomposers, 10,000 kcal, convert them into simple carbon, Phytoplanktons, compounds. These substances easily mix, with air, water and soil from where they 7.4 Pyramid of energy in an aquatic ecosystem, are again absorbed by plants and, incorporated into the food chain., You can now see that due to the food web formed by the various modes of nutrition,, energy and various nutrients circulate continuously in the ecosystem., The sun is the most important source of energy in any ecosystem. Green plants of the, ecosystem store some of the solar energy in the form of food. Before reaching the, decomposers, this energy is passed on from one trophic level to the next. Decomposers, dissipate some amount of energy in the form of heat. However, no part of the energy ever, returns to the sun. Hence, such passage of energy is referred to as ‘one way’ transport., , Use your brain power !, Why are the numbers of, tertiary consumers (apex, carnivores) always less than, those of other consumers?, , Institutes at work, The Indian Institute of Ecology and, Environment, Delhi, was established in 1980 and is, involved mainly in research, training and arranging, workshops and seminars. This institute has published, the International Encyclopaedia of Ecology and, Environment., , 83

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Hydrosphere, - atmosphere, interaction, , Atmosphere, - environment, interaction, , Interaction of hydrosphere - astmosphere lithosphere with the biosphere, Conversion of, lithosphere into rock,, soil, , Bio-geo-chemical cycle, Though the energy flow in an, ecosystem is one way, the flow of, nutrients is cyclical. All organisms, need nutrients for their growth., Study the various components in, the figure given alongside and, explain the bio-geo-chemical cycle, in your own words., The cyclical flow of nutrients, within an ecosystem is called the, bio-geo-chemical cycle., , 7.5 Bio-geo-chemical cycle, , Nutrients, necessary for the growth of organisms are continuously transferred from, abiotic to biotic factors and biotic to abiotic factors within an ecosystem. This cycle, operates continuously through the medium of the biosphere formed by the lithosphere,, atmosphere and hydrosphere. The recycling of biological, geological and chemical sources, of nutrients in this process is a complex process and depends upon the level of energy, transfer in the ecosystem., Types of bio-geo-chemical cycles, Gaseous cycle, Sedimentary cycle, * An accumulation of the main abiotic * An accumulation of the main abiotic, gaseous nutrient materials is found in, nutrient materials is found in soil,, the earth’s atmosphere., sediment and sedimentary rocks, etc. of, * Includes nitrogen, oxygen, carbon, the earth., dioxide, water vapour, etc., * Includes soil components like iron,, calcium, phosphorus, etc., The gaseous cycle is a speedier cycle than the sedimentation cycle. For example, if, CO2 has accumulated in an area, it is quickly dispersed with the wind or absorbed by, plants., Climatic changes and human activities seriously affect the speed, intensity and, equilibrium of these cycles Hence, various aspects of these cycles are extensively studied, nowadays., Do you know?, , The cycle of gases and the sedimentary cycle cannot be completely separated, , from each other. For example, nitrogen is present in the form of a gas in the atmosphere, and in the form of compounds like nitrogen oxide in the soil and sediments. Similarly,, carbon occurs in abiotic form mainly in coal, granite, diamond, limestone, etc. in the, earth's crust and in the form of carbon dioxide gas in the atmosphere. Generally, carbon, is present in plants and animals for a much shorter duration than it is in coal., , 84

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The carbon cycle, The circulation and recycling of carbon from the atmosphere to living organisms and, after their death back to the atomsphere is called the carbon cycle. Abiotic carbon atoms, are circulated and recycled into biotic form mainly through photosynthesis and respiration., Hence, the carbon cycle is one of the important bio-geo-chemical cycles., , Sunlight, Plants convert carbon, CO2 from factories, dioxide into carbohydrates by, the process of photosynthesis., Respiration in plants, Similarly, they produce carbon, compounds like proteins and, Respiration in, fats, too. Herbivores feed upon Biotic carbon, animals, plants. Carnivores feed upon, herbivores. In this way, biotic, carbon is transported from, Biotic, plants to herbivores, from, herbivores to carnivores and, decompositions, Absorption in water, from carnivores to apex, consumers., Fossil fuel, 7.6 The carbon cycle, Sunlight, , Main processes in 6 CO2 + 12 H2O Chlorophyll C6H12O6 + 6 H2O + 6 O2, the carbon cycle, Mitochondria, C6H12O6 + 6 O2, 6 CO2 + 6 H2O + Energy, Eventally, after death, all types of consumer, are decomposed by decomposers like, bacteria and fungi and carbon dioxide is released again into the atmosphere and is used, again by living organism. In this way, carbon is continuously passed on from one living, organism to another. After the death of living organisms, carbon goes to the atmosphere, and is again taken up by living organisms., Think about it, , Do you know?, Carbon dioxide is released into the, atmosphere through abiotic processes like, burning of fossil fuels and wood, forest, fires and volcanic activity. Oxygen is, released into the atmosphere by the biotic, process of photosynthesis and CO2 through, respiration. The equilibrium of oxygen and, carbon dioxide gases in the atmosphere is, maitained by plants., , 85, , 1. The carbon cycle is very effective in, the temperate region. Why is it so?, 2. Even though the carbon content on, earth is constant, why is there a rise, in temperature due to carbon, dioxide?, 3. Identify the relationship between, carbon in the air and the rise in, atmospheric temperature.

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The oxygen cycle, Oxygen forms 21% of the, amosphere. It is also present, in the hydrosphere and, lithosphere. Circulation and, recycling of oxygen within the, biosphere is called the oxygen, cycle. This cycle, too, includes, both the biotic and abiotic, components., Oxygen, is, continuously produced as well, as used up in the atmosphere., Oxygen is highly reactive, and it readily reacts with other, elements and compounds. As, oxygen is found in various, forms like molecular oxygen, (O2), water (H2O), carbon, dioxide (CO2), inorganic, compounds, etc. the oxygen, cycle of the biosphere is, extremely complex. Oxygen is, released in the process of, photosynthesis whereas it is, used up in processes like, respiration,, combustion,, decomposition,, corrosion,, rusting, etc., , Plants produce, oxygen, , Animals breathe in, oxygen, , Plants absorb, CO2 and, produce food, material, , Animals give out, CO2, Breakdown of sugar molecules by animals, 7.7 The oxygen cycle, , Do you know?, Most micro-organisms use oxygen for, respiration. Such microbes are called aerobes., Microbes which do not need oxygen are called, anaerobes. Oxygen is important for the synthesis of, proteins, carbohydrates and fats. It is also used in, various chemical reactions. Ozone (O3) is produced, from oxygen through various atmospheric processes., Can you recall?, , The nitrogen cycle, , 1. What is meant by nitrogen fixation?, 2. Which microbes bring about the, process of nitrogen fixation?, Nitrogen forms 78% i.e. the maximum, portion of the atmosphere. It is necessary, for the maintenance of the cycle of nature., The circulation and recycling of nitrogen, gas into the form of different compounds, through various biotic and abiotic processes, in nature is called the nitrogen cycle., 7.8 The nitrogen cycle, , 86

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All organisms participate in the nitrogen cycle. It is an important component of, proteins and nucleic acids. As compared to other elements, it is inactive and does not, easily combine with other elements. Most organisms cannot use the free form of nitrogen., Important processes of the nitrogen cycle, 1. Nitrogen fixation: Conversion of nitrogen into nitrates and nitrites through atmospheric,, industrial and biological processes., 2. Ammonification: Release of ammonia through decomposition of dead bodies and, excretory wastes of organisms., 3. Nitrification: Conversion of ammonia into a nitrite and then nitrate., 4. Denitrification: Conversion of nitrogen compounds into gaseous nitrogen., Surf the internet for information about, processes in the oxygen cycle and carbon cycle, Research similar to those of the nitrogen cycle., , Exercises, 1., , Complete the following table (Carefully study the carbon, oxygen and nitrogen cycles)., Bio-geo-chemical cycles, , Biotic processes, , 1. Carbon cycle, 2. Oxygen cycle, 3. Nitrogen cycle, 2. Correct and rewrite the following, statements, and, justify, your, corrections., , 5., , 6., , a. Carnivores occupy the second trophic, level in the food chain., b. The flow of nutrients in an ecosystem, is considered to be a ‘one way’, transport., c. Plants in an ecosystem are called, primary consumers., , What would you do to help maintain the, equilibrium in the various bio-geo-chemical cycles? Explain in brief., Explain in detail the inter-relationship, , between the food chain and food, web., 7. State the different types of bio-geochemical cycles and explain the, importance of those cycles., 8., , Explain the following with suitable, examples., a. What type of changes occur in the, amount of energy during its transfer, from plants to apex consumers?, b. What are the differences between, flow of matter and of energy in an, ecosystem? Why?, Activities :, 1. Prepare a model based on any natural, cycle and present it in a science, exhibition., 2. Write a paragraph on ‘Balance in an, Ecosystem’., , 3. Give reasons., a. Energy flow through an ecosystem is, ‘one way’., b. Equilibrium is necessary in the various, bio-geo-chemical cycles., c. Flow of nutrients through an ecosystem, is cyclic., , 4. Explain the following cycles in your, own words with suitable diagrams., a. Carbon cycle., b. Nitrogen cycle., c. Oxygen cycle., , Abiotic processes, , 87, , ²²²

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8. Useful and Harmful Microbes, Ø Useful micro-organisms : Lactobacilli, Rhizobium, Yeast, Ø Harmful micro-organisms : Clostridium and others., Can you recall., , 1. What is meant by microbes? What are their characteristics?, 2. How did you observe microbes?, , You are familiar with different types of microbes which are all around us but cannot, be seen with our eyes. In what way are they related to our everday life?, Useful micro-organisms, Try this, , 8.1 Lactobacilli, , Can you tell?, , Lactobacilli, Smear a drop of fresh buttermilk on a glass slide. Stain it, with methylene blue and put a coverslip over it., Observe the smear under the 10X objective of a compound, microscope and then with the more powerful 60X objective., Did you notice the blue rod-shaped organisms moving, around? They are lactobacilli, a kind of bacteria. They are, minute and rectangular in shape. Lactobacilli are anaerobic, bacteria i.e. they can produce energy without the use of oxygen., How is yoghurt made from milk? What exactly happens in, this process?, , The lactobacilli convert lactose, the sugar in the milk, into lactic acid. This process is, called fermentation. As a result, the pH of milk decreases causing coagulation of milk, proteins. Thus, milk proteins are separated from other constituents of milk. This is what, happens when milk changes into yoghurt. Yoghurt has a specific sour taste due to lactic, acid. The low pH destroys harmful microbes present in the milk., Use your brain power !, 1. Why do doctors advise you to have, yoghurt or buttermilk if you have, indigestion, or, abdominal, discomfort?, 2. Sometimes, yoghurt becomes bitter, and froths up. Why does this, happen?, 3. Which different milk products are, obtained at home by fermentation, of the cream from the milk?, , Do you know?, What is meant by ‘probiotic’ yoghurt, and other foodstuffs that are popular, nowadays?, Useful microbes like lactobacilli are, added to these eatables. Such eatables are, healthy because they kill the harmful, bacteria like clostridum in the alimentary, canal and help to improve our immunity., , 88

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1., 2., 3., 4., 5., , Uses of Lactobacilli :, Various milk products like yoghurt, buttermilk, ghee, cheese, shrikhand, etc. can be, obtained by fermentation of milk., Lactobacilli fermentation is useful for large scale production of cider, cocoa,, pickles of vegetables, etc., Lactobacilli and some other useful microbes taken together are used to treat, abdominal discomfort., Leavened fodder offered to domestic cattle like cows and buffalos, is fodder, fermented with the help of lactobacilli., The lactobacilli fermentation process is used to make wine and some types of, bread., 1. How many different industries depend upon the lactobacilli bacteria?, Research 2. Which types of cottage industries and factories can be started in areas, with abundant milk production?, , Rhizobium : Symbiotic bacteria, Let’s try this, , Take a plantlet of fenugreek, groundnut or any other bean, and sterilize it with a 3 to 5 % solution of hydrogen peroxide., , Cell division, Infection by, bacteria, Bacteria, , Rhizobium, , Infected, root hair, , Cell division, Growth of, root nodules, Bacteroid, , Bacteroid, , Conducting, tissue of, nodule, , 8.2 Root nodules of soyabean plant, , Afterwards, keep it in a 70%, solution of ethyl alcohol for 4 to 5, minutes. Clean the roots with sterile, water and take thin sections of the, root nodules. Select good section, and place it in a solution of safranin, for 2 to 3 minutes. Place the stained, section on a glass slide, cover it with, a coverslip and observe it under the, compound microscope. The pinkish, rod-shaped organisms are the, rhizobium bacteria., Note that we had to search for, the root nodules of leguminous, plants to obtain these bacteria. Are, the rhizobium bacilli useful to these, plants or harmful?, , Role and importance of rhizobium, Rhizobia living in root nodules supply nitrates, nitrites and amino acids to that plant, and in exchange get energy in the form of carbohydrates from it. Such a mutually beneficial, relationship is called symbiosis., Rhizobia produce nitrogenous compounds from atmospheric nitrogen. However, for, this process of nitrogen fixation, they need leguminous plants like beans, sweet pea,, soyabean, etc. as ‘host’. Beans and pulses are rich in proteins due to the nitrogenous, compounds made available by rhizobia., , 89

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After harvesting a leguminous, crop, the left over roots and other plant, parts are deliberately dumped in farm, soil to maintain its bacterial population., The use of rhizobium has helped to, reduce the use of chemical fertilizers, and thereby their adverse effects. It has, also helped to reduce expenses on, fertilizers and thus works to the benefit, of farmers., Yeast, Let’s try this, , Fungus, cells, , Bud, , Cell wall, Nucleus, Cytoplasm, 8.3 Yeast cells, , Nowadays, seeds are coated with, rhizobial solution or powder before, sowing. After sowing, rhizobia enter the, plantlets. This is called ‘rhizobial, inoculation’. This experiment has helped, in the supply of nitrogen to cereal and, other crops, besides leguminous crops., Activity : Bring ‘active dry yeast’ from the, market. Mix a spoonful of yeast, two spoonfuls, sugar with a sufficient quantity of lukewarm, water in a bottle. Fix a colourless, transparent, balloon on the mouth of that bottle., What changes do you observe after 10, minutes? Mix limewater with the gas, accumulated in the balloon. Collect that, limewater in a beaker and observe it. What do, you notice?, Take a drop of the solution from the bottle, on a glass slide, put a cover-slip over it and, observe it under the compound microscope., Store the solution in the bottle carefully., Do you see the colourless, oval cells of, yeast on the slide? Some of those cells may, have small round bodies attached to them., These are new daughter cells of yeast in the, process of formation., This method of asexual reproduction is, called ‘budding’. Yeast is a heterotrophic, fungal microbe that grows on carbon, compounds., Yeast is a unicellular fungus with 1500, different species in existence. The yeast cell is, a eukaryotic type of cell., , In the above experiment, yeast grows and multiplies very quickly due to the carbon, compounds in the sugar solution. In the process of obtaining nutrition, yeast cells convert, the carbohydrates in that solution into alcohol and carbon dioxide. This process called, fermentation., How is bread made ?, Find out how to use the solution prepared in the above experiment, to make bread., Follow the recipe and make the bread. Find out and note down the reasons why the dough, rises and makes the bread spongy., , 90

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Do you know?, , Use your brain power !, 1. Recently, it has been made compulsory, in India and some other countries to mix, 10% ethanol with fuels like petrol and, diesel. What is the reason for this?, 2. Why are wineries located near Nashik, in Maharashtra?, 3. Chapattis made from wheat only swell, up but bread becomes spongy, soft and, easy to digest. Why is it so?, , Often, alcohol is produced along, with sugar in sugar factories. Molasses, is produced from sugarcane juice. It, is rich in carbohydrates. Molasses is, fermented with the help of the yeast, called Saccharomyces. In this process,, ethanol (C2H5OH) alcohol is produced, as a primary product and ester and, other alcohols as secondary products., Spirit and other alcohols can be, obtained from ethanol. Ethanol is also, a smokeless and high quality fuel., Besides molasses, maize, barley, and, other grains are also used for industrial, production of ethanol., Glucose and fructose, the sugars, present in grape juice, are also fermented with the help of yeast to produce the alcohol which is used for, making wines., , Bio-remediation, A yeast, Yarrowia lipolytica is used, to absorb the toxins released during the, production of palm oil and the heavy, metals and minerals released in some, other, industrial, processes., Saccharomyces cereviceae is used for, absorption of a pollutant, arsenic., Oil spills in oceans are cleaned, with the help of Alcanivorax bacteria., , Antibiotics, Carbon compounds obtained from some bacteria and fungi for destroying or preventing, the growth of harmful micro-organisms are called ‘antibiotics’. Antibiotics, a discovery of, the 20th century, have brought about a revolution in the field of medicine. Even a disease, like tuberculosis has been almost completely eradicated from some countries., Antibiotics mainly act against bacteria. Some antibiotics can destroy protozoa., Some antibiotics are useful against a wide variety of bacteria. They are called broadspectrum antibiotics. Examples are ampicillin, amoxicillin, tetracycline, etc. When the, pathogen cannot be identified even though the symptoms of disease are visible, broad, spectrum antibiotics are used., Whenever a pathogenic micro-organism is definitely known, then narrow-spectrum, antibiotics are used. Examples are penicillin, gentamycin, erythromycin, etc., Institutes at work, The National Institute of Virology, established in 1952 in Pune, undertakes, research related to diseases like measles, jaundice, fever and diseases of the lungs,, with support from the World Health Organization., , 91

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Penicillin, Penicillin is a group of antibiotics obtained from a fungus, Penicillium, and is used for, controlling the infections caused by bacteria like Staphylococci, Clostridia, Streptococci,, etc. Medicines containing penicillin are useful to treat certain bacterial infections of the, ear, nose, throat and skin as well as diseases like pneumonia and scarlet fever., *, *, , *, , *, , *, , Caution, Antibiotics should be taken only, when prescribed by a doctor., Don’t purchase any antibiotic from, medical stores without a prescription, from a doctor., Don’t consume antibiotics on your, own to treat common diseases like a, throat infection, common cold or, influenza., Even if you feel well before, completing of the prescribed course, of the antibiotic you must continue, and complete it., Don’t suggest to others the, antibiotics which were useful to you., , Introduction to scientists, Alexander Fleming, a professor of, microbiology at St Mary’s Hospital had, cultured varieties of bacteria and fungi in, Petri dishes in his laboratory., On 3 September 1928, while, observing staphylococci cultures, he, made an interesting observation in one, Petri dish. In that Petri dish, fungal, colonies had grown but the area around, those colonies was clean and clear. i.e., bacteria had actually been destroyed., After further studies, he confirmed that, the fungus growing there was Penicillium, and its secretion had destroyed the, bacterial colonies., Thus, the first antibiotic - penicillin, had been discovered accidentlly and this, formed the basis for attempts to find cures, for incurable diseases., Shouldn’t we always be grateful to, Alexander Fleming for discovering the, life-saving antibiotics?, , Dr Alexander Fleming, , Wonderful to know, Ants grow fungi in their termitarium (anthill) and obtain food from it. Some species, of wasps and other insects lay their eggs in the fungal bodies growing on trees thus, ensuring a food supply for their larvae., Harmful micro-organisms, Fungi, 1. Which changes do you notice in leather articles and gunny, (jute) bags during the rainy season?, Can you tell? 2. For how long afterwards can you use those articles?, 3. Why do these articles not get spoilt during the summer or, winter?, , 92

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Microscopic spores of fungi are present in the air. If there is sufficient moisture, spores, germinate on cotton fabric, gunny bags, leather, wooden items, etc. The fungal hyphae, (fibres of the fungus) penetrate deep into the material to obtain nutrition and to reproduce., This causes the materials to wear and become weak. As a result, gunny bags, leather items, like shoes, purses, belts, etc. on which fungi have grown do not last long. Wooden items, also get spoilt., Sometimes, you may notice a black powder or white discs, floating on the pickle or murabba, when a jar is opened after a, Think about it long time. What exactly is this? Why are such food items not, good to eat?, Various species of fungi grow on food items like pickles, murabba, jam, sauce,, chutney, etc. They use the nutrients in these food items for growth and reproduction. During, this activity, fungi release mycotoxins, certain poisonous chemicals, into the food and thus, food becomes poisonous. Hence, the food on which fungi have grown cannot be eaten., Clostridium, Sometimes, cases of food poisoning occur during community feasts. How does the, food become poisonous all of a sudden?, The bacteria which spoil cooked food are Clostridium. Out of about 100 different, species of this bacterium, some are free living in the soil whereas some live in the alimentary, canal of humans and other animals., These bacteria are rod-shaped and produce bottle-shaped endospores in adverse, conditions. One special characteristic of these bacteria is that they cannot withstand the, normal oxygen level of the air because they grow in anaerobic conditions., Clostridium tetani, , Clostridium Perfringens Clostridium botulinum, , Clostridium difficile, , 8.4 Clostridium species, , Other harmful micro-organisms, Do only the Clostridium bacteria cause illness ?, Other kinds of micro-organisms like bacteria, viruses, protozoa and fungi are also, responsible for different diseases that affect humans. You have learnt about viruses which, are smaller than bacteria and can grow and reproduce only in living cells. Let us see how, they are harmful to us., An Introduction to scientists, It was believed that meat gets spoiled due to some bacteria of the bacillus type but the, exact type of bacillius was not known. Van Ermengem proved that the anaerobic bacterium, Clostridium botulinum, is responsible for food poisoning., Ida Bengston obtained higher education in biochemistry at Chicago University. She, conducted important research on the toxin responsible for gas gangrene and the antitoxin, useful for treating it. While she was doing research on the dreaded disease called typhus,, she herself contracted the infection. But, she overcame it and continued her research. For, this work, she was honoured with the ‘Typhus Medal’ in 1947., , 93

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The spread and prevention of disease, Name of disease, , Pathogen, , AIDS, , Virus, , Hepatitis, , Virus, , Influenza, , Virus, , Mode of infection, , Preventive measures, , Through blood and semen of, infected person and milk of, mother suffering from AIDS., Contaminated water and, food., Contact with infected person, , Safe sexual contact, avoid, reuse of needles and injections., , and Virus, Measles, Chicken pox, Bird Flu (H7N9) Virus, Swine Flu (H1N1), , Clean and filtered water,, proper storage of food., Personal hygiene and avoiding, contact with infected person, Contact with infected person Vaccination, uncontaminated, water, clean food, Contact with infected birds Personal hygiene, properly, cooked meat., and animals, , Dengue, , Virus, , Mosquito bite, , Pneumonia, , Bacteria, , Leprosy, , Bacteria, , Cholera, , Bacteria, , Malaria, , Protozoa, , Dandruff,, Fungi, ringworm, scabies, , Cleanliness of surroundings, preventing stagnation of water,, mosquito control., Droplets spread in air by Vaccination, avoiding contact, infected person, with infected person, Long term contact with Avoiding contact with infected, infected person, persons and their belongings, , Contaminated food and Clean food and water., water., Mosquito bite, uncleaned Cleanliness of surroundings,, surroundings., preventing stagnation of water,, controlling mosquitoes., Contact with infected person Personal hygiene, avoiding, or his/her belongings like contact with infected person, clothes., , Use your brain power !, 1. Salt is applied on the inner surface of pickle jars and the, pickle is covered with oil. Why is this done?, 2. Which preservatives mixed with ready-to-eat foods to keep, them from spoiling?, 3. Find out the uses of fungi to plants and animals., 4. What is the structure of lichen, a condiment? Where else, is it used?, 8.5 A lichen (dagadphool)used as a condiment, , Collect information, , Which plant and animal diseases are caused by, micro-organisms and what are the measures to be taken, against them?, , 94

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Exercises, 6. Match the pairs., , ‘A’ group , ‘B’ group, 1. Rhizobium, a. Food poisoning, 2. Clostridium b. Nitrogen fixation, 3. Penicillium, c. Bakery products, 4. Yeast, d. Production of , antibiotics, 7. Answer the following questions., a. Which vaccines are given to, infants? Why?, b. How is a vaccine produced?, c. How do antibiotics cure disease?, d. Are the antibiotics given to humans, and animals the same? Why?, e. Why is it necessary to safely store, the pathogens of a disease against, which vaccines are to be produced?, 8. Answer the following questions in, brief., a. What are ‘broad spectrum, antibiotics’?, b. What is fermentation?, c. Define ‘Antibiotic’., , 1. Complete the statements using the, proper option from those given, below. Explain the statements., (mycotoxins, budding, rhizobium), a. Yeast reproduces asexually by the, ............. method., b. Toxins of fungal origin are called, ............. ., c. Leguminous plants can produce, more proteins due to ............. ., 2, , Write the names of microbes found, in following food materials., , yoghurt, bread, root nodules of, leguminous plants, idli, dosa, spoiled, potato curry., 3. Identify the odd word out and say, why it is the odd one?, a. Pneumonia, diphtheria, chicken, pox, cholera., b. Lactobacilli, rhizobia, yeast,, clostridia., c. Root rot, rust (tambera), rubella,, mozaic., , Activity :, Collect information about generic, medicines and discuss them in the, class., , 4. Give scientific reasons., a. Foam accumulates on a the surface, of ‘dal’ kept for a long time in, summer., b. Why are naphthalene balls kept with, clothes to be put away., 5. Write down the modes of infection, and the preventive measures against, fungal diseases., , ²²², , 95

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9. Environmental, Management, 1. गतीचे नियम, Ø, Ø, , Weather and climate , Solid waste management, , Ø, Ø, , Meteorology, Disaster management, , 1. How does the atmosphere affect our daily life?, Can you recall. 2. Forecasts about which weather related factors are given, during the news bulletins on Doordarshan and Akashvani?, Weather and climate, Atmospheric conditions at a specific time at a particular place are referred to as, weather. Atmospheric conditions depend upon a variety of factors. (Figure 9.1), We frequently express our opinion about the weather by making statements like,, ‘Today, it is too cold’ or ‘It is very hot today.’, Weather depends upon, the prevailing conditions of, the air. The climate of a, particular region is the average, of daily readings of various, weather-related parameters, recorded for several years., Hence, climate is a long term, predominant condition of the, atmosphere., , Atmospheric pressure, Temperature, , Sunlight, , Weather related/, Climatic factors, Clouds, , Visibility, , Rainfall, , Humidity, , 9.1 Weather-related / climatic factors, , Changes in weather, Climate does not change continuously. Climate is that which remains constant in a, region for a long duration. Thus we see that weather is related to a specific location and, specific time whereas climate is related to a longer duration and larger area. Changes in, the weather may occur for short periods of time whereas changes in the climate take place, slowly over a much long duration., Climate plays a very important role in our day to day life. It influences our basic, needs like food, clothing and shelter as well as our occupations. Climate is especially, important for an agrarian country like India. Various climatic factors like direction and, speed of wind, temperature, atmospheric pressure, etc. are considered during construction, of runways, seaports, huge bridges and skyscrapers, etc., , Use your brain power !, , Which factors are affected favourably or, unfavourably by climate? What must we do to, minimize this effect?, , 96

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A special day, , Think and discuss., 1. Human progress is related to a conducive climate, and geography., 2. Human beings have designed a time schedule for, their lives based upon centuries of climatic, experiences., 3. Scientists find it necessary to study climate in, view of its effect on agricultural production., , 23rd, March, is, observed, as, ‘World, Meteorological Day’., Collect information, about Meteorology and, prepare charts to create, awareness about it., , Importance of weather in the living world, 1. Daily weather as also long term climatic conditions influence human lifestyle, directly or indirectly. Land, water bodies, plants and animals collectively form the, natural environment on earth. This environment is responsible for the development, of organisms., 2. The climate of a particular region helps to determine the diet, clothing, housing,, occupations and lifestyle of the people of that region. For example, the characteristic, lifestyle of Kashmiri and Rajasthani people., 3. Salinity of marine water, formation of oceanic currents, water cycle, etc. are all, related to various weather and climatic factors., 4. Various climatic factors bring about the weathering of rocks in the earth's crust., 5. Climate plays a very important role in the formation and enrichment of soil., 6. Microbes in the soil play an important role in formation of organic materials. This, process depends upon various climatic factors., Thus, it is very clear that the study of meteorology is very important from the view, point of human life., While ascertaining the climate of a particular region, a review of earlier studies of, various aspects of climate is very important. Most countries in the world have established, meteorology departments for making and recording such observations. These departments, have ‘observatories’ which are equipped with modern instruments and technology., If present climatic conditions are analysed with reference to the past climatic, conditions, we can predict climatic changes of the future. However, as climate is the net, result of a complex mixture of various atmospheric factors, forecasting it is very complicated, and difficult. Forecasting is easy for places where climatic changes are slow and of a, limited nature. However, where climatic changes are complex, interdependent and rapid,, making forecasts is very difficult., , 97

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Meteorology, The science that studies the inter-relationships between the various components of, air, natural cycles, geological movements of the earth and climate is called meteorology., Meteorology includes the study of storms, clouds, rainfall, thunder, lightning, etc., Depending upon the study of such factors, weather forecasts are made. They are useful to, common people, farmers, fisheries, aviation services, water transport and various other, organizations., Institutes at work, The World Meteorological, Organization was established by, the United Nations Organization on, 23rd March 1950. This organization, plays an important role in food, security,, water, management,, transportation and communication., , Using ICT, With the help of various search engines on, the Internet, search for links giving information, about the following institutes and prepare a, report based upon the information obtained., World Meteorological Organization (WMO), Indian Institute of Tropical Meteorology (IITM), National Oceanographic and Atmospheric, Administration. (NOAA), , India Meteorological Department, The India Meteorological Department was founded by the British in 1875 at Shimla., Its head office is at Pune and its Regional Offices are at Mumbai, Kolkata, Chennai,, Nagpur and Delhi. Maps are prepared every day which indicate the daily predictions, about the weather. Such maps are prepared and published twice in every 24 hours. In this, institute, research goes on continuously on various aspects like instruments for climatic, readings, predictions about climate made using radar, predictions about climate related to, siesmology, predictions regarding rainfall by satellites, air pollution, etc., The India Meteorological Department provides important information regarding, weather and climatic conditions to other departments like aviation, shipping, agriculture,, irrigation, marine oil exploration and production, etc. Predictions regarding calamities, like dust storms, sand storms, heavy rainfall, hot and cold waves, tsunami, etc. are, communicated to various departments, all types of mass communication media and all, citizens. For this purpose, India has launched several satellites equipped with highclass, technology. Observatories at several locations are doing excellent work in the analysis of, the information received from these satellites. (www.imdpune.gov.in), Monsoon model and climate prediction, The tradition of forecasting the monsoon season in India is older than 100 years. After, the famine of 1877, H. F. Blanford, the founder of IMD had made such a prediction for the, first time taking the snowfall in the Himalayas as a parameter for this prediction. In the, decade of the 1930's the then director of IMD, Sir Gilbert Walker had underlined the, relationship between various worldwide climatic factors and the Indian monsoon, and,, based on available observations and previous recordings related to this relationship he put, forth a hypothesis regarding the nature of the monsoon. With the initiative of, Dr Vasantrao Govarikar in the decade of the 1990's a monsoon model based upon 16, worldwide climatic parameters was developed. This model was in use from 1990 to 2002., , 98

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Mathematical model (Dynamic), Forecasts are made with the help of, mathematical models which take into, account estimates of current weather, related events and ongoing physical, interactions between them. Data about, current, climatic, parameters, is, mathematically analysed with the help, of the Param supercomputer. Various, mathematical models based upon daily, geographic events are developed by, supercomputer technology., , Holistic model, In this model, predictions are based, upon those parameters used in other, models which have the greatest effect, on the monsoon. Nowadays, predictions, declared by IMD are the collective, outcome of various models. This is, called a holistic model., , Presently, new models are being, developed at the IITM. Work is in progress, at two levels, namely, designing new models, and developing new technology. The main, focus is on development of the radar system, and satellite technology., , Statistical model : In this model,, current climatic observations in a region, are compared with earlier parameters, such, as, oceanic, temperature,, atmospheric pressure and the nature of, the monsoon rainfall of several years., This data is comparatively analysed by, statistical methods and predictions are, made about the monsoon in the present, conditions., , Always remember, Any meteorological model depends upon the inter-relationship between parameters, used in that model and the results expected from it. However, as these inter-relationships, with reference to the ocean and atmosphere are never constant, meteorological models, need to be changed continually., Solid waste management : need of the hour, Can you tell?, , 1. What is meant by pollution?, 2. In which different ways do our surroundings get polluted?, , Try this, Observe the garbage collected in, the dustbin of your classroom and make, a list of the various materials in it., Discuss with your teacher, how these, materials can be properly disposed of., Can we do the same with the, garbage generated in our house? Think, about it., , 9.2 Solid waste, , 99

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Observe and discuss., A, , B, , 9.3 Area with garbage vs clean area, , Many waste materials are, generated through the various daily, human activities. This is called solid, waste. If these waste materials are, properly disposed of, they can be a, valuable source of energy. Currently,, solid waste is a serious world wide, problem as it causes both water and, soil pollution. Solid waste is also, serious problem from the point of, view, of, economic, growth,, environmental degradation and, health. It has posed a serious threat to, nature and human habitat because of, the air, water and soil pollution it, causes., Observe, , Do you know?, Garbage production per day, Solid waste generated in the main metro, cities of the state is approximtely as followsMumbai: 5000 tons, Pune: 1700 tons, Nagpur :, 900 tons., On 26th July 2005, a serious flood calamity, had arisen in Mumbai. Improper solid waste, management was one of the main reasons behind, that calamity. Thus we see that accumulation of, solid waste can lead to various calamities., Can you tell?, , 1. What is main difference between, what we see in the two pictures, alongside (9.2 A and B)?, 2. What should we do to permanently, maintain the condition seen in, picture B?, , Make a survey of the, building or area where you live., Categorise the garbage as, degradable and non-degradable, waste. Approximately, how, much solid waste is generated in, a week? Make a list of the factors, responsible for it., , 1. What is meant by solid waste?, 2. What are the different things included in solid waste?, , We make use of many materials and articles in our daily life. They are of different, kinds. Some of them are reusable but others have to be discarded. However, if they are not, properly disposed of, it affects the environment adversely., , 100

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Make a list and discuss, , Read the following table carefully. What do, you notice?, , Classification, , Source, , Domestic waste, , Waste food, paper, plastic paper, plastic bags, vegetable waste, fruit, skins, glass and sheet metal articles, etc., Industrial waste Chemicals, pigments, sludge, ash, metals, etc., Hazardous, Chemicals generated in various industries, radioactive materials,, waste, explosives, infectious materials, etc., Farm/Garden, Leaves, flowers, branches of trees, crop residues like straw, animal, waste, urine and dung, pesticides, remains of various chemicals and, fertilizers, etc., Electronic waste Non-functional TV sets, cell phones, music systems, computers and, their parts, etc., Biomedical, Bandages, dressings, gloves, needles, saline bottles, medicines,, waste, medicine bottles, test tubes, body parts, blood, etc. from clinics,, hospitals, blood banks and laboratories., Urban waste, , Radioactive, waste, Mining waste, , Waste generated through household industries and large commercial, and industrial establishments, carry bags, glass, metal pieces and, rods, threads, rubber, paper, cans from shops, vegetable and meat, markets, construction waste, etc., Radioactive materials like Strontium-10, Cerium-141, Barium-140, and heavy water, etc. generated from atomic energy plants, uranium, mines, atomic research centres, nuclear weapons testing sites, etc., Remains of heavy metals like lead, arsenic, cadmium, etc. from, mines., , Into which two categories can the waste materials in the, Think about it. lists above be classified ?, Biodegradable waste : This type of waste is easily degraded by microbes. It mainly, includes kitchen waste (spoiled food, fruits, vegetables) ash, soil, dung, parts of the plants,, etc. This waste is mainly of organic type and is also called ‘wet solid waste’ or ‘wet, garbage’. If it is carefully decomposed, we can get compost and fuel of good quality from, it. Such bio-fuel projects have been started in many cities., Non-biodegradable waste : This type of waste is not easily degraded because it, requires a very long period of time and the use of various techniques. It includes, plastic, metal and other similar materials. This type of waste is also called ‘dry, solid waste’ or ‘dry garbage’., , Use your brain power !, , 1. Why is it necessary to recycle non-degradable, waste ?, 2. Which materials are included in solid dry waste ?, , 101

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Make a list of various waste materials and articles in your area and prepare a, chart as follows, Material, , Degradable, (Organic), , Non-degradable, (Inorganic), , Recycling, , Reuse, , Toxic, , No, , Yes, , Yes, , Yes, , Yes, , Plastic bottle, , Find out, , Nowadays, an electronic device - the cell phone - is very, popular. From a mobile shop near your house, find out how they, dispose of old and broken down cell phones., , Using ICT, Carefully, observe, figure 9.4 alongside. Based, on it, send an e-mail to, your friend explaining the, importance of solid waste, management., , Effect on biodiversity, Bad odour of waste, , Spreading, of diseases, , Harmful, effects of, solid waste, , Soil, pollution, , Water, pollution, , Production of, toxic gases, Degradation of, natural beauty, , Air pollution, , 9.4 Harmful effects of solid waste, , Necessity of solid waste management :, 1. For preventing environmental pollution and to keep the surroundings clean., 2. For energy as well as fertilizer production and through that to generate work and, employment opportunities., 3. To reduce the strain on natural resources through treatment of solid waste., 4. To improve the health and quality of life and to maintain environmental balance., It is the need of the hour, to implement solid waste, management practices to, avoid the possible problems, due to solid waste generated, from urban and industrial, areas and to maintain a, clean environment. For this, purpose,, we, should, implement measures like, increasing the efficiency of, production processes so that, minimum waste will be, generated, reducing garbage, production by recycling and, reuse of waste materials., , Separation and categoriztion of waste, Biomedical, waste, management, (Incineration), , Composting, , Scientific and, eco-friendly, waste, management, Pyrolysis (energy, production by, burning of waste at, high temperature, Ex. Biogas,, Bioelectricity), , 102, , Safe, landfill sites, Vermicomposting, , Industrial solid, waste management, (land-fill method), , 9.5 Solid waste management

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7 Principles of solid, waste management -, , Think about it., Some habits are described below., Do we have those habits ? If so, how, does it help in waste management ?, , Reuse, After use materials should be, reused for some other proper purposes., Refuse, Refusal to use articles made from, non-degradable articles like plastic, and thermocol., Recycle, Production of useful articles by, recycling solid wastes. For example,, paper and glass can be recycled., Rethink, Rethinking our habits, activities, and their consequences in connection, with the use of various articles of, daily use., Reduce, Restriction the use of resources to, avoid their wastage. Old materials, should be reused. One thing should be, shared by many. Use and throw type, of objects should be avoided., Research, Conducting research realated to, reuse of materials that are temporarily, out of use., Regulation and public awareness, Following the laws and rules, related to waste management and, motivating others to do the same., , 1. Following the 3 R ‘mantra’:, Reduce (reducing the waste),, Reuse (reuse of waste) and, Recycle (recycling of waste)., 2. Throwing plastic wrappers of, chocolates, ice-creams, biscuits,, etc. into dustbins. Avoiding, littering., 3. Avoiding the use of plastic bags, and instead using cloth bags or, bags prepared from old sarees,, bed-sheets, curtains, etc., 4. Using both sides of a paper for, writing. Reusing greeting cards, and gift papers., 5. Avoiding use of tissue paper and, preferring to use one's own, handkerchief., 6. Using, rechargeable, batteries, instead of lead batteries., 7. Implementing various programmes, of solid waste management and, educating, encouraging the family, and society in this regard., 8. Avoiding ‘use and throw’ type of, articles, like, pens,, canned, cold drinks, tetra-packs should be, strictly avoided., , America is the largest producer of electricity from solid waste. Japan has, developed the projects of production of threads, paper and other useful materials, from banana peelings. Find out about such projects in our region., Find out, , Which waste management processes are used in your, village / town / city ?, , 103

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Period required for degradation of wasteWaste Material, , Period of Natural, Degradation, , Banana peelings, Cloth bags, Rags, Woollen socks, Wood, Leather shoes, , 3 – 4 weeks, 1 month, 5 months, 1 year, 10 – 15 years, 40 – 50 years, , Tin cans, Aluminium cans, Certain plastic bags, , 50 – 100 years, 200 – 250 years, 10 lakh years, Thermocol/styrofoam Infinite duration, cup, , If the time required for, degradation of the solid waste, generated around us is long, it, seriously affects other environmental, factors. What care will you take to, avoid this ?, Figure 9.5 A, below shows a, method of storing waste and 9.5 B,, shows the use of specific dustbins, as per the type of waste. Think, about how such eco-friendly waste, management can be achieved by, following these methods in our, homes, too., , Wet, Dry, Waste Waste, , A, , B, , 9.5 Methods of storing solid waste, , A peep into the past., Ever since ancient times, special attention has been given to garbage disposal. In, the Greek city of Athens, in 320 BCE, a law had been enacted regarding garbage, disposal. It made throwing garbage in the open an offence., Disaster management, , Can you recall?, , 1. Which natural calamities have you experienced? How did, they affect the conditions in your surroundings?, 2. How will you make a plan to be safe from calamities or, to minimize the damage?, , Various natural disasters like thunderbolts (lightning), floods, fire and man-made, disasters like accidents, bomb explosions, chemical accidents in industries, stampedes in, mass gatherings, riots, etc. occur around us from time to time. They cause large scale, damage to life and property., , 104

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Disaster, management, is, action, implemented, through, proper planning, organized activitiy, and co-ordination. It includes the, following -, , Can you tell?, What are the types of casualties that, are seen to occur in differant types of, disasters?, First aid to disaster victims :, The main objective of first aid is, prevention, of, death,, preventing, deterioration of health and starting the, process of rehabilitation. Hence, it is, important to know about the emergency, measures or first aid practices to be, followed, Basic principles of first aid :, Life and Rescucitation - ABC, 1. Airway : If the victim has difficulty, breathing, the head should be held in a, backward sloping position or the chin, should be raised so that the respiratory, passage remains open., 2. Breathing : If breathing has stopped,, the victim should be given artificial, ventilation by mouth to mouth, rescucitation., 3. Circulation : If the victim is, unconscious, then after giving mouth to, mouth respiration twice, the heart, should by pressed down hard by, pressing the chest with both the palms., These two actions should be repeated, alternately about 15 times. This is, called cardio-pulmonary rescucitation, (CPR). It helps to bring the circulation, back to normal., , 1. Prevention of losses and danger., 2. Improving tolerance., 3. Providing relief from disaster,, minimising the intensity and extent, of harm., 4. Preparation to face the disaster., 5. Immediate action in the disaster, situation., 6. Assessment of damages, intensity of the disaster., , and, , 7. Arranging for rescue work and, help., 8. Rehabilitation and rebuilding., , 9.6 Artificial breathing, , Bleeding : If the victim is injured and bleeding through the wound, then the wound, should be covered with an antiseptic pad and pressure applied on it for 5 minutes with, either thumb or palm., Fracture and impact on vertebrae : If any bone is fractured, it is essential that the, fractured part be immobilized. It can be done with the help of any available wooden, rods/batons/rulers. If there is an impact on the back or vertebral column, the patient, should be kept immobile on a firm stretcher., Burns : If victims have burn injuries, it is beneficial to hold the injured part under clean, and cold flowing water for at least 10 minutes., , 105

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For injuries like sprains, twisting and contusion, the 'RICE' remedy should be applied :, , Rest : Allow the victim to sit in a relaxed position., Ice : Apply an ice-pack to the injured part., Compression : After the ice-pack treatment, the injured part should be massaged gently., Elevate : The injured part should be kept in a raised / elevated position., How to trnsport victims / patients?, , Cradle method :, Useful for children, and under-weight, victims., , Carrying piggy back :, Useful for carrying, patients, who, are, unconscious., , Human crutch method : If one of the legs is, injured, the victim should be supported with, minimum load on the other leg., , Carrying on four-hand chair : This is, useful when support is needed for the part, below the waist., , Pulling or lifting method : This is used, for carrying an unconscious patient,, through a short distance., , Carrying on two-hand chair : Useful, for those patients who cannot use their, hands but can hold their body upright., , Stretcher : In an emergency, if a, conventional stretcher is not available,, then a temporary stretcher can be made, using bamboos, blanket, etc., , Methods used by the fire-brigade, , 106

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Other emergency measures: Boats are used by the civil administration to rescue people, trapped in a flooded area. As an emergency measure, wooden boards, bamboo floats,, air-filled rubber tube from a tyre can be used to advantage., A fire-extinguisher is a portable appliance that can be easily, Find out carried anywhere. Various appliances are used to put out a fire., Visit the fire department in your city and collect detailed information., (For more information, refer to lesson 13.), , Exercises, 1. Match the items in column ‘A’ with the proper ones in coloum ‘B’, and explain their impact on the environment., Column ‘A’ , Column ‘B’, 1. Harmful waste a. Glass, rubber, carry bags, etc., 2. Domestic waste b. Chemicals, pigments, ash, etc., 3. Biomedical waste c. Radioactive material, 4. Industrial waste d. Left over food, vegetables, peelings of fruits., 5. Urban waste e. Bandages, cotton, needles, etc., 2. Complete the statements using the, given options and justify those, statements., (Geographic favourability, climate,, weather, observatory), a. Of the abiotic factors that affect, biodiversity by far the most important, is .................. ., b. A description of the climatic, conditions of short duration in a, particular area is .................. ., c. Irrespective of the progress of human, beings, we have to think about, .................. ., d. Establishments, where, various, climatic factors are recorded are, called .................. ., 3. Answer the following questions., a. How is first aid provided to victims, of disasters who are injured?, b. State the scientific and eco-friendly, methods of waste management., c. Explain with suitable examples, the, relationship, between, weather, forecasting and disaster management., d. Why is e-waste harmful? Express, your opinion about this., , e. How will you register individual your, participation, in, solid, waste, management?, 4. Write notes., Meteorology, Climatic factors, Monsoon, model, Industrial waste, Plastic waste,, Principles of first aid., 5. Give examples of the importance of, climate in the living world with, explanations, in your own words., 6. Explain with suitable examples, the, care to be taken when using the, methods of transporting patients., 7. Explain the differences., a. Weather and climate, b. Degradable and non-degradable, waste, Activity :, 1. Visit a nearby hospital and collect, information about how waste is, managed., 2. Establish a vermi compost project in, your school under the guidance of, your teachers., , 107, , ²²²

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10. Information Communication, Technology, 1. गतीचे, नियम : The new direction of progress, Ø Important components of a computer, , Ø Different types of software, , Ø Importance of information communication in science and technology, Ø Opportunities in the field of computers, , Which devices do we use directly or indirectly for collecting,, sharing, processing and communicating information?, , Can you tell?, , The term Information Communication Technology (ICT) includes communication, devices and the use of those devices as well as the services provided with their help. The, store of information generated due to the advances in science and technology is increasing, at a tremendous rate. If we ignore this explosion in information, the knowledge that we, have will become outdated., Think about it, , How is information communication technology important, for dealing with the explosion of information?, , Devices used in information communication technology : Different devices are, used for producing information, for communicating, classifying, saving/storing information,, managing information etc. For example, the telephone is used for sharing information by, conversing with someone., The following table has names of some ICT devices., Complete the table based on the questions asked. Also,, Complete the table enter the names of any additional devices that you know of., Name of the, device, , What is it used for?, , Where is it, used?, , Benefits from its, use, , Computer /, laptop, Mobile, Radio, Television set, , The computer, which is the most important device for, information communication, is considered to have gone, through five generations, since it was first created. The, computers used during the period between 1946 and 1959, are said to be ‘first generation computers.’ The ENIAC, computer was made in this period. Valves were used in its, construction. These valves were large in size. They also, consumed a lot of electricity. That generated heat and, computers would shut down many times. Today’s, computers are 5th generation computers., , 108, , Find out, Use the Internet to, collect information about, all the generations of, computers and their types., Make a note of the, differences, in, their, characteristics.

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The entry of computers in all fields in this age of technology has been possible only, due to the increased speed of computers. In which fields of work eo we see computers, being used?, Can you tell?, , How does a computer work?, Processor, , Input unit : All types of, information/data is entered into, the computer through this unit., Generally, a keyboard is used to, enter data or information, , Processing unit, , 1. Memory unit, 2. Control unit, 3. ALU unit, , Output Unit : The result / solution, / answer is eventually sent to the output, unit. Generally a screen / monitor or, printer is used as an output unit., , 10.1 Working of a computer, , Important components of a computer, Memory : Memory is the place for storing data obtained from the input and also the, generated solution or answer by the computer. There are two types of memories in a, computer., 1. Internal Memory 2. External Memory, The internal memory is of two types., 1. RAM (Random Access Memory): This is created from electronic components. Any, electronic component can function only as long as it is supplied with electricity., 2. ROM (Read Only Memory): The information stored here can only be read. We, cannot make changes to the information originally stored here., Operating system : This is a program which provides a means of communication between, the computer and the person working on it. It is called the DOS (Disk Operating System)., We cannot use a computer without its operating system., Program : A program is a group of commands to be given to a computer., Data and information : Data is information in its raw (unprocessed) form., , 109

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Two main components of computers, Hardware : Hardware consists of all the electronic and mechanical parts used in, computers., Software : Software refers to the commands given to the computer, information, supplied to it (input) and the results obtained from the computer after analysis (output)., , Make a list and discuss, , Make a list of the various hardware and software items, of a computer and discuss their working in the class., , Try this Using Microsoft Word to create a document and write equations., 1. Click on the, , icon on the desktop., , 2. Select the ‘New’ option in the ‘File’ tab, and then select the, ‘Blank document’ option., 3. Type your material on the blank page on the screen using the keyboard. Use the language,, font size, bold, etc. options in the Home tab to make the typed material attractive., 4. To type equations in the text, select the ‘Equation’ option in the ‘Insert’ tab., , 5. Select the proper equation and type it using mathematical symbols., , 110

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Using Microsoft Excel to draw graphs based on the obtained, Try this numerical information, 1. Click on the, , icon on desktop., , 2. Select the ‘New’ and then ‘Blank’ option from the ‘File’ tab., 3. Type the information which is to be used to draw the graph, on the ‘sheet’ on the screen., 4. After you have finished typing,‘Select’ the information and click on the required graph, in the ‘Insert’ tab., , 5. Analyze the information using the graph., What precautions will you take when entering data?, 1. As far as possible, the data should be kept in tabular form. Different types of data, should be entered in different cells. Data should be entered neatly and in one ‘flow’., Unnecessary space and special characters should not be used., 2. Many times we ‘drag and fill’ data. At such times, the ‘smart tag’ can be used after, ‘drag data’ to fill any data in any manner as required., 3. Once the data has been entered it can be formatted in different ways. Similarly, we, can perform different types of calculations, using different formulae., 4. While using a formula, the ‘=’ sign should be typed first. Similarly, no space should, be inserted while typing any formula., , 111

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Microsoft Powerpoint, , Try this, 1. Click on the, , Using Microsoft Powerpoint to create a presentation, icon on the Desktop., , 2. You must have with you the material and pictures related to the topic on which you, wish to make the presentation., 3. Select the ‘New’ option under the ‘File’ tab and choose the ‘Blank slide’ option., (You can select the kind of slide you need according to your presentation.), 4. Type the information you need on the blank slide and insert pictures., 5. Use the ‘Design’ tab to design your slide., 6. Use the ‘Animation’ tab to animate the slide and make a slide show., , Acrobat Reader, , A PDF or Portable Document Format file, can be used to view the file to print it or to, handle files., , 112, , Internet Explorer, This is a kind of Search Engine. It, helps to find the information we want, from all the information available on, the internet.

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Note: While studying the subject of science and technology you have to actually make, use of the information communication technology that you learnt in this lesson. Do, take the help of your teachers as well as your parents and friends if you need it., Some uses of information communication technology are given in the boxes below., What are its other uses?, Demonstration, Some experiments and, concepts in science can be, demonstrated easily and, effectively, by, using, simulation and animation, e.g. functioning of the, nervous system., , Prediction, Predictions can be, made after compiling, and processing, information e.g., meteorology ., , Collecting scientific, information, Internet, emails,, newsgroups, blogs, chat, rooms, Wikipedia, video, conferencing, etc., , Opportunities in the of computers field, 1. Software field : This is an important field. Having accepted the challenge of, creating software, many companies have entered this field. The opportunities in the, software field can be classified as follows - application program development, software, package development, operating systems and utility development, special purpose, scientific applications., 2. Hardware field : Today, there are several companies in our country too, which, make computers. They sell computers that they have themselves made. Others sell, computers brought from outside as well as repair them and take maintenance contracts, to keep computers in big companies working efficiently without a break. Plenty of jobs, are available here. There are job opportunities in hardware designing, hardware, production, hardware assembly and testing, hardware maintenance, servicing and, repairs, etc., 3. Training : The training of new entrants for various jobs is a vast field. It is very, important to have dedicated teachers who are competent in the field of computers., 4. Marketing : There are many establishments which make and sell computers and, related accessories. They need good sales personnel who are experienced in the, working of computers as well as skilled in marketing., Institutes at work, C-DAC, the welknown Centre for Development of Advanced Computing, situated, in Pune, is the leading institute in India which conducts research in the field of, computers. The first Indian supercomputer was made with help from this institute., Valuable guidance for making this computer (the Param computer) was received from, the senior scientist Vijay Bhatkar. Param means the supreme. This computer can, perform one billion calculations per second. It is used in many fields like space research,, movements in the interior of the earth, research in oil deposits, medicine, meteorology,, engineering, military etc. C-DAC has also participated in developing the ISCII code, for writing different language scripts. (Indian Script Code for Information Interchange), , 113

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Exercises, 1., , 2., , Fill in the blanks to complete the, statements. Justify the statements., a. While working with a computer, we can read the information stored, in its memory and perform other, actions in …………… memory., b. While presenting pictures and, videos about the works of scientists,, we can use ………….., c. To draw graphs based on the, quantitative information obtained, in an experiment, one uses ….., d. The first generation computers, used to shut down because of ……., e. A computer will not work unless, …. is supplied to it., , 3., , Using a spreadsheet, draw graphs, between distance and time, using, the, information, about, the, movements of Amar, Akbar and, Anthony given in the table on page, 4 , in the lesson on Laws of Motion., What precautions will you take, while drawing the graph?, , 4., , Explain the differences between the, different generations of computers., How did science contribute to these, developments?, , 5., , What devices will you use to share, with others the knowledge that you, have?, , 6., , Using information communication, technology, prepare powerpoint, presentations on at least three topics, in your textbook., , Answer the following questions., a. Explain the role and importance of, information communication in, science and technology., b. Which application software in the, computer system did you find, useful while studying science, and, how?, c. How does a computer work?, d. What precautions should be taken, while using various types of, software on the computer?, e. Which are the various devices, used in information communication? How are they used in the, context of science?, , Make a flowchart of the steps you, used, while, making, these, presentations., 7., , Which technical difficulties did you, face while using the computer?, What did you do to overcome them?, , Project :, , Taking help from your teachers,, , make a documentary about, ISRO the institute mentioned in, Chapter 18, using information, comunication devices., , ²²², , 114

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11. Reflection, of Light, 1. गतीचे नियम, Mirrors and types of mirrors Ø Spherical mirrors and images, formed by them Ø Magnification due to spherical mirrors, Ø, , Can you recall?, , 1. What is light?, 2. What is meant by reflection of light? Which are the different, types of reflection?, , Light is an agent which gives us information about what is happening in our surroundings., We can enjoy various wonders of nature like the sunrise, sunset and rainbow only because, there is light. It is only because of light that we can see the lush green vegetation, colourful, flowers, deep blue skies in the day, stars shining in the dark night sky in the beautiful world, around us. We can see the man-made objects in our surroundings as well. Light is actually, electromagnetic radiation which causes the sensation of vision., Light reflects differently from the various surfaces around us. We have already learnt, that the reflection from smooth, flat surfaces is regular reflection while rough surfaces reflect, light irregularly., Mirror and types of mirrors, Can you tell?, , What is a mirror?, , We need polished surfaces for, reflecting light. This is because polished, surfaces absorb less light and so maximum, light gets reflected., In scientific language, a surface which, reflects light and creates clear images is, called a mirror. A mirror is a reflecting, surface., We use various types of mirrors in our, daily life. Mirrors are of two types: plane, mirrors and spherical mirrors., , An introduction to scientists, The, German, scientist Justus von, Liebig coated the plane, surface of a piece of, ordinary glass with, silver metal and made, the first mirror. Such a, mirror is called a, silvered glass mirror., , Plane mirror - Plane mirrors are used in various activities, , in our day to day life. A mirror is made by coating the back, surface of a flat and smooth glass piece with a thin, reflecting, film of aluminium or silver. To protect this reflecting film and, to make that side opaque, another coat of a substance like, lead oxide is given over it., Can you recall? What are the laws of reflection of light?, , 115, , 10.1 Plane mirror

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We see a clear image of ourselves when, we stand in front of a mirror in our house. To, Incident, Reflected, understand how an image is formed in a mirror, ray, ray, let us first consider an image formed by a point, source. Light rays travel in all directions from, such a source. Several of these rays fall on the, mirror, get reflected and reach our eyes. Due to, reflection, they appear to be coming from a, point behind the mirror. That point is the image, Plain mirror, of the point source., As figure 11.2 A shows, light rays falling, A. Rays falling on a mirror normal, perpendicularly on the mirror are reflected, to its surface, back in the perpendicular direction., Image, M1, O1, O, Figure 11.2 B shows a point source O in, front of the plane mirror M1M2. Incident rays Object, OR1 and OR2 get reflected according to the, laws of reflection along paths R1S1 and R2S2, respectively. When these reflected rays are, R2, extended behind the mirror, they meet at O1., R1, When seen from E, the rays appear to be, coming from O1. Other rays starting from O, also get reflected and appear to be coming, S2, from O1. Thus, point O1 is the image of point O., S1, The reflected rays do not actually meet., Hence, such an image is called a virtual, E, image. The perpendicular distance of the Eye, M2, image from the mirror is equal to the, B. Image of a point source formed by a mirror, perpendicular distance of the source from, M1, the mirror., If we use an extended source instead of a, P1, P, point source, an image is formed of every point, of the source, thereby forming an extended, image of the whole source. As shown in figure, 11.2 C, an extended source PQ is kept in front, of the mirror M1M2. The images of P and Q are, Q1, formed at P1 and Q1 respectively. Similarly, Q, images of all points between P and Q are, formed between P1 and Q1 resulting in the, M2, image P1Q1 of the entire extended source., C. Image of an extended source formed by a, mirror, The image formed by a plane mirror is of the, 11.2 Formation of images by a mirror, same size as the source., 1. If we hold a page of a book in front of a mirror, we see laterally, inverted letters in the mirror. Why does it happen?, Can you tell? 2. Which letters of the English alphabet form images that look the, same as the original letters?, , 116

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The image of a word appears laterally inverted in the mirror. The image of every, point on the word is formed behind the mirror at the same distance from the mirror as the, point itself. This is called lateral inversion., When a person stands in front a plane mirror,, Use your brain power ! how is the image formed? What is the nature of the, image?, Place two plane mirrors at an angle of 900 to each other. Place a, Try this small object between them. Images will be formed in both mirrors., How many images do you see?, Now change the angle between the mirrors, as given in the following table and count the, number of images each time. How is this, number related to the measure of the angle?, Discuss this relationship., Angle, , Number of, images, , 120०, 90०, 60०, 45०, 30०, , 11.3 Mirrors at right angles to each other, , 3600, n=, -1, A, , n = number of images, A = angle between, the mirrors, , 1. Check if the number of images that you obtained for different values of angles is, consistent with the above formula., 2. If we keep the mirrors parallel to each other, how many images will we see?, Statement: In order to see the full image of a person standing in front of a mirror, the, minimum height of the mirror must be half the height of the person., Proof : In figure 11.4, the point at the top of the head, the eyes and a point at the feet of a, person are indicated by H, E and F respectively. R and S are midpoints of HE and EF, respectively. The mirror PQ is at a height of NQ from the ground and is perpendicular to, it. PQ is the minimum height of the mirror in order to obtain the full image of the person., For this, RP and SQ must be perpendicular to the mirror. Find out why, by studying the, figure 11.4., Minimum height of the mirror, , PQ = RS, = RE + ES, , =, , HE, EF, +, 2, 2, , =, , HF, = Half of the person’s height, 2, 117

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M, , H, R, , H1, R1, , P, , E, , Q, , S, , F, , N, , S1, , F1, , 11.4 A plane mirror and the full image of a person, , Spherical mirrors, Observe and discuss., , You must have seen the mirrors, displayed in the Laughing Chamber in a, fair. Your face appears distorted in these, mirrors. Why does this happen? These, mirrors are different from the mirrors we, have at home. They are curved. The, images formed by curved mirrors are, different from those formed by plane, mirrors. Because of this we do not see the, familiar images in these mirrors., The rear view mirrors in cars, which, enable drivers to see the vehicles coming, from behind, are curved mirrors., , 11.5 Laughing Chamber, , Try this, , A, B, , If we cut a rubber ball into two parts as shown, in figure 11.6, we can see that each of the two parts, has two types of surfaces., Generally, spherical mirrors are parts of a, hollow glass sphere like the part B in the figure. The, inner or outer surface of this part is coated with a, shiny substance to produce a spherical mirror., Reflection of light takes place either from its outer, or inner surface. Thus, there are two types of, spherical mirrors as described below., , 11. 6 Creation of spherical mirrors, , 118

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A. Concave mirror, If the inner surface of the spherical mirror is the reflecting surface, then it is called a, concave mirror., B. Convex mirror, If the outer surface of the spherical mirror is the reflecting surface then it is called a, convex mirror., Terms related to spherical mirrors, Pole : The centre of the mirror surface is called its pole. P is the pole of the mirror in figure, 11.7., Centre of curvature : The centre of the sphere of which the mirror is a part, is called the, centre of curvature of the mirror. C is the centre of curvature of the mirror in the figure., Radius of curvature, Centre of curvature, , A, M, C, , Principal focus, , F, , P, , Pole of the mirror, , 11.7 Terms related to spherical mirrors, , Radius of curvature : The radius of the sphere of which the mirror is a part, is called the, radius of curvature of the mirror. The length CP or CA in the figure is the radius of curvature, of the mirror., Principal axis : The straight line passing through the pole and centre of curvature of the, mirror is called its principal axis. PM is the principal axis of the mirror in the figure., Principal focus : Incident rays which are parallel to the principal axis of a concave mirror,, after reflection from the mirror, meet at a particular point in front of the mirror on the, principal axis. This point (F) is called the principal focus of the concave mirror. In the, case of a convex mirror, incident rays parallel to the principal axis, after reflection, appear, to come from a particular point behind the mirror lying along the principal axis. This point, is called the principal focus of the convex mirror., Focal length : The distance (f) between the pole and the principal focus of the mirror is, called the focal length. This distance is half of the radius of curvature of the mirror., Use your brain power !, , What is the difference between the principal, focus of the concave and convex mirrors?, , 119

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Drawing the reflected rays, Try this, , How do we determine the direction, that an incident ray will take after reflection, from a spherical mirror? In figure 11.8,, MN is a spherical mirror and ray AQ is, incident on it. CQ is a radius and therefore, is perpendicular to the mirror at Q. Thus,, angle AQC is the angle of incidence., According to the laws of reflection, angle, of incidence and angle of reflection are of, the same measure. Thus, while drawing, the reflected ray QB, angle CQB must be, equal to the angle AQC., , A, M, Q, C, P, B, , N, , 11.8 Drawing the reflected rays., We can study the images produced by spherical mirrors by drawing ray diagrams. A, ray diagram is the depiction of the path taken by light rays. To draw a ray diagram, we, use the following rules, which are based on the laws of reflection of light. (See figure, 11.9)., Rule 1 : If an incident ray is parallel to the principal axis then the reflected ray passes, through the principal focus., Rule 2 : If an incident ray passes through the principal focus of the mirror, the, reflected ray is parallel to the principal axis., Rule 3 : If an incident ray passes through the centre of curvature of the mirror, the, reflected ray traces the same path back., Incident ray, , C, Reflected, ray, , Incident ray, , F, , P, , F, , C, , Incident ray, , P, , Reflected ray, , Rule 1, , Rule 2, 11.9 Rules for drawing ray diagrams, , 120, , F, , C, Reflected ray, , Rule 3, , P

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Images formed by a concave mirror, Material : Candle or glass lamp, two cardboard boxes, large cardboard sheet, white paper, concave mirror, metre ruler, wooden block., , Try this, , Action : Take the cardboard box,, large enough to hold the candle or, lamp. Cut off one side and place the, candle inside. Cut out an arrow, shaped slit from one side, so that we, get an arrow shaped light source., Make a screen of size 20 cm x30 cm, by sticking a white paper on the, cardboard sheet and set it up, vertically with the help of the wooden, block. Fix the mirror vertically on, the other cardboard box by making a, slit on its top surface., , Cardboard, box, Concave mirror, , Metre scale, , 11.10 Images formed by a plane mirror, , Place the screen near a window and place the mirror in front of it such that the image, of the sun or some far away object forms clearly on the screen. Measure the distance, between the screen and the mirror in this situation. This is the focal length of the mirror., Set up the experiment as shown in figure 11.10, in a dark room. Place the mirror near, the 0 mark on the metre scale. Place the screen in front of it and place the light source in, between the two so that the distance between the mirror and the source is a little more than, the focal length of the mirror., Obtain a clear image of the source on the screen by moving the screen along the metre, scale and perpendicular to it. The image will be inverted and larger than the source. As the, image is obtained on the screen, it is a real image., Now move the source away from the mirror so that the distance between the two is, greater than twice the focal length of the mirror. Get a clear image on the screen by, moving it towards the mirror. The image is inverted, smaller than the object and real., , S, , A, B1, , C, , B, , P, , A., , N, , A, , S, Q, , F B, , P, , C, , F, , R, , 1, T A, , M, , M, , Observe, , Q, , 11.11 Images obtained in a concave mirror, , 121, , B., , N, , A1, , B1

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As shown in figure 11.11 A, an object AB is placed between the focus and the centre, of curvature of the concave mirror MN. The incident ray AQ, starting from A, and going, through the focus F, becomes parallel to the principal axis after reflection and returns, along QR. The incident ray AS, parallel to the axis, after reflection passes through the, focus and returns along the path ST. It cuts the reflected ray QR at point A1. Thus, the, image of A is formed at A1. The point B is situated on the principal axis and so its image, will also be on the axis and will be directly above A1. Thus the image of B is at B1. The, images of points between A1 and B1 will be formed between points A1 and B1. Thus, the, image of object AB is A1B1., From this we see that when the object is placed between the focus and the centre of, curvature of the mirror, the image is formed beyond the centre of curvature. This image is, larger than the object and is inverted. As the reflected rays actually cross each other, the, image is a real image and can be obtained on a screen., In figure 11.11 B, an object AB is placed between the pole and focus of the mirror., The incident ray AQ is parallel to the principal axis and the incident ray AS is in the, direction joining A with the centre of curvature. The figure shows how these rays get, reflected and form the image A1B1 of the object. This image is behind the mirror, erect and, larger than the object. As the reflected rays do not actually meet but appear to come, together behind the mirror, the image is a virtual image., The position and type of the image produced by a concave mirror when an object is, placed at different distances from it are given in the following table., Images formed by concave mirrors, No., 1, 2, 3, 4, 5, 6, , Position of the, Position of the image, Nature of, object, image, Between pole and Behind the mirror, Erect, virtual, focus, At the focus, At infinity, Inverted, real, Between focus and, centre of curvature, At the centre of, curvature, Beyond the centre, of curvature, At a very large, (infinite) distance, , Beyond the centre of, curvature, At the centre of, curvature, Between the centre of, curvature and focus, At focus, , Website for more information, , Very large, , Inverted, real, , Magnified, , Inverted, real, Inverted, real, , Same as the, object, Diminished, , Inverted, real, , Point image, , www.physicsclassroom.com, , 122, , Size of the, image, Magnified

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Draw ray diagrams and determine the position and type of, images formed by a concave mirror when the object is placed at, Try this, (1) Focus (2) Centre of curvature (3) Beyond the centre of, curvature and (4) At an infinite distance. Tally your answers with, the information given in the table., Image formed by a convex mirror, Figure 11.12 shows an object AB kept in front of a convex mirror MN. Incident rays, AQ, starting from A and travelling parallel to the axis and AR going towards the centre of, curvature are shown. How these get reflected and form the image A1B1 can be understood, from the figure. It is clear that the image is smaller than the object, behind the mirror and, erect. As the reflected rays do not actually cross one another, the image is a virtual image., , The nature of the image formed, by a convex mirror does not depend, on the distance of the object from the, mirror. These images are always, virtual, smaller than the object and, situated behind the mirror., , M, A, B, , R, P, , Q A1, B1, , F, , C, , N, 11.12 Image formed in a convex mirror, , Divergence and convergence of light, Try this, , A. Take 5 sticks from a matchbox. Arrange, them so that their heads come together, at a point. In this arrangement, the, heads of the matchsticks are said to, have converged., B. Now arrange the sticks so that their, uncoated ends are together at a point., The heads are spread apart. In this, arrangement, the heads are diverging, from the point., , 11.13 Divergence and convergence, , A concave mirror is also called a focusing mirror. This is because, as shown in figure, 11.14 A, parallel rays get focused after reflection in this mirror. The size of the image, produced by these mirrors can be larger or smaller than the object, depending upon the, distance of the object from the mirror., , 123

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A convex mirror is also called a dispersing mirror. This is because, as shown in figure, 11.14 B, parallel incident rays get dispersed after reflection in this mirror. The size of the, images produced by these mirrors is always smaller than the size of the objects., How will you find out if a mirror is concave or convex?, The special mirror which is used for shaving is a concave mirror. When held close to, the face, it gives vertical and larger image of the face. If the same mirror is taken farther, away from the face, the image gets smaller and smaller., The mirrors used in cars and motorcycles are convex mirrors. In these mirrors the, image of a face is erect and smaller and it remains erect but becomes smaller and smaller, when the mirror is taken away from the face. As a result we can see the images of the, surroundings also in the mirror. Thus, we can determine the nature of the mirror by studying, the images produced by them., When the light rays coming from an object enter our eyes, we can see the object, because, while passing through the lenses in our eyes, the rays converge, and the image of, the object forms on the retina of our eye. This image, formed by the light rays actually, converging at a point, is a real image. A real image can be obtained on a screen., , The image produced by a plane mirror, is a virtual image. This image is produced, at a point from which the reflected light, rays appear to diverge (figure 11.2 B). This, image cannot be obtained on a screen as, the rays do not actually meet there., , Concave mirror, , ., , F, , C, , When light rays collect at a point after, reflection from a spherical mirror, they are, said to converge there. When we want to, bring light rays together at a point, a, converging light beam is used. Doctors use, such a beam to converge light on a tooth,, ear, nose, etc. Equipment using solar, energy also use converging light., When light rays starting from a point, spread out after reflection by a spherical, mirror, light is said to have diverged. When, we want light rays to spread out from a, source, a divergent beam is used, as for, example, in street lamps., , P, A, Focal length, , Convex mirror, , P, , C, B, , Focal length, 11.14 Concave and convex mirror, , 124, , ., , F

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Uses of concave mirrors, 1. Barber shop, dental hospital – If the object is placed between the pole and focus of, the mirror, an erect, virtual and magnified image is obtained, 2. Torch and head lamps of vehicles- The source of light is kept at the focus of the, mirror. Thus, a parallel beam of light is obtained., 3. Flood lights- The source of light is placed a little beyond the centre of curvature of, the mirror. This gives a bright beam of light., 4. Various equipment using solar energy - Sun rays reflected by a concave mirror, come together in the focal plane., Uses of convex mirrors, 1. Mirrors on the sides of cars are convex mirrors, 2. Big convex mirrors are fitted at gate and in square., Direction of incident rays, Y axis, According to the Cartesian, sign convention, the pole of the, mirror is taken as the origin. The Distances, upward, Distances on the right, principal axis is taken as the (positive +) Distances on the left, (positve +), (negative -), X- axis of the frame of reference., X axis, The sign conventions are as, Principal axis, follows., Distances, down, 1. The object is always kept on, ward, the left of the mirror. All (negative-), distances parallel to the, principal axis are measured, from the pole of the mirror., 2. All, distances, measured, 11.15 Cartesian sign conventions, towards the right of the pole, are taken to be positive, while those measured towards the left are taken to be negative., 3. Distances measured vertically upwards from the principal axis are taken to be, positive., 4. Distances measured vertically downwards from the principal axis are taken to be, negative., 5. The focal length of a concave mirror is negative while that of a convex mirror is, positive., , Mirror formula, We get the correct values of distances, by using the Cartesian sign convention., The object distance (u) is the distance of, the object from the pole, while the image, distance (v) is the distance of the image, from the pole. The relationship between, the object distance, image distance and the, focal length (f) is called the mirror formula., , Mirror formula, , 1, 1 1, +, v, u = f, This formula is valid for all spherical, mirrors, for all positions of objects, under, all circumstances., , 125

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Magnification due to spherical mirrors, The magnification due to a spherical mirror is given by the ratio of the height of the, image (h2) to the height of the object (h1). This tells us how large the image is as compared, to the object., Magnifiction M, , =, , Height of the image, Height of the object, , =, , h2, h1, , . From this it can be shown that, , v, M= - u, , As the object is always kept above the principal axis, its height is always taken to be, positive. For virtual images, the height is positive while for real images, it is negative. As, the object is kept on the left of the mirror, its distance (u) is always negative., Try this, , Determine the sign of magnification in each of the 6 cases in the, table on page 122 using both formulae and verify that they are the, same., , Solved examples, Example : Rajashree wants to get an inverted image of height 5 cm of an object kept at, a distance of 30 cm from a concave mirror. The focal length of the mirror is 10 cm. At, what distance from the mirror should she place the screen ? What will be the type of the, image, and what is the height of the object?, Given :, Focal length = f = - 10 cm, object distance = u = - 30 cm ,, height of the image = h2 = -5 cm, Image distance = v = ?, height of object = h1 = ?, According to the mirror formula, Magnification, , v, M= =u, h1, uh, h1 = - 2, v, (- 30) (-5), h1 = - 15, h2, , 1, 1 1, +, v, u =f, 1, 1 1, =, v, f -u, 1, v, , 1, 1, = -10 --30, , h1 = (-2) (-5), , 1 -3 + 1, v = 30, , h1= 10 cm, The height of the object is 10 cm. Thus,, the image will be real and diminshed., , 1 -2, v = 30, 1, 1, =, v, -15 cm, v = -15, , Rajashree has to place the screen 15 cm to the left of the mirror., , 126

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Always remember, The image in front of the mirror which can be obtained on a screen is called a real, image. For any position of the object, a convex mirror always produces an erect, diminished image (which is smaller than the object) and is situated behind the mirror., The image which is behind the mirror and thus cannot be obtained on a screen is, called a virtual image. The magnification of such an image is less than 1., , Exercises, 1. Answer the following questions., a. Explain the difference between a, plane mirror, a concave mirror and a, convex mirror with respect to the type, and size of the images produced., b. Describe the positions of the source, of light with respect to a concave, mirror in 1.Torch light, 2. Projector lamp 3. Floodlight, c. Why are concave mirrors used in, solar devices?, d. Why are the mirrors fitted on the, outside of cars convex?, e. Why does obtaining the image of the, sun on a paper with the help of a, concave mirror burn the paper?, f. If a spherical mirror breaks, what, type of mirrors are the individual, pieces?, 2. What sign conventions are used for, reflection from a spherical mirror?, 3. Draw ray diagrams for the cases of, images obtained in concave mirrors as, described in the table on page 122., 4. Which type of mirrors are used in the, following?, Periscope, floodlights, shaving mirror,, kaleidoscope, street lights, head lamps, of a car., 5. Solve the following examples, a. An object of height 7 cm is kept at a, distance of 25 cm in front of a, concave mirror. The focal length of, , 6., , the mirror is 15 cm. At what distance, from the mirror should a screen be, kept so as to get a clear image? What, will be the size and nature of the, image?, (Answer: 37.5 cm and, 10.5 cm. Image is real), b. A convex mirror has a focal length of, 18 cm. The image of an object kept, in front of the mirror is half the height, of the object. What is the distance of, the object from the mirror?, (Answer: 18 cm), c. A 10 cm long stick is kept in front of, a concave mirror having focal length, of 10 cm in such a way that the end, of the stick closest to the pole is at a, distance of 20 cm. What will be the, length of the image?, (Answer: 10 cm), Three mirrors are created from a, single sphere. Which of the following, - pole, centre of curvature, radius of, curvature, principal axis - will be, common to them and which will not, be common?, , Project :, Make a kaleidoscope and make a, presentation in the class about how, it works., , 127, , ²²²

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12.1.Study, Sound, गतीचे of, नियम, Ø, Ø, , Sound waves, Ø Velocity of sound, Ø Reflection of sound, The human ear, audible sound, infra sound and ultrasound, , 1. How does the velocity of sound depend on its frequency?, 2. How is the direction of the oscillation of the particles of the, Can you recall?, medium related to the direction of propagation of the soundwave?, Sound is a form of energy which creates the sensation of hearing in our ears. This, energy is in the form of waves. A medium is necessary for the propagation of sound, waves. Sound waves give rise to a chain of compression (place of higher density) and, rarefaction (place of lower density) in the medium. The particles of the medium oscillate, about their central or mean positions, in a direction parallel to the propagation of the, wave. Such waves are called longitudinal waves. On the other hand, in the waves created, by dropping a stone in still water, the particles of water oscillate up and down. These, oscillations are perpendicular to the direction of propagation of the wave, such waves are, called transverse waves., Change in density, , Loudspeaker, , Observe and discuss., , A, , A sound wave can be shown, Change in pressure, in the form a graph. At any, moment during the propagation Loudspeaker, of a sound wave we would find, B, alternate bands of compression, and rarefaction of the medium, i.e. bands of greater and lesser, density., Density or, Figure 12.1 A shows the, C, pressure, changes in density while figure B, shows the changes in pressure., Average, The changes in density or pressure, density or pressure, 12.1 Sound waves, are shown in the form of a graph, in figure C., The wavelength of sound waves is indicated by the Greek letter lambda (l), while its, frequency is indicated by nu (u). The amplitude, which is the maximum value of pressure, or density, is indicated by A. The time taken for one oscillation of pressure or density at a, point in the medium is called the time period and is indicated by T., The value of frequency determines the pitch (high or low) of the sound while the value, of the amplitude determines its strength or loudness., 1. How are the frequencies of notes sa, re ga ma, pa, dha, ni related, to each other?, 2., What is the main difference between the frequencies of the voice, Research, of a man and that of a woman?, , 128

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Velocity of sound, , 1. Take your friend to a place where there are iron pipes e.g. the school, verandah, a staircase or a fence., Try this 2. Stand near one end of the pipe and ask the friend to stand 20 to 25, feet away from you near the pipe., 3. Ask the friend to gently tap the pipe with a stone. Press your ear to the pipe and listen, to the sound coming through the pipe., 4. The same sound coming through the air can also be heard. But which sound reaches, you first?, From the above activity you can see that you hear the sound through the iron pipe much, before you hear it coming through air. This shows that sound travels faster in iron than, in air., The distance covered by a point on the wave (for example the point of highest density or lowest density) in unit time is the velocity of the sound wave., Velocity =, , Distance, Time, , Any point on the sound wave covers a distance equal to l (wavelength) in time T (time period)., , Thus the velocity of sound is given by, , v = u l because 1 = u, T, , Velocity =, , Wavelength, Time period, , v =, , l, T, , Thus, the velocity of sound = wavelength x frequency., In any medium at fixed physical Velocity of sound in various mediums at 250C, conditions the velocity of sound of, State, Substance, Speed (m/s), different frequencies is very nearly the, Solid, Aluminum, 5420, same. The velocity is highest in solids, Nickel, 6040, and least in gases. It increases with an, Steel, 5960, increase in the temperature of the, Iron, 5950, medium., Brass, 4700, Glass, 3980, The Italian physicists Borelli, 1531, Liquid, Sea water, and Viviani, in the 1660s, first, Pure water, 1498, calculated the speed of sound., Ethanol, 1207, They measured the time between, Methanol, 1103, seeing the flash of a gun and, Hydrogen, 1284, Gas, hearing its sound from a long, Helium, 965, distance. Their value of 350 m/s, Air, 346, is very close to the value of 346, Oxygen, 316, m/s which is accepted today., Sulphur dioxide, 213, , 129

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Velocity of sound in a gaseous medium: The velocity of sound in a gaseous medium depends, on the physical conditions i.e. the temperature, density of the gas and its molecular weight., Temperature (T): The velocity of sound is directly proportional to the square root of the, temperature of the medium. This means that increasing the temperature four times doubles, the velocity., , v, , T, , a, , Density (r): The velocity of sound is inversely proportional to the square root of density., Thus, increasing the density four times, reduces the velocity to half its value., , v, , a, , 1, , r, , Molecular weight (M): The velocity sound is inversely proportional to the square root of, molecular weight of the gas. Thus, increasing the molecular weight four times, reduces the, 1, velocity to half its value. v a, M, Think, The molecular weight of oxygen gas (O2) is 32 while that of hydrogen gas (H2) is 2., Prove that under the same physical conditions, the velocity of sound in hydrogen is four, times that in oxygen., For a fixed temperature, the velocity of sound does not depend on the pressure of the gas., Audible, infra- and ultra-sound, The limits of hearing of the human ear are 20 Hz to 20,000 Hz. That is, the human ear, can hear sounds of frequencies in A peep into the past, this range. These sounds are called, The Italian scientist Spallanzani was the first, audible sounds. Our ears cannot to discover a special mechanism present in bats., hear sounds of frequencies lower He covered various organs of bats like the eyes,, than 20 Hz and higher than ears, nose, etc. one by one and allowed them to fly, 20,000 Hz (20 kHz). Sound with in the dark thereby discovering how they can fly, frequency smaller than 20 Hz is easily in the dark. He found that the bats with their, called infra sound. The sound ears covered began to collide with whatever came, produced by a pendulum and the in their path. Even though their eyes were open., sound generated by the vibrations of They were of no use to the bats. He thus discovered, the earth’s crust just before an that their ability to fly in the dark depends on their, earthquake are examples of such ears and not eyes., sounds. Sound waves with frequency, The ultrasonic sound produced by bats, gets, greater than 20 kHz are called reflected on hitting an obstacle. This reflected, ultrasound., sound is received by their ears and they can locate, The dog, mouse, bat, dolphin the obstacle and estimate its distance even in the, etc have a special ability to hear dark., infra sounds. Thus, they can sense, some noise which are inaudible to, us. Children under 5 years of age, and some creatures and insects can, hear waves with frequency up to, 25 kHz. Bats, mice, dolphins, etc,, can also produce ultrasound., , 130

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Uses of ultrasonic sound, 1. For communication between ships at sea., 2. To join plastic surfaces together., 3. To sterilize liquids like milk by killing the bacteria in it so that the milk keeps for a, longer duration., 4. Echocardiaography which studies heartbeats, is based on ultrasonic waves, (Sonography technology)., 5. To obtain images of internal organs in a human body., 6. In industry, to clean intricate parts of machines where hands cannot reach., 7. To locate the cracks and faults in metals blocks., , Reflection of sound, 1. Make two sufficiently long, identical, tubes out of a cardboard., 2. Arrange them on a table, in front of a, wall as shown in figure 12.2., , Try this, , 3. Place a clock near the end of one of the, tubes and try to hear the ticking of the, clock at the end of the other tube by, placing your ear there., , Wall, , 4. Adjust the angles of the two tubes till, you can hear the sound very clearly., , q1 q2, , 5. Measure the angle of incidence q1 and, the angle of reflection q2. Try to see if, they are related in any way., , Cardboard, tubes, Clock, , 12.2 Reflection of sound, Like light waves, sound waves, too, get reflected from a solid or a liquid surface., These waves also follow the laws of reflection. A smooth or a rough surface is needed for, the reflection of sound. The direction of the incident sound wave and reflected sound, wave make equal angles with the perpendicular to the surface and all these three lie in the, same plane., Good and bad reflectors of sound, How much of the incident sound gets reflected decides whether a reflector is a good, or a bad reflector. A hard and flat surface is a good reflector while clothes, paper, curtains,, carpet, furniture, etc. absorb sound instead of reflecting it and, therefore are called bad, reflectors., , 131

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In the activity on page no. 131, what will happen if, Use your brain power ! you lift one of the tubes to some height?, Echo, You must have visited an echo point at a hill, station. If you shout loudly at such a point, you, hear the same sound just after a little while. This, sound is called an echo., An echo is the repetition of the original, sound because of reflection by some surface., In order to be able to hear the original sound, and its reflection distinctly, at 22 0C, what must, the minimum distance be between the source, and the reflecting surface? At 22 0C, the velocity, of sound in air is 344 m/s. Our brain retains a, sound for 0.1 s. Thus, for us to be able to hear a, distinct echo, the sound should take more than, 0.1 s after starting from the source to get reflected, and come back to us. Thus we can determine the, minimum distance between the source and the, reflecting surface as follows:, Distance = speed ´ time, = 344 m/s ´ 0.1 s, = 34.4 m, Thus, to be able to hear a distinct echo, the, reflecting surface should be at a minimum, distance of half of the above i.e. 17.2 m. As the, velocity of sound depends on the temperature of, air, this distance depends on the temperature., , Use your brain power !, 1. To hear the echo distinctly, will, the distance from the source of, sound to the reflecting surface, be same at all temperatures?, Explain your answer., 2. When is the reflection of sound, harmful?, , Science in the surroundings......, Echo can be heard multiple, times due to continuous or, multiple, reflections., The, golghumat, at, Vijapur, in, Karnataka is an excellent, example of this., , Reverberation, Compare the two cases:, 1. Go to an empty, closed house with, your friends., 2. Once inside, chat with your friends., 3. Note what you sense., , 1. Close the doors and windows of your, house and switch on the music system., 2. Increase the loudness of the system as, much as possible., 3. Note what you sense., , 132

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Sound waves get reflected from the walls, and roof of a room multiple times. This, causes a single sound to be heard not once, but continously. This is called reverberation., The time between successive reflections of a, particular soundwave reaching us becomes, smaller and the reflected sounds get mixed, up and produce a continuous sound of, increased loudness which cannot be, deciphered clearly. This is the reason why, some auditoriums or some particular seats in Singer, an auditorium have inferior sound reception., This is shown in figure 12.3., Use your brain power !, , Reflected sound, , Direct sound, , Listener, , 12.3 Reverberation, , How will you reduce reverberation in public halls, or buildings?, , SONAR, SONAR is the short, form for Sound Navigation, Ship, and Ranging. It is used to, determine the direction,, distance and speed of an, Receiver, underwater object with the, Transmiter, help of ultrasonic sound, waves., SONAR has a, transmitter and a receiver,, Reflection pulse, Transmitted, which are fitted on ships or, pulse, boats., The, transmitter, Water, produces and transmits, ultrasonic sound waves., Seabed, These waves travel through, water, strike underwater, objects and get reflected by, them. The reflected waves, 12.4 The SONAR technique, are received by the receiver, on the ship., The receiver converts the ultrasonic sound into electrical signals and these signals are, properly interpreted. The time difference between transmission and reception is noted., This time and the velocity of sound in water give the distance from the ship, of the object, which reflects the waves., SONAR is used to determine the depth of the sea. SONAR is also used to search, underwater hills, valleys, submarines, icebergs, sunken ships etc., , 133

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Sonography, Sonography technology uses ultrasonic sound waves to generate images of internal, organs of the human body. This is useful in finding out the cause of swelling, infection,, pain, etc. The condition of the heart, the state of the heart after a heart attack as well as, the growth of foetus inside the womb of a pregnant woman are studied using this, technique. , Examination, procedure, , Sonography, machine, , Image obtained, , 12.5 Sonography machine and images obtained, , This technique makes use of a probe and a gel. The gel, is used to make proper contact between the skin and the, probe so that the full capacity of the ultrasound can be, utilized., The gel is applied to the skin outside the internal organ, to be studied. High frequency ultrasound is transmitted inside, the body with the help of the probe. The sound reflected from, the internal organ is again collected by the probe and fed to, a computer which generates the images of the internal organ., As this method is painless, it is increasingly used in medical, practice for correct diagnosis., , Find out, How is ultrasound, used, in, medical, science?, , Always remember, Developments in science have led to advances in technology, which have helped us make much progress. However, every coin, has two sides and the misuse of science has had serious, consequences for human life. The sonography technique can help, to follow the growth and well being of an unborn baby. But the, increasing incidence of female foeticide as a result of the, discrimination between the girl and the boy child is an example, of the grave misuse of this technique. Female foeticide is now a, cognizable offence under the PNDT Act., , 134

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Human ear, , Chain of three bones, Semi-circular canals, Stapes, , Cochlea, , Auditory canal, Inner ear, , Outer ear, (Pinna), , Eustachian tube, Eardrum, , Middle ear, , Tympanic cavity, , 12.6 Structure of the human ear, The ear is an important organ of the human body. We hear sounds because of our ear., When sound waves fall on the eardrum, it vibrates. These vibrations are converted into, electrical signals which travel to the brain through nerves. The ear can be divided into, three parts: 1. Outer ear 2. Middle ear 3. Inner ear., Outer ear or Pinna, The outer ear collects the sound waves and passes them through a tube to a cavity in, the middle ear. Its peculiar funnel like shape helps to collect and pass sounds into the, middle ear., Middle ear, There is a thin membrane in the cavity of the middle ear called the eardrum. When a, compression in a sound wave reaches the eardrum, the pressure outside it increases and it, gets pushed inwards. The opposite happens when a rarefaction reaches there. The pressure, outside decreases and the membrane gets pulled outwards. Thus, sound waves cause, vibrations of the membrane., Inner ear, The auditory nerve connects the inner ear to the brain. The inner ear has a structure, resembling the shell of a snail. It is called the cochlea. The cochlea receives the vibrations, coming from the membrane and converts them into electrical signals which are sent to the, brain through the nerve. The brain analyses these signals., Always remember, The ear is an important sensory organ. Sticks or other pointed objects should, never be inserted into the ear for cleaning it. Also, one should not hear very loud, music using earphones. It may cause grave injury to the eardrum., , 135

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Solved examples, Example 1 : How long will it take for a, sound wave of 25 cm wavelength and 1.5, kHz frequency of, to travel a distance of, 1.5 km?, , Example 2 : Ultrasonic waves are, transmitted downwards into the sea with, the help of a SONAR. The reflected sound, is received after 4 s. What is the depth of, the sea at that place?, , Given : Frequency (u) = 1.5 kHz, , (Velocity of sound in seawater = 1550 m/s), , = 1.5 × 103 Hz, , Given :, , Wavelength (l) = 25 cm = 0.25 m, , Velocity of sound in seawater = 1550 m/s, , distance (s) = 1.5 km = 1.5 × 103 m, , Time for echo to be heard = 4s, , time (t) = ?, , Time taken by sound waves to reach the, , Velocity of sound = Frequency × Wavelength, , v=u l, v = 1.5 x 103 × 0.25, v = 0.375 ×103, v = 375 m/s, Time=, , Distance, Velocity, , t=, , s, v, , 1.5 × 103, =, 375, , bottom of the sea =, Velocity =, , 4 =2s, 2, , Distance, Time, , Distance = Velocity × Time, =, , 1500, 375, , = 1550 x 2 = 3100 m, =4s, , Depth of the sea at that place = 3100 m, , The sound wave takes 4 s to travel the, distance of 1.5 km., Example 3 : Sound waves of wavelength 1 cm have a velocity of 340 m/s in air. What, is their frequency? Can this sound be heard by the human ear?, Given : Wavelength = l =1cm=1 x 10-2m, Velocity of sound = v = 340 m/s, , v = ul, v, \u=, l, , 340, = 1 x 10 -2 = 340 × 10 2, , \ u = 34000 Hz, , This frequency is higher than 20000 Hz and, therefore, this sound cannot be heard by, the human ear., The SONAR technology was first developed during World War I to detect enemy, submarines. This technology can be used in air also. In fact, bats use this technique to, detect obstacles in their path so that they can avoid them and fly freely even in the dark., , 136

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Exercises, 1., , Fill in the blanks and explain., a. Sound does not travel through, …………, b The velocity of sound in steel is, …............ than the velocity of, sand in water., c. The incidence of ……… in daily life, shows that the velocity of sound is, less than the velocity of light., d. To discover a sunken ship or objects, deep inside the sea, ......................., technology is used., , 2. Explain giving scientific reasons., , a. The roof of a movie theatre and a, conference hall is curved., b. The intensity of reverberation is, higher in a closed and empty house., c. We cannot hear the echo produced, in a classroom., , 3. Answer the following questions in, your own words., a. What is an echo? What factors are, important to get a distinct echo?, b. Study the construction of the, Golghumat at Vijapur and discuss, the reasons for the multiple echoes, produced there., c. What should be the dimensions, and the shape of classrooms so, that no echo can be produced, there?, 4. Where and why are sound absorbing, materials used?, 5. Solve the following examples., a. The speed of sound in air at 0 0C is, 332 m/s. If it increases at the rate, of 0.6 m/s per degree, what will be, the temperature when the velocity, has increased to 344 m/s?, (Ans: 200 0C), , b. Nita heard the sound of lightning, after 4 seconds of seeing it. What, was the distance of the lightning, from her?, (The velocity of sound in air is 340, m/s?), (Ans: 1360 m), c. Sunil is standing between two, parallel walls. The wall closest to, him is at a distance of 660 m. If he, shouts, he hears the first echo after, 4 s and another after another 2, seconds., 1. What is the velocity of sound in, air?, 2. What is the distance between the, two walls?, (Ans: 330 m/s; 1650 m), d. Hydrogen gas is filled in two, identical bottles, A and B, at the, same temperature. The mass of, hydrogen in the two bottles is 12, gm and 48 gm respectively. In, which bottle will sound travel, faster? How may times as fast as, the other?, (Ans: In A; Twice), e. Helium gas is filled in two identical, bottles A and B. The mass of the, gas in the two bottles is 10 gm and, 40 gm respectively. If the speed of, sound is the same in both bottles,, what conclusions will you draw?, (Ans: Temperature of B is 4, times the temperature of A.), Project :, Collect information about the, musical, instrument, called, Jaltarang and find out how the, different notes are produced in it., , 137, , ²²²

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13. Carbon 1., : An, Element, गतीचेImportant, नियम, Ø, Ø, , Carbon – occurrence, properties, allotropes Ø Hydrocarbons, Carbon dioxide and methane – occurrence, properties, uses, , 1. What is an element? What are the different types of elements?, 2. What remains behind on complete combustion of any organic, Can you recall?, compound?, 3. What type of element is carbon? Give some information about it., You have learnt that carbon is a non-metallic element. You have also learnt about its, occurrence in nature in the form of some compounds., Try this, , 1. Take some milk in an evaporating dish. Heat the evaporating dish, on a Bunsen burner. What remains behind at the bottom of an, evaporating dish on complete evaporation of the milk?, , 2. Take small samples of sugar, wool, dry leaves, hair, seeds, split pulses and plastic in, separate test tubes. Heat each test tube and observe the changes taking place in the, substances., What does the black substance remaining in each test tube indicate?, Carbon, The element carbon is available abundantly in the, nature and occurs in free as well as in the combined, state. In this chapter, let us study the properties of the, non-metallic element carbon., Make a list of all substances/objects that you use in, daily life from morning till night and divide those, substances into the columns in the following table., Metallic objects, , Earthen/glass objects, , 1. Symbol of carbon – C, 2. Atomic number – 6, 3. Atomic mass – 12, 4. Electron configuration, – 2,4, 5. Valency – 4, 6. Non-metallic element, Other objects/substances, , Now look at the list of objects in the last column. It contains foodstuffs, clothes,, medicines, fuels, wooden objects, etc. Carbon is the common and important constituent of, all these substances., Can you tell?, , What is a compound ? How are compounds formed ?, , Compounds obtained directly or indirectly from plants and animals are called organic, compounds and compounds obtained from minerals are called inorganic compounds. All, the organic compounds contain carbon. Carbon is the main element even in cellular DNA, and RNA that transfer hereditary characteristics from one generation to the next., , 138

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An introduction to scientists, The German chemist Wohler synthesized an organic compound, urea from an inorganic compound ammonium cyanate. Ever since, then, many organic compounds have been made from inorganic, compounds. Carbon was found to be the main element in all these, compounds. Hence, organic chemistry is also referred to as chemistry, Heat, of carbon compounds., , NH4+CNO-, , ®, , NH2CONH2, , Occurrence of carbon, The name ‘carbon’ is derived from the Latin, word ‘carbo’ meaning coal. Carbon is found in, nature in free as well as compound state. Carbon in, the free state is found as diamond and graphite, and, in the combined state in the following compounds., 1. As carbon dioxide and in the form of carbonates, such as calcium carbonate, marble, calamine, (ZnCO3), 2. Fossil fuel – coal, petroleum, natural gas, 3. Carbonaceous nutrients – carbohydrates,, proteins, fats, 4. Natural fibres – cotton, wool, silk, , Science capsule, In the earth's crust, carbon is, present to the extent of, approximately 0.27% in the form, of carbonate, coal, petroleum. In, atmosphere, the proportion of, carbon in the form of carbon, dioxide is approximately 0.03 %., Some types of plants which, grow on the ocean floor convert, carbon in marine water into, calcium carbonate., , Properties of carbon, Allotropic nature of Carbon, Allotropy - Some elements occur in nature in more than one form. The chemical properties, of these different forms are the same but their physical properties are different. This, property of elements is called allotropy. Like carbon, sulphur and phosphorus also exhibit, allotropy., Allotropes of carbon, A. Crystalline forms, 1. A crystalline form has a regular and definite arrangement of atoms., 2. They have high melting points and boiling points., 3. A crystalline form has a definite geometrical shape, sharp edges and plane surfaces., , Carbon has three crystalline allotropes., 1. Diamond, Diamonds are found in India mainly in, Govalkonda (Karnatak) and Panna, (Madhya Pradesh). Diamonds are also, found in South Africa, Brazil, Belgium,, Russia and America., , 139, , 13.1 Diamond

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Structure : In diamond, every carbon atom, is bonded to four neighbouring atoms by, covalent bonds. Due to this three, dimensional structure, diamond become, very hard., Properties, 1. Brilliant and pure diamond is the hardest, natural substance., 2. The density of diamond is 3.5 g/cm3., 3. The melting point of diamond is, 3500 0C, 4. When diamond is heated at 800 0C in, the presence of oxygen CO2 is given, away. In this process no other product, besides CO2 is formed., 5. Diamond does not dissolve in any, solvent., 6. Acids/bases have no effect on diamond., 7. Diamond is a bad conductor of electricity, as it does not have free electrons., , Carbon, , 13.2 Structure of carbon atoms in diamond, , A peep into the past, Once upon a time, India was famous for, the 'Kohinoor' diamond. This diamond, was found in the 13th century in the mine at, Guntur (Andhra Pradesh). Its weight was, 186 carats., , Uses, 1. Diamonds are used in glass cutting and rock drilling machines., 2. Diamonds are used in ornaments., 3. Diamond knives are used in the eye surgery., 4. Diamond dust is used for polishing other diamonds., 5. Diamond is used to make windows giving protection from radiation in space and in, artificial satellites., 2. Graphite, Graphite is found in the natural state in Russia, New Zealand, America and India., The lead used in pencil is made by mixing graphite with clay. This process was discovered, by Nicholas Jacques Conte in 1795., Structure : Every carbon atom in graphite, is bonded to three other carbon atoms in, such a way that a hexagonal layered, structure is formed. A graphite crystal is, made of many sheets or layers of carbon, atoms. These layers slip over each other on, applying pressure. One layer of graphite is, called graphene., , Carbon, , 13.3 Graphite and structure of carbon atoms, in graphite, , 140

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Try this, , Apparatus : Pencil, electrical wires, battery/cell, small bulb, water,, kerosene, test tubes, lead pencil, etc., , Pencil, Bulb, Cell, , 13.4 Flow of electric current, through graphite, , Procedure :, 1. Remove the lead from a pencil, and feel it with, your fingers. What colour is it? Try to break the, lead with your hand., 2. Assemble the apparatus as shown in the, diagram. Start the electric current in the circuit., Observe. What did you find?, 3. Take some water in a test tube. Take some, kerosene in another test tube. Put lead dust in, both the test tubes. What did you find?, , Properties of graphite, 1. Graphite found in nature is black, soft, brittle and slippery., 2. Inside each layer of graphite, free electrons move continuously within the entire layer., That is why graphite is a good conductor of electricity., 3. Due to the layered structure graphite can be used for writing on paper., 4. The density of graphite is 1.9 to 2.3 g/cm3., 5. Graphite does not dissolve in most solvents., Uses of graphite, 1. Graphite is used for making lubricants., 2. Graphite is used for making carbon electrodes., 3. Graphite is used in pencils for writing., 4. Graphite is used in paints and polish., 5. Graphite is used in arc lamps which give a very bright light., 3. Fullerene, Fullerene, an allotrope of carbon, is rarely found, in nature. It is found in soot and in interstellar, space. The first example of fullerene is, Buckminsterfullerene (C60). This allotrope of, carbon is named fullerene after the architect, Richard Buckminster Fuller because the structure, of C60 resembles the structure of the geodesic dome, he designed., Harold Kroto, Robert Curl and Richard, Smalley were given the Nobel prize in chemistry, 1996, for the discovery of this carbon allotrope,, fullerene C60., C60 , C70 , C76 , C82 and C86 are other examples of, fullerene. Their molecules occur in small numbers, in soot., , 141, , Buckytubes (Carbon nano-tube), , Buckyball, , (C60), , 13.5 Structure of fullerene

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Properties, 1. Molecules of fullerenes are found in, the form of buckyballs and, buckytubes., 2. There are 30 to 900 carbon atoms in, one molecule of a fullerene., 3. Fullerenes are soluble in organic, solvents such as carbon disulphide,, chlorobenzene., , Uses, , 1. Fullerenes are used as insulators., 2. Fullerenes are used as a catalyst in, water purification., 3. At a certain temperature fullerene, exhibits superconductivity., , B. Non-crystalline / Amorphous forms, The arrangement of carbon atoms in this form is not regular., Coal, coke are the non-crystalline forms of carbon., 1. Coal : Coal is a fossil fuel. It contains carbon, hydrogen and, oxygen. It also contains nitrogen, phosphorus and sulphur. It, occurs in the solid state. It is of four types., a. Peat : Formation of peat is the first step in the formation of, coal. It contains a high proportion of water and less than 60% of, carbon. Therefore, not much heat can be obtained from peat., b. Lignite : Peat was transformed into Lignite due to increased, pressure and temperature inside the earth. It contains 60 to 70%, of carbon. Lignite is the second step of the formation of coal., c. Bituminous coal : Bituminous coal was formed as the third, step of formation of coal. It contains 70 to 90% of carbon., d. Anthracite : Anthracite is known as the pure form of coal., This coal is hard and contains about 95% of carbon., 2. Charcoal : The charcoal that is made from animals is made, from their bones, horns, etc. On the other hand, the charcoal made, from plants is formed by combustion of wood in an insufficient, supply of air., Uses of coal :, 1. Coal is used as fuel in factories and homes., 2. Coal is used to obtain coke, coal gas and coal tar., 3. Coal is used in thermal power plants for generation of electricity., 4. Charcoal is used in purification of water and organic material., 3. Coke : The pure coal that remains when coal gas has been, taken away from coal, is called coke., Uses of coke :, 1. Used as domestic fuel., 2. Coke is used as a reducing agent., 3. Coke is used in production of aeriform fuel such as water gas, (CO +H2) and producer gas (CO+H2+CO2+ N2)., , 142, , Peat, , Lignite, , Bituminous coal, , Anthracite, , Coke, 13.6 Non-crystalline, forms of carbon

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Hydrocarbons : basic organic compounds, Along with carbon, the element hydrogen is also included in most organic compounds., The compounds formed from only carbon and hydrogen are called basic organic compounds., These are also called hydrocarbons., The electronic configuration of carbon is 2, 4. If four electrons are added to the second, orbit of carbon, its octet becomes complete and its electronic configuration becomes stable, like that of the nearest inert gas neon (2, 8). Therefore, the valency of carbon is 4. However,, this occurs by sharing of electron rather than a give and take of electrons. In other words, a carbon atom can form four covalent bonds with other carbon atoms or atoms of different, elements., When a carbon atom shares one electron each with four hydrogen atoms and forms, four C-H bonds, a methane CH4 molecule is formed., Properties of covalent compounds, 1. Covalent compounds have low melting, points and boiling points., 2. Generally they are insoluble in water, and soluble in organic solvents., 3. They are poor conductors of heat and, electricity., 13.7 Structural formula and electron dot model of methane, , Saturated and unsaturated hydrocarbons, A carbon atom exhibits a characteristic property. It can form a chain of carbon atoms, by forming covalent bonds with other carbon atoms. The hydrocarbons having only single, bonds between carbon atoms are called saturated hydrocarbons. For example ethane, (C2H6) which is (CH3 CH3), propane (CH3, CH2, CH3)., Some hydrocarbons have a multiple bond between two carbon atoms. A multiple bond, can be a double bond or a triple bond. Hydrocarbons having at least one multiple bond are, called unsaturated hydrocarbons. For example, ethene (H2C=CH2),, ethyne (HC, CH), propene (CH3-CH=CH2), propyne (CH3-C CH)., Does an electric charge form on, Use your brain power ! atoms when a covalent bond is, formed between them? Why is a, single bond between two carbon, Solubility of carbon, atoms strong and stable?, Try this, Apparatus : 3 conical flasks, stirrer., Chemicals : Water, kerosene, cooking oil, coal powder, etc., Procedure : Take 3 conical flasks and take cooking oil, water, and kerosene respectively in each. Add half a spoonful of coal, powder in each of the conical flasks and stir with the help of, stirrer. Observe the mixtures in the three conical flasks., , 143, , 13.8 Solubility of coal in, water

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Use your brain power!, , 1. In which of the solvents- water, kerosene and cooking oil, does the coal powder dissolve?, 2. What inference will you draw about the solubility of, carbon?, , Reaction of carbon with oxygen, Apparatus : Coal, match box, moist litmus, paper, etc., Procedure : Ignite the coal. Hold the moist, blue litmus paper over the gas released on, igniting the coal. Note the observation., 1. With which gas in the air does the coal, react on igniting?, 2. What is the substance formed?, 3. What change takes place in the litmus, paper?, 4. Write down the chemical reaction taking, place in the above procedure., , Try this, Moist blue litmus, , Coal, , Blowing air, , 13.9 Reaction of carbon with oxygen, , Apparatus : Test tube, straw, limewater,, etc., Procedure : Take freshly prepared, limewater in a test tube. Blow for sometime, into the limewater through the straw and, observe the limewater. What did you see?, What might be the reason behind the, change?, , Limewater, , 13.10 Reaction of limewater with CO2, , Carbon dioxide, Molecular formula: CO2, molecular mass : 44, melting point : - 56.6 0C, Occurrence : Carbon dioxide occurs in the air in the free state to the extent of about 0.03%., Exhaled air contains about 4% of CO2. CO2 is present as a salt in chalk and Shahabad, tiles/ marble/ limestone. CO2 is given out in the combustion of wood and the fossil fuel, coal., , Try this, , Apparatus : Retord stand, round bottom flask, thistle funnel, gas, delivery tube, gas jars., Chemicals : Calcium carbonate (Pieces of Shahabad tiles / marble, pieces / limestone), dilute hydrochloric acid., , 144

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Procedure :, 1. Assemble the apparatus as shown in, the figure. While assembling place, CaCO3 in the round bottom flask., 2. Add dilute HCl in the flask through, thistle funnel. See to it that the end of, the funnel dips in the acid., 3. CO2 is formed as a result of the, reaction between CaCO3 and HCl., Collect this gas in four to five gas jars., The chemical equation of the above, reaction is as follows., , Dilute hydrochloric acid, , CaCO3, , CaCO3+ 2 HCl ® CaCl2 + H2O + CO2, , CO2, , Upward, displacement, of air, , ®, , 13.11 Preparation of carbon dioxide, , Physical and chemical properties of carbon dioxide, 1. Observe the colour of the gas formed in the above experiment., 2. Smell the gas in the gas jar., Use separate gas jars for the activities 3 to 7 below:, 3. Remove the lid of a gas jar and put some limewater in it., 4. Place a burning candle in a gas jar., 5. Drop a small amount of a solution of some universal indicator in one gas jar filled with, CO2 and shake it., 6. Pour some water in a gas jar and shake it., 7. Moisten a blue and a red litmus paper and drop them in a gas jar of CO2., Enter your observations in all the above activities in the following table., Physical properties of CO2, Test, Odour, Colour, , Observations, , Chemical properties of CO2, Test, Burning candle, Universal indicator, Limewater, Water, , Observations, , Litmus paper, Use your brain power! Is the density of CO2 more or less than that of air?, , 145

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Some more chemical properties of carbon dioxide, 1. Sodium carbonate is formed when carbon dioxide is passed through an aqueous solution, of sodium hydroxide (Sodium carbonate = washing soda), Chemical equation of the reaction 2NaOH + CO2® Na2CO3 + H2O, 2. Sodium bicarbonate is formed on passing CO2 through an aqueous solution of sodium, carbonate. (sodium bicarbonate = baking soda), Chemical equation of the reaction Na2CO3 + H2O + CO2 ® 2NaHCO3, a. Write down the equation of the chemical reaction taking place between water and, carbon dioxide in the above experiment., b. Write down the equation of the chemical reaction taking place on putting limewater, in the gas jar of CO2., Uses of carbon dioxide, 1. CO2 is used to make aerated drinks, 2. Solid carbon dioxide is used in cold storage and also to keep milk and milk products, and frozen substances cool during transport. It is also used for getting special effects of, a mist in dramas and movies., 3. CO2 obtained by chemical reaction or kept under pressure is used in fire extinguishers., 4. Liquified CO2 is used to remove caffeine from coffee., 5. Liquid CO2 is used as solvent in modern eco-friendly dry cleaning., 6. Plants use CO2 in air for photosynthesis., Regular fire extinguisher, A fire extinguisher contains sodium, bicarbonate powder. There is also dilute sulphuric, acid placed in a glass capsule. The capsule, breaks on pressing the knob, the sulphuric acid, comes in contact with the sodium bicarbonate, and the two react chemically to release CO2, The knob, which comes out., CO2 based fire extinguishers do not cause, Capsule, corrosion and are non conductors of electricity., Therefore these are used when electrical and, electronic equipment catches fire., Sulphuric, CO2 based fire extinguishers are used to, acid, extinguish small scale fire. It is beyond their, capacity to extinguish a big fire., In modern fire extinguishers liquid and solid, Powder of, sodium, CO2 is filled under pressure. On reducing the, bicarbonate, pressure it becomes gaseous and comes out, forcefully through the horn-like hose pipe., 13.12 Internal structure of fire extinguisher, , 2NaHCO3 + H2SO4® Na2SO4 + 2 H2O + 2 CO2, , ®, , Chemical reaction, , Nowadays, many types of fire extinguishers are used. Collect more information, about the way CO2 is used in them to extinguish a fire., , 146

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Methane – molecular formula CH4, molecular mass – 16, Occurrence, 1., 2., 3., 4., 5., , Methane occurs in natural gas to the extent of 87%., Decomposition of organic matter in the absence of air (anaerobic) produces methane., Methane is present in biogas., Methane is found in coal mines., Methane is found at the surface of marshy places which is why it is also called marsh, gas., 6. On heating a mixture of hydrogen and carbon monoxide gases at 300 0C in the presence, of nickel (catalyst) methane gas is formed., 7. Fractional distillation of natural gas gives methane in pure form., Physical properties of methane, 1. Melting point of methane is (-182.5 0C)., 2. Boling point of methane is (-161.5 0C)., 3. It is a colourless gas., 4. The density of liquid methane is less than that of water., 5. Methane is sparingly soluble in water. It is highly soluble in organic solvents like, gasoline, ether and alcohol., 6. Methane is in gaseous state at room temperature., Chemical properties of methane, 1. Methane is highly inflammable. It burns by reacting with oxygen to give a bluish flame., In this reaction, 213 kcal/mol of heat is given out. Methane burns completely., Chemical reaction CH4+2O2 ® CO2+ 2H2O + heat, 2. Chlorination, Methane and chlorine gases react with each other at the temperature of 250 0C to, 400 0C in presence of ultraviolet light and form mainly methyl chloride (chloromethane), and hydrogen chloride. This reaction is called chlorination of methane., Chemical reaction, , CH4+Cl2 Light, ® CH3Cl + HCl, , Uses of methane, 1. Methane in the form of natural gas is used in industries such as fabric mills, paper, mills, food processing industry, petrol purification., 2. Being the smallest hydrocarbon, the proportion of CO2 released in the combustion of, methane is small and, therefore, it is used as a domestic fuel., 3. Methane is used for production of organic compounds such as ethanol, methyl chloride,, methylene chloride and acetylene., Methane gas was discovered by the Italian scientist Alessandro Volta between 1776, and 1778 while he was studying the gases found in marshy land., , 147

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Using ICT, Prepare a detailed report on carbon. Use computer applications such as Notepad,, Word for this purpose and send the reports to others., Websites -https://www.boundless.com/chemistry/,www.rsc.org/learn-chemistry, Biogas plant : Animal dung, dry leaves, wet garbage get decomposed by anaerobic, microbes in a biogas plant. This produces methane gas also called biogas. Biogas is a very, cheap fuel option which meets the demand for cooking gas. It is also used for production, of an electricity. Biogas contains about 55% to 60% methane and the rest is carbon dioxide., Biogas is a fuel which is convenient to use and, in addition to this, a very good manure is, also produced as a side product of the process., Exit of gas, , Mixing tank, (Slurry of cattle dung), , Slab cover, , Overflow tank, , Spent slurry, Inlet chamber, Outlet chamber, Dung and, water mixture, , Underground, digester tank, 13.13 Biogas plant, , Biogas production process, Production of biogas is an anaerobic process. It takes place in two stages., 1. Production of acids, The microbes act on the biodegradable complex, organic compound and produce organic acids., 2. Methane gas production, The methanogenic bacteria act on the organic, acids to produce methane gas, , ®, , CH3COOH ® CH4 + CO2, , 148, , Find out, , Visit a biogas plant, and get to know the actual, functioning of the plant., Find out which electrical, instruments are run on that, plant.

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Exercises, 1. Select the proper option and complete, the statements, (single, all, double, ionic, carbon, give, and take, hydrogen, multiple, share,, most, covalent), a. A carbon atom forms a …… bond, with other atoms. In this bond the, two atoms ….electrons., b. All the carbon bonds in a saturated, hydrocarbon ....…. electrons., c. At least one carbon bond in an, unsaturated hydrocarbon is …., d. ….. is the essential element in all, the organic compounds., e. The element hydrogen is present in, ….. organic compound., 2. Answer the following questions, a. Why are carbon and its compounds, used as fuels?, b. In which compound forms does, carbon occur?, c. Write the uses of diamond., 3. Explain the difference:, a. Diamond and graphite., b. Crystalline and non-crystalline, forms of carbon., 4. Write scientific reasons, a. Graphite is a conductor of electricity., b. Graphite is not used in ornaments., c. Limewater turns milky when CO2, is passed through it., d. Biogas is an eco-friendly fuel., , 5. Explain the following., a. Diamond, graphite and fullerenes, are crystalline forms of carbon., b. Methane is called marsh gas., c. Petrol, diesel, coal are fossil fuels., d. Uses of various allotropes of carbon., e. Use of CO2 in fire extinguisher., f. Practical uses of CO2., 6. Write two physical properties each., a. Diamond, b. Charcoal, c. Fullerene, 7. Complete the following Chemical, reactions., 1. ........+.......® CO2 + 2H2O + Heat, , 2. ...........+.........® CH3Cl + HCl, 3. 2 NaOH + CO2®........+........, , 8. Write answers to the following in, detail., a. What are the different types of coal?, What are their uses?, b. How will you prove experimentally, that graphite is good conductor of, electricity?, c. Explain the properties of carbon., d. Classify carbon., 9. How will you verify the properties of, carbon dioxide?, Project, Make a model of a biogas plant and, make a presentation in the class about, the process of gas production., , ²²², , 149

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1. गतीचेinनियम, 14. Substances, Common Use, Ø, Ø, , Important salts in day to day life -NaCl, NaHCO3, Na2CO3 , Radioactive substances Ø Some chemical substances in day to day life, , 1. What are the important substances that we use in day to day, life? For what purposes do we use them?, Can you recall?, 2. How are the various substances in day to day use classified, from the scientific point of view?, We use various substances in day to day life. We have previously learnt in some, detail about a few of them, their uses and constituents and the method of their preparation., The names of some substances in everyday use are given, below., Classify them into groups like acids, bases, metals, nonClassify, -metals and salts., Substances :Table salt, soap, toothpaste, baking soda, water, curds, milk, alum, iron,, sulphur, washing powder., Important salts in daily life, Can you tell?, , What are salts?, , The ionic compounds which do not contain H+ and, OH- ions and contain only one kind of cation and anion, are called simple salts. For example, Na2SO4, K3PO4,, CaCl2., Inorganic substances occur naturally in the form of, salts rather than acids or bases. About 80 million tons of, salts are added every year to seawater. Therefore, the, sea is said to be a rich source of salts. In fact, the sea is, a rich source of several salts of various elements such as, chlorine, sodium, magnesium, potassium, calcium,, bromine., However, we also use other salts apart from, these in day to day life. Let us learn more about them., Salt, , Original, color (of, the, solution), , Try this, Prepare saturated, solutions of some salts, and put 2-3 drops of the, universal indicator in, them and note your, observations in the table, alongside., , Do you know?, The important salts found, in sea water, 1. Sodium chloride, 2. Magnesium chloride, 3. Magnesium sulphate, 4. Potassium chloride, 5. Calcium carbonate, 6. Magnesium bromide, , Color on, addition of, universal, indicator, , Table salt, Colorless Green, Soap, Washing soda, Baking soda, Baking, powder, POP, , 150, , pH, value, , Nature, , 7, , Neutral

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Can you tell?, , 1. What is the strip shown below? What is it used for?, 2. How is it determined whether a substance is acidic, basic or, neutral?, 3. Make a list of substances in day to day use in accordance, with their pH value (1 to 14)., , We have seen in the previous lesson that a salt is neutral when its pH value is 7. Such, a salt is made from a strong acid and a strong base. The pH value of a salt made from a, strong acid and a weak base is less than 7 and it is acidic. On the other hand, the pH value, of a salt made from a weak acid and strong base is more than 7 and it is basic. Let us now, learn about some salts of everyday use., Sodium chloride, Properties and uses, (Table salt- NaCl), 1. Common salt is a colourless and crystalline ionic, Table salt, or common, compound. There is no water of crystallization in its, salt, which gives a salty taste, crystalline structure., to food, is the most used of all, 2. It is a neutral salt, salty in taste., salts. Its chemical name is, 3. This compound is used for the production of salts, sodium chloride. Sodium, like Na2CO3, NaHCO3., chloride is formed by a, 4. When an electric current is passed through a saturated, neutralization, reaction, solution of sodium chloride (brine) it is electrolysed, between sodium hydroxide, and hydrogen gas is released at the cathode while, and hydrochloric acid., chlorine gas is released at the anode. This method, We have already seen that, is used for production of chlorine gas. In this method, this is a neutral salt and that, an important basic compound NaOH is formed in, the pH value of its aqueous, the cell., solution is 7., , Do you know?, , ®, , ®, , 2NaCl + 2H2O ® 2NaOH + Cl2 + H2, , 5. When salt is heated to a high temperature (about, 800 0C), it melts. This is called the fused state of the, salt., 6. When fused salt is electrolysed, chlorine gas is, released at the anode and liquid sodium metal, at the, cathode., Salt is also obtained from a certain type of rock. This, salt is called rock salt. The mineral halite and Himalayan, rock salt are some examples of rock salt. This salt is used, to treat many diseases., , 1, , The 25% aqueous solution of salt is called saturated brine. When, of this solution, 5, is evaporated the dissolved salt gets crystallized and salt gets separated from the, solution., , 151

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Sodium bicarbonate (Baking soda –, NaHCO3), Your mother brings cake on your, birthday or makes it at home. She also, makes crisp bhaji. Have you ever asked, your mother what makes the cake porous, or the bhaji crisp?, Mother adds baking soda in the, batter. Baking soda is a white noncrystalline powder. Its chemical name is, sodium hydrogen carbonate or sodium, bicarbonate and its molecular formula is, NaHCO3., Research, , Properties and uses, 1. NaHCO3 reacts with moist litmus paper, and red litmus turns blue which means, that it is basic in nature., 2. It is used to make bread, cake, dhokla., 3. Being basic in nature it is used to reduce, acidity in the stomach., 4. NaHCO3 is used to make the active, substance CO2 in the fire extinguisher., 5. Baking soda is used to clean an oven., , What are the constituents of baking powder? Where is the, baking powder used?, , Bleaching powder (Calcium oxychloride CaOCl2), Try this, , Take a piece of coloured cloth. Put some saturated solution of, bleaching powder on a small part and observe., What change takes place in the colour of the cloth?, , CaOCl2 + CO2 ® CaCO3 + Cl2­­­­­­­­­­­­­, , ®, , Tap water has a typical strong odour in the rainy season. Have you experienced it?, Water in a swimming pool also has the same odour. It is the odour of the chlorine gas, used to destroy the microbes in the water. Chlorine gas is a strong oxidizing agent and, therefore, it has a strong disinfecting as well as bleaching action., Chlorine is inconvenient to handle because of its gaseous state. Instead, the solid, bleaching powder which has the same effect is more convenient to use. Bleaching powder, undergoes slow decomposition due to the carbon dioxide in air and chlorine gas is released., Bleaching powder gets its property because of this release of chlorine gas., , Bleaching powder is obtained by the, reaction of chlorine gas with slaked lime., , Ca(OH)2 + Cl2 ® CaOCl2 + H2O, , Find out, , 1. About various types of bleaching powder available in the market., 2. What distinguishes these different types?, , 152

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Properties and uses, 1. Bleaching powder is a yellowish white coloured solid substance., 2. Its chemical name is calcium oxychloride., 3. It has a strong odour of chlorine gas., 4. It is used for disinfection of drinking water at the water works and the water in the, swimming pool., 5. It is used for bleaching of cloth., 6. It is used for disinfection by the road side and garbage sites., 7. Dilute sulphuric acid and dilute hydrochloric acid react rapidly with bleaching, powder to release chlorine gas completely., CaOCl2 + H2SO4, CaSO4 + Cl2 + H2O, 8. Calcium oxychloride reacts slowly with carbon dioxide to form calcium carbonate, and chlorine., Washing soda Na2CO3.H2O, Procedure : Take a sample of water from a well or a bore-well, in, a beaker, add some soap to it and stir. Then take another sample, add, Try this one spoonful of washing soda and stir; then add some soap and stir, again. Observe the changes that take place. Which changes did occur?, Why do they occur?, The hard water from a well or a bore-well becomes soft on adding washing soda, and we come to know this from the lather formed on it. The hardness of water is due to the, presence of chlorides and sulphates of calcium and magnesium in it. Na2CO3 is added to, it to soften such water and make it suitable for use. The reaction with Na2CO3 causes the, formation of insoluble carbonate salts of magnesium and calcium., , MgCl2 (aq)+ Na2CO3 (s) ® MgCO3(s) + 2 NaCl (s), Sodium carbonate is a water soluble salt of sodium. Crystalline sodium carbonate,on, keeping, loses its water of crystallization readily and a white powder is obtained. This, powder is called washing soda., , - H2O, Na2CO3 .10 H2O ® Na2CO3 .H2O, , white powder (washing soda), , Properties and uses, 1. Washing soda is a whitish and odourless powder at room temperature., 2. Litmus has a blue color in its aqueous solution., 3. It is hygroscopic, that is, it absorbs moisture if left exposed to air., 4. It is used mainly for washing clothes., 5. Sodium carbonate is used in the glass and paper industry and also in refining of, petrol., Write down the reaction of Na2CO3, with H2SO4, , 153

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Some crystalline salts, You have learnt about water of crystallization in the previous chapter. We use various, salts which contain water of crystallization., Some substances in our daily use which contain water of crystallization, 1. Alum (Potash alum - K2SO4.Al2(SO4)3 .24H2O ), 2. Borax (Na2B4O7.10H2O), 3. Epsom salt (Magnesium sulphate MgSO4.7H2O), 4. Barium chloride (BaCl2.2H2O), 5. Sodium sulphate (Glauber’s salt Na2SO4.10 H2O), Collect more information on the properties and uses of the substances listed above., You have learnt that alum is used in the process of water purification. Because of, property of coagulation, the solid impurities in water come together, become heavy and, settle to the bottom. As a result, the water above becomes clear., Blue vitriol is used in the blood test for diagnosing anaemia. In the Bordeaux mixture, which is used as a fungicide on fruits like grapes, musk melon, slaked lime it is used with, blue vitriol., Soap, 1. What are detergents?, 2. Which chemicals and apparatus will you use in the, Can you recall?, laboratory for making soap?, When oil or animal fat is boiled with an aqueous solution of sodium or potassium, hydroxide, sodium or potassium salts of carboxylic acids (fatty acids) are formed. These, salts are called soap. When soap is mixed with hard water calcium and magnesium salts, of fatty acids are formed. These being water insoluble they form a precipitate and that is, why lather is not formed., Complete the table by writing the differences between bathing soap and washing, soap, Bathing soap, , Washing soap, , 1. High grade fats and oils are used as the 1., raw material, , 2., , Low grade fats and oils are used, , 2., , Radioactive substances, Elements with a high atomic number such as uranium, thorium, radium have a property, of spontaneously emitting invisible, highly penetrating and high energy radiation. This, property is called radioactivity. A substance having this property is called a radioactive, substance. The nucleus of radioactive elements is unstable. Radiation occurs from an, unstable nucleus. Radioactive substances are relevant to our day to day life. However,, before going further, let us learn something more about these substances., Three types of radiation are given out by radioactive substances. These are alpha,, beta and gamma rays., , 154

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An introduction to scientists, The French scientist Henry, Becquerel was studying pitchblende, a compound of uranium., He had kept some unused, photographic plates in a, cardboard box in a drawer. A, key was lying on the box. He, happened to leave the uranium, compounds on it. After a few, days, he washed the plates only, to find that the plates were, cloudy and showed the shape of, the key. As this incidence, occurred in the dark, Becquerel, inferred that the uranium, compounds might be emitting, from their interiors, rays like, x-rays, which, penetrate, substances. These rays were, called Becquerel rays. After a, few days, Madame Curie, discovered similar properties in, compounds of thorium., , Nature of radioactive radiation, In 1889 Rutherford discovered that the, radiations emitted by radium were of two types., They are called alpha and beta radiation. Willard, discovered the third type namely gamma radiation., When these rays are allowed to pass through, two oppositely charged plates they get separated., This method was introduced by Rutherford in, 1902. Rutherford and Willard studied the radiation, emitted by radioactive substances. For this purpose,, the rays were allowed to pass through an electrical, field and a photographic plate was held in their, path. It was found that the radiation was divided, into three types. One type of radiation deviated, slightly towards the negatively charged plate,, while the second type of radiation deviated, substantially towards the positively charged plate., However, the third type of radiation did not deviate, at all in the electrical field. The rays which deviated, slightly toward negatively charged plate are called, alpha rays, those which deviate substantially, towards the positively charged plate are called, beta rays and those which do not deviate at all are, called gamma rays., , Lead block, , b rays, g rays, , Radioactive substance, , Slit, , Electrically, charged plates, , a rays, a किरण, ZnS पडदा, , ZnS coated, photographic plate, , 14.1 Alpha, beta and gamma rays, , An introduction to scientists : Ernest Rutherford (1871-1937),, a scientist from New Zealand did research on radioactivity under, the guidance of J.J. Thomson at the Cavendish Laboratory at, Cambridge and McGill University, Canada. He showed that the, nitrogen atom could be split by bombarding it with alpha particles., This experiment ushered in a new era in the field of Physics., , 155

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Characteristics of alpha, beta and gamma rays, Sr. Property, No., , Alpha rays (a), , 1. Nature, , Current of alpha (He++) Current of beta (e-), particles, particles, , 2. Mass, 3. Charge, 4. Velocity, 5. Deviation in, 6., , the electric, field, Penetrating, power, , 7. Ionization, , 8., , power, Power to, produce, fluorescence, , Beta rays (b), , Gamma rays (g), , Electromagnetic, radiation, No mass, 4.0028 u, 0.000548 u, Electrically neutral, +2, -1, 1/5 to 1/20 times the 1/5 to 9/10 times the Same as the velocity, velocity of light, velocity of light, of light, Attracted toward, Attracted toward, Not deviated, negatively charged, positively charged, plate, plate, Can penetrate an Can penetrate an, Can penetrate 15, aluminum sheet of aluminium sheet of, cm thick lead, thickness < 0.02 mm thickness 2mm,, screen which is, which is 100 times, 10,000 times the, the penetration of, penetration of alpha, alpha particles., particles, Very high, Low, Very low, Very high, , Very low, , Low, , Uses of radioactive isotopes : It is a misconception that radioactive elements are used, only for making an atom bomb. Radioactive isotopes are used in various fields such as, scientific research, agriculture, industry, medicine, etc. Radioactive substances are used in, two ways., a. By using the radiation alone., b. By using the radioactive element itself., Natural radioactivity : Generally, the, elements with atomic numbers from 82 to 92, are found to radiate spontaneously in nature., These are called natural radioactive elements., Artificial radioactive elements – The couple, Fredric Joliot Curie and Irene Joliot Curie, first invented induced radioactivity. The, radioactive elements produced in the nuclear, fission processes brought about in the, laboratory by bombardment of particles are, called artificial radioactive elements. They were awarded the Nobel prize in 1935 for, this invention., , 156

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Radioactive isotopes are used in various fields as follows, , 1. Industrial field, Radiography – Internal cracks and voids in cast iron articles and iron solder can be detected, with the help of gramma rays. For this purpose, isotopes like cobalt-60, iridium-192 are used in, the radiography camera. This technique is used for detecting flaws in metal work., Measurement of thickness, density and level- It is necessary to maintain the required thickness, in the manufacture of aluminium, plastic, iron sheets of differing thickness. In the manufacturing, process, a radioactive substance is placed on one side and an instrument to measure radiation, on the other. The radiation read by the measuring instrument varies with the thickness of the, sheet. Material inside a packing can also be examined by the same technique., Luminescent paint and radioluminescence – The radioactive substances radium, promethium,, tritium with some phosphor are used to make certain objects visible in the dark, for example,, the hands of a clock, and certain other objects. Krypton-85 is used in HID (High Intensity, Discharge) lamps while promethium-147 is used in portable X-ray units as the source of beta, rays., Use in Ceramic articles – Luminous colours are used to decorate ceramic tiles, utensils, plates,, etc. Earlier uranium oxide was used in these paints., , 2. Field of agriculture, 1. The genes and chromosomes that give seeds properties like fast growth, higher productivity,, etc. can be modified by means of radiation., 2. The radioactive isotope cobalt-60 is used for food preservation., 3. Onions, potatoes are irradiated with gamma rays from cobalt-60 to prevent their sprouting., 4. Strontium-90 is used as a tracer in the research on various crops., , Medical science, 1. Polycythemia : The red blood cell count increases in the disease polycythemia. Phosphorus32 is used in its treatment., 2. Bone cancer : Strontium-89, strontium-90, samarium-153 and radium-223 are used in the, treatment of bone cancer., 3. Hyperthyroidism : Enlargement of thyroid gland, weight loss in spite of appetite, insomnia, are the symptoms of hyperthyroidism. It occurs due to overproduction of hormones by the, thyroid gland. Iodine-123 is used in the treatment of hyperthyroidism ., 4. Tumour detection : Boron-10, iodine-131, cobalt-60 are used in treatment of brain tumour,, while arsenic-74 is used in detection of small tumours in the body., , 1., 2., 3., 4., 5., 6., 7., , Hazards of radioactive substances and radiation, The central nervous system is affected by radioactive radiations., Hereditary defects are generated by bombardment of radiation on D.N.A in the body., Radioactive radiation can penetrate the skin, and causes diseases like skin cancer,, leukemia., The radiative pollutants created due to explosions enter the body through air and it is, difficult to control them., The radioactive pollutants released in the sea enter the bodies of fishes and through, them enter the human body., The radioactive paint on the watch can cause cancer., The radioactive isotopes strontium-90 can enter the body through plants, fruits,, flowers, cereals, milk, etc. and cause diseases like bone cancer, leukemia., , 157

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A peep into the past, Chernobyl disaster : On 26th April 1986 the graphite reactor in the Chernobyl atomic power, plant exploded, and suddenly the radioactive isotopes and radiation came out. Due to this, episode radioactive isotopes entered the human body through water and land and caused, genetic disorders. These got carried further into the next generation. Thyroid disorders, increased in children as well as adults. As a result, the incidence of throat diseases is greater, there than in other places., , Some chemical substances in day to day life., The food that we eat, objects like clothes, utensils, watches, medicines and other, objects are made from various kinds of matter. These affect our health directly or indirectly., Let us learn about some such substances., 1. A sweets shop looks attractive because of the colorful sweets, displayed there. Which colours are used in these substances?, Can you tell?, 2. A doctor gives you medicines when you fall ill. What are the, medicines made from?, Food colours and essences, Food colours are mixed in most soft drinks, and foodstuffs available in the market. These food, colours are in the form of powders, gels and pastes., Food colours are used in domestic as well as, commercial products. Certain colours and essences, are added to ice cream, ice candies, sauce, fruit, juices, cold drinks, pickles, jams and jelly. Food, colors are often found to be added to packaged, meat (chicken, mutton), chilli powder, turmeric,, sweets and other similar substances so as to give, 14.2 Colourful eatables, them a good colour., Harmful effects of artificial food colours, 1. Food colours added to pickles, jam and sauce contain small quantities of lead and, mercury. These can be harmful for those who consume these products on a regular, basis., 2. Diseases like ADHD (Attention Deficit Hyperactivity Disorder) can affect children, due to excessive consumption of foods with added food colours., , Always remember, Food colours are natural as well as artificial. The food colours prepared from, seeds, beetroot, flowers and fruit concentrate are natural. Tetrazene, sunset yellow, are artificial food colours used extensively. However, over-consumption of artificial, food colours can be detrimental to health. Therefore, usage of natural food colours, is always good., , 158

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Dye, The coloured substance which on applying, to an article, imparts that colour to the article,, is called a dye. Generally, a dye is soluble in, water and insoluble in oil. Often a mordant has, to be used to fix the colour after dying a cloth., Plants are the main source of colour for, preparing a natural dye. Roots, leaves, flowers,, bark, fruits, seeds, fungus and pistil are used, for making dyes. In Kashmir a very good dye is, made from saffron, which is used to dye fibres, from which saris, shawls and dresses are made., These are very costly. Many people are engaged, in this occupation as their means of earning a, livelihood.The use of henna leaves to colour, hair is safe for health., William Henry Perkin invented an, artificial dye in 1856. Artificial dyes are, classified into many types on the basis of, chemical properties and solubility. Petroleum, products and minerals are used in these dyes., Artificial colours, Can you tell?, , 1. What problems do you get after playing colours on Rang, Panchami? Why?, 2. Which colors will you use to prevent the occurence of these, problems?, 3. What problem do you have on painting the house and furniture?, , We regularly use artificial colours, on Rang Panchami, decorating the, housd by painting. The red color use, on Rang Panchami is very dangerous., It contains a high proportion of mercury, in it. This poses risks like blindness,, skin cancer, asthma, itching of the, skin, permanent blocking of sweat, pores etc. Therefore, it is necessary, that artificial colours are used, cautiously., Find out, , Try this, , Uses, 1. They are used for colouring cloth, and hair., 2. Fluorescent colours are used to, make street boards that are visible, at night., 3. Dyes are used to polish leather, shoes, purses and chappals., Adverse effects, 1. Dyeing hair can have adverse, effects like hair fall, damage to hair, texture, burning of skin, adverse, effect on eyes, etc., 2. Lipstick contains a dye named, carmine. It does not affect lips but, causes stomach disorders., 3. Excessive use of plants for making, natural dyes results in deterioration, of the environment., , 14.3 Harmful effects of artificial colours, , Find out the hazardous chemicals present in the artificial, colours and their harmful effects., Prepare colours for Rang Panchami from natural resources, such as beet root, flowers of flame of forest, spinach, flame tree, (gulmohar) and protect your health by using these., , 159

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Deodorant, Body odour is caused by the bacterial decomposition of the sweat. A deodorant is used to, prevent this odour. Everybody likes a fragrant deodorant to remain fresh the whole day., School children use deo on a large scale. This large scale use of deo in adolescent is a, result of the advertisements shown on television. Deodorants contain parabens (methyl,, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions. Aluminium, compounds and silica are also used., 1. Ordinary deo – It contains a smaller proportion of aluminium. It decreases the odour, of the sweat., 2. Antiperspirant deo – This decreases the extent of sweating. It contains about 15% of, aluminium chlorohydrate. It clogs the sweat pores on the skin., 3. Clinical deo – Some people sweat heavily and it has harmful effects on the skin. Clinical, deo is meant for such people. It contain 20 to 25% aluminium. It is used during the night., Harmful effects, 1. Aluminium – Zirconium compounds are the most harmful chemicals in the deodorant., Disorders like headache, asthma, respiratory disorders, heart disease are likely to occur, without our knowledge., 2. There is a possibility of various skin disorders and also skin cancer due to the aluminium, chlorohydrates., Teflon, Teflon is used for coating cooking utensils and, industrial equipment to avoid sticking. It is the, polymer of tetrafluoroethylene. Roy J. Plunkett, discovered it in 1938. Its chemical name is, polytetrafluoroethene (C2F4)n ., 14.4 Teflon coating, , Can you tell?, , What is the property of Teflon because of which it is used in, nonstick ware ?, , Properties, 1. The atmosphere and chemical, substances have no effect on, Teflon., 2. Neither water nor oil will stick, to Teflon coated articles., 3. High temperatures do not affect, Teflon as its melting point is, 327 0C., 4. Teflon coated articles are easy, to clean., , Uses, 1. Teflon is a poor conductor of electricity., Therefore, Teflon cladded wires and parts, are used in high technology electronics, instruments., 2. It is used for making non-stick kitchenware., 3. The colored metal sheets of two-wheelers, and four-wheelers are given a Teflon, coating to protect them from damage due, to high temperature and rain., , 160

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Powder coating : Powder coating is a method of applying a layer harder than paint on, the surface of an iron object to prevent rusting. In this method, a polymer resin, a pigment, and some other ingredients are melt mixed, cooled and ground into a uniform powder., This powder is sprayed on the polished metal surface by electrostatic spray deposition, (ESD). In this method, the particles of the powder are given an electrostatic charge due to, which a uniform layer of the powder sticks to the metal surface. Then the object is heated, in the over along with the coating. A chemical reaction occurs in the layer, resulting in the, formation of long cross-linked polymeric chains. This powder coating is highly durable,, hard and attractive. Powder coating can be done on plastic and medium density fibre, (MDF) board in day to day use as well., Anodizing : A protective layer is formed naturally on the surface of aluminium metal by, reaction with oxygen in air. In the anodizing process, this layer can be made of the desired, thickness. Anodizing is done by electrolysis. Dilute acid is taken in the electrolytic cell and, the aluminium article is dipped in it as the anode. When an electric current is passed, hydrogen gas is released at the cathode and oxygen gas at the anode. A reaction with, oxygen occurs and a layer of hydrated aluminium oxide is formed on the anode, i.e. the, iron article..This layer can be made attractive by adding colour in the cell during electrolysis., We use anodized cooking utensils like griddles and cookers. Why?, Ceramic : Ceramic is a heat resistant substance formed by kneading an, inorganic substance in water and then shaping it and hardening it by, heating. Pots made by a potter, Mangalore roofing tiles , construction, bricks, pottery, terracotta articles are some examples of common ceramic, articles that we see around., This is how a ceramic article is made, When clay is kneaded in water, shaped, and then fired in a kiln at a temperature of, 1000 to 11500C , a porous ceramic is formed., To overcome the porosity the fired object is, covered with finely ground glass powder, suspended in water (glaze) and is then fired, again. As a result, the surface of the ceramic, becomes shiny and its porosity disappears, , 14.5 Ceramics, , Porcelain : This is a hard, translucent and white coloured ceramic. It is made by using the, white clay called kaolin, found in China. Glass, granite and the mineral feldspar is mixed, with kaolin and kneaded with water. The resulting mixture is shaped and fired in a kiln, at a temperature of 1200 to 1450 0C. On firing again after glazing, beautiful articles of, porcelain are obtained. Which porcelain vessels are used in the laboratory?, Bone china – Bone china is made by adding some ash of animal bones in the mixture of china, clay, feldspar and fine silica while making porcelain. This ceramic is harder than porcelain., Advanced ceramics : Oxides like Alumina (Al2O3), Zirconia (ZrO2) Silica (SiO2) and, some other compounds like silicon carbide (SiC), boron carbide (B4C) are used instead, of clay for making advanced ceramic. This ceramic requires a temperature of 1600 to, 1800 0C and an oxygen free atmosphere for firing. This process is called sintering., , 161

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Ceramics can withstand high temperatures without decomposing. Ceramic is brittle,, water resistant and an electrical insulator. Therefore, it is used in electrical instruments,, for coating the interior of a kiln, the outer surfaces of ships and blades of jet engines. A, certain type of ceramic tiles are fixed on the outer layer of a space shuttle. Some types, of ceramics are used as superconductors., , Exercises, 1. Fill in the blanks., a. The number of molecules of water, of crystallization in washing soda is, ….., b. The chemical name of baking soda, is …., c. ….. is used in treatment of, hyperthyroidism., d. The chemical name of Teflon is …., 2. Match the pairs, Group A, Group B, 1. Saturated brine a. sodium metal freed, 2. Fused salt, b. basic salt, 3. CaOCl2 , c. crystallization of salt, 4. NaHCO3, d. oxidation of colour, , 3. Write answers to the following, a. What is meant by radioactivity?, b. When is said to be the nucleus, unstable?, c. Which diseases are caused by, artificial food colours ?, d. Where in the industrial field is, radioactivity used?, e. Write down properties of teflon., f. What type of colours will you use to, celebrate, ecofriendly, Rang, Panchami? Why?, g. Why has the use of methods like, Teflon coating become more, common?, 4. Give scientific explanation, a. Bleaching powder has the odour of, chlorine., b. The hard water of a well becomes, soft on adding washing soda to it., c. Soap forms a precipitate in hard, water., d. The particles of powder are given an, electric charge while spraying them, to form the powder coating., , 162, , e. The aluminium article is used as an, anode in the anodising process., f. When the radiation coming out from, certain radioactive substance is passed, through an electric field, marks are, found at three places on the, photographic plate placed in its path., g A certain type of ceramic tiles are, fixed on the outer layer of a space, shuttle., 5. Write answers to the following, a. Write about artificial food colours,, the substances used in them and, their harmful effects., b. What is meant by water of, crystallization? Give examples of, salts with water of crystallization,, and their uses., c. Write briefly about the three methods, of electrolysis of sodium chloride., 6. Write the uses., a. Anodizing b. Powder coating, c. Radioactive substances d. Ceramic, , 7. Write the harmful effects, , a. Artificial dye b. Artificial food colour, c. Radioactive substances d. Deodorant, , 8. Write the chemical formula, , Bleaching powder, common, baking soda, washing soda, , salt,, , 9. Explain what you see in the following, picture, , Project : Visit the places where powder, coating, Teflon coating is done. Get, information about the process and, present it in the class., , ²²²

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15. Life Processes, Living Organisms, 1. गतीचेinनियम, Ø, Ø, , Transportation in Plants Ø Excretion: Plants, Animals and Humans., Co-ordination: Plants and Humans, , Can you recall? How do the digestive system and respiratory system work?, We have studied how digested food or oxygen inhaled by lungs is transported to, every cell of the human body. The farmer also tries to transport the water from wells or, dams through a main channel to every plant. The food absorbed by the digestive system is, converted into energy. This energy and oxygen are both transported via blood throughout, the body., Transportation, By the process of transportation, a substance either synthesised or absorbed in one, part of the body reaches another., Transportation in plants, Discuss, , 1. Why do we eat fruits and vegetables? Do the plants also need, minerals like we do?, 2. From where do the plants get inorganic substances other than, carbon dioxide and oxygen?, , Most animals move from place to place but plants do, not. There are many dead cells in the plant body. They, need less energy as compared to animals. Plants need, inorganic substances like nitrogen, phosphorus, magnesium,, manganese, sodium, etc. Soil is the nearest and richest, source of these substances. Roots of plants absorb these, substances from the soil and transport them. There are, specific types of tissues to perform this function. The xylem, conducts the water whereas the phloem conducts the food., All parts of the plant are connected with these conducting, tissues., Transportation of water in plants :, , Use your brain power !, , Which types of plant, tissues are xylem and, phloem?, , Veins, (turned red), Stem, , Try this, , Stand, , Root pressure, Take a small plant like balsam or tuberose with its, roots intact. Wash and clean its roots. As shown in the, fig. 15.1, keep it in the water containing a stain like, safranin or eosin. Observe the stem and the veins of the, leaves after 2 – 3 hours., , 163, , Beaker, Eosin, solution, 15.1 Root pressure

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Observe, , Take a transverse section of the stem of a plant and observe the, stained xylem under a compound microscope., Xylem, Cortex, , Soil particles, , Roots, , Root hairs, , Water, 15.2 Absorption with the help of roots, , Root cells are in contact with water and minerals in the soil. Water and minerals enter, the cells on the root surface due to differences in concentration. As a result, these cells, become turgid. These turgid cells exert pressure on the adjacent cells. This is called ‘root, pressure’. Under the effect of this pressure, water and minerals reach the xylem of the, roots and to reduce this difference in concentration they are continuously pushed forward., As a result of this continuous movement, a water column is formed, which is continuously, pushed ahead. This pressure is sufficient to lift the water up in shrubs, small plants and, small trees., Transpiration pull, Previously you have performed the activity of observing a, Can you recall? branch covered in a plastic bag. What did you observe in that, activity?, Water, , Thin layer, , Leaf, , Sugar, Tissue, , Minerals, , Water, , Guard, cells, , Stomatal, opening, , Water, , 15.3 Transpiration through Leaves, , Plants give out water in the form of vapour through the stomata on their leaves. Two, cells called guard cells are present around the stomata. These cells control the opening, and closing of stomata. Transpiration occurs through these stomata. Water is released into, the atmosphere by leaves through the process of evaporation. As a result, water level in, the epidermal layer of the leaf decreases. Water is brought up to the leaves through the, xylem so as to compensate for the lost water. Transpiration helps in absorption of water, and minerals and distribution to all parts of the plant whereas root pressure performs the, important role of pushing the water up during the night time., , 164

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Do you know?, The oak tree releases about 1,51,000 litres, of water into the air by the process of transpiration, in one year whereas a maize crop in an area of, one acre gives out about 11,400 to 15,100 litres, of water per day., Transportation of food and other substances in plants :, The food produced in leaves is transported to each cell in the plant body. Excess food,, except amino acids, is stored in roots, fruits and seeds. This process is called ‘translocation’, of materials. It is carried out in both the upward and the downward directions by the, phloem. Translocation of materials is not a simple physical process; it requires energy., This energy is obtained from ATP., Whenever food material like sucrose is transported towards a part of a plant via the, phloem with the help of ATP, the water concentration decreases in that part. As a result,, water enters the cell by the process of diffusion. The pressure on the cell wall increases due, to the increase in cellular contents. Due to the increased pressure, food is pushed into the, neighbouring cells where the pressure is low. This process helps the phloem to transport, the materials as per the need of the plant. During flowering season, the sugar stored in, roots or stem is transported towards the floral buds to make them open and blossom., Excretion, At least a small quantity of garbage or waste is produced, Think about it every day in each house. What will happen if you keep this, garbage for many days in your house?, Many harmful and waste substances like, urea, uric acid, ammonia, etc. are produced in, living organisms. If these substances accumulate, in the body or are retained in the body for long, it, can lead to serious harm or even death. Hence, it is, necessary to remove such harmful and waste, substances from the body. Different organisms, have different methods of doing this. Removal of, waste or harmful substances from the body is, called excretion. In unicellular organisms, waste, materials are directly eliminated across the cell, surface whereas the process of excretion in, multicellular organisms is complex., , 165, , Always remember, Retention of unwanted, and harmful substances in the, body is dangerous. Hence, just, as the process of excretion, occurs in living organisms,, similarly, proper disposal of, the garbage produced in our, locality and home is also, necessary. This will help you, lead a healthy life.

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Excretion in plants, Can you tell?, , Why does this happen?, , 1. Leaves of plants fall off in a particular season., 2. Fruits, flowers fall off after a certain period of time., 3. Substances like resin, gum, etc. are given out of the plant, body., Excretion is a simpler process in plants than in animals., There is no special organ or system for excretion in plants., Gaseous substances are given out by diffusion. Most of the waste, substances of plants are stored in vacuoles of leaf-cells and in, flowers, fruits and the bark of the stem. After some time these, parts fall off. Some other waste materials are stored in old and, worn xylem in the form of resin and gum. Some waste materials, are also given out through roots into the surrounding soil., , 15.4 Leaf fall, , Observe and find out., Observe your mother while she cuts elephant’s foot, (Amorphophallus) or arum leaves. Your hands may also begin, to itch if you try to cut those leaves. Why does this happen?, Try to find out. Ask your mother what she does to prevent the, itching., In some plants, waste materials are present in the form of, crystals of calcium oxalate. They are called raphides. As they, are needle-shaped, they prickle and cause irritation of the, skin., Some waste materials of plants are useful to humans, for, example, gum, resin, latex of rubber, etc., 15.5 Gum and latex, Excretion in human beings, 1. Which waste materials are produced in our body through, metabolic activities?, Can you tell?, 2. How does the process of excretion take place in humans?, , There are different organ systems in the human body to bring about the different life, processes, such as the digestive system for digestion of food, respiratory system for, respiration, etc. The process of digestion leading to energy production is an important, process of our body. Various waste materials are formed during this process. Removal of, these wastes from the body is very important and it is the excretory system that carries out, this function., The human excretory system consists of a pair of kidneys, a pair of ureters, the urinary, bladder and the urethra. Urine is formed by the kidneys by separating the waste and, unwanted excess substances from the blood., , 166

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Inferior vena, cava, , Renal capsule, , Adrenal gland, Renal artery, , Renal pelvis, , Cortex, , Renal pyramid, , Renal vein, Kidney, , Medulla, Cortex, , Renal artery, Abdominal, aorta, , Renal vein, , Ureter, Bladder, , मूत्राशय, , Ureter, , Urethra, , Renal calyx, , 15.6 Excretory system and kidneys, , The two bean-shaped kidneys are situated one on either side of the vertebral column,, on the posterior side of abdomen. The functional unit of the kidney that performs the basic, function of filtration is called a nephron. Each nephron has a cup-like, thin-walled upper, part called the Bowman’s capsule. The network of capillaries in it is called a glomerulus., The urea produced in the liver comes into the blood. When the urea-containing blood, comes into the glomerulus, it is filtered through its capillaries and urea and other similar, substances are separated from it., Water molecules and small molecules, Distal, of, some, other substances can cross the, Bowman’s, convoluted, capsule, tubule, semipermeable membrane of Bowman’s, Proximal, convoluted, capsule. The solution accumulated in the, Glomerulus, tubule, cavity of Bowman’s capsule passes into, the tubular part of the nephron. Here,, molecules of water and some other useful, substances are reabsorbed into the blood., Cortex, Urine is formed from the remaining solution, which is full of waste materials. The urine, is carried by the ureters and stored in the, Medulla, urinary bladder. Afterwards, urine is given, Colout through the urethra. The urinary bladder, Loop of, lecting, Henle, duct, is muscular and it is under the control of, nerves. Hence, we are able to keep a control, to ureter, on urination. Though the kidneys are the, Kidney, main organs of excretion in human beings,, the skin and lungs also help in the process, 15.7 Nephron, of excretion., The right kidney is in a slightly lower position than the left. Each kidney has, approximately 10 lakh nephrons. The approximately 5 litre of blood which is present in a, normal healthy person’s body is filtered by the kidneys about 400 times every day. Thus,, every day, the kidneys filter about 190 litres of blood from which about 1 to 1.9 litres of, urine is formed. The remaining liquid is reabsorbed., , 167

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Dialysis, , Vein, , Arterial pressure, monitor, Blood pump, , Artery, , Used dialysate, , Blood, flow, diverted, towards, dialysis, Dialysis, machine, , Air trap, , Dialysis machine, , Fresh Compressed, dialysate, air, , 15.8 Dialysis of blood, , The efficiency of kidneys can be adversely affected by injury, infection or decreased, blood supply. In case this happens, an excess of toxic substances accumulates in the body, and it can lead to death. If kidneys fail, nitrogenous wastes are separated from the blood, with the help of a man-made machine. The process of separating the nitrogenous waste, from blood with the help of this machine is called dialysis. About 500 ml of blood is sent, at one time through this machine. Purified blood is reinfused into the body of the patient., 1. As compared to the monsoons and winter a very small, quantity of urine is produced in the summer season., Use your brain power !, Why is it so?, 2. In adults, the process of urination is under their control, but not in infants. Why is it so?, Co-ordination, Think about it, , 1. Sometimes, while eating we bite our own finger or, tongue by mistake., 2. Sometimes, we choke while eating in a hurry., , Several different organ systems function in multicellular organisms. Their life goes on, smoothly if there is co-ordination between the different organ systems or organs and the, stimuli in the surrounding. Depending upon this, we can say that systematic regulation of, different processes can be called control and bringing about the different processes in the, proper sequence can be called co-ordination., If any activity in the body is to be completed successfully, proper co-ordination, between different systems and organs participating at different steps of that activity is, necessary. If due to lack of co-ordination or some other factor, there is confusion at any, step the activity may not get completed. There should not be any randomness at any step., There needs to be proper co-ordination between internal activities of the body resulting, from various factors like body temperature, water-level, enzyme-level, etc. or stimuli, arising in the surrounding environment. Proper co-ordination between various systems of, an organism helps to maintain a state of equilibrium called ‘homeostasis’ which is, necessary for the optimal efficiency of the body., , 168

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Co-ordination in plants, Plant do not have systems like the nervous system or muscular system of animals., Then, how do plants bring about movements? In plants, movements are mainly in the form, of responses given to the stimuli., , Observe, , Observe the following figures carefully., Sun, , Pollen grains, Tendrils, Pollen tube, Plantlet bent, towards the sun, , Ovule, Ovary, , Pollen tube growing, towards the ovule, , Phototropic response, 15.9 Co-ordination in plants, , Thigmotropic, response, , Movement or growth of any part of the plant, in response to an external stimulus is called, ‘tropism’ or ‘tropic movement’., , Do you know?, *, , The shoot system of any plant responds to the, light stimulus i.e. it grows towards the source of, light. The movement shown by plants towards the, source of light is called ‘Phototropic movement’., , Tendrils of climbers are, sensitive to touch., , *, , The root system of plants responds to stimuli, like gravitation and water. These responses are, called ‘gravitropic movement’ and ‘hydrotropic, movement’ respectively., , A hormone called auxin, produced in the apical part, of the shoot helps in, enlargement of cells., , *, , Movement shown by plants in response to, specific chemicals is called ‘chemotropic, movement’. For exmaple, the growth of the pollen, tube towards the ovule., , Hormones like gibberellins, help in stem elongation and, cytokinins help in cell, division., , *, , The hormone, abscisic, acid, is effective in, prevention and retardation, of growth, leaf wilting, etc., , All the above-mentioned movements of plants, are related with growth; hence all such movements, are collectively called ‘growth relevant movements’., , 169

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Observe, , Touch-me-not, , Observe the pictures carefully and think about them., , Lotus, , Venus fly trap, , Balsam, , 15.10 Various plants, , On careful observation it is seen that, in plants like touch-me-not (Mimosa),, movement also occurs at the places other, than where it has been touched. Hence, we, can infer that the information about the, touch must have been relayed within the, plant from one place to another. Plants use, electro-chemical impulses for transfer of, information from one place to another., Plant cells change their shape by increasing, or decreasing their water content and, thereby bring about the movements of, plants., Some specific movements of the, plants do not lead to the plant’s growth., Such movements are called ‘growthirrelevant movements’. As a response to, changes in the surroundings, plant, hormones bring about various movements, in plants., , Do you know?, In the plant called Venus fly trap,, there is a trap that appears and smells, like flowers and deceives insects. When, an insect visits that flower-like trap, the, trap closes up and the trapped insect is, digested by the plant., The lotus flower opens during daytime while that of the tuberose, (Polyanthus) opens at night., Fibrils present on the leaves of the, insectivorous plant Drosera, bend, inwards as soon as an insect lands on, the leaves and surround the insect from, all sides., In Balsam, the ripened fruit dehisces, (bursts-open) at the right time to disperse, the seeds., , Co-ordination in human being, Observe, , As you watch the match being played on your school ground, you, will see the control and co-ordination among the movements of the, players. Make a list of of all such different actions., , 170

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Different processes go on simultaneously in the human body. All these process need, to be efficiently and effectively conrolled and co-ordinated. This is done with the help of, two systems., A. Nervous control : Humans can respond to changes in their surroundings due to nervous, control. Impulses are generated in the human body, in accordance with changes in the, surroundings. Nervous control plays the important role of empowering the body cells with, ability to respond to these impulses. This ability depends upon the complexity of, organization in the organism’s body structure. Unicellular animals like the amoeba do, not have a nervous system which produces such impulses and responses. However,, multicellular animals like humans, have a nervous system to respond to the stimuli., Control and co-ordination is brought about with the help of a special type of cells called, nerve cells or neurons., Nucleus, , Dendrites, , Neurons (Nerve cells) : Special types of cells, which conduct impulses from one place to, Cell body, another in the body are called neurons. Neurons, are the structural and functional units of the, nervous system. Nerve cells, the largest cells, in the human the body, may measure up to a, few metres in length. Nerve cells have the, ability to generate and conduct electroMyelin, sheath, chemical impulses. The cells that support the, nerve cells and help in their functioning are, called neuroglia. Nerve cells and neuroglial, cells together form the nerves., All the information about our surroundings, is collected by the ends or dendrites of the, neuron. The chemical process begins at those, ends and electric impulses are generated which, are conducted from the dendrites to the cell, body, from the cell body to the axon and from, the axon to its terminal. These impulses are, then to be transferred from this nerve cell to, the next. Now the impulse that reaches the, terminal of an axon, stimulates the nerve cell, to secrete certain chemicals. These chemicals, pass through a minute space, called the, synapse, between two adjacent neurons and, generate the impulse in the dendrites of next, neuron. In this way, impulses are conducted in, the body and these impulses are finally, conveyed by nerve cells to muscle cells or, glands., , Axon, , Schwann’s cell, Node of Ranvier, , Nerve, cell, , Axon, terminal, , Pre-synaptic, terminal, , Synaptic vesicles, , Synaptic cleft, Post-synaptic, membrane, 15.11 Nerve cell and neuro-muscular junction, , 171

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When an action or movement is to be brought about in the body, the work of the, muscular tissue comes last in the sequence. Movement of muscle cells is essential to bring, about any activity. When cells contract to change their shape, movement occurs at cellular, level. Muscle cells have the ability to change their shape due to a special type of protein., Besides, due to these same proteins, cells become able to respond to electrical impulses of, nerves., Thus, we can say that the nervous system consists of a well-organized network of, nerves which can conduct information in the form of electrical impulses from one part of, the body to other., 1. Which are the sensory organs of an organism? What is their, function?, Can you tell? 2. Where are the gustatory and olfactory nerves to be found?, 3. Collect information about the function of all the above, mentioned parts and present it in the class., Types of nerve cells/neurons, According to their function, nerve cells are classified, into three types., , CNS, , 1. Sensory neurons : Sensory neurons conduct impulses, from sensory organs to the brain and the spinal cord., 2. Motor neurons : Motor neurons conduct impulses, from the brain or spinal cord to effector organs like, muscles or glands., , PNS, , 3. Association neurons : Association neurons perform, the function of integration in the nervous system., The human nervous system, The human nervous system is devided into the, following three parts., 1. Central nervous system, 2. Peripheral nervous system, 3. Autonomic nervous system, Central Nervous System or CNS, , 15.12 Human nervous system, , The central nervous system consists of the brain and spinal cord., The organization of the brain is extremely delicate and highly evolved. The brain is, the main controlling part of the nervous system and it is safely located in the cranial, cavity. The spinal cord is protected by the vertebral column. In the space between the, delicate central nervous system and its bony covering are the protective layers called the, meninges. Cavities present in various parts of the brain are called ‘ventricles’ whereas, the long tubular cavity of the spinal cord is called the ‘central canal’. The ventricles,, central canal and spaces between the meninges are filled with cerebro-spinal fluid. This, fluid supplies nutrients to the central nervous system and protects it from shock., , 172

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Convolutions of the cerebrum, , Cerebrum, , Cerebellum, , Spinal cord, , Medulla oblongata, , Pons, Cerebellum, Spinal cord, , 15.11 Structure of Brain, , The brain of an adult human, weighs about 1300 – 1400 grams and, consists of approximately 100 billion, neurons., The left side of our brain controls, the right side of our body and right, side of our brain controls left side of, the body. In addition, the left side of, the brain controls our speech and, conversation,, writing,, logical, thinking, etc. whereas the right side, controls artistic abilities., , Function of the left brain, Analytical thinking, Logical thinking, Language, Science and, Mathematics, , Medulla, oblongata, , Function of the right brain, Holistic thinking, Intuition, Creativity, Art and music, , 15.14 Left and right sides of brain, , Cerebrum :, This is largest part of our brain and consists of two cerebral hemispheres. These, hemispheres are joined with each other with the help of tough fibres and nerve tracts. The, cerebrum occupies two-thirds of the brain. Hence, it is also called the large brain. Its, surface has deep, irregular ridges and grooves which are called convolutions. Convolution, increases the surface area of the cerebrum and therefore a large number of nerve cells can, be accommodated., Cerebellum :, This is the smaller part of the brain situated below the cerebrum at the back of the, cranial cavity. Its surface shows shallow grooves instead of deep convolutions., Medulla oblongata :, This is the hind-most part of brain. There are two triangular swollen structures called, pyramids on the upper side of medulla oblongata. The medulla oblongata continues, downwards as the spinal cord., , 173

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Think about it, , An injury to the medulla oblongata can lead to death. Why?, , Spinal cord, The spinal cord is a part of the central nervous system and it is held within the, vertebral column. It is slightly thick but gradually tapers towards the end. There is a, thread-like fibrous structure at its end. It is called the Filum terminale., Spinal cord, , Brain, , Find out., You may have, seen how a drunken, person struggles to, maintain his body, balance. An excess of, Vertebral, column, alcohol in the body, (Backbone) causes one to lose, control over it. Why, does this happen? Find, out the reason with the, help of the internet., , Nerve, Spinal cord, , Vertebra, , Spinal, cord, , 15.15 Brain and spinal cord, , Brain: different regions and functions, Parts of the Brain, , Functions, , Cerebrum, , Control of voluntary movements, concentration, planning,, decision-making, memory, intelligence, and intellectual, activities., , Cerebellum, , 1. Co-ordination of voluntary movements., 2. Maintaining the body’s balance., , Medulla oblongata, , Control of involuntary activities like the beating of the heart,, blood circulation, breathing, sneezing, coughing, salivation,, etc., , Spinal cord, , 1. Conduction of impulses from the skin towards the brain., 2. Conduction of impulses from brain to muscles and glands., 3. Functions as centre of co-ordination of reflex actions., , 174

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Peripheral nervous system, The peripheral nervous system consists of the nerves originating from the central, nervous system. These nerves connect the central nervous system with all parts of the, body. They are of two types., A. Cranial nerves, Nerves originating from the brain are called cranial nerves. They are associated with, various parts in the head, thorax and abdomen. There are 12 pairs of cranial nerves., B. Spinal nerves, Nerves originating from the spinal cord are called spinal nerves. These are associated, with arms, legs, skin and some other parts of the body. There are 31 pairs of spinal nerves., 3. Autonomic nervous system, The autonomous nervous system consists of the nerves of involuntary organs like the, heart, lungs, stomach, etc. It is is not under the control of our will., Reflex action, , An immediate and, involuntary response given to, a, stimulus, from, the, environment is called a reflex, action. Sometimes we react to, an incident without any, thinking on our part or control, over the reaction. This is a, response given to a certain, stimulus, from, the, surroundings., In, such, situations, proper control and, co-ordination is achieved, even without intervention of, the brain., , 2, , 4, , 1, 5, , 3, 7, , 6, , 15.16 Reflex action, , Observe the above figure carefully and as per the numbers in that figure, answer, the following questions., a. What is happening at 1 and 2?, b. Which nerve carried the impulse to the point marked 3? In which direction is it conducting, the impulse?, c. Which is the nerve shown by 4?, d. Which is the organ marked as 5?, e. At 6, which nerve is conducting the response impulse?, f. At 7, where has the impulse reached? What is its effect?, , Try this, , Sketch and label the above figure., Try to sketch any other example of a reflex action., , 175

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B. Chemical control, Control and co-ordination in our body is also brought about with the help of certain, chemical substances called hormones. Hormones are secreted by endocrine glands. These, glands are also called ductless glands. These glands do not have any arrangement of their, own to either store or carry their secretions. Hence, as soon as hormones are produced,, they are directly released into the blood circulation. Thus, though these endocrine glands are, present at specific locations in our body, their secretions reach all parts of the body via blood., Endocrine glands along with the nervous system are responsible for the control and, co-ordination in our body. These two systems help each other to control and integrate the, various activities of the body. A marked difference between these two systems is that, nerve impulses are fast but short lived whereas the action of hormones is very slow but, long lasting., Hypothalamus, , It is very important, that hormones are secreted, only in the required, quantity and there is a, special mechanism which, controls the quantity and, timing, of, hormone, secretion. For example,, whenever there is an, increase in blood-glucose, level, certain cells in the, pancreas get stimulated, and as a response, they, release a greater quantity, of insulin., , Pineal gland, Pituitary gland, Thyroid gland and, Parathyroid gland, Thymus, , Adrenal, glands, , Ovary, Testis, , 15.17 Endocrine glands, , Using ICT :, Using the following websites and with the help of your teachers, prepare a power, point presentation on the human excretory system and the structure of the human, brain and present it in the classroom., www.nationalgeographic.com/science/health-and-humanbody/humanbody, www.webmed.com/brain, www.livescience.com/humanbrain, , 176

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Endocrine glands: Location and important functions, Glands, Hypothalamus, , Location, Above the pituitary, gland, in the, forebrain, , Pituitary, , At the base of brain, , Thyroid, , Anterolateral sides, of trachaea in neck, region, , Parathyroid Four glands behind, thyroid gland, Pancreas, Behind the stomach., Four types of cells, Alpha-cells (20%), Beta-cells (70%), Delta-cells (5%), P.P. cells or F-cells, (5%), Adrenal, Gland, , Hormones, Secretes the, hormones which control, the activity of the, secretory cells of the, pituitary gland, Growth Hormone, Adrenocorticotropic, hormone, Thyroid stimulating, hormone, Prolactin, Follicle stimulating hormone, Luteinizing hormone, Oxytocin, Antidiuretic hormone, Thyroxine, Calcitonin, Parathormone, , Glucagon, Insulin, Somatostatin, Pancreatic Polypeptide, , Anterior end of each Adrenaline and, kidney, Nor-adrenaline, , Corticosteroid, Ovary, , On either side of, uterus in women, , Testis, , In scrotum, , Thymus, , In thoracic cage,, near the heart, , Oestrogen, , Functions, - Controls the pituitary gland, , - Stimulates growth of bones, - Stimulates adrenal gland, - Stimulates thyroid gland, - Stimulates milk production, - Controls growth of gonads, - Controls menstrual cycle and ovulation, - Contracts uterus during parturition., - Regulates water-level in the body, - Controls growth of body and metabolic, activities, - Controls calcium metabolism and, calcium level in blood, Controls metabolism of calcium and, phosphorus, - Stimulates liver to convert glycogen into, glucose, - Stimulates liver to convert excess bloodglucose into glycogen, - Controls levels of insulin and glucagon, - Controls movements of intestine and, thereby glucose absorption, - Controls secretion of pancreatic juice, -Controls behaviour during crisis and, emotional situations, - Stimulates heart and its conducting tissue, and metabolic processes., Maintains balance of Na+ and K+ and, stimulates metabolism, -Stimulates growth of endometrium, -Stimulates growth of secondary sexual, characterstics in women, -Prepares the endometrium for conception, and maintains the pregnancy., Stimulates growth of secondary sexual, characterstics like beard, mustache, hoarse, voice, etc. in men, Controls the cells which give rise to, immunity, , Progesterone, Testosterone, , Thymosin, , 177

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Exercises, 1., , Match the pairs and explain., ‘A’, 1. Growth of pollen tube towards ovule, 2. Growth of shoot system, 3. Growth of root system, 4. Growth towards water, , 2. Complete the paragraph., The milk was on the stove. Rasika was, engrossed watching television. She, smelled something burning. She ran, towards the kitchen. The milk was, boiling over. She held the vessel with, her bare hands but, screaming, she let, it go at once. This activity was, controlled by .................... cells., Special ends of .................... in these, cells collected the information, from, where it was transferred to the, .................... and then towards the, terminal end of the .................... The, chemicals produced at the terminal end, passed through the minute space i.e., ................... . In this way, ...................., were conducted in the body and the, process of .................... was completed, by conducting the impulses from, .................... to .................., (Nerve, muscle cell, impulse, dendrite,, synapse, axon, reflex action, cell body), 3. Write notes onRoot pressure, Transpiration, Nerve, cell, Human brain, Reflex action, 4. Name the hormones of the following, endocrine glands and the function of, each., Pituitary, Thyroid, Adrenal, Thymus,, Testis, Ovary., 5. Draw and label the diagrams., Human endocrine glands, Human, , 178, , ‘B’, a. Gravitropic movement, b. Chemotropic movement, c. Phototropic movement, d. Growth-irrelevant movement, e. Hydrotropic movement, brain, Nephron, Nerve cell, Human, excretory system., 6. Answer the following., a. Explain chemical co-ordination in, humans and give the names and, functions of some hormones., b. Explain the difference between the, excretory system of humans and, plants., c. Explain co-ordination in plants, with the help of suitable examples., 7. Explain in your own words with, suitable examples., a. What is meant by co-ordination?, b. How does excretion occur in human, beings?, c. How is excretion in plants useful to, human beings?, d. Describe the transportation system, in plants., Activity :, 1. Collect information about the evolution of the brain of vertebrates and, present it in the classroom., 2. Explain the functions of various, endocrine glands by presenting an act, like ‘Why I Am Important?’, 3. Collect the information to justify the, statement ‘Human beings are intelligent and different from other animals’, and present it in the classroom., , ²²²

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16. Heredity, 1. गतीचेand, नियमVariation, Inheritance Ø Heredity: Characteristics and their appearance, Ø Mendel’s laws of inheritance Ø Diseases due to chromosomal, , aberrations, Ø, , 1. Do all the boys and girls of your class look alike?, Think about it 2. Think about the following characteristics and note similarities, and differences. (Teachers should help in this activity.), Sr., No., , Personal, characteristics, , Own, , 1, , Colour of skin, , 2, , Shape of face (Round/, Oblong), Height, Colour of eyes, Orientation of thumb, , 3, 4, 5, , Grandfather, , Granmother, , Father, , Mother, , Earlier, we have seen that there is great variation within every species in nature. In, this chapter, we shall study the factors that give rise to these variations., Inheritance, The branch of biology which studies the transfer of characteristics of organisms from, one generation to the next, and genes in particular, is called ‘genetics’., New progeny is formed through the process of reproduction. Except for a few minor, differences, the offspring shows great similarities with parents. Organisms produced by, asexual reproduction show minor variations. However, offspring produced through sexual, reproduction, show comparatively greater variations., Observe, 1. Carefully, observe, classmate’s earlobes., , your, , 2. Irrespective of all of us being, humans, what difference do, you notice in our skin colour?, 3. All of you are in std. IX. Why, then are some students tall and, some short?, , Facial features, , Attachment of the earlobe, , The nose and lips, , Hairline, , 16.1 Some differences in facial features, , 179

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Heredity :, Transfer of characteristics from parents to offspring is called heredity. It is due to, heredity that puppies are similar to dogs, squabs are similar to pigeons and infants are, similar to humans., Inherited traits and expression of traits :, Can you tell?, , How do specific traits or characteristics appear in organisms?, , Though there are many similarities between parents and their offsprings there are, some differences too. These similarities and differences are all the effect of heredity. Let, us study the mechanism of heredity. Information necessary for protein synthesis in the cell, is stored in DNA. The segment of DNA which contains all the information for synthesis, of a particular protein is called a ‘gene’ for that protein. It is necessary to know the, relationship of these proteins with the characteristics of organisms., To understand the concept of heredity let us consider the characteritic ‘plant height’., We know that there are growth hormones in plants. Increase in height of plants depends, upon the quantity of growth hormones., The quantity of growth hormones produced by a plant depends upon the efficiency of, the concerned enzyme. Efficient enzymes produce a greater quantity of the hormone due, to which the height of the plant increases. However, if the enzymes are less efficient, a, smaller quantity of hormone is produced leading to a stunting of the plant., Chromosomes, The structure in the nucleus of cells that carries, the hereditary characteristics is called the, chromosome. It is made up mainly of nucleic acids, Arms of, chromosomes, and proteins. During cell division chromosomes, can be clearly seen under the compound microscope., ‘Genes’ which contain the information about, p Arm, hereditary characteristics in coded form are located, on chromosomes. Each species has a specific, Centromere, number of chromosomes., Each chromosome is made up of DNA and it, appears dumbell-shaped midway during cell, q Arm, division. There is a constricted region on each, chromosome. It is called the ‘Primary constriction’, or ‘Centromere’. This divides the chromosome, (DNA), into two parts. Each part is called an ‘arm’. The, centromere has a specific position in each, chromosome. Depending upon this, there are four, 16.2 Organization of chromosome, types of chromosomes., Types of chromosomes :, Find out, , Number of chromosomes in different organisms, , 180

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Types of chromosomes can be easily, identified during cell division., 1. Metacentric : The centromere is exactly, at the mid-point in this chromosome, and, therefore the chromosome looks like the, English letter ‘V’. The arms of this, chromosome are equal in length., 2. Sub-metacentric : The centromere is, somewhere near the mid-point in this, chromosome which therefore looks like, English letter ‘L’. One arm is slightly shorter, than the other., 3. Acrocentric : The centromere is near one, end of this chromosome which therefore, looks like the English letter ‘j’. One arm is, much smaller than other., 4. Telocentric : The centromere is right at, the end of this chromosome making the, chromosome look like the English letter ‘i’., This chromosome consists of only one arm., Generally, in somatic cells chromosomes, are in pairs. If the pair consists of similar, chromosomes by shape and organization,, they are called ‘homologous chromosomes’, and if they are not similar they are called, ‘heterologous chromosomes’. In case of, organisms that reproduce sexually one of the, chromosomal pairs is different from all than, others. Chromosomes of this different pair, are called ‘sex chromosomes’ or allosomes, and all other chromosomes are called, ‘autosomes’., , Chromosome number of some, organisms has been given in the, following table Sr., , Organism, , No. of, Chromosomes, , Crab, Maize, Frog, Roundworm, Potato, Human, , 200, 20, 26, 04, 48, 46, , No., , 1, 2, 3, 4, 5, 6, , Arm, Centromere, , Metacentric, , Acrocentric, , Sub-metacentric, , Telocentric, , 16.3 Types of chromosomes, , Deoxyribonucleic acid (DNA), Chromosomes are mainly made up of DNA. This acid was discovered by the Swiss, biochemist, Frederick Miescher in 1869 while studying white blood cells. Initially this, acid was reported to be only in the nucleus of cells. Hence, it was named nucleic acid., However, it was later realized that it is present in other parts of the cell too. Molecules of, DNA are present in all organisms from viruses and bacteria to human beings. These, molecules control the functioning, growth and division (reproduction) of the cell and are, therefore called ‘Master Molecules’., The structure of the DNA molecule is the same in all organisms. In 1953, Watson and, Crick produced a model of the DNA molecule. As per this model, two parallel threads of, nucleotides are coiled around each other. This arrangement is called a ‘double helix’. This, sturcture can be compared with a coiled and flexible ladder., , 181

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Each strand in the molecule of DNA is, made up of many small molecules known, as ‘nucleotide’. There are four types of, nitrogenous bases adenine, guanine,, cytosine and thymine. Adenine and guanine, are called as ‘purines’ while cytosine and, thymine are called ‘pyrimidines’., In the structure of the nucleotide, a, molecule of a nitrogenous base and, phosphoric acid are each joined to a, molecule of sugar., As there are four types of nitrogenous, bases, nucleotides also are of four types., Nucleotides are arranged like a chain,, in a molecule of DNA. The two threads of, the DNA molecule are comparable to the, two rails of a ladder and each rail is made, up of alternately joined molecules of sugar, and phosphoric acid. Each rung of the, ladder is a pair of nitrogenous bases joined, by hydrogen bonds. Adenine always pairs, with thymine and cytosine always pairs, with guanine., , Cell, Gene, , Nucleus, of cell, , गुChromosome, णसूत्र, , Gene, Each chromosome is made up of a, single DNA molecule. Segments of the, DNA molecule are called genes. Due to, variety in the sequence of nucleotides,, different kinds of genes are formed. These, genes are arranged in a line. Genes control, the structure and function of the cells and, of the body. Also, they transmit the, hereditary characteristics from parents to, offspring. Hence, they are said to be the, functional units of heredity. That is why,, many similarities are seen between parents, and their offspring. Information about, protein synthesis is stored in the genes., 16.4 DNA (Watson and Crick’s Model), , DNA fingerprinting : The sequence of the genes in the DNA of a person i.e. the genome, of the person is identified. It is useful to identify the lineage and to identify criminals, because it is unique to every person., , 182

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Adenine Thymine, Pair of nitrogenous, bases (nucleotides), Guanine, , Cytosine, , Rails of the DNA, made up of sugar, and, phosphoric, acid, 16.5 Structure of DNA, , Seeds of technology :, In 1990, the ‘Human Genome Project’ was together undertaken by all the, geneticists of the world. In June 2000, scientists of this project and Celera Genomics, Corporation (a private industry in USA) collectively announced the discovery of the, complete DNA sequence of the human genome. Depending upon the findings of this, project, scientists confirmed that the number of genes in the human genome is about, 20,000 to 30,000. Later, scientists discovered the genomic sequence of many microorganisms. Due to research in genomics, disease causing genes can be identified. If, disease causing genes are identified, genetic diseases can be diagnosed and properly, treated., Website : www.genome.gov, , Ribonucleic acid (RNA) :, RNA is the second important nucleic acid of the cell. This, nucleic acid is made up of ribose sugar, phosphate molecules and, four types of nitrogenous bases adenine, guanine, cytosine and, uracil. The nucleotide i.e. smallest unit of the chain of the RNA, molecule is formed by combination of a ribose sugar, phosphate, molecule and one of the nitrogenous bases. Large numbers of, nucleotides are bonded together to form the macromolecule of, RNA. According to function, there are three types of RNA., 1. Ribosomal RNA (rRNA) : The molecule of RNA which is a, component of the ribosome organelle is called a ribosomal RNA., Ribosomes perform the function of protein synthesis., 2. Messenger RNA (mRNA) : The RNA molecule that carries the, information of protein synthesis from genes i.e. DNA chain in the, cell nucleus to ribosomes in the cytoplasm which produce the, proteins, is called messenger RNA., 3. Transfer RNA (tRNA) : The RNA molecule which, according, to the message of the mRNA carries the amino acid up to the, ribosomes is called transfer RNA., , 183, , mRNA, , rRNA, , tRNA, 16.6 Types of RNA

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Mendel’s principles of heredity, Genetic material is transferred in equal quantity from parents to progeny. Principles, of heredity are based upon this fact. If both the parents make equal contribution to, inheritance of characteristics, which characteristics will appear in the progeny? Mendel, carried out research in this direction and put forth the principles of heredity responsible for, such inheritance. The experiments performed by Mendel, almost a century ago are quite, astonishing. All of Mendel’s experiments were based upon the visible characteristics of, the pea plant (Pisum sativum). These characteristics are as follows Dominant, , Recessive, , (R), , Wrinkled, , Shape of, the seed, Round, Colour, of seed, , Yellow, , Colour of, flower, , Purple, , An introduction to scientists, , (r), , (Y), , Green (y), , (C), , White, , (c), , Shape of pod, Inflated, Colour of, pod, , Position of, flower, , Height of, plant, , (I), , Constricted, , (i), , Yellow, , Green, (G), , (g), , Axillary, (A), , (T), , Gregor Johann Mendel was an, Austrian scientist. He studied the, inheritance of some characteristics of the, pea plant. He showed that inheritance of, these characteristics follows certain, principles. Later, these principles becomes, popular by his name. Mendel’s work was, recognized only in the 20th century. After a, reconfirmation of these principles, the, same principles now form the basis of, modern genetics., Do you know?, , Terminal, (a), , Tall, , Gregor Johann Mendel, (Birth: 20 July 1822, Death: 6th Jan 1884), th, , Some dominant and recessive, characteristics of human beings, , Dwarf, , (t), , 16.7 Seven mutually contrasting visible, characteristics, , Dominant, Rolling tongue, , Recessive, Non-rolling tongue, , Presence of hair on, arms, Black and curly, hair, Free earlobe, , Absence of hairs on, arms, Brown and straight hair, , 184, , Attached earlobe

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We shall study the following crosses to clearly understand the conclusions of Mendel’s, experiments., Monohybrid cross, In this experiment, Mendel brought about the cross between two pea plants with only, one pair of contrasting characters. This type of cross is called a monohybrid cross., So as to study the monohybrid ratio, let us consider the characteristic ‘plant height’, with a pair of contrasting characteristics tall plant and dwarf plant., Parental generation (P1) :, Tall pea plants and dwarf pea plant were used in this cross. Hence, this is parent, generation (P1). Mendel referred to the tall and dwarf plants as dominant and recessive, respectively. The tall plant was referred to as dominant because all the plants in the next, generation were tall. The dwarf plant was referred to as recessive because this characteristic, did not appear in next generation at all. This experiment has been presented by the ‘Punnet, Square’ method as shown below., Mendel’s experiment of the Monohybrid Cross, Parental Generation (P1), , Phenotype:, , Tall, , Genotype:, , TT, , Gametes:, , T, , Dwarf, tt, t, , First Filial, Generation (F1), , Tt, , Phenotype:, , Tall, , Parental Generation (P2), , Selfing in F1, , Phenotype:, , Tall, , Tall, , Genotype:, Gametes:, , Tt, T and t, , Tt, T and t, , First Filial, Generation (F2), , Male, gamete, Female, gamete, , T, , t, , T, , TT (Tall) Tt (Tall), , t, , Tt (Tall) tt (Dwarf), , 185, , Depending upon these, observations,, Mendel, proposed that the factors, responsible for inheritance of, characteristics are present in, pairs. Today, we refer to these, factors as genes. Dominant, genes are denoted by capital, letters whereas recessive, genes are denoted by small, letters. As genes are present in, pairs, tall plants are denoted, by TT and dwarf plants are, denoted by tt. During, gametogenesis, these genes, separate from each other. Due, to this, two types of gametes, one containing factor T and, other containing factor t are, formed.

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First filial generation (F1) :, In this experiment, Mendel observed, that all plants of first filial generation, (F1) were tall. But, he realised that tall, plants of F1 generation were different, from the tall plants of P1 generation, because parents of F1 tall plants are tall, as well as dwarf plants. Depending upon, observations of F1 generation, Mendel, concluded that factors of tall plants are, dominant over the factors of dwarf, plants. Though all the plants in F1, generation were tall, they contained the, factor responsible for dwarfness. i.e., though the phenotype of F1 plants is tall,, their genotype is mixed. Phenotype, means external appearance or visible, charactersistics of organisms, for, example, tallness or dwarfness of plants, whereas genotype means the pairs of, genes (factors) responsible for the visible, characteristics. Genotype of P1 tall plants, is TT and produces only one type of, gametes (T). Genotype of F1 tall plants, is Tt and it produces two types of gametes,, T and t. Thus, based on this, we can say, that in case of tall plants of F1 and P1, generations, though they show similar, phenotype, their genotypes are different., Mendel further continued this experiment, and brought about self-fertilization in F1, plants from which a second filial (F2), generation was produced., , Second filial generation (F2):, In the second filial generation (F2),, both i.e. tall and dwarf types of plants, appeared. According to the data collected, by Mendel, out of 929 pea plants, 705, were tall and 224 were short. Thus, the, phenotypic ratio of these plants is, 3(tall):1(dwarf) and genotypic ratio is, 1(TT):2(Tt):1(tt). Thus, it can be inferred, that in the F2 generation, phenotypically, there are two types of plants whereas, genotypically there are three types., These types are shown in the following, table., , F2 Pure dominant (TT) Homozygous, - tall plants, F2 Pure recessive (tt) Homozygous, - dwarf plants, F2 Hybrid plants (Tt), Heterozygous, –tall plants, , Mendel’s experiment on dihybrid cross:, In the dihybrid cross, two pairs of contrasting characteristics are under consideration., Mendel performed more experiments on hybridization in which he considered more than, one pair of contrasting characteristics. He brought about a cross between a pea plant, producing rounded and yellow coloured seeds and a pea plant with wrinkled and green, coloured seeds. In this cross, two pairs of contrasting characteristics were considered, colour of seeds and shape of seeds. Hence, it is called a dihybrid cross., Parental generation (P1) :, Mendel selected the pea plants producing rounded yellow seeds and wrinkled green, seeds as parent plants, as shown in the chart -, , 186

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Based on the conclusions from the monohybrid cross, Mendel expected that in the F2, generation of dihybrid cross, plants would produce rounded-yellow seeds. He was proved, right. Though the genotype of these plants was RrYy, their phenotype was like the parents, producing rounded-yellow seeds, because yellow colour is dominant over green and round, shape is dominant over wrinkled. Due to the combination of two different characteristics, in the F1 generation of the dihybrid cross, these plants are called dihybrid plants., Plants of the F1 generation of dihybrid cross produce four types of gametes RY, Ry,, rY, ry. Of these gametes, RY and ry are similar to those of the P1 generation., F2 generation is formed through the selfing of F1 plants. The pattern of inheritance of, charactistics from F1 to F2 is shown in brief in the table given on page 187 and an activity, about its presentation in the form of a ratio has been given in a box, beside it. The 16, different possible combinations through the union of 4 types of male gametes and 4 types, of female gametes are shown in a chess-board like table (Punnet Square / Checker board), on page 187. Male gametes are shown at the top of table and female gametes are shown, in left column. Observations based on a study of the F2 generation will be according to the, table on page 187., Genetic disorders, Diseases or disorders occurring due to abnormalities in chromosomes and mutations, in genes are called genetic disorders. Chromosomal abnormalities include either increase, or decrease in numbers and deletion or translocation of any part of the chromosome., Examples are physical disorders like cleft lip, albinism and physiological disorders like, sickle cell anaemia, haemophilia, etc., Human beings have 46 chromosomes in the form of 23 pairs. There is great variation, in the size and shape of these chromosomal pairs. These pairs have been numbered. Out, of 23 pairs, 22 pairs are autosomes and one pair is of sex chromosomes (allosomes)., Chromosomes in women are represented as 44+XX and in men as 44+XY., Mendel has shown in his, experiments that there exist two type, of genes, dominant and recessive., If we take into account the, number of chromosomes in human, cells, their sex-related types, the types, of genes on the chromosomes dominant and recessive - we can see, where genetic disorders originate and, how they are inherited., , 1, , 2, , 3, , 6, , 7, , 8, , 13, , 14, , 15, , 19, , 20, , Autosomes, , 9, , 21, , 22, , 4, , 5, , 10, , 11, , 12, , 16, , 17, , 18, , 23, , or, , Sex chromosomes, , 16.8 Human karyotype (Chromosome chart), , 188

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A. Disorders due to chromosomal abnormalities:, Following are the disorders that occur due to numerical changes in chromosomes., Offspring are not sterile if there is change in the number of autosomes is less. Instead, if, there is an increase in number of any autosomal pair, physical or mental abnormalities, arise and the lifespan is shortened with a shortened life span. Following are some disorders., 1. Down syndrome (46+1, Trisomy of 21st Chromosome) :, , Down syndrome is a disorder arising due to, , chromosomal abnormality. This is the first discovered and, described chromosomal disorder in human beings. This, disorder is characterised by the presence of 47, chromosomes. It is described as trisomy of the 21st, chromosome. Infants with this disorder have one extra, chromosome with the 21st pair in every cell of their body., Therefore they have 47 chromosomes instead of 46., Children suffering from Down’s syndrome are usually, mentally retarded and have a short lifespan. Mental, retardation is the most prominent characteristic. Other, symptoms include short height, short wide neck, flat nose,, short fingers, scanty hair, single horizontal crease on palm,, and a life expentancy of about 16–20 years., 2. Turner syndrome (Monosomy of X chromosome) :, , 16.9 Child with Down, syndrome, , As with autosomes, abnormalities in sex chromosomes, also cause some disorders. Turner syndrome (or 44+X), arises due to either inheritance of only one X chromosome, from parents or due to inactivation of the gender-related, part of X-chromosomes. Instead of the normal 44+XX, condition, women suffering from Turner syndrome show, a 44+X condition. Such women are sterile i.e. unable to, have children due to improper growth of the reproductive, organs., 16.10 Hand of a child with, Turner syndrome, 3. 3. Klinefelter syndrome (44+XXY) :, This disorder arises in men due to abnormalities in sex chromosomes. In this disorder,, men have one extra X chromosome; hence their chromosomal condition becomes 44+XXY., Such men are sexually sterile because their reproductive organs are not well developed., National Health Mission, Under the National Health Mission, the National Rural Health Mission has been, started since April 2005 and the National Urban Health Mission since 2013., The main objectives of this mission are strengthening of the rural and urban, health facilities, controlling various diseases and illnesses, increasing public, awareness about health, and offering financial assistance to patients through various, schemes., , 189

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B. Diseases occuring due to mutation in single gene (monogenic disorders) :, Disorders or diseases occurring due to mutation in any single gene into a defective, one are called monogenic disorders. Approximately 4000 different disorders of this type, are now known. Due to abnormal genes, their products are either produced in insufficient, quantity or not at all. It causes abnormal metabolism that may lead to death at a tender, age. Examples of such disorders are Hutchinson’s disease, Tay-Sachs disease,, galactosaemia, phenylketonuria, sickle cell anaemia, cystic fibrosis, albinism,, haemophilia, night blindness, etc., 1. Albinism :, This is a genetic disorder. Our eyes,, skin and hair have colour due to the, brown pigment, melanin. In this disease,, the body cannot produce melanin. The, skin becomes pale, hairs are white and, eyes are usually pink due to absence of, melanin pigment in the retina and sclera., 16.11 Hair and eyes of child with albinism, , 2. Sickle-cell anaemia :, Even minor changes in molecular structure of proteins and DNA may lead to diseases, or disorders. Normal haemoglobin has glutamic acid as the 6th amino acid in its molecular, structure. However, if it is replaced by valine, the shape/structure of the haemoglobin, molecule changes. Due to this, the erythrocytes or red blood corpuscles (RBC), which are, normally biconcave become sickle-shaped. This condition is called ‘sickle-cell anaemia’., The oxygen carrying capacity of haemoglobin in such individuals is very low., In this condition, clumping and thereby destruction of erythrocytes occurs most often., As a result blood vessels are obstructed and the circulatory system, brain, lungs, kidneys,, etc. are damaged. Sickle-cell anaemia is a hereditary disease. It occurs due to changes in, genes during conception. If the father and mother are both affected by sickle-cell anaemia, or if they are carriers of this disorder, their offspring are likely to suffer from this disease., Hence, marriages between the persons who are carriers of or suffering from sickle-cell, anaemia should be avoided., , There are two types of persons affected by, sickle-cell anaemia :, 1. Sickle-cell anaemia carrier (AS), 2. Sufferer from sickle-cell anaemia (SS), Symptoms of sickle-cell anaemia :, Swelling of hands and legs, pain in joints,, severe general body aches, frequent colds and, cough, constant low grade fever, exhaustion, pale, face, low haemoglobin content., , 190, , Do you know?, In Maharashtra, there are, more than 2.5 lakh people, suffering from sickle-cell, anaemia and about 21 districts, including 11 districts from, Vidarbha are affected by this, disorder.

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Let’s get our blood, tested !, Let’s overcome, sickle cell anaemia !, Affected, sufferer, , Normal, , 16.12 Sickle cells, , Sickle cell anaemia occurs as follows :, Symbols: AA = Normal, AS = Carrier, SS = Sufferer, Sr., No., , Man, , 1, 2, , AA, AA Normal progeny if both parents are normal., AA or AS or 50% progeny normal and 50% carrier, if one parent is normal, AS, AA and one is a carrier., AA or SS or All progeny will be carrier, if one parent is normal and one is, SS, AA a sufferer., AS, AS, 25% progeny normal, 25% sufferer and 50% carrier if both, parents are carriers., AS or SS or 50% progeny carrier and 50% sufferer if one parent is carrier, SS, AS, and one is a sufferer., SS, SS, All progeny will be sufferers if both parents are sufferers., , 3, 4, 5, 6, , Woman, , Progeny, , Diagnosis of sickle-cell anaemia : Under the National Health Mission scheme, the, ‘Solubility Test’ for diagnosis of sickle-cell anaemia is available at all district, hospitals. Similarly, the confirmatory diagnostic test- ‘Electrophoresis’ is performed, at rural and sub-district hospitals., , Remedies :, This disease is spread in only one way i.e., reproduction. Hence, husband and wife should, get their blood exmined either before marriage or, after it., 1. A carrier or sufferer should avoid marriage with, another carrier or sufferer., 2. A person suffering from sickle cell anaemia, should take a tablet of folic acid daily., , 191, , 16.13 Hand of a child with, sickle-cell anaemia

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C. Mitochondrial disorder :, Mitochondrial DNA may also become defective due to mutation. During fertilization,, mitochondria are contributed by the egg cell (ovum) alone. Hence, mitochondrial disorders, are inherited from the mother only. Leber hereditary optic neuropathy is an example of a, mitochondrial disorder., D] Disorders due to mutations in multiple genes : (Polygenic disorders), Sometimes, disorders arise due to mutations in more than one gene. In most such, disorders, their severity increases due to effects of environmental factors on the foetus., Common examples of such disorders are cleft lip, cleft palate, constricted stomach, spina, bifida (a defect of the spinal cord), etc. Besides, diabetes, blood pressure, heart disorders,, asthma, obesity are also polygenic disorders. Polygenic disorders do not strictly follow, Mendel’s principles of heredity. These disorders arise from a complex interaction between, environment, life style and defects in several genes., Always remember, Inter-relationship between tobacco addiction and, cancer (Uncontrolled growth of cells), Many people consume tobacco, either by smoking or by, chewing. Consumption of tobacco in any form can cause, cancer. Smoking of cigarettes and bidi adversely affects the, process of digestion. It causes a burning sensation in the, throat and a cough. Excessive smoking causes instability, and trembling of fingers. A dry cough causes sleeplessness., Tobacco consumption can also lead to shortening of life, span, chronic bronchitis, pericarditis, cancer of the lungs,, mouth, larynx (voice box), pharynx, pancreas, urinary, bladder, etc., Harmful effects of smoking are due to the nicotine, present in tobacco. It affects the central and peripheral, nervous system. Arteries become hard i.e. it causes, arteriosclerosis and hypertension., Tobacco smoke contains harmful chemicals like, pyridine, ammonia, aldehyde furfural, carbon monoxide,, nicotine, sulphur dioxide, etc. They cause uncontrolled cell, division. Tobacco smoke is full of minute carbon particles, which causes normal tissue of the lung to transform into, thickened black tissue. This causes cancer. While chewing, tobacco or tobacco products much of the extract is absorbed, into the body. Excessive tobacco consumption may cause, cancer of lips or tongue, visual disorders or tremors., To protect one’s body from cancer one must avoid smoking, and consumption of tobacco and tobacco products in any, form., , 192, , Compose and present a, street play against tobacco, consumption and participate, in a drive against tobacco.

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Exercises, 1. Complete the following sentences by, choosing the appropriate words from, the brackets., (Inheritance,, sexual, reproduction,, asexual reproduction, chromosomes,, DNA, RNA, gene), a. Hereditary characters are transferred, from parents to offsprings by ............,, hence they are said to be structural, and functional units of heredity., b. Organisms produced by ............, show minor variations., c. The component which is in the nuclei, of cells and carries the hereditary, characteristics is called ............., d. Chromosomes are mainly made up, of ............., e. Organisms produced through ............, show major variations., 2. Explain following., a. Explain Mendel’s monohybrid, progeny with the help of any one, cross., b. Explain Mendel’s dihybrid ratio, with the help of any one cross., c. Distinguish between monohybrid, and dihybrid cross., d. Is it right to avoid living with a, person suffering from a genetic, disorder?, 3. Answers the following questions in, your own words., a. What is meant by ‘chromosome’., Explain its types., b. Describe the structure of the DNA, molecule., c. Express your opinion about the use, of DNA fingerprinting., d. Explain the structure, function and, types of RNA., e. Why is it necessary for people to, have their blood examined before, marriage?, , 4. Write a brief note on each., a. Down syndrome, b. Monogenic disorders, c. Sickle cell anaemia: symptoms and, treatment., 5. How are the items in groups A, B and, C inter-releated?, A, , B, , C, , Leber, 44+XXY Pale skin,, hereditary optic, white hairs, neuropathy, Diabetes, 45+X, Men are sterile, Albinism, MitoWomen are, chondrial sterile, disorder, Turner, Polygen- This disorder, arises during, syndrome, ic, disorder development, of zygote., Klinefelter, MonoEffect on, blood-glucose, syndrome, genic, disorder level., , 6. Filling the blanks based on the given, realationship., a. 44+X:Turner syndrome: :44+XXY:.............., b. 3:1 Monohybrid: : 9:3:3:1 : ............., c. Women : Turner syndrome : : Men : ......., 7. Complete the tree diagram below, based on types of hereditary, disorders., Hereditary disorders, , Activity, a. Prepare a model of the DNA and, give a presentation based on it., b. Prepare a power point presentation, on awareness about tobacco, consumption and cancer and, present it in the class., , 193, , ²²²

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17. Introduction, Biotechnology, 1. गतीचे to, नियम, Tissues: animal tissues and plant tissues, Ø Agritourism, Ø Agri-business, Ø, , Can you recall?, , Ø, , Tissue culture, , 1. Which components bring about important processes in the, living organisms?, 2. Which is the smallest structural and functional unit of the, body of living organisms?, , Tissue, In the case of amoeba-like unicellular organisms, all functions are performed by, organelles of that single cell. However, most of the organisms are multicellular. How, are the various processes brought in their body? Groups of cells come together, so as to, perform the various functions of the body., Are you familiar with the sequence- lettersg words g sentences g lessons g text book?, Similarly, organization of the body of organisms follows a definite hierarchy. You, have already studied cells and cell organelles in that hierarchy., ‘A group of cells having the same origin, same structure and same function is called, ‘tissue’. Millions of cells are present in the body of multicellular organisms. These cells, are divided into different groups and each group performs a definite function. For example,, we can perform movements due to contraction-relaxation of muscles. Conducting tissues, in plants transport water and food to all its parts. All functions of the body occur with full, efficiency due to the specific organization of cells and their division of work., Types of tissue, Complex tissue, Complex Tissues, Made up of more than one type of, cells Ex. Blood of animals, Xylem, and phloem of plants, , Simple tissue, Simple Tissues, Made up of only one type of cells, Ex. Epithelial tissue of animals,, Meristematic tissue of plants, , Think about it, , Are the sturcture and functions of the bodies of plants and, animals the same?, , Plants being sedentary, most of their tissues are of the type that give support. There, are dead cells in some tissues and these do not need much attention. Growth of the plants, occurs in specific parts of their body where the tissues contain dividing cells. As animals, have to move from place to place in search of food, shelter and partners, their energy, needs are greater. Most of the tissues of animals are made up of living cells. Uniform, growth occurs through out the body of an animal and they do not have different dividing, and non-dividing tissue. This means that plants and animals have different types of tissue, to performing the necessary functions., , 194

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Animal tissue, Think about it, , Why can we not see our organs like the heart, blood vessels, and intestines?, , In the body of animal, different organs come together, to perform a specific function., Organs like the lungs and trachea,, with the help of the contraction, and relaxation of some muscles, bring about the function of, respiration. Different tissues, perform different functions in the, organs. Accordingly, tissues are, classified into different types., There are four main types of, animal tissues, namely epithelial, tissue,, connective, tissue,, muscular tissue and nervous, tissue., , Muscular tissue, Connective, tissue, , Nervous, tissue, , Epithelial, tissue, 17.1 Types of animal tissues, , Do you know?, Blood is also a type of connective tissue. It circulates in our body from one part, to another and transports different materials. For example, it transports oxygen and, nutrients to all cells in the body. Similarly, it transports waste materials generated, all over the body to the kidney for excretion., , Observe, , Observe the skin of the back of your hand with the help of, a magnifying lens. Do you see the closely attached squarish and, pentagonal shapes?, , Epithelial tissue, Protective coverings in the animal body are called epithelial tissues. Cells in this, tissue are closely packed and form continuous layers. Any material that enters the body, first encounters epithelial tissue. Cells of epithelial tissue are separated from the cells of, other underlying tissues by a fibrous membrane. The skin, mucous layer of the mouth, cavity, inner surface of blood vessels, walls of the alveoli, etc. are made up of epithelial, tissues., Use your brain power !, , What keeps the various organs and organ systems, separate from each other? How?, , 195

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Types of epithelial tissues, Name, , Location, , Sturcture, , Squamous, epithelium, , Inner surface of, mouth,, oesophagus,, blood-vessels,, alveoli, , Thin, small, flat, cells form, semipermeable, membrane., , Selective, transport of, substances., , Stratified, epithelium, , Outer layer of, skin, , Many layers of, cells, , Prevention of, wearing of, organs,, protection of, organs., , Glandular, epithelium, , Inner layer of, skin, etc., , Cells contain, vesicles packed, with secretory, material, , Secretion of, sweat, oil, (sebum),, mucus, etc., , Columnar, epithelium, , Inner surface, (mucosa) of, , Appearance (diagrammatic), , Column-like tall, cells. Upper free, surface bears, intestine,, folds made of, alimentary, these cells at, canal, places of, absorption, Inner surface of Upper free, respiratory tract surface of cells, bears minute, hair-like, processes, , Ciliated, Epithelium, , Cuboidal, epithelium, , Tubules of, kidney, (nephron),, salivary gland, , Use your brain power !, , Observe, , Cells are, cuboidal, , Function, , Secretion of, digestive, juice,, absorption of, nutrients, , Push mucus, and air, forward to, keep the air, passage free, Reabsorption, of useful, materials from, urine,, secretion of, saliva, , Why are epithelial tissues said to be simple tissues?, , Observe a permanent slide of a blood smear under a compound, microscope. What did you see?, Cells of different types, colour and shape are mixed together., Hence, blood is a type of complex tissue., , 196

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Connective tissue : Tissues which join different parts of the body are called connective, tissues. Cells in this type of tissue are loosely arranged with a ground substance in the free, spaces in between. The ground substance may be solid, liquid like water or jelly-like., Types of connective tissue, Type, , Appearance, (diagrammatic), , Location, , Blood, , Closed, circulatory, system, , Lymph, , All around, the cells in, the body., , Areolar, Tissue, , Between the, skin and, muscles,, around blood, vessels, , Adipose, Tissue, , Below the, skin and, around, internal, organs., Nose, ear,, larynx,, trachea, , Cartilage, , Bones, , Skeleton, (A specific, structure, extending, throughout, the body, , Tendons, and, ligaments, , At the joints, , 197, , Structure, , Function, , Erythrocytes,, leucocytes and, platelets in a liquid, plasma, , Transport of, oxygen, nutrients,, hormones and, waste., Fluid oozed out of Protection of, blood capillaries, body from, contains leucocytes infections., and liquid ground, substance, Different types of, Supports, cells loosely arran- internal organs, ged and supported, by a jelly-like, ground substance, and elastic fibres, Cells filled with, Insulation,, fat droplets,, supply of, jelly-like ground, energy, storage, substance, of fats, Cells supported by, fibrous, flexible, Jelly-like ground, substance, Osteocytes, embedded in solid, ground substance, made up of, calcium phosphate, Tendons: fibrous,, strong, less elastic, Ligaments: strong, and highly flexible, , Lubricates the, surfaces of bones,, gives support and, shape to organs, , Supports and, protects, different organs,, helps in, movement, Tendons: join, muscles to, bones, Ligaments: join, two bones to, each other

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Use your brain power !, Muscular tissue, , 1. Why do slim persons feel more cold in winter, than those who are obese?, 2. Why can bones not be folded?, , Bend your arm at elbow. Observe the muscles in the front and the, back, of the arm. Straighten the arm and observe the same muscles again., Try this, Do the same with your leg folding it at the knee joint. Did you experience, the contraction and relaxation of muscles at every movement?, Muscle fibres and muscular tissues are formed from special type of contractile proteins, due to which this contraction and relaxation is possible. Muscular tissues are made up, of the long cells of muscle fibres. Muscular movement occurs due to contraction and, relaxation of the contractile proteins in these cells., Types of muscular tissues, Straited muscles, , Non-striated muscles, , Cardiac muscles, Nucleus, , Striations, , Nucleus, , Striations, , Nucleus, , Muscle cells are long,, cylindrical, multinucleate, and have no branches., Structure: There are alternate dark and light bands, on these muscles at they are, attached to bones, they are, also called skeletal muscles. They move as per our, will, hence they are called, voluntary muscles., Function: These muscles, bring about movements of, arms and legs, running,, speaking, etc., , Can you recall?, , Try this, , Muscle cells are short,, spindle-shaped, uninucleate, and have no branches., Structure: Dark and light, bands are absent. Not, attached to bones. Their, movements are not under the, control of our will, hence, they are called involuntary, muscles. They are present in, the alimentary canal, blood, vessels, etc., Function: Movements of eye, lids, passage of food through, alimentary canal, contraction and relaxation of blood, vessels, , Muscle cells are, cylindrical, uninucleate, and branched., Structure: Dark and light, bands are present. The, heart is made of these, muscles. Their movements, are not under the control, of our will. They contract, and relax rhythmically., , Function: Contraction and, relaxation of the heart., , Which type of muscle is the diaphragm of the respiratory, system?, , Close your eyes and try to identify different objects by feeling them, with your hand. Why is it possible for you to identify things like a notebook, text-book, bench, compass-box, etc, only by touching them?, , 198

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Nervous tissue, Often you must have identified the singer by, Nucleus, merely listening to the song or identified what is, being cooked in the kitchen by the mere smell! What, helps us do this?, Nerve cell, Nervous tissue enables us to respond to stimulii, like touch, sound, odour, colour, etc., Cells of the nervous tissue are specially made, Dendrites, to be come excited and to conduct that excitation, form one part of body to other. The cell body which, Cell body, contents the cytoplasm and the nucleus is the main, part of each nerve cell. Numerous, small, branched, fibres called dendrites arise from the cell body. One, of the fibres, however, is extremely long. It is called, Axon, as the axon. The length of a nerve cell may even, be up to one meter. Many nerve cells are bound, together with the help of connective tissue to form a, nerve. Nervous tissue is present in the brain, spinal, cord and the network of nerves spread all through, the body. In most animals, action in response to a, stimules occurs due to the integrated functioning of, 17.2 Nerve cell : A unit of nervous tissue, nervous tissue and muscular tissue., , Plant tissue, , 1. What is the main difference between the growth of animals, and plants?, Can you recall? 2. Why does the growth of a plant occur only at specific parts, of the plant body?, As shown in the figure 17.3, place an, Try this, onion on each gas jar in such a way that its, base (roots) will remain dipped in water., roots, Measure and record the length of the roots, of both onions on the first, second and third, day. On the fourth day, cut off 1 cm of the, roots of the onion in flask B., B, , A, 17.3 Changes in roots of onion, , Length (cm), Flask A, , Day 1, , Day 2, , Measure the length of the roots of both, onions for the next five days and record, your observations in the following table., Day 3, , Flask B, 1. Which onion has longer roots? Why?, 2. Why did the roots of the onion in jar B stop growing?, , 199, , Day 4, , Day 5

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Meristematic tissue, As meristematic tissue is present in specific parts of a plant, growth occurs in those, parts only. Cells of meristematic tissue contain thick cytoplasm, a conspicuous nucleus, and a thin cell wall and are compactly packed together. Vacuoles are usually absent in, these cells. These cells are highly active. To bring about plant growth is the main function, of meristematic tissue. According to the location, meristematic tissue is of three types as, given below., Figure, , Location, Apical meristem : At the, tip of the root and stem, , Function, Increases the length of, the root and stem., , Intercalary meristem : At Growth of branches,, the base of the petiole of formation of leaves and, flowers., leaves and of branches., Lateral meristem :, , Lateral sides of root and, stem, , Increases girth, (diameter) of the root, and stem., , 17.4 Location of meristematic tissues in plants, , Permanent tissue, After their growth is complete, new cells formed by division of meristematic tissue, lose their ability to divide and start to perform a specific function at specific place. Thus,, they permanently acquire a specific structure, shape and location and perform a specific, function. This is called as differentiation and permanent tissues are formed from these, differentiated cells. There are two types of permanent tissues-simple permanent and, complex permanent tissue., Simple permanent tissues, These are made up of only one type of cells. According to function, they are of the, following different types., Epidermis, Take a fresh and fleshy leaf of Rhoeo, lily or any other, plant. Pull and press it, tearing it obliquely in such a way that its, Try this, transparent epidermis will be visible at the cut margins. Take the, transparent epidermis with the forceps and keep it in dilute safranin, solution. for 1 minute. Spread it on a slide, cover with a cover-slip, and observe it under a compound microscope., The entire outer surface of a plant is made up of only one layer, of cells. That layer is called ‘epidermis’. Cells of the epidermis are, flat and as there are no intercellular spaces between them, a single, continuous layer is formed. The epidermis of the stem and leaves, is covered by a waxy layer of ‘cuticle’ due to which water in the, 17.5 Tissue of Rhoeo plant underlying parts is retained., , 200

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Types of simple permanent tissues, Name of, Tissue, Figure, , Parenchyma, , Collenchyma, , Inter-cellular spaces, , Vacuole, , Sclerenchyma, , Vacuole, , Simple pit pair, Lumen, (cavity), , Vacuole, Cell wall, , Chloroplasts, , Structure, of Cells, , Living cells with thin cell, wall and intercellular spaces, , Location, , All parts like roots, stem,, leaves, flowers and seeds, , Functions, , Support, storage of food and, filling vacant spaces, , Sub-types, , Chlorenchyma: Leaves,, performs photosynthesis., Aerenchyma : Helps aquatic, plants, leaves and stem to float, , Lignified thick cell wall, , Elongated living cells, with thickened cell wall, at corners due to, cellulose and pectin, At the base of leaf, petiole, branches and, stem, , Dead and fibrous cells, with tapering ends, cell, wall contains lignin, , Support and flexibility, to various parts, , Give strength and, rigidity to parts of the, plants., , Stem, veins of leaves,, hard coats of seeds, outer covering of coconut, , Types of complex permanent tissues, Name of, tissue, , Xylem, , Phloem, , Figure, Tracheid, Sieve tube, , Vessel, element, , Companion, cell, Phloem, , Xylem, Characteris- Consists of thick-walled dead, tics, cells, , Consists of cytoplasm containing living, cells, , Types of, cells, , Tracheids, vessels and xylem, fibres-dead cells, Xylem parenchyma-living cells, , Sieve tubes, companion cells, phloem, parenchyma- living cells, Phloem fibres- dead cells, , Function, , Structure like interconnected, tubes,conduct water and minerals, only in upward direction., , Tubes joined to each other, conduct sugar, and amino acids from leaves to various, parts in upward and downward direction, , 201

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Some cells in the body of living organisms are ‘totipotent’, that is if provided a, proper environment, a new organism can grow from these cells. It was realized that with, the help of this property of the cells and their genetically controlled biochemical processes,, varieties of high yielding crops and new species of animals and various vaccines could be, produced. This led to the rise of a new branch in biology, ‘biotechnology’., Biotechnology, With the help of this technique it has become possible to produce plants and animals, bearing some new characterstics in addition to their natural ones. The techniques of bringing, about improvements in living organisms by artificial genetic changes and by hybridization, for the welfare of human beings, are together called ‘Biotechnology’. It includes the, techiques of genetic engineering and tissue culture. Its uses are in the production of cash, crops, improvement in varieties of cash crops, increase in abilities of plants to withstand, environmental stresses, vaccine production, early diagnosis of congenital diseases, organ, transplant, cancer research, production of artificial skin, cartilage, etc. in laboratories., Tissue culture, Suppose you want to grow a garden like the one shown, Can you tell? in the picture, around your home or school. What would you, do to achieve that? By which methods will you cultivate those, seedlings?, You must have, seen flowers of same, variety but of 2 or 3, different colours borne, by same plant. How is, this possible?, Let us learn about, a modern technique, related to farming and, gardening., 17.6 Tissue culture: Plantlets of banana and farming with their help, , ‘Ex vivo growth of cells or tissues in an aseptic and nutrient-rich medium’ is called, tissue culture. Nowadays, a complete organism can be developed from a single cell or, from tissue with help of the tissue culture technique., A liquid, solid or gel-like medium prepared from agar, which supplies nutrients and, energy necessary for tissue culture is used in this technique., Using ICT, With the help of the following websites, collect information about tissue culture, and make a presentation in the class., , www.britannica.com/science/tissue-culture, www.encyclopedia.com/plants and animals/agriculture and horticulture, , 202

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An introduction to, scientists, , Bulb corm, of source, plant, , Secondary, hardening, , Source plant, , Primary, hardening, , Shooting, and, rooting, , Primary, treatment, , Reproduction / Multiplication, 17.7 Various processes in tissue-culture, , Changes in agricultural, biotechnology, , management, , due, , to, , 1. Genetically Modified Crops (GM crops) are being, produced by introducing changes in DNA of natural, crops. Normally, such varieties are not found in nature., Thus, new varieties are produced artificially. Different, useful characters are introduced in such varieties., 2. Ability to withstand environmental stress- Some, naturally occurring varieties cannot withstand, envioromental stresses like frequently changing, temperature, wet and dry famines, changing climate,, etc. However, GM crops can grow in any of such, adverse conditions., 3. As GM crops are resistant to insect pests, pathogens,, chemical weedicides, etc, the use of harmful chemicals, like pesticides can be avoided., 4. Due to use of seeds of GM crops, there is improvement, in nutritive value and decrease in loss of crops., , 203, , Frederick Campion, Steward (1904–1993) was, a British Botanist. He had, shown that cells and tissues, can be grown ex vivo. To, prove this, he isolated the, cells from carrot root and, cultured them in a nutrient, medium. He also proved, that each cell has the, ability to produce a new, plant.

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In this way, as seeds of a better quality of crops, are being produced, farmers all over the world are, Find out, cultivating the GM crops on large scale. The area, under its cultivation is increasing day by day. High, Collect information, Yielding Varieties of GM crops like banana, maize, about GM varieties of, rice, potato, soybean, tomato, cotton, apple, brinjal, crops in your area and, papaya, beet, rose, tobacco, wheat, etc. are available. make a note of them. Also, Pest-resistant genes have been introduced in some of these find out if there are any, GM crops. For example,, adverse effects of GM, Maize : MON 810, MON 863., crops on human beings and, Potato : Amflora, the environment., Rice : Golden Rice, Soybean : Vistive Gold, Tomato : Vaishali, Cotton : BT cotton, In this way, a ‘green evolution’ is being achieved through tissue culture and a country, like India with a huge population is meeting with success in producing sufficient foodgrains for all., Establish your own plant nursery near your school or home. Prepare, the seedlings of flowering plants, fruit plants, and ornamental plants, Try this being grown in your area. Can you start a business in the future with, the help of this activity? Think it over., Application of biotechnology in floriculture, nurseries and forestry, Nurseries are necessary for various purposes like growing gardens on a large scale,, afforestation, reforestation, etc. Seedlings have to be supplied in large numbers for all, these purposes. It is profitable in such cases to produce plantlets with the help of tissue, culture techniques., 1. Tissue culture can be used to grow, those plants on a large scale, which, bear flowers, fruits of excellent quality., , 1, , 2, , 2. Fully grown plants can be produced, in shorter durations., 3. Plants can be grown on a large, scale even if means of pollination or, germinating seeds are not available., For example, orchids or pitcher plant, do not germinate but these plants can, easily be produced by means of tissue, culture., 4. In a bioreactor, cells can be grown in, a more nutritive medium and protected, from pathogens. Bioreactors are useful, for producing plantlets on a very large, scale., , 3, , 17.8 Bioreactor and production of plantlets, , 204

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5. Large numbers of seedlings/plantlets can be produced in a short time using minimum, resources and materials., 6. Usually, plants produced by tissue culture and genetic modification techniques are, disease-free. Plantlets produced by tissue culture of the meristem are virus-free., 7. Embryos formed by conventional hybridization technique between two or more, varieties may not grow fully for some reasons. However, embryos produced by tissue, culture technique always complete their growth., 8. Rare and endangered plants can be grown by tissue culture technique and can thus, be protected from extinction. Similarly, various parts and seeds of such plants can be, preserved by tissue culture and those varieties can be protected., These are the uses of tissue culture and biotecnology in the case of plants. Next year,, we will study the use of this technique in the medical field and for conservation of, animals., Use your brain power !, 1. Which other industries can be developed as an extension of the of plant nursery business?, 2. To which places do people choose to go on vacation in order to relax when they are tired, of crowds and a stressful life?, What is inter-relationship between the two questions above?, Agritourism, If sufficient land is, available, the emerging field of, ‘agri-tourism would be a good, business. Plantlets of flowering,, medicinal,, ornamental,, vegetable plants and fruit trees, can be produced on a large, scale by the tissue culture, technique. And, by growing, some of the plants fully a selfsufficient agritourism centre, 17.9 Some of the fruit trees in the agritourism centre, can be developed., l, , l, l, l, l, l, , Mango, chikoo (sapota), guava, coconut, custard apple and some other regional fruit, trees., Shade giving local or exotic attractive plants., Ornamental and flowering plants., Butterfly garden., Medicinal plant garden., Organic vegetables and fruits., , People visit places with such attractions in large numbers. Selling plantlets / seedlings,, fruits, vegetables at such place can be quite profitable., Using ICT :, , www.ecotourdirectory.com/agritourism, www.agritourism.in, , 205

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Agro-complementary occupations :, Observe and discuss., A. Animal husbandry, Visit a modern cowshed nearby and record, the following points The number of cattle, their variety, total, milk production, cleanliness in cattle-shed,, arrangements for health care of cattle., In India, animal husbandry is practised, for milk production and for using the catttle, as help in farming operations. Ex. Cows and, buffaloes are raised for milk and bulls and, male buffaloes for pulling the heavy loads., Local Indian varieties of cows like sahiwal,, sindhi, gir, lal kandhari, devni, khillari, dangi,, etc. and exotic varieties like jersey, brown, Swiss, Holstein, etc. are kept for their milk., Proper care of cattle is necessary for a clean, and high yield of milk., 1. A balanced diet i.e. which includes all, constitents of food should be given to, cattle. It must include fibre-rich coarse, food, fodder, and sufficient water., 2. The cattle-shed should be clean and dry, with proper ventilation and a roof., 3. Cattle should be regularly vaccinated., , Find out, 1., , What is meant by ‘white revolution?, Who was its pioneer? What benefits, did it bring?, , 2., , Collect more information, animal husbandry., , 3., , Find out from the internet the average, daily milk yield from local and exotic, varieties of cows., , about, , 17.10 Animal husbandry, , 206

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B. Poultry farming, Rearing of egg and meat yielding chickens is called poultry farming., The objectives behind development of new hybrid varieties from a cross between, Indian varieties like Aseel and exotic varieties like leghorn are as follows : to produce good, quality chickens in large numbers, to develop the ability to withstand high temperature, to, use by-products of agriculture as poultry feed, etc., Rhode Island Red, New Hampshire, Plymouth Rock, Black Rock are varieties of, chicken reared for eggs as well as meat., Layers, , Broilers, , Chickens raised for eggs., Leghorn, Minorca, Ancona, Lehman, , Chickens raised for meat., Brahma, Long, Cochin, Aseel, , E. Sericulture, Silkworms (moths) are reared for, production of silk. Bombyx mori is the most, commonly used variety for this purpose. The, life cycle of the silk moth consists of four, stages, namely egg, larva, pupa and adult., Thousands of eggs deposited by female, moths are incubated artificially to shorten, the incubation period. Larvae hatching out of, eggs are released on mulberry plants. Larvae, are nourished by feeding on mulberry leaves., After feeding for 3 – 4 days, larvae move to, branches of mulberry plant. The silk thread, is formed from the secretion of their salivary, glands. Larvae spin this thread around, themselves to form a cocoon. The cocoon, may be spherical in shape., Ten days before the pupa turns into an, adult, all the cocoons are transferred into, boiling water. due to the boiling water, the, pupa dies in the cocoon and silk fibres become, loose. These fibres are unwound, processed, and reeled. Various kinds of fabric is woven, from silk threads., , 207, , Egg, , Larva, , Adult moth, , Pupa, , 17.10 Life cycle of the silk moth

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Use your brain power !, , Why are the cocoons transferred to boiling water, before the pupa develops into an adult?, , Exercises, 1. Each of the following statements is, wrong. Rewrite them correctly by, changing either one or two words., a. Simple squamous epithelium is, present in respiratory tract., b. Glandular epithelium is present in, kidneys., c. Chlorenchyma helps the plant to, float in water., d. Striated muscles are also called involuntary muscles., e. Chloroplast is present in permanent, tissue., 2. Identify the odd word and explain, why it is odd., a. Xylem, phloem, permanent tissue,, meristematic tissue., b. Epithelium, Muscle fibre, nerve, fibre, epidermis., c. Cartilage, bone, tendon, cardiac, muscle., 3. Write the names of the following, tissues., a. Tissue lining inner surface of, mouth., b. Tissue joining muscles and bones., c. Tissue responsible for increasing, height of plants., d. Tissue responsible for increasing, girth of stem., 4. Write the differences., Simple tissue and complex tissues, in plants., , 208, , 5. Write short notes., a. Meristematic tissue., b. Xylem, c. Striated muscles., d. Agro-complementary business., e. Genetic engineering, f. Sericulture, 6. Explain the meaning of biotechnology, and its impact on agricultural, management with suitable examples., 7. Which two main techniques are used, in biotechnology? Why?, 8. Discuss ‘Agritourism’ in the class, and write a project on an agrotourism centre nearby. Present it in, the class in groups., 9. Define the term tissue and explain, the concept of tissue culture., 10. ‘Rearing of sheep is a livestock’., Justify this statement., Activity :, 1. Obtain information about the, diversity of butterflies. Collect, detailed information about what, would have to be done to establish, a butterfly garden in your school., 2. Visit an apiculture centre and, gather information about it., , ²²²

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18. Observing, Space, 1. गतीचे, नियम: Telescopes, Ø Forms of light, , Ø Telescopes and types of telescopes, , Ø Telescopes in space Ø Indian Space Research Orgnaisation (ISRO), , Can you recall?, , 1. What is the difference between the sky and space?, 2. What is meant by space observation? Why is it important?, , From early days, man has been curious about the sun as well as the moon and stars, seen in the night sky. Using his boundless imagination, he tried to understand the sky as, observed by the naked eyes. He noticed that the position of the stars changed with time, and had something to do with the occurrence of seasons. As the knowledge of the cycle of, seasons was necessary for agriculture, sky watching began to prove useful to him. The, position of the constellations was also useful to sea goers for navigation. Man began to, make determined efforts to find answers to questions which arose out of his sky watching., But he did not have any equipment to get a closer view of the stars and planets in the sky., Today, 400 years after Galileo’s, use of the telescope, tremendous, progress has been made in telescope, technology and in space science and, technology on the whole. This great, leap in technology has helped to, construct for us an astounding picture, of our universe. Space science and, technology are not only important for, research purposes, but also to help, provide us with many of the comforts, and facilities we enjoy in our everday, life. A telescope is used to observe, space, but will one telescope be, sufficient for us to observe space, completely? Why do we need different, telescopes for the purpose? Are, telescopes installed even in space? In, this chapter, we are going to study the, science behind many such questions., , An introduction to scientists, In 1608, spectacle maker and researcher,, Hans Lippershey discovered that seeing through, two lenses kept one behind the other, seems to, brings objects closer to us. He thus made the, first telescope. Galileo made a telescope in, 1609 and used it for space observations. He, realized that there are many more stars than, what could be seen with naked eyes. Using his, telescope, he also discovered the moons of, Jupiter, the black spots on the sun, etc., , Galileo Galilei, , Different forms of light, Light is an electromagnetic wave. Every wave has a characteristic wavelength. Our, eyes can see only that light which has wavelengths between 400 nm to 800 nm. Such light is, called visible radiation. However, there are electromagnetic waves of wavelengths other, than the visible ones most of which we cannot ‘see’ as our eyes are not sensitive to them., , 209

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Study the following table., 1 nm (nanometer) = 10-9 m and 1 pm (picometer) = 10-12 m, Type of radiation, Wavelength, Radio waves, Longer than about 20 cm, Micro waves, 0.3 mm – 20 cm, Infrared waves, 800 nm – 0.3 mm, Visible light rays, 400 nm – 800 nm, 300 pm – 400 nm, Ultraviolet rays, X-rays, 3 pm – 300 pm, Gamma rays, Shorter than 3pm, Of all the above types, our eyes are only capable of seeing the visible radiation. Thus, we, use the visible radiation telescopes i.e. optical telescopes, made from regular lenses or mirrors, to see the visible radiation coming from the space. However many heavenly bodies emit, radiations other than the visible light. Thus we need different types of telescopes like the, X-ray, gamma-ray and radio telescopes to receive such radiation and to study their sources., Optical telescopes, Most optical telescopes are made, with two or more lenses as shown in, figure 18.1. To collect the maximum, amount of light coming from a, heavenly object, the objective lens, should be made as large as possible., Eye-piece, Using the light collected by the, Source of, Objective, lens, objective a smaller lens, called the, light, Eye-piece, eyepiece, produces a large image of, the source. Light rays change their, direction as they enter a lens from the, atmosphere and again when they enter, the atmosphere after passing through, the lens. This is called refraction., Hence such telescopes are called, 18.1 A refracting telescope, refracting telescopes. We shall study, image formation by lenses in the next, standard., Even though such a telescope is useful for space observations, it presents certain, difficulties., 1. As we saw above, if we wish to obtain a bright image of a source by collecting the, maximum possible light from it, the objective lens must be made as large as possible., However, it is very difficult to make very large lenses. Also, large lenses are very, heavy and tend to get distorted., 2. As the objective and eyepiece are placed at the opposite ends of the telescope, the, length of the telescope also increases with increase in the size of the lenses and the, telescope becomes difficult to manage., 3. The images formed by lenses have erorrs of colours. This is called chromatic aberration., , Telescopes, , 210

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To overcome these difficulties, telescopes are made using concave mirrors. As light, rays get reflected by mirrors in these telescopes, they are called reflecting telescopes. In, order to get a bright image of a source, large mirrors are necessary (so that they can collect, a large amount of light from the source), but it is easier to make large mirrors as compared, to making large lenses. Also, big mirrors can be made by combining several smaller, pieces. The weight of a large mirror too is less than that of a lense of the same size. The, images formed by mirrors do not have errors of colour. Only by using these large telescopes,, can we see far away stars and galaxies, which we could never have seen using our naked, eyes., The reflecting telescopes are, mainly of two types: Newtonian and, Eyepiece, Cassegrain. As shown in figure 18.2, Concave mirror, light rays coming from space are, reflected by the concave mirror., Light source, Before these reflected rays converge, at the focus, they are deflected again, by a small plane mirror. As a result,, Plane mirror, they get focused at a point lying on, the perpendicular to the axis of the, Light source, telescope’s cylinder., They pass, through the eyepiece and we get a, 18.2 The Newtonian telescope, magnified image of the source., The construction of a Cassegrain, type of telescope is shown in figure, 18.3. The Cassegrain telescope also, uses a concave mirror. However, here, light rays, after reflection from the, concave mirror, are reflected back, towards it by a small convex mirror., They pass through a hole at the centre, of the concave mirror and then through, the eyepiece situated at the back of, the mirror. The eyepiece gives us a, magnified image of the source., , Light source, Eyepiece, Convex, mirror, , Light source, , Concave mirror, , 18.3 The Cassegrain telescope, , In India, we have several telescopes, with concave mirrors of 2 m diameter that, have been in use for many years. The, biggest optical telescope in India, having a, mirror of 3.6 m diameter is situated in the, Aryabhatt, Research, Institute, of, Experimental Sciences, Nainital. This is, the largest optical telescope in Asia., , 211

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Radio telescope, Many heavenly objects emit radio waves in addition to visible radiation. We cannot, see this radiation with our eyes. Hence, a special type of telescope is used to receive these, rays. It is called a radio telescope. It is made from one or more dishes of a particular, parabolic shape. As in optical telescope the incident radio waves are reflected by these, dishes and converge at the focus. A radio receiver is placed at the focal point. The, information gathered by this receiver is passed on to a computer which analyses it and, constructs an image of the source., A large radio telescope called the, Giant Meterwave Radio Telescope, (GMRT) has been erected at, Narayangaon near Pune. It uses radio, waves having wavelengths of about a, metre, coming from planets and stars to, study those heavenly bodies. This, telescope is actually a collection of 30, dishes, each having a diameter of 45 m., It is called a giant telescope as the, arrangement of the 30 dishes over an, area which measures up to 25 km, across, is made in such a way that it, works as a single dish having a diameter, of 25 km. This means that the GMRT, gives the same data that we would have, got from a telescope having a single, dish of 25 km diameter! GMRT has, been made by Indian scientists and, engineers at minimum cost. It is a world, standard research facility. Scientists, study the solar system, solar winds,, pulsars,, supernova,, interstellar, hydrogen clouds, etc. with the help of, the GMRT. Scientists from all over the, world come to India to make use of this, facility., , A, , B, Radio waves, Receiver, Dish, Computer, , Amplifier, , 18.4 A. Radio telescope (photograph), , B. The structure of a radio telescope, , Telescopes in space, Visible light and the radio waves emitted by heavenly bodies in space can pass through, the earth’s atmosphere and reach the earth’s surface. So, optical and radio telescopes can, be erected on the surface of the earth. However, these earth-based telescopes present some, problems in making good quality observations., , 212

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The visible light coming from a heavenly body has to pass through the earth’s, atmosphere to reach the earth’s surface. During this journey, some of the light is absorbed, by the atmosphere and the intensity of the light reaching the earth’s surface decreases. A, second problem is caused by the changes in atmospheric pressure and temperature. These, changes cause turbulence in the atmosphere which in turn cause of the light rays to change, their path slightly and thereby shake the position of the image. Also, because of Sunlight,, we cannot use optical telescopes during the day. During the night too city lights and cloudy, weather can cause difficulties in observing the heavenly bodies. To reduce these problems,, optical telescopes are situated on top of mountains, at in uninhabitated places. However,, if we want to get rid of all the above problems completely, we should place the telescope, above the earth’s atmosphere, in space itself. These problems do not exist in the space and, thus the image obtained by space telescopes would be bright and very clear and will, ramain at one place. Scientists have turned this idea into reality., In 1990, the National Aeronautics and, Space Administration launched into space, an optical telescope called the Hubble, telescope. It has a mirror of diameter 94, inches and is orbiting the earth at a height, of 589 km from it. This telescope is still, working and has helped to make important, discoveries., , In 1999, the National Aeronautics and, Space Administration launched an X-ray, telescope named Chandra, in space, to, study X-rays coming from heavenly, objects. Special mirrors which can, reflect X-rays were used in this telescope., Chandra has given us very useful, information about stars and galaxies., The telescope is named after the famous, Indian, scientist, Subramanian, Chandrashekhar., , Indian Space Research Organization (ISRO) Bengaluru, This institute was established in 1969 with the aim of developing technology for, making and launching of artificial satellites. Till date, ISRO has successfully launched a, large number of satellites. ISRO’s programme is foremost among the successful programs, undertaken by independent India. India’s progress in space science has played a big role, in national and social development., The INSAT and GSAT series of satellites support our telecommunication network,, television broadcasting and meteorological services. It is because of them that telephone,, television and internet services are available everywhere in the country. The EDUSAT, satellite in this series is used exclusively for education. The IRS satellite series is used for, the monitoring and management of natural resources as well as disaster management., Website : www.isro.gov.in, , 213

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Astrosat, In 2015, Indian Space Research Organization, (ISRO) launched an artificial satellite called, Astrosat, in space. This satellite has ultraviolet, and X-ray telescopes and detectors. Most of the, parts used in this satelite are made in India. It is, a unique system having different kinds of, telescopes on a single satellite. Indian scientists, are studying various aspects of the Universe, using the data obtained with these telescopes., , Find out, , Collect more information about telescopes that, work in space apart from the Hubble and Chandra, telescopes., , Exercises, 1. Fill in the blanks with the proper, words., a. The wavelength of visible light is, between …….. and ………, b. GMRT is used for ……. waves., c. A certain X-ray telescope is named, after scientist ……….., d. The first scientist to use a telescope, for, space, observationwas, ................... ., e. The biggest optical telescope in, India is situated at ………., 2. Form pairs, ‘A’ Groups, ‘B’ Groups, (i) X-rays , (a) GMRT, (ii) Optical Telescope (b) ISRO, (iii) Indian radio , (c) Hubble, telescope, (iv) Launching , (d) Chandra, artificial satellites, 3. What are the difficulties in using, ground based optical telescopes?, How are they overcome?, 4. Which type of telescopes can be made, using a concave mirror, convex, mirror, plane mirror and a lens?, Draw diagrams of these telescopes., , 214, , 5. Study the figure and answer the, following questions, , a. What type of telescope is shown in, the figure?, b. Label the main parts of the telescope., c. Which type of mirror does the, telescope use?, d. What other type of telescope uses a, curved mirror?, e. Explain the working of the above, telescope., 6. Answer the following questions., a. Explain the construction of Galileo’s, telescope., b. Explain the construction of a radio, telescope., c. Why are optical telescopes located, in uninhabited places on mountains?, d. Why can an X-ray telescope not be, based on the earth?, Project : Collect information about various, observatories in India and present it, in the class., , ²²²

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Science and Technology - Educational Planning, There are altogether eighteen chapters in which the subject of Science and Technology has, been covered. Of these, the first ten chapters deal with the topics included in the portion of, Paper I and Paper II to be studied the first term. There are two separate papers for the two subjects, namely Science and Technology in each term. The sequence of the chapters in the textbook has, been planned accordingly. Paper I includes physics and chemistry while Paper II deals with, Biology and the rapidly developing and indispensable topics related to Environment, Space,, Weather and climate, Disaster management and Information communication technology all of, which have a great impact on all our lives., Even though, in both terms, the subject has been separated into Paper I (physics and chemistry), and Paper II (biology and other Science-related subjects such as environment, space, weather and, climate, disaster management and information communication technology), teachers must adopt, an integrated approach and consistently teach with that attitude. Some important points which, teachers may keep in mind for the purpose of making annual plans are given below., Term-wise plan of chapters, First Term, Part I, Chapter, No., , Name of chapter, , Part II, Name of chapter, , Chapter, No., , 1, 2, , Laws of Motion, Work and Energy, , 6, 7, , Classification of plants., Energy Flow in an Ecosystem, , 3, 4, , Current Electricity, Measurement of matter, , 8, 9, , Useful and Harmful Micro-organisms, Environmental Management, , 5, , Acids Bases and Salts, , 10, , Information Communication Technology (ICT) :, The new direction of progress, , Second Term, Chapter, No., , Part I, Name of chapter, , Chapter, No., , Part II, Name of chapter, , 11, 12, 13, , Reflection of Light, Study of Sound, Carbon : An important element, , 15, 16, 17, , Life Processes in Living Organisms, Heredity and Variation, Introduction to Biotechnology, , 14, , Substances in Common Use, , 18, , Observing Space.........Telescopes, , 1. Practical work, written exams and all information about it will be given separately., 2. While doing practical work, along with the given experiments, the various activities given in the, textbook must also be done., 3. A record of practical work done should be organized under the heads Title, Apparatus/Materials/, Chemicals, Diagram, Procedure, Observations, Inference/Conclusion., 4. As the questions given at the end of each lesson are based on the content of the lesson as well as the, various activities and projects, a deliberate effort will have to be made to guide the students to the, expected answers., 5. Several of the given activities are newly included in our textbooks and each of them should be completed, separately. The report of the activity should be written in the following order : Preface, Need/ Necessity,, Methodology, Observations, Inferences and Conclusion., , 215

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