Page 1 :
SCIENCE, TEXTBOOK, , FOR, , CLASS VI, , 2018-19

Page 2 :
ISBN 81-7450-512-1, First Edition, March 2006 Phalguna 1927, , ALL RIGHTS RESERVED, , Reprinted, December 2006 Pausa 1928, February 2008 Magha 1929, January 2009 Pausa 1930, November 2009 Agrahayana 1931, November 2010 Kartika 1932, January 2012 Magha 1933, October 2013 Kartika 1935, December 2014 Pausa 1936, December 2015 Agrahayana 1937, January 2017 Magha 1938, December 2017 Agrahayana 1939, , q, , No part of this publication may be reproduced, stored in a retrieval system or, transmitted, in any form or by any means, electronic, mechanical, photocopying,, recording or otherwise without the prior permission of the publisher., , q, , This book is sold subject to the condition that it shall not, by way of trade, be lent,, re-sold, hired out or otherwise disposed of without the publisher’s consent, in any, form of binding or cover other than that in which it is published., , q, , The correct price of this publication is the price printed on this page, Any revised, price indicated by a rubber stamp or by a sticker or by any other means is incorrect, and should be unacceptable., , OFFICES OF THE PUBLICATION, DIVISION, NCERT, , PD 750T RPS, , © National Council of Educational, Research and Training, 2006, , NCERT Campus, Sri Aurobindo Marg, New Delhi 110 016, , Phone : 011-26562708, , 108, 100 Feet Road, Hosdakere Halli Extension, Banashankari III Stage, Bengaluru 560 085, , Phone : 080-26725740, , Navjivan Trust Building, P.O.Navjivan, Ahmedabad 380 014, , Phone : 079-27541446, , CWC Campus, Opp. Dhankal Bus Stop, Panihati, Kolkata 700 114, , Phone : 033-25530454, , CWC Complex, Maligaon, Guwahati 781 021, , Phone : 0361-2674869, , ` 55.00, , Publication Team, , Printed on 80 GSM paper with NCERT, watermark, , Head, Publication, Division, , : M. Siraj Anwar, , Chief Editor, , : Shveta Uppal, , Chief Business, Manager, , : Gautam Ganguly, , Chief Production, Officer (Incharge), , : Arun Chitkara, , Editor, , : Bijnan Sutar, , Production Assistant, , : Deepak Jaiswal, , Cover, Published at the Publication Division by the, Secretary, National Council of Educational, Research and Training, Sri Aurobindo Marg,, New Delhi 110 016 and printed at Ana Print O, Grafix Pvt. Ltd., 347-K, Udyog Kendra Extn.-II,, Sector Ecotech-III, Greater Noida- 201 306, , 2018-19, , Shweta Rao, Layout and Illustrations, Ashwani Tyagi

Page 3 :
FOREWORD, The National Curriculum Framework (NCF), 2005, recommends that children’s life, at school must be linked to their life outside the school. This principle marks a, departure from the legacy of bookish learning which continues to shape our system, and causes a gap between the school, home and community. The syllabi and, textbooks developed on the basis of NCF signify an attempt to implement this basic, idea. They also attempt to discourage rote learning and the maintenance of sharp, boundaries between different subject areas. We hope these measures will take us, significantly further in the direction of a child-centred system of education outlined, in the National Policy on Education (1986)., The success of this effort depends on the steps that school principals and, teachers will take to encourage children to reflect on their own learning and to, pursue imaginative activities and questions. We must recognise that, given space,, time and freedom, children generate new knowledge by engaging with the, information passed on to them by adults. Treating the prescribed textbook as the, sole basis of examination is one of the key reasons why other resources and sites, of learning are ignored. Inculcating creativity and initiative is possible if we, perceive and treat children as participants in learning, not as receivers of a fixed, body of knowledge., These aims imply considerable change in school routines and mode of, functioning. Flexibility in the daily time-table is as necessary as rigour in, implementing the annual calendar so that the required number of teaching days, are actually devoted to teaching. The methods used for teaching and evaluation, will also determine how effective this textbook proves for making children’s life at, school a happy experience, rather than a source of stress or boredom. Syllabus, designers have tried to address the problem of curricular burden by restructuring, and reorienting knowledge at different stages with greater consideration for child, psychology and the time available for teaching. The textbook attempts to enhance, this endeavour by giving higher priority and space to opportunities for, contemplation and wondering, discussion in small groups, and activities requiring, hands-on experience., National Council of Educational Research and Training (NCERT) appreciates, the hard work done by the Textbook Development Committee responsible for this, book. We wish to thank the Chairperson of the advisory group in Science and, Mathematics, Professor J.V. Narlikar and the Chief Advisor for this book,, Dr. N. Rathnasree for guiding the work of this committee. Several teachers, contributed to the development of this textbook; we are grateful to their principals, for making this possible. We are indebted to the institutions and organisations, which have generously permitted us to draw upon their resources, material and, personnel. We are especially grateful to the members of the National Monitoring, Committee, appointed by the Department of Secondary and Higher Education,, Ministry of Human Resource Development under the Chairpersonship of Professor, Mrinal Miri and Professor G.P. Deshpande, for their valuable time and contribution., As an organisation committed to systemic reform and continuous improvement in, the quality of its products, NCERT welcomes comments and suggestions which will, enable us to undertake further revision and refinement., Director, National Council of Educational, Research and Training, , New Delhi, December 2005, , 2018-19

Page 4 :
2018-19

Page 7 :
A NOTE FOR STUDENTS, The team of Paheli and Boojho will be, with you as you journey through this, textbook. They love to ask questions., All kinds of questions come to their, minds and they collect them in their, sacks. Sometimes, they may share, some of these questions with you, as, you read through the chapters., Paheli and Boojho are also on the, lookout for answers to many, questions — sometimes the questions, seem answered after they discuss, them with each other, sometimes, through discussions with other, classmates, teachers or their parents., Answers to some questions do not, seem available even after all these. They might need to experiment on their own,, read books in the library, send questions to scientists. Just dig and dig and dig, into all possibilities and see if the questions can be answered. Perhaps, they, would carry some of the unanswered questions in their sacks to higher classes., What will really thrill them, would be your adding questions to their sacks, or answer to their questions. Sometimes activities are suggested in the textbook,, results or findings of these by different groups of students would be of interest to, other students and teachers. You can complete the suggested activities and send, your results or findings to Paheli and Boojho. Do keep in mind that activities, that involve using blades, scissors or fire need to be done strictly under the care, of your teachers. Stick to the precautions given and then enjoy doing all the, suggested activities. Mind, the book will not be able to help you much, if the, activities are not completed!, You can send your feedback for Paheli and Boojho at., , To, The Head, Department of Education in, Science and Mathematics,, NCERT, Sri Aurobindo Marg,, New Delhi 110016, , 2018-19

Page 8 :
CONSTITUTION OF INDIA, Part IV A (Article 51 A), , Fundamental Duties, Fundamental Duties – It shall be the duty of every citizen of India —, (a) to abide by the Constitution and respect its ideals and institutions, the National, Flag and the National Anthem;, (b) to cherish and follow the noble ideals which inspired our national struggle for, freedom;, (c) to uphold and protect the sovereignty, unity and integrity of India;, (d) to defend the country and render national service when called upon to do so;, (e) to promote harmony and the spirit of common brotherhood amongst all the people, of India transcending religious, linguistic and regional or sectional diversities; to, renounce practices derogatory to the dignity of women;, (f) to value and preserve the rich heritage of our composite culture;, (g) to protect and improve the natural environment including forests, lakes, rivers,, wildlife and to have compassion for living creatures;, (h) to develop the scientific temper, humanism and the spirit of inquiry and reform;, (i) to safeguard public property and to abjure violence;, (j) to strive towards excellence in all spheres of individual and collective activity so, that the nation constantly rises to higher levels of endeavour and achievement;, (k) who is a parent or guardian, to provide opportunities for education to his child or,, as the case may be, ward between the age of six and fourteen years., , 2018-19

Page 9 :
CONTENTS, iii, vii, , FOREWORD, A NOTE FOR STUDENTS, CHAPTER, , 1, , FOOD: WHERE DOES IT COME FROM?, C H A P T E R, , 1, , 2, , COMPONENTS OF FOOD, C H A P T E R, , 8, , 3, , FIBRE TO FABRIC, C H A P T E R, , 18, 4, , SORTING MATERIALS INTO GROUPS, C H A P T E R, , 26, , 5, , SEPARATION OF SUBSTANCES, C H A P T E R, , 35, , 6, , CHANGES AROUND US, C H A P T E R, , 46, 7, , GETTING TO KNOW PLANTS, C H A P T E R, , 52, , 8, , BODY MOVEMENTS, C H A P T E R, , 66, 9, , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, C H A P T E R, , 10, , MOTION AND MEASUREMENT OF DISTANCES, C H A P T E R, , 95, , 11, , LIGHT, SHADOWS AND REFLECTIONS, C H A P T E R, , 107, , 12, , ELECTRICITY AND CIRCUITS, C H A P T E R, , 79, , 116, , 13, , FUN WITH MAGNETS, , 125, , 2018-19

Page 10 :
x, C H A P T E R, , 14, , WATER, C H A P T E R, , 136, 15, , AIR AROUND US, C H A P T E R, , 147, 16, , GARBAGE IN, GARBAGE OUT, , 155, , 2018-19

Page 11 :
1, , Food:, Where Does it Come From?, , W, , hat did you eat at home, today? Find out what your, friend ate today. Did you eat, the same kind of food yesterday and, today? We all eat different kinds of food, at different times, isn’t it?, , 1.1 FOOD VARIETY, Activity 1, Ask your friends in the school about the, items they would be eating during a day., See if you can also get this information, from friends staying in different states, of India. List all the items in your, notebook as given in Table 1.1, for as, many friends as possible., Table 1.1 What do we eat?, Name of the, student/friend, , Food items, eaten in a day, , There seems to be so much variety, in the food that we eat (Fig 1.1). What, are these food items made of?, Think about rice, cooked at home. We take, raw rice and boil it in, water. Just two materials, or ingredients are, needed to prepare a dish of boiled rice., On the other hand, some food items, are made with many ingredients. To, prepare vegetable curry, we need, different kinds of vegetables, salt, spices,, oil and so on., , Activity 2, Choose some of the items you listed in, Table 1.1 and try to find out what, ingredients are used to prepare these,, by discussing with your friends and, elders at home. List them in Table 1.2., Some examples are given here. Add, some more items to this list., Table 1.2 Food items and their, ingredients, Food Item, , Ingredients, , Roti/chapati, , Atta, water, , Dal, , Pulses, water, salt, oil/, ghee, spices, , Fig. 1.1 Different food items, , 2018-19

Page 12 :
What do we find? Do we find some ingredients common, for different food items? Discuss in class., So, where do these ingredients come from?, , 1.2 FOOD MATERIALS, , AND, , SOURCES, , It may be easy for us to guess the sources of some of the, ingredients that we listed in Table 1.2. Fruits and, vegetables, for instance (Fig. 1.2a). Where do they come, from? Plants, of course! What are the sources of rice or, wheat? You may have seen paddy or wheat fields with rows, and rows of plants, which give us these grains (Fig. 1.3)., And then, there are food items like milk, eggs and meat,, which come from animals (Fig. 1.2b)., , Activity 3, , (a) Plant sources, , Fig. 1.2 Sources of, food ingredients, , Let us take the food items listed earlier, and try to find out where they come from, — the ingredients and their sources., Some examples are shown in Table 1.3., Fill in the blanks in Table 1.3 and add, more examples to this list., , (b) Animal sources, , Table 1.3 Ingredients used to, prepare food items and, their sources, Food Item Ingredients, Idli, , Rice, , Sources, Plant, , Urad dal, Salt, Water, Chicken, curry, (a), , Chicken, , Animal, , Spices, Oil/ghee, , Plants/, Animals, , Water, Kheer, (b), Fig. 1.3 Source of food grains, (a) Paddy field (b) Wheat grains transported, , Milk, , Animal, , Rice, , Plant, , Sugar, , 2, , SCIENCE, , 2018-19

Page 13 :
What do we conclude from Activity, 3? Plants are the sources of food, ingredients like grains, cereals,, vegetables and fruits. Animals provide, us with milk, meat products and eggs., Cows, goats and buffaloes are some, common animals which give us milk., Milk and milk products like butter,, cream, cheese and curd are used all over, the world. Can you name some other, animals which give us milk?, , Flower, , Fruit, Stem, Leaf, , Node, Internode, , {, , Bud, , 1.3 PLANT PARTS AND ANIMAL, PRODUCTS AS FOOD, Plants are one source of our food. Which, parts of a plant?, We eat many leafy vegetables. We eat, fruits of some plants. Sometimes roots,, sometimes stems and even flowers, (Fig 1.4). Have you ever eaten pumpkin, , Paheli wants to know if any of our, food comes from sources other, than plants and animals., , Shoot, system, , Primary, root, Root, Secondary system, root, , Fig. 1.4 Different edible parts of plants, , flowers dipped in rice paste and fried?, Try it!, Some plants have two or more edible, (eatable) parts. Seeds of mustard plants, give us oil and the leaves are, used as a vegetable. Can you think of, the different parts of a banana plant that, are used as food? Think of more, examples where two or more parts of a, single plant are used as food., , Table 1.4 Plant parts as food, Food item with plant, as the major source, 1. Brinjal curry, , Ingredients/source, , Plant part which gives, us the ingredient, , Brinjal, , Fruit, , Chilli as spice (any other), , Fruit, , Oil from groundnut, mustard,, soybean, any other plant, , Seed, , 2., 3., FOOD: WHERE DOES IT COME FROM?, , 3, , 2018-19

Page 14 :
Do not try to taste unknown plants, around you to see if they are edible!, Some plants could be poisonous., , Activity 4, From all the food items you have listed, in Table 1.3, choose those items whose, ingredients are obtained from plants., Which part of a plant? Identify these, and list the food items and plant parts, as shown in Table 1.4., , Fig. 1.6 Chana (gram) and its sprouts, , covered with a wet cloth. The next day,, see if the seeds have sprouted., After washing these sprouted seeds,, you can eat them. They can also be, boiled. Add some spices and get a tasty, snack to eat., Do you know where honey comes, from, or how it is produced? Have you, seen a beehive where so many bees keep, buzzing about? Bees collect nectar, (sweet juices) from flowers, convert it, , Activity 5, Take some dry seeds of moong or chana., Put a small quantity of seeds in a, container filled with water and leave this, aside for a day. Next day, drain the water, completely and leave the seeds in the, vessel. Wrap them with a piece of wet, cloth and set aside. The following day,, do you observe any changes in the seeds?, Fig. 1.7 Beehive, , Fig. 1.5 Whole moong and its sprouts, , A small white structure may have grown, out of the seeds. If so, the seeds have, sprouted (Fig. 1.5 and 1.6). If not, wash, the seeds in water, drain the water and, leave them aside for another day,, , into honey and store it in their hive, (Fig. 1.7). Flowers and their nectar may, be available only for a part of the year., So, bees store this nectar for their use, all through the year. When we find such, a beehive, we collect the food stored by, the bees as honey., , 1.5 WHAT, , DO, , ANIMALS EAT?, , Do you have cattle or a pet that you take, care of? A dog, cat, buffalo or a goat?, , 4, , SCIENCE, , 2018-19

Page 15 :
eat is also given. Fill in the blanks in, the table., , Activity 7, , Fig. 1.8 Squirrel eating nuts, , You will then surely be aware of the food,, the animal eats. What about other, animals? Have you ever observed what, a squirrel (Fig 1.8), pigeon, lizard or a, small insect may be eating as their food?, , Activity 6, Several animals are listed in Table 1.5., For some of them, the type of food they, Table 1.5 Animals and their Food, Name of the, animal, , Have a look again at Table 1.5 and group, the animals entered here as follows., Place animals which eat only plants or, plant products in Group 1. These are, called herbivores. There are some, animals which eat other animals., Place these in Group 2. These animals, are called carnivores. Do you find, some animals which eat both plants, and animals? Place them in Group 3., These are called omnivores. Prepare, a table as in Table 1.6 and enter, these separately in the three columns,, as shown., Table 1.6, Herbivores Carnivores Omnivores, , Food the, animal eats, , Buf falo, , Grass, oilcake,, hay, grains, , Cat, , Small animals,, birds, milk, , Cow, , Lion, , Dog, , Rat, Lion, T iger, Spider, , Paheli wants to know where you, would place human beings,, while filling Table 1.6., , House lizard, Cow, Human beings, Butter fly, Crow, Others, , We know that there are many, amongst us, who do not get sufficient, , FOOD: WHERE DOES IT COME FROM?, , 5, , 2018-19

Page 16 :
food. We need to find ways by which, more food can be produced in the, country. That will not be enough; we, , will need to find ways to ensure that, this food is made easily available to each, one of us., , Ingredients, Edible, Nectar, Sprouted seeds, Herbivore, Car nivore, Omnivore, , n, , There is a lot of variation in the food eaten in different regions of India., , n, , The main sources of our food are plants and animals., , n, , Animals which eat only plants are called herbivores., , n, , Animals which eat only animals are called carnivores., , n, , Animals which eat both plants as well as other animals are called, omnivores., , 1., , Do you find that all living beings need the same kind of food?, , 2., , Name five plants and their parts that we eat., , 3., , Match the items given in Column A with that in Column B, Column A, , Column B, , Milk, curd, paneer, ghee,, , eat other animals, , Spinach, cauliflower, carrot, , eat plants and plant products, , Lions and tigers, , are vegetables, , Herbivores, , are all animal products, , 6, , SCIENCE, , 2018-19

Page 17 :
4., , Fill up the blanks with the words given:, herbivore, plant, milk, sugarcane, carnivore, (a) Tiger is a ____________________ because it eats only meat., (b) Deer eats only plant products and so, is called ______________., (c) Parrot eats only _________________ products., (d) The ________________ that we drink, which comes from cows, buffaloes and, goats is an animal product., (e) We get sugar from ___________________., , SUGGESTED PROJECTS AND ACTIVITIES, 1., , You must have seen a garden lizard around your home. Next time whenever you see it, observe carefully and find out what it takes for food. Is the, food different from that of a house lizard?, , 2., , Make a list (with pictures, when possible) of food items generally taken by, people of different regions of India. Place these on a large outline map of, India to display in your classroom., , 3., , Find out the names of plants that grow in water and which are eaten, as food., , 4., , In Chapter 10, you will find out ways of measuring length of curved lines., In your mathematics classes you will learn to prepare bar graphs. After, you learn these, try the following interesting project. Prepare some sprouts, of moong as discussed in the chapter. Wash them in water everyday and, drain all the water. Let them grow for a week until the whole of the seeds, grow into young plants. Measure the lengths of the sprouts everyday using, a string. Take care that they do not break. Prepare a bar graph of the, number of sprouts having lengths in different ranges., , THINGS TO THINK ABOUT, 1., , Does everyone around you get enough food to eat? If not, why?, , 2., , What are the ways we can think of to avoid wastage of food?, , FOOD: WHERE DOES IT COME FROM?, , 7, , 2018-19

Page 18 :
2, , Components of Food, , n Chapter 1, we made lists of the, food items that we eat. We also, identified food items eaten in, different parts of India and marked, these on its map., A meal could consist of chapati, dal, and brinjal curry. Another may be rice,, sambar and a vegetable preparation of, lady’s finger (bhindi). Yet another meal, could be appam, fish curry and, vegetables., , I, , curd, butter milk and pickles. Some, examples of meals from different regions, are given in Table 2.1. Select food items, you depicted on the map in Chapter 1., Add some more meals to this list and, enter these in Table 2.1., Sometimes, we may not really have, all this variety in our meals. If we are, travelling, we may eat whatever is, available on the way. It may not be, possible for some of us, to eat such a, variety of items, most of the time., There must be some reason though,, why meals usually consist of such a, distribution. Do you think that our body, needs different kinds of food for some, special purpose?, , Activity 1, , 2.1 WHAT DO DIFFERENT FOOD, ITEMS CONTAIN?, , Our meals usually have at least one item, made of some kind of grain. Other items, could be a dal or a dish of meat and, vegetables. It may also include items like, , We know that each dish is usually made, up of one or more ingredients, which, we get from plants or animals. These, , Table 2.1 Some common meals of different regions/states, Region/, State, Punjab, Andhra, Pradesh, , Item of grain, , Item of, dal/meat, , Vegetables, , Rajma, Sarson saag, Makki (cor n) roti (Kidney beans) (Mustard leaf curry), Rice, , Tuar dal and, rasam (charu), , 8, , Kunduru (dondakai), , Others, Curd, ghee, Butter milk, ghee,, pickle (aavakai), , SCIENCE, , 2018-19

Page 19 :
ingredients contain some components, that are needed by our body. These, components are called nutrients. The, major nutrients in our food are named, carbohydrates, proteins, fats, vitamins, and minerals. In addition, food contains, dietary fibres and water which are also, needed by our body., Do all foods contain all these, nutrients? With some simple methods, we can test whether cooked food or a, raw ingredient contains one or more of, these nutrients. The tests for presence, of carbohydrates, proteins and fats, are simpler to do as compared to the, tests for other nutrients. Let us do these, tests and record all our observations, in Table 2.2., For carrying out these tests, you will, need solutions of iodine, copper, sulphate and caustic soda. You will also, need a few test tubes and a dropper., Try these tests on cooked food items, as well as raw materials. Table 2.2 shows, you a way to record the observations, from these tests. Some food items are, given in this table. You can conduct the, tests either with these or any other, available food items. Do these tests, carefully and do not try to eat or taste, any chemicals., If the required solutions are not, available in readymade form, your, teacher can prepare them as given in, the box., Let us begin by testing different, food items to see if they contain, carbohydrates. There are many, types of carbohydrates. The main, carbohydrates found in our food are in, , A dilute solution of iodine can be, prepared by adding a few drops of, tincture iodine to a test tube half filled, with water., Copper sulphate solution can be, pr epar ed by dissolving 2 gram (g) of, copper sulphate in 100 millilitre (mL), of water., 10 g of caustic soda dissolved in, 100 mL of water makes the required, solution of caustic soda., , the form of starch and sugars. We can, easily test if a food item contains starch., , Activity 2, Test for Starch, Take a small quantity of a food item or, a raw ingredient. Put 2-3 drops of dilute, iodine solution on it (Fig. 2.1). Observe, if there is any change in the colour of, the food item. Did it turn blue-black?, , COMPONENTS OF FOOD, , Fig. 2.1 Testing for starch, 9, , 2018-19

Page 20 :
A blue-black colour indicates that it, contains starch., Repeat this test with other food items, to find out which of these contain starch., Enter all your observations in Table 2.2., , Test for Protein, , test tube (Fig. 2.2). Shake well and let, the test tube stand for a few minutes., What do you see? Did the contents of, the test tube turn violet? A violet colour, indicates presence of proteins in the, food item., Now, you can repeat this test on other, food items., , Take a small quantity of a food item for, testing. If the food you want to, Table 2.2 Nutrients present in some, test is a solid, you first need to, food items, make a paste of it or powder it., Grind or mash a small quantity, Starch, Protein, Fat, Food item, of the food item. Put some of this, (present), (present) (present), in a clean test tube, add 10 drops, Raw potato, Yes, of water to it and shake the, Milk, Yes, test tube., Now, using a dropper, add Groundnut, Yes, two drops of solution of copper, ncooked, sulphate and ten drops of U, powdered, solution of caustic soda to the rice, Cooked rice, Dry coconut, Uncooked, tuar dal, (powdered), Cooked dal, A slice of any, vegetable, A slice of any, fruit, Boiled egg, (white, portion), , Fig. 2.2 Testing for protein, 10, , SCIENCE, , 2018-19

Page 21 :
Test for Fats, Take a small quantity of a food item., Wrap it in a piece of paper and crush it., Take care that the paper does not tear., Now, straighten the paper and observe, it carefully. Does it have an oily patch?, Hold the paper against light. Are you, able to see the light faintly, through, this patch?, An oily patch on paper shows that, the food item contains fat. The food, items may sometimes contain a little, water. Therefore, after you have rubbed, an item on paper, let the paper dry for a, while. If there were any water that may, have come from food, it would dry up, after some time. If no oily patch shows, up after this, the food item does not, contain any fat., What do these tests show? Are fats,, proteins and starch present in all the, food items that you tested? Does a food, item contain more than one nutrient?, Do you find any food item that does not, contain any of these nutrients?, We tested food items for three, nutrients — carbohydrates, proteins, and fats. There are also other nutrients, like vitamins and minerals that are, present in different food items. Why do, we need all these nutrients?, , 2.2 WHAT, , VARIOUS NUTRIENTS, BODY?, , DO, , FOR OUR, , fats and carbohydrates are also, called ‘energy giving foods’ (Fig. 2.3, and Fig. 2.4)., Proteins are needed for the growth, and repair of our body. Foods, Sweet potato, , Potato, , Sugarcane, Papaya, , Wheat, Melon, Mango, Rice, Maize, , Bajra, , Fig. 2.3 Some sources of carbohydrates, , Nuts, , Groundnuts, , Til, (a), , Meat, , DO, , Carbohydrates mainly provide energy, to our body. Fats also give us energy., In fact, fats give much more energy, as compared to the same amount of, carbohydrates. Foods containing, , Eggs, Fish, , (b), , Fig. 2.4 Some sources of fats: (a) plant sources, and (b) animal sources, , COMPONENTS OF FOOD, , 11, , 2018-19

Page 22 :
Gram, , Moong, , Tuar dal, Beans, , Peas, , small quantities. Vitamin A keeps our, skin and eyes healthy. Vitamin C helps, body to fight against many diseases., Vitamin D helps our body to use, calcium for bones and teeth. Foods that, are rich in different vitamins are shown, in Fig. 2.6 to Fig. 2.9., Minerals are needed by our body in, small amounts. Each one is essential, Papaya, , Soyabeans, (a), , Carrot, , Meat, , Mango, Fig. 2.6 Some sources of Vitamin A, Wheat, , Rice, , Fish, , Liver, Fig. 2.7 Some sources of Vitamin B, Eggs, , Paneer, , Guava, , Orange, , (b), , Tomato, , Fig. 2.5 Some sources of proteins: (a) plant, sources and (b) animal sources, , proteins are often called ‘body building, foods’ (Fig 2.5)., Vitamins help in protecting our body, against diseases. Vitamins also help in, keeping our eyes, bones, teeth and gums, healthy., Vitamins are of different kinds, known by different names. Some of these, are Vitamin A, Vitamin C, Vitamin D,, Vitamin E and K. There is also a group, of vitamins called Vitamin B-complex., Our body needs all types of vitamins in, 12, , Green, Chilli, Lemon, Amla, Fig. 2.8 Some sources of Vitamin C, , Fish, , Egg, Liver, Fig. 2.9 Some sources of Vitamin D, SCIENCE, , 2018-19

Page 23 :
Some sources of, iodine, , Our body also, prepares Vitamin D in the, presence of sunlight. Nowadays,, insufficient exposure to sunlight is, causing Vitamin D deficiency in, many people., , Ginger, Some sources of, phosphorous, , for proper growth of body and to, maintain good health. Some sources of, different minerals are shown in Fig. 2.10., Most food items, usually, have more, than one nutrient. You may have noticed, this, while recording your observations, in Table 2.2. However, in a given raw, material, one particular nutrient may, be present in much larger quantity than, in others. For example, rice has more, carbohydrates than other nutrients., Thus, we say that rice is a “carbohydrate, rich” source of food., Besides these nutrients, our body, needs dietary fibres and water. Dietary, fibres are also known as roughage., Roughage is mainly provided by plant, products in our foods. Whole grains and, pulses, potatoes, fresh fruits and, vegetables are main sources of roughage., Roughage does not provide any nutrient, to our body, but is an essential, component of our food and adds to its, bulk. This helps our body get rid of, undigested food., , Some sources, of iron, , COMPONENTS OF FOOD, , Some sources, of calcium, , Fig. 2.10 Sources of some minerals, 13, , 2018-19

Page 24 :
Water helps our body to absorb, nutrients from food. It also helps in, throwing out some wastes from body as, urine and sweat. Normally, we get most, of the water that our body needs from, the liquids we drink — such as water,, milk and tea. In addition, we add water, to most cooked foods. Let’s see if there, is any other source which provides water, to our body., , Activity 3, Take a tomato or a fruit like lemon. Cut, it into small pieces. Do your hands get, wet while doing so?, Carefully, observe, whenever, vegetables and fruits are being cut,, peeled, grated or mashed at your, home. Do you find any fresh vegetables, or fruits that do not contain some, amount of water?, We see that many food materials, themselves contain water. To some, extent, our body needs are met by this, water. Apart from this, we also add water, while cooking many food items., , think that, what we need for a balanced, diet would depend on the amount of, physical work that we do?, Prepare a chart of whatever you eat, over a period of a week. Check whether, all the nutrients mentioned are present, in one or the other food items being, eaten within a day or so., Pulses, groundnut, soyabean,, sprouted seeds (moong and Bengal, gram), fermented foods (South Indian, foods such as idlis), a combination of, flours (missi roti, thepla made from, cereals and pulses), banana, spinach,, sattu, jaggery, available vegetables and, other such foods provide many, nutrients. Therefore, one can eat a, balanced diet without expensive food, materials., Eating the right kind of food is not, enough. It should also be cooked, , Paheli wonders whether animal, food also consists of these, different components and do, they also need a balanced diet?, , 2.3 BALANCED DIET, The food we normally eat in a day is our, diet. For growth and maintenance of, good health, our diet should have all, the nutrients that our body needs, in, right quantities. Not too much of one, and not too little of the other. The diet, should also contain a good amount of, roughage and water. Such a diet is called, a balanced diet., Do you think that people of all ages, need the same type of diet? Do you also, , properly so that its nutrients are not, lost. Are you aware that some nutrients, get lost in the process of cooking and, preparations?, If the vegetables and fruits are, washed after cutting or peeling them, it, , 14, , SCIENCE, , 2018-19

Page 25 :
may result in the loss of some vitamins., The skins of many vegetables and fruits, contain vitamins and minerals., Similarly, repeated washing of rice and, pulses may remove some vitamins and, minerals present in them., We all know that cooking improves, the taste of food and makes it easier to, digest. At the same time, cooking also, results in the loss of certain nutrients., Many useful proteins and considerable, amounts of minerals are lost if excess, water is used during cooking and is, then thrown away., Vitamin C gets easily destroyed by, heat during cooking. Would it not be, sensible to include some fruits and raw, vegetables in our diet?, Boojho thought that fats would be, the best foods to eat, all the time. A katori, (bowl) of fat will give much more energy, than a katori of carbohydrate rich food,, isn’t it? So, he ate nothing but food rich, , in fats — fried food like samosa and poori, (snacks), malai, rabdi and peda (sweets)., Do you think he was right? No, of, course not! It can be very harmful for, us to eat too much of fat rich foods and, we may end up suffering from a, condition called obesity., , 2.4 DEFICIENCY DISEASES, A person may be getting enough food to, eat, but sometimes the food may not, contain a particular nutrient. If this, continues over a long period of time, the, person may suffer from its deficiency., Deficiency of one or more nutrients can, cause diseases or disorders in our body., Diseases that occur due to lack of, nutrients over a long period are called, deficiency diseases., If a person does not get enough, proteins in his/her food for a long time,, he/she is likely to have stunted growth,, swelling of face, discolouration of hair,, skin diseases and diarrhoea., If the diet is deficient in both, carbohydrates and proteins for a long, period of time, the growth may stop, completely. Such a person becomes very, lean and thin and so weak that he/she, may not even be able to move., Deficiency of different vitamins and, minerals may also result in certain, diseases or disorders. Some of these are, mentioned in Table 2.3., All deficiency diseases can be, prevented by taking a balanced diet., In this chapter, we asked ourselves, the reason why widely varying food from, different regions had a common, , COMPONENTS OF FOOD, , 15, , 2018-19

Page 26 :
Table 2.3 – Some diseases/disorders caused by, deficiency of vitamins and minerals, Vitamin/, Mineral, Vitamin A, , Vitamin, B1, , Deficiency, disease/disorder, Loss of vision, , Beriberi, , Vitamin C, , Scurvy, , Vitamin D, , Rickets, , Calcium, , Bone and tooth, decay, , Balanced diet, , Symptoms, Poor vision, loss of, vision in darkness, (night), sometimes, complete loss of vision, , Beriberi, Carbohydrates, Energy, Fats, , Weak muscles and, very little energy to, work, , Bleeding gums,, , Minerals, Nutrients, , wounds take longer, time to heal, , Bones become soft, , Proteins, Roughage, , and bent, , Scurvy, , Weak bones, tooth, decay, , Starch, , Glands in the neck, , Vitamins, , Iodine, , Goiter, , appear swollen,, mental disability in, children, , Iron, , Anaemia, , Weakness, , distribution. This distribution, we find, ensures that, our meals have a balance of the different nutrients, needed by the body., , n, , The major nutrients in our food are carbohydrates, proteins, fats, vitamins, and minerals. In addition, food also contains dietary fibres and water., , n, , Carbohydrates and fats mainly provide energy to our body., , n, , Proteins and minerals are needed for the growth and the maintenance, of our body., , n, , Vitamins help in protecting our body against diseases., , n, , Balanced diet provides all the nutrients that our body needs, in right, quantities, along with adequate amount of roughage and water., , n, , Deficiency of one or more nutrients in our food for a long time may cause, certain diseases or disorders., , 16, , SCIENCE, , 2018-19

Page 27 :
1., , Name the major nutrients in our food., , 2., , Name the following:, (a) The nutrients which mainly give energy to our body., (b) The nutrients that are needed for the growth and maintenance of our body., (c) A vitamin required for maintaining good eyesight., (d) A mineral that is required for keeping our bones healthy., , 3., , Name two foods each rich in:, (a) Fats, (b) Starch, (c) Dietary fibre, (d) Protein, , 4., , Tick (√) the statements that are correct., (a) By eating rice alone, we can fulfill nutritional requirement of our body. ( ), (b) Deficiency diseases can be prevented by eating a balanced diet. ( ), (c) Balanced diet for the body should contain a variety of food items. ( ), (d) Meat alone is sufficient to provide all nutrients to the body. ( ), , 5. Fill in the blanks., (a) ______________ is caused by deficiency of Vitamin D., (b) Deficiency of ______________ causes a disease known as beri-beri., (c) Deficiency of Vitamin C causes a disease known as ______________., (d) Night blindness is caused due to deficiency of ____________ in our food., , SUGGESTED PROJECTS AND ACTIVITIES, 1., , Prepare a diet chart to provide balance diet to a twelve year old child. The, diet chart should include food items which are not expensive and are commonly available in your area., , 2., , We have learnt that excess intake of fats is harmful for the body. What about, other nutrients? Would it be harmful for the body to take too much of proteins, or vitamins in the diet? Read about diet related problems to find answers to, these questions and have a class discussion on this topic., , 3., , Test the food usually eaten by cattle or a pet to find out which nutrients are, present in animal food. Compare results obtained from the whole class to, conclude about balanced diet requirements for different animals., , COMPONENTS OF FOOD, , 17, , 2018-19

Page 28 :
3, , Fibre to Fabric, , P, , aheli and Boojho won the first, prize in a Science Quiz, competition held at their school., They were very excited and decided to, use the prize money to buy clothes for, their parents. When they saw a large, variety of cloth material, they got, confused (Fig. 3.1). The shopkeeper, explained that some clothes or fabrics, were cotton and some were synthetic., He also had woollen mufflers and, shawls. There were many silk sarees as, well. Paheli and Boojho felt very excited., They touched and felt these different, fabrics. Finally, they bought a woollen, muffler and a cotton saree., After their visit to the cloth shop,, Paheli and Boojho began to notice, various fabrics in their surroundings., They found that bed sheets, blankets,, , curtains, tablecloths, towels and, dusters were made from different kinds, of fabrics. Even their school bags and, the gunny bags were made from, some kind of fabric. They tried to, identify these fabrics as cotton, wool,, silk or synthetic. Can you also identify, some fabrics?, , 3.1 VARIETY, , IN, , FABRICS, , Activity 1, Visit a nearby tailoring shop., Collect cuttings of, fabrics leftover after, stitching. Feel and, touch each piece, of fabric. Now,, try to label some, of the fabrics as, Fig.3.2 Enlarged view, cotton, silk, wool of a piece of fabric, or synthetic after, asking for help from the tailor., Do you wonder what these different, fabrics are made of? When you look at, any fabric, it seems a continuous piece., Now, look at it closely. What do you, notice (Fig. 3.2)?, , Activity 2, , Fig. 3.1 A cloth shop, , Select a piece of cotton fabric you, labelled in Activity 1. Now, try to find a, loose thread or yarn at one of the edges, and pull it out (Fig. 3.3). If no loose, , 18, , SCIENCE, , 2018-19

Page 29 :
Fig. 3.3 Pulling a thread from a fabric, , yarns are visible, you can gently pull, one out with a pin or a needle., We find that a fabric is made up of, yarns arranged together. What are these, yarns made of?, , 3.2 FIBRE, Activity 3, Take out a yarn from a piece of cotton, fabric. Place this piece of yarn on the, table. Now, press one end of the yarn, with your thumb. Scratch the other end, of the yarn along its length with your, nail as shown in Fig. 3.4. Do you find, that at this end, the yarn splits up into, thin strands (Fig. 3.5)?, , You might have observed something, similar when you try to thread a, needle. Many a time, the end of the, thread is separated into a few thin, strands. This makes it difficult to pass, the thread through the eye of the, needle. The thin strands of thread that, we see, are made up of still thinner, strands called fibres., Fabrics are made up of yarns and, yarns are further made up of fibres., Where do these fibres come from?, The fibres of some fabrics such as, cotton, jute, silk and wool are obtained, from plants and animals. These are, called natural fibres. Cotton and jute, are examples of fibres obtained from, plants. Wool and silk fibres are obtained, from animals. Wool is obtained from the, fleece of sheep or goat. It is also obtained, from the hair of rabbits, yak and, camels. Silk fibre is drawn from the, cocoon of silkworm., For thousands of years natural fibres, were the only ones available for making, fabrics. In the last hundred years or so,, fibres are also made from chemical, , Boojho has seen in the, museums, items like the, one shown here. These, were worn by warriors. He, wants to know if these, are made of some, kinds of fibre., , Fig.3.4 Splitting the yarn into thin strands, , Fig. 3.5 Yarn split up into thin strands, FIBRE TO FABRIC, , 19, , 2018-19

Page 30 :
substances, which are not obtained, from plant or animal sources. These are, called synthetic fibres. Some examples, of synthetic fibres are polyester, nylon, and acrylic., , 3.3 SOME PLANT FIBRES, Cotton, Have you ever made wicks for oil lamps?, What do you use for making these, wicks? This cotton wool is also used for, filling mattresses, quilts or pillows., Take some cotton wool, pull it apart, and look at its edges. What do you, observe? The small, thin strands that, you see are made up of cotton fibres., Where does this cotton wool come, from? It is grown in the fields. Cotton, plants are usually grown at places, having black soil and warm climate. Can, you name some states of our country, where cotton is grown? The fruits of the, cotton plant (cotton bolls) are about the, size of a lemon. After maturing, the bolls, burst open and the seeds covered with, cotton fibres can be seen. Have you ever, , Fig.3.6 Field of cotton plants, , seen a cotton field that is ready for, picking? It looks like a field covered with, snow (Fig.3.6)., From these bolls, cotton is usually, picked by hand. Fibres are then, separated from the seeds by combing., This process is called ginning of cotton., Ginning was traditionally done by hand, (Fig.3.7). These days, machines are also, used for ginning., , Fig. 3.7 Ginning of cotton, , Jute, Jute fibre is obtained from the stem of, the jute plant (Fig 3.8). It is cultivated, during the rainy season. In India, jute is, mainly grown in, West Bengal, Bihar, and Assam. The, jute, plant, is, normally harvested, when it is at, flowering stage., The stems of the, harvested plants, are immersed in, water for a few, days. The stems rot, and fibres are, separated by hand., Fig. 3.8 A jute plant, , 20, , SCIENCE, , 2018-19

Page 31 :
Fig. 3.9 Making yarn from cotton, , To make fabrics, all these fibres are, first converted into yarns. How is, it done?, , 3.4 SPINNING COTTON YARN, You can try making cotton yarn yourself., , Activity 4, Hold some cotton wool in one hand., Pinch some cotton between the, thumb and forefinger of the other hand., Now, gently start pulling out the cotton,, while continuously twisting the fibres, (Fig. 3.9). Are you able to, make a yarn?, The process of making yarn, from fibres is called spinning., In this process, fibres from a, mass of cotton wool are drawn, out and twisted. This brings, the fibres together to form, a yarn., A simple device used, for spinning is a hand, spindle, also called takli, (Fig. 3.10). Another hand, operated device used for, spinning, is, charkha, (Fig. 3.11). Use of charkha was, popularised by Mahatma, Gandhi as part of the, Independence movement. He Fig. 3.10, encouraged people to wear A Takli, , Fig. 3.11 Charkha, , clothes made of homespun yarn termed, as khadi and shun imported cloth made, in the mills of Britain. To popularise and, promote khadi, the Government of India, constituted a body called Khadi and, Village Industries Commission in 1956., Spinning of yarn on a large scale is, done with the help of spinning, machines. After spinning, yarns are, used for making fabrics., , 3.5 YARN, , TO, , FABRIC, , There are many ways by which fabrics, are made from yarns. The two main, processes are weaving and knitting., , Weaving, In Activity 2, you might have noticed, that a fabric is made up of two sets of, yarns arranged together. The process of, arranging two sets of yarns together to, make a fabric is called weaving. Let us, try to weave some paper strips., , Activity 5, Take two sheets of paper of different, colours. Cut square pieces of length and, width equal to 30 cm from each sheet., Now, fold both the sheets into half. On, one sheet draw lines as shown in the, , FIBRE TO FABRIC, , 21, , 2018-19

Page 32 :
(a), , (b), (c), , (d), , Fig. 3.12 Weaving with paper strips, , Fig 3.12 (a) and on the other as shown, in Fig.3.12 (b). Cut both the sheets, along the dotted lines and then unfold., Weave the strips one by one through the, cuts in the sheet of paper as shown in, Fig.3.12 (c). Fig. 3.12 (d) shows the, pattern after weaving all the strips., Fig 3.14 Knitting, , used to make a piece of fabric (Fig. 3.14)., Have you ever pulled the yarn from a, torn pair of socks? What happens? A, single yarn gets pulled out continuously, as the fabric gets unravelled. Socks and, many other clothing items are made of, knitted fabrics. Knitting is done by, hand and also on machines., Fig. 3.13 Handloom, , In a similar manner, two sets of yarn, are woven to make a fabric. The yarns, are much thinner than our paper strips,, of course! Weaving of fabric is done on, looms (Fig. 3.13). The looms are either, hand operated or power operated., , Paheli wants to know if you have, seen any fabrics that are made, of the fibres on the outer covering, of coconut. What are these, fibres normally used for?, , Knitting, Have you noticed how sweaters are, knitted? In knitting, a single yarn is, 22, , SCIENCE, , 2018-19

Page 33 :
Weaving and knitting are used for, making different kinds of fabric., These fabrics are used for a variety of, clothing items., , 3.6 HISTORY OF CLOTHING MATERIAL, Have you ever wondered what materials, people used in ancient times for clothes?, It appears that in those times people, used the bark and big leaves of trees or, animal skins and furs to cover, themselves., After people began to settle in, agricultural communities, they learnt to, weave twigs and grass into mats and, baskets. Vines, animal fleece or hair were, twisted together into long strands. These, were woven into fabrics. The early Indians, wore fabrics made out of cotton that grew, in the regions near the river Ganga. Flax, Cotton Rolls, , Ginning, , is also a plant that gives natural fibres., In ancient Egypt, cotton as well as flax, were cultivated near the river Nile and, were used for making fabrics., In those days, stitching was not, known. People simply draped the fabrics, around different parts of their body., Many different ways of draping fabrics, were used. With the invention of the, sewing needle, people started stitching, fabrics to make clothes. Stitched clothes, have gone through many variations, since this invention. But, is it not, amazing that even today saree, dhoti,, lungi or turban is used as an un-stitched, piece of fabric?, Just as there is a large variety in the, food eaten all over our country, a large, variety exists also in fabrics and, clothing items., , Fibre, , Spinning, , Yarn, Knitting, , Weaving, Fabric, , Cotton wool, Fabric, Fibre, Knitting, Spinning, Weaving, Yar n, , , , There is a variety of clothing material or fabric, such as, cotton, silk,, wool and polyester., , FIBRE TO FABRIC, , 23, , 2018-19

Page 34 :
, , Fabrics are made from yarns, which in turn are made from fibres., , , , Fibres are either natural or synthetic. Cotton, wool, silk and jute are, some natural fibres, while nylon and polyester are some examples of, synthetic fibres., , , , Fibres like cotton and jute are obtained from plants., , , , The process of making yarn from fibres is called spinning., , , , Fabric from yarns is made by weaving and knitting., , 1., , Classify the following fibres as natural or synthetic:, nylon, wool, cotton, silk, polyester, jute, , 2., , State whether the following statements are true or false:, a) Yarn is made from fibres., b) Spinning is a process of making fibres., c) Jute is the outer covering of coconut., d) The process of removing seed from cotton is called ginning., e) Weaving of yarn makes a piece of fabric., f) Silk fibre is obtained from the stem of a plant., g) Polyester is a natural fibre., , 3., , Fill in the blanks:, a) Plant fibres are obtained from_________ and ________ ., b) Animals fibres are __________ and ___________ ., , 4., , From which parts of the plant cotton and jute are obtained?, , 5., , Name two items that are made from coconut fibre., , 6., , Explain the process of making yarn from fibre., , SUGGESTED PROJECTS AND ACTIVITIES, 1., , Visit a nearby handloom or powerloom unit and observe the weaving or knitting, of fabric., , 2., , Find out if any crop is grown in your region for obtaining fibre. If yes, what is, it used for?, , 3., , India has been a major producer of cotton and its fabric. India exports cotton, fabrics and items to many other countries. Find out, how it helps us?, , 24, , SCIENCE, , 2018-19

Page 35 :
4., , Do you know that famous Sufi Saint and poet Kabir, was a weaver? Find out, about his life and teachings., , 5., , You can do an activity to identify the yarns of a fabric under the supervision, of your teacher or parents. Pull out six to eight yarns from the fabric. Hold one, end of the yarn with a tong and bring the other end over the flame of a candle., Observe carefully. Do the yarns shrink away from the flame? Do the yarns, melt or burn? What type of odour is given off? Note down your observations., If these are cotton yarns, they burn but do not shrink or melt. The burning, yarn gives an odour similar to burning paper. The silk yarn shrinks away, from the flame and burns but does not melt. It has the odour of charred meat., The wool yarn also shrinks and burns but does not melt. It has a strong odour, of burning hair. The synthetic yarns shrink and burn. They also melt and, give out an odour similar to burning plastics., , Boojho knows that burning of, cotton yarn gives an odour similar, to burning paper. He is wondering, if he can assume that paper is also, made from plants., , FIBRE TO FABRIC, , 25, , 2018-19

Page 36 :
4, , Sorting Materials into Groups, , 4.1 OBJECTS AROUND, , US, , We have seen that our food and clothes, have so much variety in them. Not just, food and clothes, there is such a vast, variety of objects everywhere. We see, around us, a chair, a bullock cart, a, cycle, cooking utensils, books, clothes,, toys, water, stones and many other, objects. All these objects have different, shapes, colours and uses (Fig. 4.1)., Look around and identify objects, that are round in shape. Our list may, include a rubber ball, a football and a, glass marble. If we include objects that, are nearly round, our list could also, include objects like apples, oranges, and, an earthen pitcher (gharha). Suppose, , we were looking for objects that are, edible. We might include all the items, that we have listed in Tables 1.1, 1.2, and 1.3 in Chapter 1. We might also, find that some of those round shaped, objects we just listed out, are also in, this group., Let us say, we wish to make a group, of objects that are made of plastics., Buckets, lunch boxes, toys, water, containers, pipes and many such, objects, may find a place in this group., There are so many ways to group objects!, In the above examples we have grouped, objects on the basis of their shape or the, materials they are made from., All objects around us are made of one, or more materials. These materials may, be glass, metal, plastics, wood, cotton,, paper, mud or soil. Can you think of, more examples of materials?, , Activity 1, , Fig. 4.1 Objects around us, , Let us collect as many objects as, possible, from around us. Each of us, could get some everyday objects from, home and we could also collect some, objects from the classroom or from, outside the school. What will we have, in our collection? Chalk, pencil,, notebook, rubber, duster, a hammer,, nail, soap, spoke of a wheel, bat,, , 26, , SCIENCE, , 2018-19

Page 37 :
matchbox, salt, potato. We can also list, objects that we can think of, but, cannot, bring to the classroom. For example,, wall, trees, doors, tractor, road., Separate all objects from this, collection that are made from paper or, wood. This way we have divided all objects, into two groups. One group has the, objects that are made from paper or wood, while the other group has the objects, that are not made of these materials., Similarly, we could separate the things, that are used for preparing food., Let us be a little more systematic. List, all objects collected, in Table 4.1. Try to, identify the materials that each one is, made of. It would be fun to make this a, large table – collecting information, about as many objects as possible. It, may seem difficult to find out the, materials out of which some of these, objects are made. In such cases, discuss, with your friends, teacher and parents, to identify the materials., , Boojho wants to know, whether, we found some materials that, were used for making more than, one type of an object., , Column 1 that are known to you. Now,, try and think of everyday objects you, know, that are made mainly of these, materials, and list them in Column 2., Table 4.2 Different types of objects, that are made from the same, material, Material, , Chair, table,, plough, bullock cart, and its wheels, ..., , Paper, , Books, notebooks,, newspaper, toys,, calendars,..., , Plastics, Cotton, , Materials they are, made of, , , glass, plastics, Plate (thali) (Satneyelo, ther), Pen, , Wood, , Leather, , Table 4.1 Objects and the materials, they are made of, Objects, , Objects made of, these materials, , Plastics, metal, , Activity 2, Table 4.2 lists some common materials., You can also add more materials in, , What do we find from these tables?, First, we grouped objects in many, different ways. We then found that, objects around us are made of different, materials. At times, an object is made of, a single material. An object could also, be made of many materials. And then, again, one material could be used for, making many different objects. What, decides which material should be used, , SORTING MATERIALS INTO GROUPS, , 27, , 2018-19

Page 38 :
for making any given object? It seems, that we need to know more about, different materials., , 4.2 PROPERTIES OF MATERIALS, Have you ever wondered why a tumbler, is not made with a piece of cloth? Recall, our experiments with pieces of cloth in, Chapter 3 and also keep in mind that, we generally use a tumbler to keep a, liquid. Therefore, would it not be silly,, if we were to make a tumbler out of cloth, (Fig 4.2)! What we need for a tumbler is, glass, plastics, metal or other such, material that will hold water. Similarly,, it would not be wise to use paper-like, materials for cooking vessels., , Fig. 4.2 Using a cloth tumbler, , We see then, that we choose a, material to make an object depending, on its properties, and the purpose for, which the object is to be used., So, what are all the properties of, materials that would be important for, their usage? Some properties are, discussed here., , Appearance, Materials usually look different from, each other. Wood looks very different, from iron. Iron appears different from, copper or aluminium. At the same time,, there may be some similarities between, iron, copper and aluminium that are not, there in wood., , Activity 3, Collect small pieces of different materials –, paper, cardboard, wood, copper wire,, aluminium sheet, chalk. Do any of these, appear shiny? Separate the shiny, materials into a group., Now, observe as the teacher cuts each, material into two pieces and look at the, freshly cut surface (Fig. 4.3). What do, you notice? Does the freshly cut surface, of some of these materials appear shiny?, Include these objects also in the group, of shiny materials., Do you notice such a shine or lustre, in the other materials, cut them anyway, as you can? Repeat this in the class with, as many materials as possible and make, a list of those with and without lustre., Instead of cutting, you can rub the, surface of material with sand paper to, see if it has lustre., , Fig. 4.3 Cutting pieces of materials to see if they, have lustre, , 28, , SCIENCE, , 2018-19

Page 39 :
Materials that have such lustre are, usually metals. Iron, copper, aluminium, and gold are examples of metals. Some, metals often lose their shine and, appear dull, because of the action of air, and moisture on them. We therefore,, notice the lustre, only on their freshly, cut sur face. When you visit an, ironsmith or a workshop, look out for, freshly cut surfaces of metal rods to see, if they have lustre., , beakers. Fill each one of them about twothirds with water. Add a small amount, (spoonful) of sugar to the first glass,, salt to the second and similarly, add, small amounts of the other substances, into the other glasses. Stir the contents, of each of them with a spoon. Wait for a, few minutes. Observe what happens to, the substances added to water (Fig. 4.4)., Note your observations as shown, in Table 4.3., , Hardness, When you press different materials with, your hands, some of them may be hard, to compress while others can be easily, compressed. Take a metal key and try, to scratch with it, the surface of a piece, of wood, aluminium, a piece of stone, a, nail, candle, chalk, any other material, or object. You can easily scratch some, materials, while some cannot be, scratched so easily. Materials which can, be compressed or scratched easily are, called soft while some other materials, which are difficult to compress are called, hard. For example, cotton or sponge is, soft while iron is hard., In appearance, materials can have, different properties, like lustre,, hardness, be rough or smooth. Can you, think of other properties that describe, the appearance of a material?, , Soluble or Insoluble?, Activity 4, Collect samples of some solid substances, such as sugar, salt, chalk powder, sand, and sawdust. Take five glasses or, , Fig. 4.4 What disappears, what doesn’t?, , Table 4.3 Mixing different solid, materials in water, Substance, Salt, , Disappears in water/, does not disappear, Disappears completely in, water, , Sugar, Sand, Chalk, powder, Sawdust, , You will notice that some substances, have completely disappeared or, dissolved in water. We say that these, substances are soluble in water. Other, substances do not mix with water and, do not disappear even after we stir for a, , SORTING MATERIALS INTO GROUPS, , 29, , 2018-19

Page 40 :
long time. These substances are, insoluble in water., Water plays an important role in the, functioning of our body because it can, dissolve a large number of substances., Do liquids also dissolve in water?, , We notice that some liquids get, completely mixed with water. Some, others do not mix with water and form, a separate layer when kept aside for, some time., , Activity 5, Collect samples of vinegar, lemon juice,, mustard oil or coconut oil, kerosene or, any other liquid. Take a glass tumbler., Fill it up to half with water. Add a few, spoonfuls of one liquid to this and stir, it well. Let it stand for five minutes., Observe whether the liquid mixes with, water (Fig. 4.5). Repeat the same with, other liquids, as many different liquids, as are available to you. Write your, observations in Table 4.4., Table 4.4 Solubility of some, common liquids in water, Mixes well/, Does not mix, , Liquid, Vinegar, , Mixes well, , Lemon juice, Mustard oil, Coconut oil, Kerosene, , (a), , (b), , Fig. 4.5 (a) Some liquids mix well with, water while (b) some others do not, , Boojho suggests that we, also check if the liquids that we, used in Activity 5, mix well with, some liquid other than water., Paheli is curious to know, whether gases also dissolve, in water., , Some gases are soluble in water, whereas others are not. Water, usually,, has small quantities of some gases, dissolved in it. For example, oxygen gas, dissolved in water is very important for, the survival of animals and plants that, live in water., , Objects may float or sink in, water, While doing Activity 4, you might have, noticed that the insoluble solids, separated out from water. You may have, also noticed this with some liquids in, Activity 5. Some of these materials that, did not mix with water, floated to the, surface of water. Others may have sunk, to the bottom of the tumbler, right? We, notice many examples of objects that, float in water or sink (Fig. 4.6). Dried, leaves fallen on the surface of a pond, a, stone that you throw into this pond, few, , 30, , SCIENCE, , 2018-19

Page 41 :
Figure 4.6 Some objects float in water while, others sink in it, , drops of honey that you let fall into a, glass of water. What happens to all, of these?, Boojho would like you to give him, five examples each, of objects that float, and those that sink in water. What, about testing these same materials to, see if they float or sink in other liquids, like oil?, , hide behind a glass window? Obviously, not, as your friends can see through that, and spot you. Can you see through all, the materials? Those substances or, materials, through which things can be, seen, are called transparent (Fig. 4.7)., Glass, water, air and some plastics are, examples of transparent materials., Shopkeepers usually prefer to keep, biscuits, sweets and other eatables in, transparent containers of glass or, , Transparency, You might have played the game of hide, and seek. Think of some places where, you would like to hide so that you are, not seen by others. Why did you choose, those places? Would you have tried to, , Fig. 4.8 Transparent bottles in a shop, , plastic, so that buyers can easily see, these items (Fig. 4.8)., On the other hand, there are some, materials through which you are not, able to see. These materials are called, opaque. You cannot tell what is kept, in a closed wooden box, a cardboard, carton or a metal container. Wood,, cardboard and metals, are examples of, opaque materials., Do we find that we can group all, materials and objects, without any, confusion, as either opaque or, transparent?, , Activity 6, Fig. 4.7 Looking through opaque, transparent or, translucent material, , Take a sheet of paper and look through, it towards a lighted bulb. Make a note, of your observation. Now, put 2-3 drops, , SORTING MATERIALS INTO GROUPS, , 31, , 2018-19

Page 42 :
of some oil and spread it on the sheet of, paper. Look again towards the lighted, bulb through that portion of the paper, on which the oil has been spread. Do, you find that the bulb is more clearly, visible than before? But, can you see, clearly through the oiled paper? Is, everything on the other side of it visible?, Perhaps not. The materials through, which objects can be seen, but not, clearly, are known as translucent., Remember the oily patch on paper when, we tested food items for presence of fats?, That was translucent too. Can you, think of some more examples of, translucent materials?, We can therefore group materials as, opaque, transparent and translucent., Paheli suggests, covering the glass, of a torch with your, palm at a dark, place. Switch on, the torch and, observe the other, Fig. 4.9 Does torch, side of the palm., light pass through, your palm?, She wants to know, , whether palm of your hand is opaque,, transparent or translucent?, We learnt that materials differ in their, appearance and the way they mix in, water or other liquids. They may float, or sink in water or may be transparent,, opaque or translucent. Materials can be, grouped on the basis of similarities or, differences in their properties., Why do we need to group materials?, In everyday life, we often group materials, for our convenience. At home, we, usually store things in such a manner, that similar objects are placed together., Such an arrangement helps us to locate, them easily. Similarly, a grocer usually, keeps all type of biscuits at one corner, of his shop, all soaps at another while, grains and pulses are stored at some, other place., There is another reason why we find, such grouping useful. Dividing, materials in groups makes it convenient, to study their properties and also, observe any patterns in these properties., We will study more about this in, higher classes., , Hard, , Opaque, , Insoluble, , Rough, , Lustre, , Soluble, , Material, , T ranslucent, , Metals, , T ransparent, , 32, , SCIENCE, , 2018-19

Page 43 :
, , Objects around us are made up of a large variety of materials., , , , A given material could be used to make a large number of objects. It is, also possible that an object could be made of a single material or of, many different types of materials., , , , Different types of materials have different properties., , , , Some materials are shiny in appearance while others are not. Some are, rough, some smooth. Similarly, some materials are hard, whereas some, others are soft., , , , Some materials are soluble in water whereas some others are insoluble., , , , Some materials such as glass, are transparent and some others such, as wood and metals are opaque. Some materials are translucent., , , , Materials are grouped together on the basis of similarities and differences, in their properties., , , , Things are grouped together for convenience and to study their, properties., , 1., , Name five objects which can be made from wood., , 2., , Select those objects from the following which shine:, Glass bowl, plastic toy, steel spoon, cotton shirt, , 3., , Match the objects given below with the materials from which they could be, made. Remember, an object could be made from more than one material and a, given material could be used for making many objects., Objects, , 4., , Materials, , Book, , Glass, , Tumbler, , Wood, , Chair, , Paper, , Toy, , Leather, , Shoes, , Plastics, , State whether the statements given below are True or False., (i), , Stone is transparent, while glass is opaque., , (ii), , A notebook has lustre while eraser does not., , (iii), , Chalk dissolves in water., , (iv), , A piece of wood floats on water., , SORTING MATERIALS INTO GROUPS, , 33, , 2018-19

Page 44 :
5., , (v), , Sugar does not dissolve in water., , (vi), , Oil mixes with water., , (vii), , Sand settles down in water., , (viii), , Vinegar dissolves in water., , Given below are the names of some objects and materials:, Water, basket ball, orange, sugar, globe, apple and earthen pitcher, Group them as:, (a) Round shaped and other shapes, (b) Eatables and non eatables, , 6., , List all items known to you that float on water. Check and see if they will float on, an oil or kerosene., , 7., , Find the odd one out from the following:, a) Chair, Bed, Table, Baby, Cupboard, b) Rose, Jasmine, Boat, Marigold, Lotus, c) Aluminium, Iron, Copper, Silver, Sand, d) Sugar, Salt, Sand, Copper sulphate, , SUGGESTED ACTIVITY, 1., , You may have played a memory game with your friends. Several objects are, placed on a table, you are asked to observe them for a few minutes, go into, another room and write down the names of all objects that you can remember., Play this game, with a difference! Ask all the participants in the game to, remember objects with some particular property while playing this memory, game — remember and write down the names of objects that were made of, wood or objects that are edible and so on. Have fun!, , 2., , From a large collection of materials, make groups of objects having different, properties like transparency, solubility in water and other properties. In later, chapters you will also learn about properties of materials related to electricity, and magnetism. After making different groups from the collected materials,, try and find out if there are any patterns in these groups. For instance, do all, materials which have lustre conduct electricity?, , 34, , SCIENCE, , 2018-19

Page 45 :
5, , Separation of Substances, , I, , n our daily life, there are many, instances when we notice a substance, being separated from a mixture, of materials., Tea leaves are separated from the, liquid with a strainer, while preparing, tea (Fig. 5.1)., , Fig. 5.2 Butter is taken out by churning milk or, curd, , Fig. 5.1 Separating tea leaves with a strainer, , Grain is separated from stalks, while, harvesting. Milk or curd is churned to, separate the butter (Fig. 5.2). As we, learned in Chapter 3, we gin cotton to, separate its seeds from the fibre., Perhaps you might, have eaten salted, daliya or poha. If you, found that it had, chillies in it, you may, have carefully taken, them out before eating., Suppose you are given a basket, containing mangoes and guavas and, asked to separate them. What would you, do? Pick out one kind and place them, in a separate container, right?, Seems easy, but what if the materials, we want to separate are much smaller, , than mango or guava? Imagine you are, given a glass of sand with salt mixed in, it. Impossible, even to think of, separating salt from this mixture by, picking out grains of sand by hand!, But, why would we need to, separate substances like this, at all, is what Paheli wants, to know., , Activity 1, In Column 1 of Table 5.1, are given a, few processes of separation. The purpose, of separation and the way separated, components are used is mentioned in, Column 2 and 3 respectively. However,, the information given in Columns 2 and, 3 is jumbled up. Can you match each, , 2018-19

Page 46 :
Table 5.1 Why do we separate substances?, Separation, process, , Purpose for which we do, the separation, , 1) Separate, stones from rice, , What do we do with the, separated components?, , a) To separate two different, i) We throw away the soild, but useful components., component., , 2) Chur ning milk b) To remove non-useful, to obtain butter, components., , ii) We throw away the, impurities., , 3) Separate tea, leaves, , iii) We use both the, components., , c) To remove impurities or, har mful components., , process with its purpose and the way, separated components are used?, We see that, before we use a, substance, we need to separate harmful, or non-useful substances that may be, mixed with it. Sometimes, we separate, even useful components if we need to, use them separately., The substances to be separated may, be particles of different sizes or, materials. These may be in any three, states of matter i.e., solid, liquid or gas., So, how do we separate substances, mixed together if they have so many, different properties?, , 5.1 METHODS, , OF, , the sheet of paper? Are there pieces of, stone, husks, broken grain and particles, of any other grain in it? Now, remove, with your hand the pieces of stone,, husks and other grains from it., This method of handpicking can, be used for separating slightly larger, sized impurities like the pieces of dirt,, stone, and husk from wheat, rice or, pulses (Fig. 5.3). The quantity of such, impurities is usually not very large., In such situations, we find that, handpicking is a convenient method of, separating substances., , SEPARATION, , We will discuss some simple methods of, separating substances that are mixed, together. You may come across some of, these methods being used in day to day, activities., , Handpicking, Activity 2, , Fig. 5.3 Handpicking stones from grain, , Bring a packet of food grain purchased, from a shop to the classroom. Now,, spread the grains on a sheet of paper., Do you find only one kind of grain on, , Threshing, You must have seen bundles of wheat, or paddy stalks lying in fields after, , 36, , SCIENCE, , 2018-19

Page 47 :
harvesting the crop. Stalks are dried in, the sun before the grain is separated, from them. Each stalk has many grain, seeds attached to it. Imagine the, number of grain seeds in hundreds of, bundles of stalk lying in the field! How, does the farmer separate grain seeds, from those bundles of stalks?, One may pluck mangoes or guavas, from the trees. But, grain seeds are, much smaller than mangoes or guavas., So, plucking them from their stalks, would be impossible. How does one, separate grain seeds from their stalks?, The process that is used to separate, grain from stalks etc. is threshing. In, this process, the stalks are beaten to free, the grain seeds (Fig. 5.4). Sometimes,, , this mixture on a plate or a newspaper., Look at this mixture carefully. Can the, two different components be made out, easily? Are the sizes of particles of the, two components similar? Would it be, possible to separate the components by, handpicking?, Now, take your mixture to an open, ground and stand on a raised platform., Put the mixture in a plate or sheet of, paper. Hold the plate or the sheet of, paper containing the mixture, at your, shoulder height. Tilt it slightly, so that, the mixture slides out slowly., What happens? Do both the, components — sand and sawdust (or, powdered leaves) fall at the same place?, Is there a component that blows away?, Did the wind manage to separate the, two components?, This method of separating, components of a mixture is called, winnowing. Winnowing is used to, separate heavier and lighter components, of a mixture by wind or by blowing air., direction of the air, soop, , Fig. 5.4 Threshing, husk, , threshing is done with the help of, bullocks. Machines are also used to, thresh large quantities of grain., , Winnowing, grain, , Activity 3, Make a mixture of dry sand with, sawdust or powdered dry leaves. Keep, SEPARATION OF SUBSTANCES, , Fig. 5.5 Winnowing, 37, , 2018-19

Page 48 :
This method is commonly used by, farmers to separate lighter husk particles, from heavier seeds of grain (Fig. 5.5)., The husk particles are carried away, by the wind. The seeds of grain get, separated and form a heap near the, platform for winnowing. The separated, husk is used for many purposes such, as fodder for cattles., , Sieving, Sometimes, we may wish to prepare a, dish with flour. We need to remove, impurities and bran that may be present, in it. What do we do? We use a sieve, and pour the flour into it (Fig. 5.6)., Sieving allows the fine flour particles, to pass through the holes of the sieve, while the bigger impurities remain on, the sieve., In a flour mill, impurities like husk, and stones are removed from wheat, before grinding it. Usually, a bagful of, wheat is poured on a slanting sieve. The, sieving removes pieces of stones, stalk, and husk that may still remain with, wheat after threshing and winnowing., , Fig. 5.6 Sieving, , You may have also noticed similar, sieves being used at construction sites, , Fig. 5.7 Pebbles and stones are removed from, sand by sieving, , to separate pebbles and stones from, sand (Fig. 5.7)., , Activity 4, Bring a sieve and a small quantity of, flour from home, to the class. Sieve the, flour to separate any impurities in it., Now, make a fine powder of chalk pieces, and mix it with the flour. Can we, separate the flour and the powdered, chalk by sieving?, Sieving is used when components of, a mixture have different sizes., , Sedimentation, Decantation, and Filtration, Sometimes, it may not be possible to, separate components of a mixture by, winnowing and handpicking. For, example, there may be lighter impurities, like dust or soil particles in rice or, pulses. How are such impurities, separated from rice or pulses before, cooking?, Rice or pulses are usually washed, before cooking. When you add water to, these, the impurities like dust particles, , 38, , SCIENCE, , 2018-19

Page 49 :
get separated. These impurities go into, water. Now, what will sink to the bottom, of the vessel — rice or dust? Why? Have, you seen that the vessel is tilted to pour, out the dirty water?, When the heavier component in a, mixture settles after water is added to, it, the process is called sedimentation., When the water (along with the dust) is, removed, the process is called, decantation (Fig. 5.8). Let us find a, few other mixtures that can be separated, through, sedimentation, and, decantation., The same principle is used for, separating a mixture of two liquids that, do not mix with each other. For example,, oil and water from their mixture can be, separated by this process. If a mixture of, such liquids is allowed to stand for some, time, they form two separate layers. The, component that forms the top layer can, then be separated by decantation., Let us again consider a mixure of a, solid and liquid. After preparing tea,, what do you do to remove the tea leaves?, Usually, we use stainer to remove tea, leaves. Try decantation. It helps a little., But, do you still get a few leaves in your, tea? Now, pour the tea through a, mixture, (soil + water), , undissolved, material, (soil), Fig. 5.8 Separating two components of a mixture, by sedimentation and decantation, , strainer. Did all the tea leaves remain, in the strainer? This process is called, filtration (Fig. 5.1). Which method of, separating tea leaves from prepared tea, is better, decantation or filtration?, Let us now consider the example, of water that we use. Do all of us, at, all times, get safe water to drink?, Sometimes, water supplied through taps, may be muddy. The water collected from, ponds or rivers may also be muddy,, especially after rains. Let us see if we, can use some method of separation to, remove insoluble impurities like soil, from the water., , Activity 5, Collect some muddy water from a pond, or a river. If it is not available, mix some, soil to water in a glass. Let it stand for, half an hour. Observe the water, carefully and note your observations., Does some soil settle at the bottom, of water? Why? What will you call this, process?, Now, slightly tilt the glass without, disturbing the water. Let the water from, the top flow into another glass (Fig. 5.8)., What will you call this process?, Is the water in the second glass still, muddy or brown in colour? Now filter, it. Did the tea strainer work? Let us try, filtering the water through a piece of, cloth. In a piece of cloth, small holes or, pores remain in between the woven, threads. These pores in a cloth can be, used as a filter., If the water is still muddy, impurities, can be separated by a filter that has even, , SEPARATION OF SUBSTANCES, , 39, , 2018-19

Page 50 :
smaller pores. A filter paper is one such, filter that has very fine pores in it., Fig. 5.9 shows the steps involved in, using a filter paper. A filter paper folded, in the form of a cone is fixed onto a, funnel (Fig. 5.10). The mixture is then, poured on the filter paper. Solid, particles in the mixture do not pass, through it and remain on the filter., , Fig. 5.11 Heating a beaker containing salt water, , Fig. 5.9 Folding a filter, paper to make a cone, , Fig. 5.10 Filtration, using a filter paper, , Fruit and vegetable juices are usually, filtered before drinking to separate the, seeds and solid particles of pulp. The, method of filtration is also used in the, process of preparing cottage cheese, (paneer) in our homes. You might have, seen that for making paneer, a few drops, of lemon juice are added to milk as it, boils. This gives a mixture of particles, of solid paneer and a liquid. The paneer, is then separated by filtering the mixture, through a fine cloth or a strainer., , Evaporation, Activity 6, Add two spoons of salt to water in, another beaker and stir it well. Do you, , see any change in the colour of water?, Can you see any salt in the beaker, after, stirring? Heat the beaker containing the, salt water (Fig. 5.11). Let the water boil, away. What is left in the beaker?, In this activity, we used the process, of evaporation, to separate a mixture of, water and salt., The process of conversion of water, into its vapour is called evaporation., The process of evaporation takes place, continuously wherever water is present., Where do you think, salt comes, from? Sea water contains many salts, mixed in it. One of these salts is the, common salt. When sea water is allowed, to stand in shallow pits, water gets, heated by sunlight and slowly turns into, water vapour, through evaporation. In, a few days, the water evaporates, completely leaving behind the solid salts, (Fig. 5.12). Common salt is then, obtained from this mixture of salts by, further purification., , 40, , SCIENCE, , 2018-19

Page 51 :
Fig. 5.12 Obtaining salt from sea water, , Use of more than one method, of separation, We have studied some methods for, separation of substances from their, mixtures. Often, one method is not, sufficient to separate the different, substances present in a mixture. In such, a situation, we need to use more than, one of these methods., , Activity 7, Take a mixture of sand and salt. How, will we separate these? We already saw, that handpicking would not be a, practical method for separating these., Keep this mixture in a beaker and, add some water to it. Leave the beaker, aside for some time. Do you see the sand, settling down at the bottom? The sand, can be separated by decantation or, filtration. What does the decanted liquid, contain? Do you think this water, contains the salt which was there in the, mixture at the beginning?, Now, we need to separate salt and, water from the decanted liquid. Transfer, this liquid to a kettle and close its lid., Heat the kettle for some time. Do you, , notice steam coming out from the spout, of the kettle?, Take a metal plate with some ice on, it. Hold the plate just above the spout, of the kettle as shown in Fig. 5.13. What, do you observe? Let all the water in the, kettle boil off., When the steam comes in contact, with the metal plate cooled with ice, it, condenses and forms liquid water. The, water drops that you observed falling, from the plate, were due to condensation, of steam. The process of conversion of, water vapour into its liquid form is, called condensation., Did you ever see water drops, condensed under a plate that has been, used to cover a vessel containing milk, that has just been boiled?, After all the water has evaporated,, what is left behind in the kettle?, We have thus, separated salt, sand, and water using processes of, decantation, filtration, evaporation and, condensation., Paheli faced a problem while, recovering salt mixed with sand. She, has mixed a packet of salt in a small, , SEPARATION OF SUBSTANCES, , Fig. 5.13 Evaporation and condensation, 41, , 2018-19

Page 52 :
amount of sand. She then tried the, method suggested in Activity 7, to, recover the salt. She found, however,, that she could recover only a small part, of the salt that she had taken. What, could have gone wrong?, , Can water dissolve any, amount of a substance?, In chapter 4, we found that many, substances dissolve in water and form, a solution. We say that these substances, are soluble in water. What will happen, if we go on adding more and more of, these substances to a fixed quantity of, water?, , Activity 8, You will need a beaker or a small pan, a, spoon, salt and water. Pour half a cup, of water in the beaker. Add one, teaspoonful of salt and stir it well, until, the salt dissolves completely (Fig 5.14)., Again add a teaspoonful of salt and stir, well. Go on adding salt, one teaspoonful, at a time, and stir., After adding a few spoons of salt, do, you find that some salt remains, undissolved and settles at the bottom, of the beaker? If yes, this means that, no more salt can be dissolved in the, amount of water we have taken. The, solution is now said to be saturated., Here is a hint as to what might have, gone wrong when Paheli tried to recover, large quantity of salt mixed with sand., Perhaps the quantity of salt was much, more than that required to form a, saturated solution. The undissolved salt, , Fig 5.14 Dissolving salt in water, , would have remained mixed with the, sand and could not be recovered. She, could solve her problem by using a, larger quantity of water., Suppose, she did not have sufficient, quantity of water to dissolve all the salt, in the mixture. Is there some way that, water could be made to dissolve more, salt before the solution gets saturated?, Let us try and help Paheli out., , Activity 9, Take some water in a beaker and mix, salt in it until it cannot dissolve any, more salt. This will give you a saturated, solution of salt in water., Now, add a small quantity of salt to, this saturated solution and heat it. What, do you find? What happens to the, undissolved salt in the bottom of the, beaker? Does it dissolve, now? If yes,, can some more salt be dissolved in this, solution by heating it?, Let this hot solution cool. Does the, salt appear to settle at the bottom of the, beaker again?, The activity suggests that larger, quantity of salt can be dissolved in water, on heating., , 42, , SCIENCE, , 2018-19

Page 53 :
Table 5.2, , Does water dissolve equal amounts, of different soluble substances? Let us, find out., , Substance, , Activity 10, Take two glasses and pour half a cup, of water in each of them. Add a teaspoon, of salt to one glass and stir till the salt, dissolves. Go on adding salt, one, teaspoon at a time, till the solution, saturates. Record the number of spoons, of salt that dissolved in the water, in, Table 5.2. Now, repeat the same, activity with sugar. Repeat this with, some other substances that are soluble, in water., What do you notice from Table 5.2?, Do you find that water dissolves different, substances in different amounts?, , , , Number of spoons of, substance that, dissolved in water, , Salt, Sugar, , We have discussed a few methods of, separating substances. Some of the, methods of separation presented in this, chapter are also used in a science, laboratory., We also learnt that a solution is, prepared by dissolving a substance in a, liquid. A solution is said to be saturated, if it cannot dissolve more of the, substance in it., , Chur ning, , Saturated solution, , Condensation, , Sedimentation, , Decantation, , Sieving, , Evaporation, , Solution, , Filtration, , Threshing, , Handpicking, , Winnowing, , Handpicking, winnowing, sieving, sedimentation, decantation and, filtration are some of the methods of separating substances from their, mixtures., , SEPARATION OF SUBSTANCES, , 43, , 2018-19

Page 54 :
, , Husk and stones could be separated from grains by handpicking., , , , Husk is separated from heavier seeds of grain by winnowing., , , , Difference in the size of particles in a mixture is utilised to separate, them by the process of sieving and filtration., , , , In a mixture of sand and water, the heavier sand particles settle down, at the bottom and the water can be separated by decantation., , , , Filtration can be used to separate components of a mixture of an insoluble, solid and a liquid., , , , Evaporation is the process in which a liquid gets converted into its vapour., Evaporation can be used to separate a solid dissolved in a liquid., , , , A saturated solution is one in which no more of that substance can be, dissolved., , , , More of a substance can be dissolved in a solution by heating it., , , , Water dissolves different amount of soluble substances in it., , 1., , Why do we need to separate different components of a mixture? Give two, examples., , 2., , What is winnowing? Where is it used?, , 3., , How will you separate husk or dirt particles from a given sample of pulses before, cooking., , 4., , What is sieving? Where is it used?, , 5., , How will you separate sand and water from their mixture?, , 6., , Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?, , 7., , How would you obtain clear water from a sample of muddy water?, , 8., , Fill up the blanks, (a) The method of separating seeds of paddy from its stalks is called ___________., (b) When milk, cooled after boiling, is poured onto a piece of cloth the cream, (malai) is left behind on it. This process of separating cream from milk is an, example of ___________., (c) Salt is obtained from seawater by the process of ___________., (d) Impurities settled at the bottom when muddy water was kept overnight in a, bucket. The clear water was then poured off from the top. The process of, separation used in this example is called ___________., , 9., , True or false?, (a) A mixture of milk and water can be separated by filtration., (b) A mixture of powdered salt and sugar can be separated by the process of, winnowing., , 44, , SCIENCE, , 2018-19

Page 55 :
(c) Separation of sugar from tea can be done with filtration., (d) Grain and husk can be separated with the process of decantation., 10. Lemonade is prepared by mixing lemon juice and sugar in water. You wish to, add ice to cool it. Should you add ice to the lemonade before or after dissolving, sugar? In which case would it be possible to dissolve more sugar?, , SUGGESTED PROJECTS AND ACTIVITIES, 1. Visit a nearby dairy and report about the processes used to separate cream, from milk., 2. You have tried a number of methods to separate impurities like mud from, water. Sometimes, the water obtained after employing all these processes could, still be a little muddy. Let us see if we can remove even this impurity completely., Take this filtered water in a glass. Tie a thread to a small piece of alum., Suspend the piece of alum in the water and swirl. Did the water become clear?, What happened to the mud? This process is called loading. Talk to some elders, in your family to find out whether they have seen or used this process., , THINGS TO SEE, , “The winnowers”, painted by Gustav Courbet in 1853, Reproduced with permission from Museè de Beaus Arts, Nantes, France, , SEPARATION OF SUBSTANCES, , 45, , 2018-19

Page 56 :
6, , Changes Around us, , W, , hat a fun would it be if you, suddenly get some magical, powers to change things, around you. What are the things you, would want to change?, , Can some of the changes be grouped, together?, How can we group various changes?, It might help, if we find some similarities, between them., , 6.1 C AN ALL C HANGES A LWAYS B E, REVERSED?, Activity 1, Take a balloon and blow it. Take care, that it does not burst. The shape and, size of the balloon have changed, (Fig. 6.1). Now, let the air escape the, balloon., We do not have magical powers, of, course. But, we can still change a few, things around us, perhaps many things., Can you list a few things you can, change around you, with no magic, involved?, Many changes are taking place, around us on their own. In the fields,, the crops change from time to time., Sometimes, leaves fall from trees, change, colour and dry out. The flowers bloom, and then wither away. Are any changes, happening in your body? Your nails, grow, your hair grows, you grow taller, and your weight increases as you grow., Did you realise earlier that so many, changes are taking place around you all, the time?, , Fig 6.1 A balloon changes its size and shape on, blowing air into it, , Activity 2, Take a piece of paper and fold it as, shown in Fig.6.2. You have changed the, sheet of paper into a toy aeroplane. You, may have lots of fun in flying this plane., Once you are tired of it, unfold the, paper again., , 46, , SCIENCE, , 2018-19

Page 57 :
Activity 4, Take the same balloon, which you used, in Activity 1. Blow it to its full size and, tie its mouth with a string tightly. Prick, it with the pointed tip of your pencil., Oops! It burst., Fig 6.2 A toy aeroplane made by folding paper, , Activity 5, , Activity 3, Take some dough and make a ball. Try, to roll out a roti (Fig. 6.3). May be you, are not happy with its shape and, wish to change it back into a ball of, dough again., , Take the same piece of paper, which you, used in Activity 2. Draw an aeroplane, on it and cut along its outline (Fig.6.4)., , Fig. 6.4 An aeroplane cut out of paper, , Activity 6, Fig 6.3 A ball of dough and a rolled out roti, , Now, think about the three changes, you observed in Activity 1, 2 and 3., What do they have in common?, Was it possible to get the balloon back, to its original shape and size?, Was the size of the paper same as, before and after making an aeroplane?, Was it possible to get back the ball of, dough again?, What do you conclude? In each of, the three activities, is it possible to get, back to the material with which we, started our activity? If the answer is yes,, it means that the changes occurring in, these activities can be reversed. Now, let, us repeat the same activities with, a difference., , Roll out a roti from the ball of dough, again and bake it on a tawa (Fig.6.5)., , Fig 6.5 A roti, , Suppose, you are asked the same, three questions which you answered, after Activity 3. What would your, answers be, now?, We see that, the changes which have, occurred in the Activity 4, 5 and 6 can, not be reversed., You use a pencil and an eraser. With, repeated use, their shape and size, change. Can we reverse this change?, , CHANGES AROUND US, , 47, , 2018-19

Page 58 :
You must have seen a potter working, on his wheel. He shapes a lump of clay, into a pot. Can this change be reversed?, He then bakes the pot in an oven. Now,, can this change be reversed?, Some common changes are given in, Table 6.1. Which of these changes, do, you think can be reversed?, We find that one way we can group, changes is to see if they can be, reversed., Table 6.1 Some common changes, , 6.2 COULD THERE BE OTHER WAYS, TO BRING A CHANGE?, We all have seen the tools which are used, to dig the soil (Fig. 6.6 ). Have you ever, seen how the iron blade in these tools, is fixed to the wooden handle?, The iron blade of these tools has a, ring in which the wooden handle is, fixed. Normally, the ring is slightly, smaller in size than the wooden handle., To fix the handle, the ring is heated and, it becomes slightly larger in size, (expands). Now, the handle easily fits, into the ring. When the ring cools down, it contracts and fits tightly on to, the handle., , Fig. 6.6 Tools are often heated before fixing, wooden handles, , Such a change is also used for fixing, the metal rim on a wooden wheel of a, cart as shown in Fig.6.7. Again the, metal rim is made slightly smaller than, the wooden wheel. On heating, the rim, expands and fits onto the wheel. Cold, water is then poured over the rim, which, contracts and fits tightly onto the wheel., 48, , SCIENCE, , 2018-19

Page 59 :
Paheli wants to know if, you have ever seen a, blacksmith making some, tools. How does a, blacksmith change a, piece of iron into different tools? A, piece of iron is heated till it becomes, red-hot. It then becomes soft and is, beaten into a desired shape. What, change has taken place in iron, on, being heated?, , Fig. 6.7 Cart wheel with metal rim fixed to it, , When we heat water in a pan, it, begins to boil after some time. If we, continue to heat further, the quantity, of water in the pan begins to decrease., The water changes into its vapour., In Activity 7, Chapter 5 you have, observed that water vapour gets changed, into liquid water when it is cooled. We, all have noticed melting of ice. Ice melts, when it is heated. What does it change, into? Is it possible to change this water, back into ice?, Let us observe some more changes., , Activity 7, Take a small candle and measure its, length with a scale. Now, fix it at a, suitable place and light it. Let it burn, for some time. Now blow out the candle, and measure its length again (Fig.6.8)., Can the change in the length of the, candle be reversed? If we were to take, some wax in a pan and heat it, can this, change be reversed (Fig. 6.9)?, , Fig.6.8 Burning of a, candle, , Boojho has often noticed that road, construction workers heat a black, material (tar) for repairing a road., He wants to know whether the, change caused in tar, by, heating, can be reversed?, , Fig.6.9 Heating wax, CHANGES AROUND US, , 49, , 2018-19

Page 60 :
Repeat Activity 7 with an incense, stick. Wait till it burns away completely., What are the changes that occur in the, incense stick? The stick burns to, produce some new material. These are, ash and some gases. We cannot see, these gases but can sense them due to, their pleasant smell. Can this change, be reversed? And what about the, change, which occurred in the, matchstick you used for lighting the, candle or incense stick?, So far we have discussed the changes, occurring in a given object or its, material. What about the changes, that occur when two substances are, mixed together?, In Chapter 4, we dissolved salt in, water. Do you think a change occured, in salt or in water? Is it possible to, reverse this change? Wait, in Chapter, 5, we learnt how to separate salt from, its solution in water. So, can we say that, , the change due to dissolving salt in, water be reversed?, Paheli asks if you have ever seen curd, being set. A small quantity of curd is, added to warm milk. The milk is stirred, and is set aside for a few hours at a warm, place. In a few hours, the milk changes, into curd. Can this change be reversed?, We find that a few ways to bring about, a change in a substance could be, by, heating it or by mixing it with some, other substance. We also find that some, changes can be reversed, while some, others cannot be reversed. There must, be many other ways of changing things, around us. It is possible that some of, them could be reversed. Thus, changes, around us could be grouped as those, that can be reversed or cannot be, reversed. In higher classes, you will, learn more about the ways in which, changes can be made and the way these, can be grouped., , Changes, Contraction, Evaporation, Expansion, Melting, , , , Some changes can be reversed and some cannot be reversed., , , , A change may occur by heating a substance or by mixing it with some, other., , 50, , SCIENCE, , 2018-19

Page 61 :
1., , To walk through a waterlogged area, you usually shorten the length of your, dress by folding it. Can this change be reversed?, , 2., , You accidentally dropped your favourite toy and broke it. This is a change you, did not want. Can this change be reversed?, , 3., , Some changes are listed in the following table. For each change, write in the, blank column, whether the change can be reversed or not., S. No., , Change, , Can be reversed (Yes/ No), , 1., , The sawing of a piece of wood, , 2., , The melting of ice candy, , 3., , Dissolving sugar in water, , 4., , The cooking of food, , 5., , The ripening of a mango, , 6., , Souring of milk, , 4., , A drawing sheet changes when you draw a picture on it. Can you reverse this, change?, , 5., , Give examples to explain the difference between changes that can or cannot be, reversed., , 6., , A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage, on a fractured bone. It becomes hard on drying to keep the fractured bone, immobilised. Can the change in POP be reversed?, , 7., , A bag of cement lying in the open gets wet due to rain during the night. The, next day the sun shines brightly. Do you think the changes, which have occurred, in the cement, could be reversed?, , SUGGESTED PROJECTS AND ACTIVITIES, 1. Take a lemon, a paintbrush and a piece of paper. Cut the lemon and squeeze, out its juice in a cup. Dip the brush in the lemon juice and write a message, on the paper. Let the paper dry and you find that the letters of your message, become invisible. Now, press the paper with hot iron or warm it by holding it, above the flame of a candle (Take care that it does not catch fire). As the, paper gets warm, invisible letters change into dark brown colour. Identify the, changes that can be reversed in this process., 2. Observe preparation of dishes at your home. Identify two changes that can, be reversed., 3. Maintain a record for one year of the seasonal changes in vegetables, clothing,, nature and events around you. Identify the changes that can or cannot be, reversed., , CHANGES AROUND US, , 51, , 2018-19

Page 62 :
7, , Getting to Know Plants, , G, , o outside and observe all the, plants around you (Fig. 7.1)., Do you see that some plants, are small, some very big, while some, are just patches of green on, the soil? Some have green, leaves, while some others have, reddish ones. Some have huge, red flowers, some have tiny, blue ones, while some have, none. We do see a variety of, plants existing all around us, — near our homes, in the, school ground, on the way to, , the school, in the parks and gardens,, isn’t it?, Let us get to know the different, parts of any plant. This will help us, , Fig. 7.1 A Nature walk!, , understand the differences between, plants of different kinds. Can you label, the stem, branch, root, leaf, flower and, fruit of the plant shown in Fig.7.1?, Colour the parts of the plant., , 7.1 HERBS, SHRUBS, , AND, , TREES, , Activity 1, , Fig. 7.2 Parts of a plant, , Look closely at the stem and branches, of:, 1. Plants much smaller than you., 2. Plants that are about your size, and, 3. Plants which are much taller than, you., Feel their stem and try to bend them, gently to see if they are tender or hard., , 52, , SCIENCE, , 2018-19

Page 63 :
Table 7.1 Categories of plants, , Take care that the stem does not break., Hug the tall plants to see how thick their, stems are!, We also need to notice from where the, branches grow in some plants — close to, the ground or higher up on the stem., We will now group all the plants we, observed, in Table 7.1. Some examples, are shown. You can fill the Columns 1,, , 2 and 3 for many more plants., Fill Column 4 later after studying, the section., Based on these characters most, plants can be classified into three, categories: herbs, shrubs and trees. An, example of each is shown in Fig.7.3., , Suggestion: Student can work in, groups of 4-5 so that a minimum, number of plants are harmed/, damaged., You may also use weeds with soft, stems for the activities. Do you know, what weeds are? In crop fields, lawns,, or in pots, often some unwanted, plants or weeds start growing. Have, you seen farmers removing these, weeds from their fields?, , (a), , (b), , (c), , Fig.7.3 (a) Herb, (b) shrub and (c) tree, , GETTING TO KNOW PLANTS, , 53, , 2018-19

Page 64 :
Plants with green and tender stems, are called herbs. They are usually short, and may not have many branches, [Fig.7.3 (a)]., Some plants develop branches near, the base of stem. The stem is hard but, not very thick. Such plants are called, shrubs [Fig .7.3(b)]., Some plants are very tall and have, hard and thick stem. The stems have, branches in the upper part, much above, the ground. Such plants are called trees, [Fig.7.3(c)]., Based on the above characteristics, can you now classify the plants listed, by you and complete column 4 in, Table 7.1?, , Fig. 7.4 Creepers, , Fig. 7.5 Climbers, , two trees, shrubs, herbs or creepers, growing in your house or school., , 7.2 STEM, , Observe closely the stems of different, plants around you. Note down different, structures/parts borne by, Paheli wonders what kind of stem — the, the stem. Compare you, money plant, beanstalk, gourd plants and, observations with the that of, grape vines have. Do observe some of these, your friends. What do you, plants. How are these different from a herb,, find? Stems bear leaves,, a shrub or a tree? Why do you, branches, buds, flowers, think some of them need support, and fruits., to climb upwards?, , Activity 2, Plants with weak stems that cannot, stand upright but spread on the ground, are called creepers (Fig.7.4), while those, that take support and climb up are called, climbers (Fig.7.5). These are different, from the herbs, shrubs and trees., Perhaps there are some plants in, your school or at home that you take, care of. Write down the names of any, , We would require a glass, water, red/, blue ink and a soft stem. Pour water to, fill one-third of the glass. Add a few, drops of red/blue ink to the water. Cut, the base of the stem and put it in the, glass as shown in Fig.7.6., Observe the set-up. Does the colour, appear in the stem? You will find that, the colour rises in the stem. If this is, kept for a longer period, the colour, , 54, , SCIENCE, , 2018-19

Page 65 :
Stem, , Lamina, , Petiole, Fig. 7.8 A leaf, , Fig. 7.6 Stem in a glass with coloured water, , appears in the veins of leaves also. How, do you think the colour reached there?, From this activity, we see that the, stem helps in upward movement of, water. The water and minerals go to, leaves and other plant parts attached to, the stem., , (a), , (b), Fig. 7.7 (a) Water moves up the stem and, reaches leaves, (b) Enlarged view of open end of stem, , 7.3 LEAF, Observe the leaves of some plants, around you and draw them in your, notebook. Are all the leaves of same size,, shape and colour?, How are leaves attached to the stem?, The part of leaf by which it is attached, to the stem is called petiole. The broad,, green part of the leaf is called lamina, (Fig. 7.8). Can you identify these parts, of the leaves in plants around you? Do, all the leaves have petioles?, , Let us get to know the leaf better by, taking its impression! If you thought, that leaves cannot sign, here is an, activity which will make you think again., , Activity 3, Put a leaf under a white sheet of paper, or a sheet in your notebook. Hold it in, place as shown in Fig. 7.9. Hold your, pencil tip sideways and rub it on the, portion of the paper having the leaf below, it. Did you get an impression with some, lines in it? Are they similar to those on, the leaf?, These lines on, the leaf are called, veins. Do you see, a prominent line, in the middle of the, leaf? This is called, the midrib. The, Fig. 7.9 Taking an, design made by, impression of a leaf, veins in a leaf is, called the leaf venation. If this design is, net-like on both sides of midrib, the, venation is reticulate [Fig. 7.10 (a)]. In, the leaves of grass you might have seen, that the veins are parallel to one another., This is parallel venation [(Fig. 7.10 (b)]., Observe the venation in as many leaves, as you can without removing them from, the plant. Draw the pattern and write, , GETTING TO KNOW PLANTS, , 55, , 2018-19

Page 66 :
Midrib, , Veins, , (a), , Transparent, polythene, cover/bag, , (b), , Fig. 7.10 Leaf venation (a) reticulate and, (b) parallel, , Fig. 7.11 What does the leaf do?, , names of some plants having reticulate, and parallel venation., Shall we now find out some of the, functions of a leaf?, , Activity 4, We will require a herb, two transparent, polythene bags and thread., Do this activity during day time on a, sunny day. Use a healthy, well watered, plant that has been growing in the sun., Enclose a leafy branch of the plant in a, polythene cover and tie up its mouth as, shown in Fig. 7.11. Tie up the mouth of, another empty polythene cover and keep, it also in the sun., After a few hours, observe the inner, surface of the covers. What do you see?, Are there any droplets of water? How do, you think they got there? [Don’t forget, to remove the polythene bag after the, activity!], Water comes out of leaves in the form, of vapour by a process called, transpiration. Plants release a lot of water, into the air through this process. We will, learn more about this in Chapter 14., Why did we tie a cover around the, leaves? Would we have seen the water, , evaporate if we had not tied a polythene, cover? What makes the water appear on, the polythene bag? In Chapter 5, we, noticed water changing into different, forms in some of our activities. Can you, think of these and name the process that, makes water drops appear on the, polythene cover?, Leaves also have another function., Let us study this., , Activity 5, We would require a leaf, spirit, a beaker,, test tube, burner, water, a watch glass, and iodine solution for this activity., Take a leaf in a test tube and pour, spirit to completely immerse the leaf., , 56, , Green, leaf, , Iodine, solution, Purplish, coloured, leaf, , Fig. 7.12 What does the leaf contain?, SCIENCE, , 2018-19

Page 67 :
Note: Since the activity involves the, use of spirit and heating, it is advised, that it is demonstrated by the teacher, in the class., Now, place the test tube in a beaker half, filled with water. Heat the beaker till all, the green colour from the leaf comes out, into the spirit in the test tube. Take out, the leaf carefully and wash it in water., Place it on a watch glass and pour some, iodine solution over it (Fig. 7.12)., What do you observe? Compare your, observations with those done in, Chapter 2, when you tested food for, presence of different nutrients. Does this, mean that the leaf has starch in it?, In Chapter 2, we saw that a slice of, raw potato also shows the presence of, starch. Potatoes get this starch from, their leaves and store it. Leaves prepare, their food in the presence of sunlight, and a green coloured substance present, in them. For this, they also use water, and carbon dioxide. This process is, called photosynthesis. Oxygen is given, out in this process. The food prepared, by leaves ultimately gets stored in, different parts of plant., We have seen that the stem supplies, leaf with water. The leaf uses the water, to make food. The leaves also lose water, through transpiration. How do the stem, and leaves get water? That is where the, roots come in!, , Fig. 7.13 Watering the plants, , Which part of the plant is in the soil?, Let us learn more about this part from, the following activities., , Activity 6, You would require two pots, some soil,, khurpi (for digging), blade or a pair of, scissors and water. This activity is to be, done in groups of 4-5 students., Select two plants of the same kind, from an open ground and dig them out, with roots. Take care that their roots do, not break. Plant one of them in pot A, [Fig. 7.14 (a)]. Cut off the roots from the, , 7.4 ROOT, , A, , B, , Look at Fig. 7.13. Who do you think is, watering their plant correctly, Paheli or, Boojho? Why?, , (a), , (b), , GETTING TO KNOW PLANTS, , Fig. 7.14 (a) Plant with roots, and, (b) without roots, 57, , 2018-19

Page 68 :
other plant and plant it in pot B [Fig., 7.14 (b)]. Water them regularly. Observe, the plants after a week. Are both plants, healthy?, Both the plants are watered, regularly, but, one is without roots, isn’t, it? Does this activity help you, understand an important function of the, root?, Let us do an activity to study another, function of root., , Activity 7, We would require seeds of gram and, maize, cotton wool, katori (bowl) and, some water., Take two katoris (bowl). Place some, wet cotton in them. Put 3 or 4 seeds of, gram in one and maize in the other., Keep the cotton wet by sprinkling, water every day, until the sprouts have, grown into young plants. After a week, try to separate the young plants from, the cotton (Fig. 7.15)., , holding the plant firmly to the soil. They, anchor the plant to the soil., You have seen that there are different, kinds of stems and leaves. Do the roots, also show a variety? Let us find out., , Activity 8, Study Fig. 7.16 (a) and (b) carefully., Now, look at the roots of the gram plants, you have pulled out from the cotton in, the previous activity. Do they look like, the roots shown in Fig. 7.16 (a) or those, in Fig. 7.16 (b)? How about the roots of, , (a), Fig 7.16, , (b), , (a) Roots of_______________, (b) Roots of_______________, , maize plant? Write ‘gram’ or ‘maize’ in, the blank spaces in the figure after, matching the roots with the figures., In what way are the roots of gram, and maize similar? In what way are they, different? There seem to be two different, types of roots, isn’t it? Are there also, other types of roots? Let us find out., , Activity 9, Fig. 7.15 Young plants grown on cotton, , Was it easy to separate the cotton, from the roots? Why?, In Activity 6, we could not pull out, the plants from the soil, right? We dug, them out. This is because roots help in, , Go to an open ground where many wild, plants are growing. Dig out a few, wash, the soil off the roots and observe them., Do you find that all of them have either, the kind of roots shown in Fig. 7.17 (a), or as in Fig. 7.17 (b)?, , 58, , SCIENCE, , 2018-19

Page 69 :
a very interesting way? In Table 7.2, can, you match the type of leaf venation and, the type of roots for some plants you have, studied in all the activities so far?, Table 7.2 Types of roots and types of, leaf venation, Name of, plant, , (a), , Type of leaf, venation, , Type of, roots, , (b), , Fig. 7.17 (a) Taproot and (b) fibrous roots, , For roots of the kind shown in, Fig.7.17 (a), the main root is called tap, root and the smaller roots are called, lateral roots. Plants with roots as shown, in Fig. 7.17 (b) do not have a main root., All roots seem similar and these are, called fibrous roots., Separate the plants you have, collected into two groups. In group (a), put those that have tap roots and in, group (b) those that have fibrous roots., Look at the leaves of the plants in Group, (a). What kind of venation do they have?, What kind of venation do you see for, plants of Group (b)?, Do you notice that leaf venation and, the type of roots in a plant are related in, , We have learnt that roots absorb, water and minerals from the soil and, the stem conducts these to leaves and, other parts of the plant. The leaves, prepare food. This food travels through, the stem and is stored in different parts, of plant. We eat some of these as roots—, like carrot, radish, sweet potato, turnip, and tapioca. We also eat many other, parts of a plant where food is stored., Do you agree that stem is like a street, with two way traffic (Fig. 7.18)? Write, the name of material that goes up in, the stem and that which comes down., , Boojho has a brilliant idea! If he, wants to know what kind of roots a, plant has, he need not pull it out., He just has to look at its leaves!, , Fig. 7.18. Stem as two-way traffic street, , In the next section, we will study, about the structure of a flower., GETTING TO KNOW PLANTS, , 59, , 2018-19

Page 70 :
7.5 FLOWER, You are shown three branches of a rose, in Fig 7.19 (a), (b) and (c). Which one, will help you best to recognise the plant?, , These are the petals. Different flowers, have petals of different colours., Where do you think the petals are in a, closed bud? Which is the most prominent, part in a bud? Did you see that this part, is made of small leaf-like structures? They, Petals, , Sepals, (a), , (b), , (c), Fig. 7.20 Bud and flower, , Fig 7.19 Rose: (a) A leafless branch, (b) A branch with leaves, (c) A branch with leaves and flowers, , Which colour did you use for the, flower in Fig. 7.19 (c)? Are all flowers, colourful? Have you ever seen flowers, on grass, wheat, maize, mango or, guava? Are those brightly coloured?, Let us study a few flowers., When choosing flowers to study, avoid, using marigold, chrysanthemum or, sunflower. You will learn in higher, classes that they are not single flowers,, but groups of flowers., , Activity 10, We would require one bud and two fresh, flowers each, of any of the following–, datura, china rose, mustard, brinjal,, lady’s finger, gulmohur. Also a blade, a, glass slide or a sheet of paper, a, magnifying glass and water., Observe Fig. 7.20 carefully. Look at, the prominent parts of the open flower., , are called sepals. Take a flower and, observe its petals and sepals. Now,, answer the following questions:, How many sepals does it have?, Are they joined together?, What are the colours of the petals, and the sepals?, How many petals does the flower have?, Are they joined to one another or are, they separate?, Do the flowers with joint sepals have, petals that are separate or are they also, joined together?, Fill the table based on the, observations of the whole class, (Table 7.3). Add observations to this, table, from a field trip to a locality where, there are plants with flowers. Fill the, last two columns later., To see the inner parts of the flower, clearly, you have to cut it open, if its, petals are joined. For example, in datura, and other bell-shaped flowers, the petals, have to be cut lengthwise and spread, , 60, , SCIENCE, , 2018-19

Page 71 :
Table 7.3 Observations on flowers, Name of, flower/, plant, , Number, and colour, of sepals, , Number, and colour, of petals, , Are the, Are the, Stamens – are, sepals joined petals joined, they free or, or separate? or separate? joined to petals, , Pistil –, Present/, absent, , Rose, , Many, (Colour?), , 5 (Colour?), , Separate, , Present, , out so that the inner parts can be seen, clearly (Fig. 7.21)., Remove the sepals and petals to see, the other parts. Study the Fig. 7.22, carefully, compare your flower with the, illustration and identify the stamens and, pistil in your flower., Look at Fig 7.23 carefully. It shows, different kinds of stamens present in, different flowers. Can you recognise the, two parts of the stamens in your flower?, How many stamens are there in your, flower? Draw one stamen and label, its parts., , Fig. 7.21 A bell-shaped flower, Anthers, (yellow, colour), , Fig. 7.22 Parts of a flower, , Anther, (yellow, colour), Filament, (cream, colour), Fig. 7.23 Parts of a stamen, , The innermost part, of flower is called the, pistil. If you cannot see, it completely, remove, the remaining stamens., Identify the parts of the, pistil with the help of, Fig. 7.24., Draw, a, neat,, labelled diagram of the, pistil of your flower., , Stigma, Style, , Ovary, , Fig. 7.24 Parts, of a pistil, , Activity 11, , Pistil, (green, colour), , Stamens, (cream, colour), , Free, , Let us now study the structure of ovary, (Fig. 7.24). It is the lowermost and, swollen part of the pistil. We will cut this, part to study what is inside! Look at Fig., 7.25 (a) and (b) carefully to understand, how to cut the ovary of a flower., , GETTING TO KNOW PLANTS, , 61, , 2018-19

Page 72 :
(a), , (b), , Fig. 7.25 Cutting an ovary (a) longitudinal cut, and (b) transverse cut, , Cut the ovary in two different ways, as shown in Fig. 7.25. To prevent them, from drying, put a drop of water on, each of the two pieces of the ovary, you, have cut., Ovules, , Fig. 7.26 Inner structure of an ovary, (a) longitudinal cut, (b) transverse cut, , Observe the inner parts of the ovary, using a lens (Fig. 7.26). Do you see some, small bead like structures inside the, ovary? They are called ovules. Draw and, label the inner parts of the ovary in your, notebook., Try to find out the names of as many, flowers as you can by asking the, gardener or any other person., Remember, not to pluck more flowers, than you need. Based on what you have, filled in Table 7.3, answer the following, questions., Do all flowers have sepals, petals,, stamens and pistils? Are there flowers that, do not have one or more of these? Are, there flowers which have parts other than, these?, Did you find any flower which has, no difference between sepals and petals?, Did you find any flower in which the, number of stamens is different from the, number of petals?, Do you now agree that the structure, of the flower is not always the same?, The number of sepals, petals, stamens, and pistils may also be different in, different flowers. Some of these parts, may even be absent at times!, We have studied some features and, functions of leaves, stems and roots., We studied the structure of different, flowers. We will learn about the function, of flowers in higher classes. We will also, learn about fruits in higher classes., , 62, , SCIENCE, , 2018-19

Page 73 :
Climbers, , Petiole, , Conduct, , Photosynthesis, , Creepers, , Pistil, , Fibrous roots, , Reticulate venation, , Herbs, , Sepal, , Lamina, , Shrubs, , Lateral roots, , Stamen, , Midrib, , Taproot, , Ovule, , T ranspiration, , Parallel Venation, , T rees, , Petal, , Veins, , n, , Plants are usually grouped into herbs, shrubs and trees based on their, height, nature of stem and branches., , n, , The stem bears leaves, flowers and fruits., , n, , Leaf usually has a petiole and lamina., , n, , The pattern of veins on the leaf is called venation. It can be reticulate or, parallel., , n, , Leaves give out water vapour through the process of transpiration., , n, , Green leaves make their food by the process of photosynthesis using, carbon dioxide and water in the presence of sunlight., , n, , Roots absorb water and minerals from the soil. They also anchor the, plant firmly in the soil., , n, , Roots are mainly of two types: tap root and fibrous root., , n, , Plants having leaves with reticulate venation have tap roots while plants, having leaves with parallel venation have fibrous roots., , n, , The stem conducts water from roots to the leaves (and other parts) and, food from leaves to other parts of the plant., , n, , The parts of a flower are sepals, petals, stamens and pistil., , GETTING TO KNOW PLANTS, , 63, , 2018-19

Page 74 :
1. Correct the following statements and rewrite them in your notebook., (a) Stem absorbs water and minerals from the soil., (b) Leaves hold the plant upright., (c) Roots conduct water to the leaves., (d) The number of petals and stamens in a flower is always equal., (e) If the sepals of a flower are joined together, its petals are also joined, together., (f) If the petals of a flower are joined together, then the pistil is joined to the, petal., 2. Draw (a) a leaf, (b) a taproot and (c) a flower, you have studied for Table 7.3., 3. Can you find a plant in your house or in your neighborhood, which has a long, but weak stem? Write its name. In which category will you place it?, 4. What is the function of a stem?, 5. Which of the following leaves have reticulate venation?, Wheat, tulsi, maize, grass, coriander (dhania), China rose, 6. If a plant has fibrous root, what type of venation do its leaves have?, 7. If a plant has leaves with reticulate venation, what kind of roots will it have?, 8. Is it possible for you to find out whether a plant has taproot or fibrous roots by, looking at the impression of its leaf on a sheet of paper?, 9. What are the parts of a flower., 10. From the following plants, which of them have flowers?, Grass, maize, wheat, chilli, tomato, tulsi, peepal, shisham, banyan, mango, jamun,, guava, pomegranate, papaya, banana, lemon, sugarcane, potato, groundnut, 11. Name the part of plant which produces food. Name the process., 12. In which part of a flower, you will find the ovary?, 13. Name two plants in which one has joined sepals and the other has separate, sepals., , 64, , SCIENCE, , 2018-19

Page 75 :
SUGGESTED PROJECT AND ACTIVITIES, 1., , BECOME A LEAF EXPERT, Do this activity with a number of leaves over a period of few weeks. For every, leaf that you wish to study, pluck it and wrap it in a wet cloth and take it, home. Now, place the leaf between the folds of a newspaper and place a, heavy book on it. You can also put it under your mattress or a trunk! Take, out the leaf after a week. Paste it on a paper and write a poem or story about, it. With your leaf collection pasted in a book, you can become an expert about, leaves!, , 2., , Names of plant parts are hidden in this grid. Search them by going up, down,, diagonally, forward or backward. Have fun!, O, , V, , U, , L, , E, , L, , Y, , T, , S, , T, , E, , M, , V, , E, , I, , N, , W, , Q, , H, , E, , R, , B, , P, , I, , A, , N, , I, , M, , A, , L, , Z, , E, , X, , R, , N, , D, , R, , F, , I, , L, , A, , M, , E, , N, , T, , M, , U, , R, , Y, , A, , R, , A, , B, , L, , C, , O, , D, , B, , E, , I, , L, , E, , E, , U, , O, , F, , O, , L, , G, , H, , I, , B, , A, , L, , H, , I, , I, , R, , J, , A, , L, , K, , U, , R, , T, , M, , T, , N, , O, , T, , P, , P, , Q, , R, , R, , A, , E, , E, , N, , S, , T, , U, , F, , E, , H, , V, , W, , N, , P, , Y, , A, , M, , G, , I, , T, , S, , Z, , Z, , N, , C, , F, , L, , O, , W, , E, , R, , E, , H, , T, , N, , A, , H, , S, , T, , A, , M, , E, , N, , N, , S, , E, , P, , A, , L, , GETTING TO KNOW PLANTS, , 65, , 2018-19

Page 76 :
8, , Body Movements, , S, , it absolutely still. Observe the, movements taking place in your, body. You must be blinking your, eyes, time to time. Observe the, movements in your body as you, breathe. There are so many movements, that happen in our bodies., When you are writing in your, notebook which part of the body are you, moving? Or, when you turn and look at, your friend? Different parts of your body, move while you remain at the same, place, in these examples. You also move, from one place to another — you get up, and go to your teacher or to the school, compound, or go home after school. You, walk, run, skip, jump and move from, place to place., Let us see how animals move from, place to place by filling up Table 8.1,, after discussing with our friends,, teachers and parents., , Boojho wonders about movements, in plants. He knows they do not, move from place to place, but, do, they show any other kind of, movements?, , Table 8.1 How do animals move, from place to place?, , Animal, , Body part used How does, for moving, e animal, from place to thm, ove?, place, , Cow, , Legs, , Walk, , Whole body, , Slither, , Humans, Snake, Bird, Insect, Fish, , Walk, run, fly, jump, creep, crawl,, slither and swim – these are only a few, of the ways in which animals move from, one place to another. Why are there so, many differences in the way that, animals move from place to place? Why, is it that many animals walk while a, snake slithers or crawls and a fish, swims?, , 8.1 HUMAN BODY AND ITS MOVEMENTS, Let us look closely at some of our own, movements to begin with, before looking, at all these varieties of movements in, animals., Do you enjoy doing physical exercise, at school? How do you move your hands, and legs while doing different exercises?, , 66, , SCIENCE, , 2018-19

Page 77 :
Let us try some of the many movements,, our body is capable of., Bowl an imaginary ball at an, imaginary wicket. How did you move, your arm? Did you rotate it at the, shoulder in a circular movement? Did, your shoulder also move? Lie down and, rotate your leg at the hip. Bend your, arm at the elbow and the leg at the knee., Stretch your arm sideways. Bend your, arm to touch your shoulder with your, fingers. Which part of your arm did you, bend? Straighten your arm and try to, bend it downwards. Are you able to, do it?, Try to move the various parts of your, body and record their movements in, Table 8.2., , Why is it that we are able to move a, few parts of our body easily in various, directions and some only in one, direction? Why are we unable to move, some parts at all?, , Activity 1, Place a scale length-wise on your arm, so that your elbow is in the centre, (Fig. 8.1)., Ask your friend to tie the scale and, your arm together. Now,, try to bend your elbow., Are you able to do it?, , Fig. 8.1 Can you bend your, arm now?, , Table 8.2 Movements in our body, Movement, Body Part, , Rotates, completely, , Neck, , Rotates, partly/turns, , Bends, , Lifts, , Does not, move at all, , Yes, , Wrist, Finger, Knee, Ankle, Toe, Back, Head, Elbow, Ar m, , Yes, , BODY MOVEMENTS, , 67, , 2018-19

Page 78 :
Did you notice that we are able to bend, or rotate our body in places where two, parts of our body seem to be joined, together — like elbow, shoulder or neck?, These places are called joints. Can you, name more such joints? If our body has, no joints, do you think it would be, possible for us to move in any way at all?, What exactly is joined together at, these joints?, Press your fingers against the top of, your head, face, neck, nose, ear, back of, the shoulder, hands and legs including, the fingers and toes., Do you get a feel of something hard, pressing against your fingers? The hard, structures are the bones. Repeat this, activity on other parts of your body. So, many bones!, Bones cannot be bent. So, how do, we bend our elbow? It is not one long, bone from the upper arm to our wrist. It, is different bones joined together at the, elbow. Similarly, there are many bones, present in each part of the body. We, can bend or move our body only at those, points where bones meet., There are different types of joints in, our body to help us carry out different, movements and activities. Let us learn, about some of them., , Bowl, Ball, , Paper Cylinder, , Fig. 8.2 Making a ball and socket joint, , Does the ball rotate freely inside the bowl?, Does the paper cylinder also rotate?, Now, imagine that the paper cylinder, is your arm and the ball is its end. The, bowl is like the part of the shoulder to, which your arm is joined. The rounded, end of one bone fits into the cavity, (hollow space) of the other bone, (Fig.8.3). Such a joint allows movements, in all directions. Can you name another, such joint you can think of, recollecting, the body movements we tried at the, beginning of this section?, Ball and, Socket Joint, , Thigh Bone, Hip Bone, , Fig. 8.3 A ball and socket joint, , Ball and socket joints, , Pivotal Joint, , Activity 2, Roll a strip of paper into a cylinder. Make, a small hole in an old rubber or plastic, ball (under supervision) and push the, paper cylinder into it as shown in, Fig. 8.2. You can also stick the cylinder, on the ball. Put the ball in a small bowl., , The joint where our neck joins the head, is a pivotal joint (Fig. 8.4). It allows us, to bend our head forward and backward, and turn the head to our right or left., Try these movements. How are these, movements different from those of our, arm that can rotate a complete circle in, , 68, , SCIENCE, , 2018-19

Page 79 :
Pivotal joint, , Fig. 8.4 A pivotal joint, , its ball and socket joint? In a pivotal, joint a cylindrical bone rotates in a ring., , Hinge joints, Open and close a door a few times., Observe the hinges of the door carefully., They allow the door to move back, and forth., , Activity 3, Let us look at the kind of movement, allowed by a hinge. Make a cylinder with, cardboard or thick chart paper, as, shown in Fig. 8.5. Attach a small pencil, to the cylinder by piercing the cylinder, at the centre, as shown. Make a hollow, half cylinder from cardboard such that, the rolled up cylinder can fit inside it, easily. The hollow half cylinder with the, rolled up cylinder sitting inside it, allows, movement like a hinge. Try to move the, rolled up cylinder. How does it move?, How is this movement different from, what we saw with our constructed ball, and socket joint? We saw this kind of, , Fig. 8.5 Directions of movement allowed by a hinge, like joint, , Fig. 8.6 Hinge joints of the knee, , movement at the elbow in Activity 1., What we have constructed in Fig. 8.4 is, different from a hinge, of course. But, it, illustrates the direction in which a hinge, allows movement. The elbow has a hinge, joint that allows only a back and forth, movement (Fig. 8.5). Can you think of, more examples of such joints?, , Fixed joints, Some joints between bones in our head, are different from those we have, discussed so far. The bones cannot move, at these joints. Such joints are called, fixed joints. When you open your, mouth wide, you can move your lower, jaw away from your head, isn’t it? Try, to move your upper jaw, now. Are you, able to move it? There is a joint between, the upper jaw and the rest of the head, which is a fixed joint., We discussed only some of the joints, that connect parts of our body., What gives the different parts of the, body their different shapes?, If you wanted to make a doll, what, will you make first? Perhaps a, framework to give the doll shape before, making its outer structure, isn’t it? All, the bones in our body also form a, framework to give a shape to our body., , BODY MOVEMENTS, , 69, , 2018-19

Page 80 :
The human skeleton is composed of, around 305 bones at birth. The, number of bones in the skeleton, changes with age. It decreases to 206, bones by adulthood after some bones, have fused together., This framework is, called the skeleton, (Fig. 8.7.), How do we know, that this is the shape, of a human skeleton?, How do we know the, shapes of the different, bones in our body? We, can have some idea, about the shape and, number of bones in, some parts of our body, by feeling them. One, way we could know, this shape better, would be to look at Xray images of the, Fig. 8.7 The, Human skeleton, human body., Did you or anyone in your family, ever have an X-ray of any part of your, body taken? Sometimes when we are, hurt, or have an accident, doctors use, these X-ray images to find out about, any possible injuries that might, have happened to the bones. The Xrays show the shapes of the bones in, our bodies., Feel the bones in your forearm,, upper arm, lower leg and upper leg. Try, to find the number of bones in each part., , Similarly, feel the bones of your ankle, and knee joints and compare these with, the X-ray images (Fig. 8.8)., , Fig 8.8 X-ray images of ankle and knee joints, , Bend your fingers. Are you able to, bend them at every joint? How many, bones does your middle finger have?, Feel the back of your palm. It seems to, have many bones, isn’t it (Fig. 8.9)? Is, your wrist flexible? It is made up of, several small bones called carples. What, will happen if it has only one bone?, , Fig. 8.9 Bones of the hand, , Activity 4, Take a deep breath and hold it for a, little while. Feel your chest bones and the, back bone by gently pressing the middle, of the chest and back at the same time., Count as many ribs (bones of the chest), , 70, , SCIENCE, , 2018-19

Page 81 :
Fig. 8.12 Shoulder bones, , Fig. 8.10 The rib cage, , as possible. Observe Fig. 8.10 carefully, and compare with what you feel of the, chest bones. We see that the ribs are, curiously bent. They join the chest bone, and the backbone together to form a, box. This is called the rib cage. There, are 12 ribs on each side of chest. Some, important internal parts of our body lie, protected inside this cage., Ask some friends to touch their toes, without bending their knees. Starting, from the neck, move your, fingers downwards on the, back of your friend. What, you feel is the backbone. It, is made up of many small, bones called vertebrae. The, backbone consists of 33, vertebrae (Fig. 8.11). The rib, cage is joined to these bones., If backbone was made, up of only one long bone,, will your friend be able to, bend?, Make your friend stand, with both hands pressed to, the, wall and ask her to push, Fig. 8.11, The backbone the wall. Do you notice two, , bones on the back are prominent where, the shoulders are? They are called, shoulder bones (Fig. 8.12)., Observe Fig. 8.13 carefully. This, structure is made of pelvic bones. They, enclose the portion of your body, below the stomach. This is the part, you sit on., , Fig. 8.13 Pelvic bones, , The skull is made up of many bones, joined together (Fig. 8.14). It encloses, and protects a very important part of, the body, the brain., We discussed many bones and, the joints of our skeleton. There are, , BODY MOVEMENTS, , Fig. 8.14 The skull, 71, , 2018-19

Page 82 :
some additional parts of the skeleton, that are not as hard as the bones and, which can be bent. These are called, cartilage., Feel your ear. Do you find any hard, bony parts that can be bent, (Fig. 8.15)? There do not seem to be any, bones here, isn’t it? Do you notice, anything different between the ear lobe, and the portions above it (Fig. 8.16), as, you press them between your fingers?, , Fig. 8.15 Upper part, of ear has cartilage, , Fig. 8.16, The ear lobe, , You do feel something in the upper parts, of the ear that is not as soft as the ear, lobe but, not as hard as a bone, isn’t it?, This is cartilage. Cartilage is also found, in the joints of the body., We have seen that our skeleton is, made up of many bones, joints and, cartilage. You could feel, bend and move, many of them. Draw a neat figure of the, skeleton in your notebook., We have learnt about the bones in our, body and about joints that help us move, in different ways. What makes the bones, move the way they do? Let us find out., Make a fist with one hand, bend your, arm at the elbow and touch your, shoulder with the thumb (Fig. 8.17). Do, you see any change in your upper arm?, Touch it with the other hand. Do you, , (a), , (b), , Fig. 8.17 Two muscles work together to move, a bone, , observe a swollen region is the upper, arm? This is a muscle. The muscle, bulged due to contraction (it became, smaller in length). Now bring your arm, back to its normal position. What, happened to the muscle? Is it still, contracted? You can observe similar, contraction of muscles in your leg when, you walk or run., When contracted, the muscle, becomes shorter, stiffer and thicker. It, pulls the bone., Muscles work in pairs. When one of, them contracts, the bone is pulled in, that direction. The other muscle of the, pair relaxes. To move the bone in the, opposite direction, the relaxed musle, contracts to pull the bone towards its, original position, while the first relaxes., A muscle can only pull. It cannot push., Thus, two muscles have to work together, to move a bone. (Fig. 8.17), Are muscles and bones always, required for movement? How do other, animals move? Do all animals have, bones? What about an earthworm or a, , 72, , SCIENCE, , 2018-19

Page 83 :
snail? Let us study the manner of, movement, that is, the gait of some, animals., , 8.2 “GAIT, , OF, , ANIMALS”, , Earthworm, Activity 5, Observe an earthworm moving on soil, in a garden. Gently lift it and place it, on a piece of blotting or filter paper., Observe its movement (Fig. 8.18). Then, place it on a smooth glass plate or any, slippery surface. Observe its movement, now. Is it different from that on paper?, In which of the above two surfaces do, you find that the earthworm is able to, move easily?, The body of an earthworm is made, up of many rings joined end to end. An, , contractions, the earthworm can move, through soil. Its body secretes a slimy, substance to help the movement., How does it fix parts of its body to, the ground? Under its body, it has a, large number of tiny bristles (hair like, structures) projecting out. The bristles, are connected with muscles. The bristles, help to get a good grip on the ground., The earthworm, actually, eats its way, through the soil! Its body then throws, away the undigested part of the material, that it eats. This activity of an earthworm, makes the soil more useful for plants., , Snail, Activity 6, Observe a snail in your garden or in field., Have you seen the rounded structure it, carries on its back (Fig. 8.19)?, , Fig. 8.19 A snail, Fig. 8.18 Movement of earthworm, , earthworm does not have bones. It has, muscles which help to extend and, shorten the body. During movement,, the earthworm first extends the front, part of the body, keeping the rear, portion fixed to the ground. Then it fixes, the front end and releases the rear end., It then shortens the body and pulls the, rear end forward. This makes it move, forward by a small distance. Repeating, such muscle expansions and, , This is called the shell and it is the, outer skeleton of the snail, but is not, made of bones. The shell is a single unit, and does not help in moving from place, to place. It has to be dragged along., Place the snail on a glass plate and, watch it. When it starts moving,, carefully lift the glass plate along with, the snail over your head. Observe its, movements from beneath., A thick structure and the head of the, snail may come out of an opening in, , BODY MOVEMENTS, , 73, , 2018-19

Page 84 :
the shell. The thick structure is its foot,, made of strong muscles. Now, carefully, tilt the glass plate. The wavy motion of, the foot can be seen. Is the movement of, a snail slow or fast as compared to an, earthworm?, , Cockroach, Activity 7, Observe a cockroach (Fig. 8.20)., Cockroaches walk and climb as well, as fly in the air. They have three pairs, of legs. These help in walking. The body, is covered with a hard outer skeleton., This outer skeleton is made of number, , Fig. 8.21 Skeleton of a bird, , bony parts of the forelimbs are modified, as wings. The shoulder bones are strong., The breastbones are modified to hold, muscles of flight which are used to move, the wings up and down (Fig. 8.21)., , Fish, Activity 8, Fig. 8.20 A cockroach, , of plates joined together and that, permits movement., There are two pairs of wings attached, to the body behind head. The, cockroaches have distinct muscles —, those near the legs move the legs for, walking. The body muscles move the, wings when the cockroach flies., , Make a paper boat. Put it in water and, push it with one narrow end pointing, forward [Fig. 8.22 (a)]. Did it go into the, water easily? Now hold the boat, sideways and push it into the water, from the broad side [Fig. 8.22 (b)]. Are, you able to make the boat move in water, when you push it from this side?, , Birds, Birds fly in the air and walk on the, ground. Some birds like ducks and, swans also swim in water. The birds can, fly because their bodies are well suited, for flying. Their bones are hollow and, light. The bones of the hind limbs are, typical for walking and perching. The, 74, , (a), , (b), Fig. 8.22 Playing with boats, SCIENCE, , 2018-19

Page 85 :
Fish also have other fins on their, body which mainly help to keep the, balance of the body and to keep, direction, while swimming. Did you ever, notice that under water divers wear fin, like flippers on their feet, to help them, move easily in water?, , How do snakes move?, , Fig. 8.23 Fish, , Have you noticed that the shape of a, boat is somewhat like a fish (Fig 8.23)?, The head and tail of the fish are smaller, than the middle portion of the body –, the body tapers at both ends. This body, shape is called streamlined., The shape is such that water can flow, around it easily and allow the fish to, move in water.The skeleton of the fish, is covered with strong muscles. During, swimming, muscles make the front part, of the body curve to one side and the, tail part swings towards the opposite, side. The fish forms a curve as shown, in Fig. 8.24. Then, quickly, the body and, tail curve to the other side. This makes, a jerk and pushes the body forward. A, series of such jerks make the fish swim, ahead. This is helped by the fins of, the tail., , Have you seen a snake slither? Does it, move straight(Fig. 8.25)?, Snakes have a long backbone. They, have many thin muscles. They are, connected to each other even though they, are far from one another. Muscles also, interconnect the backbone, ribs and skin., The snake’s body curves into many, loops. Each loop of the snake gives it a, forward push by pressing against the, ground. Since its long body makes, many loops and each loop gives it this, push, the snake moves forward very fast, and not in a straightline., We have learned about the use of, bones and muscles for the movements, of different animals. Paheli and Boojho, have many questions in their sacks, about the different movements in, animals. So must you be having many, unanswered questions buzzing in your, , Fig. 8.24 Movement in Fish, , Fig. 8.25 Movement in a snake, , BODY MOVEMENTS, , 75, , 2018-19

Page 86 :
minds? The ancient Greek philosopher, Aristotle, in his book Gait of Animals,, asked himself these questions. Why do, different animals have the body parts, that they do have and how do these, body parts help animals to move the, way they do? What are the similarities, and differences in these body parts, between different animals? How many, body parts are needed by different, animals for moving from place to, , place? Why two legs for humans and, four for cows and buffaloes? Many, animals seem to be having an even, number of legs, why? Why is the, bending of our legs different from that, of our arms?, So many questions and perhaps, we have looked for some answers, through our activities in this chapter, and we need to look for many, more answers., , Yoga — For Better Health, Yoga is an invaluable gift of the ancient Indian tradition. The United Nations, declared 21 June as International Day of Yoga. Yoga keeps a person healthy. It, helps in keeping the backbone erect, enabling you to sit straight and not, slouch. Many postures in yoga require you to lift your own weight, which help, in making the bones strong and help ward off osteoporosis. It also helps in, relieving joint pain, which is mostly observed in elderly people. It tunes all, muscles in the body and keeps them active. It keeps the heart healthy and, makes it work more efficiently. Certain yoga postures should be performed, under the supervision of a trained person., , 76, , SCIENCE, , 2018-19

Page 87 :
Backbone, , Muscle, , Ball and socket joint, , Outer skeleton, , Bristles, , Pelvic bones, , Cartilage, , Pivotal joint, , Cavity, , Rib cage, , Fixed joint, , Shoulder bones, , Gait of animals, , Skeleton, , Hinge joint, , Streamlined, , n, , Bones and cartilage form the skeleton of the human body. It gives the, frame and shape to the body and helps in movement. It protects the, inner organs., , n, , The human skeleton comprises the skull, the back bone, ribs and the, breast bone, shoulder and hipbones, and the bones of hands and legs., , n, , The bones are moved by alternate contractions and relaxations of two, sets of muscles., , n, , The bone joints are of various kinds depending on the nature of joints, and direction of movement they allow., , n, , Strong muscles and light bones work together to help the birds fly. They, fly by flapping their wings., , n, , Fish swim by forming loops alternately on two sides of the body., , n, , Snakes slither on the ground by looping sideways. A large number of, bones and associated muscles push the body forward., , n, , The body and legs of cockroaches have hard coverings forming an outer, skeleton. The muscles of the breast connected with three pairs of legs, and two pairs of wings help the cockroach to walk and fly., , n, , Earthworms move by alternate extension and contraction of the body, using muscles. Tiny bristles on the underside of the body help in gripping, the ground., , n, , Snails move with the help of a muscular foot., , BODY MOVEMENTS, , 77, , 2018-19

Page 88 :
1., , Fill in the blanks:, (a) Joints of the bones help in the ——————— of the body., (b) A combination of bones and cartilages forms the _______ of the body., (c) The bones at the elbow are joined by a ______________________ joint., (d) The contraction of the _____________ pulls the bones during movement., , 2., , Indicate true (T) and false (F) among the following sentences., (a) The movement and locomotion of all animals is exactly the same. ( ), (b) The cartilages are harder than bones. (, (c) The finger bones do not have joints. (, , ), ), , (d) The fore arm has two bones. ( ), (e) Cockroaches have an outer skeleton. (, 3., , ), , Match the items in Column I with one or more items of Column II., Column I, , Column II, , Upper jaw, , have fins on the body, , Fish, , has an outer skeleton, , Ribs, , can fly in the air, , Snail, , is an immovable joint, , Cockroach, , protect the heart, shows very slow movement, have a streamlined body, , 4., , Answer the following:, (a) What is a ball and socket joint?, (b) Which of the skull bones are movable?, (c) Why can our elbow not move backwards?, , THINGS TO THINK ABOUT, We discussed the many movements our bodies are capable of. Healthy bones,, muscles, joints and cartilages are needed by the body for all these movements., Some of us suffer from conditions that could make these movements not so easy. In, a whole class activity, try to find ways that one would manage everyday activities, if, any one of our body movements was not possible. In Activity 1, for instance, you, tied a scale on your arm and disabled the elbow movement. Think of other ways of, restricting normal body movements and find ways that everyday activities could, then be managed., 78, , SCIENCE, , 2018-19

Page 89 :
9, P, , The Living Organisms —, Characteristics and Habitats, , aheli and Boojho went on, vacation to many places of, interest. One such trip took, them to the river Ganga in Rishikesh., They climbed the mountains of the, Himalayas, where it was very cold. They, saw many kinds of trees on these, mountains — oaks, pines and deodars,, very different from the ones near their, home on the plains! In yet another trip,, they travelled to Rajasthan and moved, on camels through the hot desert. They, collected different kinds of cactus plants, from this trip. Finally, they went on a, trip to Puri and visited the sea beach,, dotted with casuarina trees. While, recollecting all the fun that they had on, these trips, a thought struck them. All, these places were so different from one, another, some were cold, some very hot, and dry, and some places so humid. And, yet all of them had many organisms, (living creatures) of various kinds., They tried to think of a place on Earth, where there may not be any living, creatures. Boojho thought of places near, his home. Inside the house, he tried the, cupboards. He had thought that there, may not be any living organisms here,, but he found one tiny spider in the, cupboard. Outside the home too, there, did not seem to be any place, he could, think of, that did not have living creatures, , of some kind or the other (Fig. 9.1). Paheli, started thinking and reading about far, away places. She read that people have, even found tiny living organisms in the, openings of volcanoes!, , Fig. 9.1 Search for living organisms, , 9.1 ORGANISMS AND THE, SURROUNDINGS WHERE THEY LIVE, Another thought that occurred to Paheli, and Boojho was about the kinds of living, organisms that were present in different, locations that they had visited. The, deserts had camels, the mountains had, goats and yak. Puri had some other, creatures — crabs on the beach and, such a variety of fish being caught by, the fishermen at the sea! And then,, there did seem to be some creatures like, ants that were present in all these, different locations. The kinds of plants, found in each of these regions were so, different from the plants of the other, regions. What about the surroundings, , 2018-19

Page 90 :
in these different regions? Were they, the same?, , will discuss the table as we travel, through many more interesting places., , Activity 1, , 9.2 HABITAT AND ADAPTATION, , Let us start with a forest. Think of all, the plants, animals and objects that can, be found there. List them in Column 1, of Table 9.1. List things, animals and, plants, found in the other regions that, are also shown in the table. You can, collect the examples scattered through, this chapter to fill Table 9.1. Discuss, also with your friends, parents and, teachers, to find more examples to fill, the tables. You can also consult many, interesting books in libraries that talk, of animals, plants and minerals of, different regions., T ry and include many plants,, animals and objects, big and small, in, each of the columns in this table. What, kind of objects will we find that may not, be animals or plants? Perhaps parts of, plants like dried leaves, or parts of, animals, like bones. We may also find, different kinds of soils and pebbles., Water in the oceans may have salts, dissolved in it as discussed in Chapter, 5. There could be many more objects., As we go through the chapter, keep, adding more examples to Table 9.1. We, , What do you find from the plants and, animals listed in Activity 1? Did you find, a large variety in them? Look at what you, have entered in the column for the desert, and the column for the sea in Table 9.1., Did you list very different kind of, organisms in these two columns?, What are the surroundings like, in, these two regions?, In the sea, plants and animals are, surrounded by saline (salty) water. Most, of them use the air dissolved in water., There is very little water available in, the desert. It is very hot in the day time, and very cold at night in the desert. The, animals and plants of the desert live on, the desert soil and breathe air from the, surroundings., The sea and the desert are very, different surroundings and we find very, different kind of plants and animals in, these two regions, isn’t it? Let us look, at two very different kind of organisms, from the desert and the sea – a camel, and a fish. The body structure of a camel, helps it to survive in desert conditions., Camels have long legs which help to, , Table 9.1 Animals, plants and other objects found in different surroundings, In the forest, , On mountains, , In the desert, , 80, , In the sea, , Any other?, , SCIENCE, , 2018-19

Page 91 :
keep their bodies away from the heat of, the sand (Fig. 9.2). They excrete small, amount of urine, their dung is dry and, they do not sweat. Since camels lose, very little water from their bodies, they, can live for many days without water., Let us look at different kinds of fish., Some of these are shown in Fig. 9.3., There are so many kinds of fish, but, do, you see that they all have something, common about their shape? All the ones, shown here have the streamlined shape, that was discussed in Chapter 8. This, shape helps them move inside water., Fish have slippery scales on their bodies., These scales protect the fish and also, help in easy movement through water., We discussed in Chapter 8, that fish, have flat fins and tails that help them, to change directions and keep their body, balance in water. Gills present in the, fish help them to use oxygen dissolved, in water., We see that the features of a fish help, it to live inside water and the features of, a camel help it to survive in a desert., , We have taken only two examples, from a very wide variety of animals and, plants that live on the Earth. In all this, variety of organisms, we will find that, they have certain features that help, them live in the surroundings in which, they are normally found. The presence, of specific features or certain habits,, which enable an organism to live, naturally in a place is called adaptation., Adaptation of organisms differ, depending on their place of dwelling., That is why a fish cannot live out of, water and a camel cannot live in sea., The place where organisms live is, called habitat. Habitat means a dwelling, place (a home). The habitat provides, food, water, air, shelter and other needs, to organisms. Several kinds of plants, and animals live in the same habitat., The plants and animals that live on, land are said to live in terrestrial, habitats. Some examples of terrestrial, habitats are forests, grasslands, deserts,, coastal and mountain regions. On the, other hand, the habitats of plants and, , Fig. 9.2 Camels in their surroundings, , Fig. 9.3 Different kinds of fish, , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 81

Page 92 :
There are some changes that can happen in an organism over a short period of, time to help them adjust to some changes in their surroundings. For instance,, if we live in the plains and suddenly go to high mountain regions, we may, experience difficulty in breathing and doing physical exercise for some days., We need to breathe faster when we are on high mountains. After some days,, our body adjusts to the changed conditions on the high mountain. Such small, changes that take place in the body of a single organism over short periods, to, overcome small problems due to changes in the surroundings, are called, acclimatisation. These changes are different from the adaptations that take, place over thousands of years., animals that live in water are called, aquatic habitats. Lakes, rivers and, oceans are some examples of aquatic, habitats. There are large variations, among terrestrial habitats like forests,, grasslands, deserts, coastal and, mountain regions located in different, parts of the world., The organisms, both plants and, animals, living in a habitat are its biotic, components. The non-living things such, as rocks, soil, air and water in, the habitat constitute its abiotic, components. Are sunlight and heat, biotic or abiotic components?, We know that some plants grow from, seeds. Let us look at some abiotic factors, and their effect on seeds as they grow, into young plants., , Activity 2, Recall Activity 5 in Chapter 1 — we made, sprouts from moong and chana seeds., When the seed turned into a sprout, it, is said to have germinated. This is the, beginning of life of a new plant., Collect some dry moong seeds. Keep, 20-30 seeds aside and soak the rest in, , water for a day. Divide the soaked seeds, into four parts. Keep one part, completely submerged in water for 3-4, days. Do not disturb the dry seeds and, those submerged in water. Keep one part, of soaked seeds in a sunny room and, another in a completely dark, region like a cupboard that does not, allow any light to come in. Keep the last, part in very cold surroundings, say, in, a refrigerator or with ice around them., Rinse them and replace the water every, day. What do you notice, after a few, days? Do the seeds in all the five, conditions germinate uniformly? Do you, find slower or no germination in any of, these?, Do you realise that abiotic factors like, air, water, light and heat are important, for the growth of plants. In fact, abiotic, factors are important for all living, organisms., We find that organisms exist in very, cold as well as very hot climates, isn’t, it? How do they manage to survive?, Adaptation is the method by which, organisms get well adjusted to the, climate., , 82, , SCIENCE, , 2018-19

Page 93 :
Adaptation does not take place in a, short time because the abiotic factors of, a region also change very slowly. Those, organisms which cannot adapt to these, changes die, and only the adapted ones, survive. Organisms adapt to different, abiotic factors in different ways. This, results in a wide variety of organisms in, different habitats., Let us look at some habitats,, understood the abiotic factors and the, adaptations of animals in these habitats., , Fig. 9.4 Desert animals in burrows, , 9.3 A JOURNEY THROUGH DIFFERENT, HABITATS, Some Terrestrial Habitats, Deserts, We discussed the abiotic factors of a, desert and the adaptations in camels., What about other animals and plants, that are found in deserts? Do they, have the same kind of adaptations?, There are desert animals like rats, and snakes, which do not have long legs, that a camel has. To stay away from the, intense heat during the day, they stay, in burrows deep in the sand (Fig 9.4)., These animals come out only during the, night, when it is cooler., Fig. 9.5 shows some typical plants, that grow in a desert. How are these, adapted to the desert?, , Activity 3, Bring a potted cactus and a leafy plant, to the classroom. Tie polythene bags to, some parts of the two plants, as was, done for Activity 4 in Chapter 7, where, we studied transpiration in plants., , Fig. 9.5 Some typical plants that grow in desert, , Leave the potted plants in the sun and, observe after a few hours. What do you, see? Do you notice any difference in the, amount of water collected in the two, polythene bags?, Desert plants lose very little water, through transpiration. The leaves in, desert plants are either absent, very, small, or they are in the form of spines., This helps in reducing loss of water from, the leaves through transpiration. The, leaf-like structure you see in a cactus, is, in fact, its stem (Fig. 9.5)., Photosynthesis in these plants is, usually carried out by the stems. The, , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 83

Page 94 :
stem is also covered with a thick waxy, layer, which helps to retain water in the, tissues of cacti. Most desert plants have, roots that go very deep into the soil for, absorbing water., Mountain regions, These habitats are normally very cold, and windy. In some areas, snowfall may, take place in winters., There is a large variety of plants and, animals living in the mountain regions., Have you seen the kind of trees shown, in Fig. 9.6?, , also present on mountains. They may, have different kind of adaptations to, survive on the mountains., Animals living in the mountain regions, are also adapted to the conditions there, (Fig. 9.7). They have thick skin or fur to, protect them from cold. For example, yaks, have long hair to keep them warm. Snow, leopard has thick fur on its body, , (a), , Fig. 9.6 Trees of a mountain habitat, , If you live in a mountain region or, have visited one, you may have seen a, large number of such trees. But, have, you ever noticed such trees naturally, growing in other regions?, How are these trees adapted to the, conditions prevailing in their habitat?, These trees are normally cone shaped, and have sloping branches. The leaves, of some of these trees are needle-like., This helps the rainwater and snow to, slide off easily. There could be trees with, shapes very different from these that are, , (b), , Fig. 9.7 (a) Snow, leopard, (b) yak, and (c) mountain, goat are adapted to, mountain habitats, , 84, , (c), SCIENCE, , 2018-19

Page 95 :
including feet and toes. This protects its, feet from the cold when it walks on the, snow. The mountain goat has strong, hooves for running up the rocky slopes, of the mountains., As we go up in the mountainous, regions, the surroundings change and, we see different kinds of adaptations at, different heights., Grasslands, A lion lives in a forest or a grassland, and is a strong animal that can hunt, and kill animals like deer. It is light, brown in colour. Look at the picture of, a lion and that of a deer (Fig. 9.8). How, are the eyes placed in the face for these, two animals? Are they in the front or, on the side of the face? Lions have long, claws in their front legs that can be, withdrawn inside the toes. Do the, features of a lion help it in any way to, , survive? It’s light brown colour helps it, to hide in dry grasslands when it hunts, for prey (animals to eat). The eyes in, front of the face allow it to have a correct, idea about the location of its prey., A deer is another animal that lives in, forests and grasslands. It has strong teeth, for chewing hard plant stems of the, forest. A deer needs to know about the, presence of predators ( animals like lion, that make it their prey ) in order to run, away from them and not become their, prey. It has long ears to hear movements, of predators. The eyes on the side of its, head allow it to look in all directions for, danger. The speed of the deer helps them, to run away from the predators., There are many other features of a, lion, a deer or other animals and plants, that help them to survive in their, habitat., , Some Aquatic Habitats, Oceans, We already discussed how fish are, adapted to live in the sea. Many other, sea animals have streamlined bodies to, help them move easily in water. There, are some sea animals like squids and, octopus, which do not have this, streamlined shape. They stay deeper in, the ocean, near the seabed and catch, any prey that moves towards them., However, when they move in water they, make their body shapes streamlined., These animals have gills to help them, use oxygen dissolved in water., There are some sea animals like, dolphins and whales that do not have, , (a), , (b), Fig. 9.8 (a) Lion and (b) deer, THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 85

Page 96 :
gills. They breathe in air through, nostrils or blowholes that are located, on the upper parts of their heads. This, allows them to breathe in air when they, swim near the surface of water. They can, stay inside the water for a long time, without breathing. They come out to the, surface from time to time, to breathe in, air. Did you ever see this interesting, activity of dolphins in television, programme or films on ocean life?, Ponds and lakes, Have you seen plants growing in ponds,, lakes, rivers and even some drains? Go, on a field trip to a nearby pond, if possible,, and try to observe the kinds of plants that, are seen there. Observe the leaves, stems, and roots of these plants., Some of these plants have their roots, fixed in the soil below the water, , Fig. 9.9 Some aquatic plants float on water., Some have their roots fixed in the soil at the, bottom. Some aquatic plants are, submerged in water., , (Fig. 9.9). In terrestrial plants, roots, normally play a very important role in the, absorption of nutrients and water from, the soil. However, in aquatic plants, roots, are much reduced in size and their main, function is to hold the plant in place., The stems of these plants are long,, hollow and light. The stems grow up to, the surface of water while the leaves and, flowers, float on the surface of water., Some aquatic plants are submerged, in water. All parts of such plants are, under water. Some of these plants have, narrow and thin ribbon-like leaves., These can bend in the flowing water. In, some submerged plants, leaves are often, highly divided, through which the water, can easily flow without damaging them., Frogs usually live in ponds. Frogs, can stay both inside the water as well, as move on land. They have strong back, legs that help them in leaping and, catching their prey. They have webbed, feet which help them swim in water., We have discussed only a few common, animals and plants compared to the wide, variety that live in different habitats. You, may have also noticed the very wide, variety in plants around you, when you, prepared a herbarium as part of the, suggested activities in Chapter 7., Imagine the kind of variety that you, could see in a herbarium of leaves of, plants from all regions of the Earth!, , 9.4 CHARACTERISTICS, , OF, , ORGANISMS, , We went on a journey through different, habitats and discussed many plants and, , 86, , SCIENCE, , 2018-19

Page 97 :
animals. In Activity 1, we listed objects,, plants and animals found in different, surroundings. Suppose we stop a while, and think which examples in our list, are living? Let us think of examples from, a forest. Trees, creepers, small and big, animals, birds, snakes, insects, rocks,, soil, water, air, dry leaves, dead animals,, mushrooms and moss may be only some, of the objects that are present in the, forest. Which of these are living?, Think of objects that you can see, around you at this moment and group, them as living and non-living. In some, cases, it is easy for us to know. For, example, we know that objects like chair, or table are not alive. Paheli was reading, this rhyme from Complete Nonsense, written by Edward Lear:, , Chair,, ble to the, a, T, e, th, id, Sa, ware,, ardly be a, ’You can h, e heat,, th, er from, ff, u, s, t!, I, w, o, ’H, on my fee, chilblains, m, o, fr, d, n, ’A, lk,, a little wa, ’If we took, le talk!, tt, li, have a, t, h, ig, m, e, ’W, air!’, s take the, ’Pray let u, Chair., e, th, able to, T, e, th, id, a, S, e table,, hair to th, C, e, !, th, id, a, S, re not able, know we a, u, o, y, w, o, ’N, lk,, shly you ta, lk!’, ’How fooli, cannot wa, e, w, know, u, o, y, n, e, ,, h, h, ’W, a sig, able with, Said the T, try,, to, no harm, o, d, n, a, c, t, ’I, you,, ny legs as, a, m, s, a, e, ’v, ’I, n two?’, we walk o, ’t, n, a, c, y, h, ’W, , Paheli and Boojho found the poem, very funny, because they knew that a, chair or a table is not alive and it cannot, talk or walk., Chair, table, stone or a coin are not, alive. Similarly, we do know that we are, alive and so are all the people of the, world. We also see animals around us, that are so full of life — dogs, cats,, monkeys, squirrels, insects and many, others., How do we know that something is, living? Often, it is not so easy to decide., We are told that plants are living, but, they do not move like a dog or a pigeon., On the other hand, a car or a bus can, move, still we consider them as nonliving. Plants and animals appear to, grow in size with time. But then, at, times, clouds in the sky also seem to, grow in size. Does it mean that clouds, are living? No! So, how does one, distinguish between living and nonliving things? Do living things have, some common characteristics that, make them very different from the, non-living?, You are a wonderful example of a living, being. What characteristics do you have, which make you different from a nonliving thing? List a few of these, characteristics in your notebook. Look at, your list and mark those characteristics, that you have listed, which may also be, found in animals or plants., Some of these characteristics are, perhaps common to all living things., , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 87

Page 98 :
Do all organisms need food?, In Chapters 1 and 2, we learnt that all, living things need food and how, essential it is to animals and to us. We, have also learnt that plants make their, own food by the process of, photosynthesis. Animals depend on, plants or other animals for their food., Food gives organisms the energy, needed for them to grow. Organisms also, need energy for other life processes that, go on inside them., , Do all organisms show, growth?, Does the kurta you had four years back,, still fit you? You cannot wear it any, more, isn’t it? You must have grown, taller during these years. You may not, realise it, but you are growing all the, time and in few more years you will, become an adult. (Fig 9.10)., Young ones of animals also grow, into adults. You would surely have, , Fig. 9.10 A baby grows into an adult, , noticed pups grow, into adults. A chick, hatched from an, egg, grows into, a hen or a cock., (Fig 9.11)., Plants also grow., Look around you, and see a few plants, of a particular type., Some are very small, Fig. 9.11 A chicken, and young, some grows into an adult, are bigger. They, may all be in different stages of growth., Look at the plants after a few days and, weeks. You may find that some of them, have grown in size. Growth seems to be, common to all living things., Do you think, non-living things show, growth?, , Do all organisms respire?, Can we live without breathing? When, we inhale, the air moves from outside to, the inside of our body. When we breathe, out, the air moves from inside our body, to outside. Breathing is part of a process, called respiration. In respiration, some, of the oxygen of the air we breathe in, is, used by the body. We breathe out carbon, dioxide produced in this process., The process of breathing in animals, like cows, buffaloes, dogs or cats is, similar to humans. Observe any one of, these animals while they are taking rest,, and notice the movement of their, abdomen. This slow movement indicates, that they are breathing., , 88, , SCIENCE, , 2018-19

Page 99 :
Respiration is necessary for all living, organisms. It is through respiration that, the body finally obtains energy from the, food it takes., Some animals may have different, mechanisms for the exchange of gases,, which is a part of the respiration process., For example, earthworms breathe, through their skin. Fish, we have learnt,, have gills for using oxygen dissolved in, water. The gills absorb oxygen from the, air dissolved in water., Do plants also respire? Exchange of, gases in plants mainly takes place, through leaves. The leaves take in air, through tiny pores in them and use the, oxygen. They give out carbon dioxide to, the air., We learnt that in sunlight, plants, use carbon dioxide to produce food and, give out oxygen. The amount of oxygen, released in the process of food, preparation by plants is much more, than the oxygen they use in respiration., Respiration in plants takes place day, and night., , Do all organisms respond to, stimuli?, How do you respond, if you suddenly, step on a sharp object like a thorn, while, walking barefoot? How do you feel when, you see or think about your favourite, food? You suddenly move from a dark, place into bright sunlight. What, happens? Your eyes shut themselves, automatically for a moment till, they adjust to the changed bright, , surroundings. Your favourite food,, bright light and a thorn, in the above, situations are some examples of changes, in your surroundings. All of us respond, immediately to such changes. Changes, in our surroundings that makes us, respond to them, are called stimuli., Do other animals also respond to, stimuli? Observe the behaviour of, animals, when food is served to them., Do you find them suddenly becoming, active on seeing the food? When you, move towards a bird, what does it do?, Wild animals run away when bright, light is flashed towards them. Similarly,, cockroaches begin to move to their, hiding places if the light in the kitchen, is switched on at night. Can you give, some more examples of responses of, animals to stimuli?, Do plants also respond to stimuli?, Flowers of some plants bloom only at, night. In some plants flowers close after, sunset. In some plants like Mimosa,, commonly known as ‘touch-me-not’,, leaves close or fold when someone, touches them. These are some examples, of responses of plants towards changes, in their surroundings., , Activity 4, Place a potted plant in a room a little, away from a window through which, sunlight enters some time during the, day (Fig. 9.12). Continue watering the, plant for a few days. Does the plant grow, upright, like plants out in the open?, Note the direction in which it bends, if, , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 89

Page 100 :
Do all organisms, reproduce their own, kind?, Have you ever seen nests of, some birds like pigeons?, Many birds lay their eggs in, the nest. Some of the eggs hatch and, young birds come out of them, (Fig. 9.13)., Fig. 9.12 Plant respond to light, , it is not growing upright. Do you think,, this may be in response to some, stimulus?, All living things respond to changes, around them., , Living organisms and excretion, All organisms need food. Not all the, food that is eaten is completely used,, only a part of it is utilised by the body., What happens to the rest? This has to, be removed from the body as wastes. Our, body produces some wastes in other life, processes also. The process of getting, rid of wastes by organisms is known as, excretion., Do plants also excrete? They do, but, not as seen in animals. The mechanisms, in plants are a little different. Some plants, find it possible to store the waste products, within their parts in a way that they do, not harm the plant as a whole. Some, plants remove waste products as, secretions., Excretion is another characteristic, common to all organisms., , (b), (a), Fig. 9.13 (a) Birds lay eggs which after hatching, produce (b) young ones, , Animals reproduce their own kind., The mode of reproduction may be, different, in different animals. Some, animals produce their young ones, through eggs. Some animals give birth, to the young ones (Fig. 9.14)., Plants also reproduce. Like animals,, plants also differ in their mode of, reproduction. Many plants reproduce, through seeds. Plants produce seeds,, , 90, , Fig. 9.14 Some animals which give birth to, their young ones, , SCIENCE, , 2018-19

Page 101 :
Living things produce more of their, own kind through reproduction. It, takes place in many different ways, for, different organisms., , Do all organisms move?, Fig. 9.15 A seed from a plant germinates into a, new plant, , which can germinate and grow into new, plants (Fig.9.15)., Some plants also reproduce through, parts other than seeds. For example, a, part of a potato with a bud, grows into a, new plant (Fig 9.16)., , Fig. 9.16 A new plant grows from a bud of potato, , Plants also reproduce through, cuttings. Would you like to grow a plant, in this way yourself?, , Activity 5, Take a cutting from a rose or a menhdi, plant. Fix it in the soil and water it, regularly. What do you observe, after a, few days?, It may not be easy to grow plants from, cuttings. Do not be disappointed if your, cutting does not grow. Talk to a gardener,, if possible, on the care to be given to, cuttings to make them grow into plants., , In Chapter 8, we discussed the various, ways in which animals move. They move, from one place to another and also show, other body movements., What about plants? Do they also, move? Plants are generally anchored in, soil so they do not move from one place, to another. However, various substances, like water, minerals and the food, synthesised by them move from one part, of the plant to other. Have you noticed, any other kind of movement in plants?, Opening or closing of flowers? Do you, recall how some plants show movement, in response to certain stimuli?, We also have some non-living, things moving, of course. A bus, car, a, small piece of paper, clouds and so on., Is there something different in these, movements from the movements of, living beings?, There is such a variety of living, organisms, but, all of them show some, common characteristics, as we have, discussed. Yet another common, characteristic is that living beings die., Because organisms die, particular types, of organisms can survive over thousands, of years only if they reproduce their own, kind. One single organism may, die without ever reproducing, but, the, type of organism can exist only if there, is reproduction., , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 91

Page 102 :
We see that, all living things seem to, have some common characteristics., They all need food, respire, respond to, stimuli, reproduce, show movement,, grow and die., Do we find some non-living things that, also show some of these characteristics?, Cars, bicycle, clocks and the water in, the river move. The moon moves in the, sky. A cloud grows in size right in front, of our eyes. Can such things be called, living? We ask ourselves, do these objects, also show all the other characteristics, of living things?, In general, something that is living, may have all the characteristics that we, have discussed, while non-living things, may not show all these characteristics, at the same time., Is this always true? Do we always find, that living things definitely show all the, characteristics of the living that we have, discussed? Do we always find that nonliving things may show only some of these, characteristics and never all of them?, To understand this a little better, let, us look at a specific example. Consider, any seed, say, moong. Is it living? It can, , stay in a shop for months and not show, any growth or some of the other, characteristics of life. However, we bring, the same seed and plant it in soil, water, it and it turns into a whole plant. Did, the seed — need food, did it excrete,, grow or reproduce when it was in the, shop for many months?, We see that there can be cases when, we cannot easily say that a thing has all, the characteristics that we have discussed,, for it to be called living., , “What then is life?”, Push your hand deep inside a sack of, wheat. Do you find it is warm inside?, There is some heat being produced, inside the sack of wheat. The seeds, respire and in that process give out, some heat., We see that respiration is a process, that takes place in seeds even when, some of the other life processes may not, be very active., It may not be very easy to answer, our question — “what then is life”?, However, looking at all the diversity of, living beings around us, we can, conclude that “life is beautiful”!, , Adaptation, , Habitat, , Aquatic habitat, , Living, , Biotic component, , Reproduction, , Excretion, , Respiration, , Growth, , Stimulus, , 92, , SCIENCE, , 2018-19

Page 103 :
, , The surroundings where plants and animals live, is called their habitat., , , , Several kinds of plants and animals may share the same habitat., , , , The presence of specific features and habits, which enable a plant or an, animal to live in a particular habitat, is called adaptation., , , , There are many types of habitats, however, these may be broadly grouped, as terrestrial (on the land) and aquatic (in water)., , , , There is a wide variety of organisms present in different habitats., , , , Plants, animals and microorganisms together constitute biotic, components., , , , Rocks, soil, air, water, light and temperature are some of the abiotic, components of our surroundings., , , , Living things have certain common characteristics — they need food,, they respire and, excrete, respond to their environment, reproduce, grow, and show movement., , 1., , What is a habitat?, , 2., , How are cactus adapted to survive in a desert?, , 3., , Fill up the blanks, (a) The presence of specific features, which enable a plant or an animal to live, in a particular habitat, is called, ., (b) The habitats of the plants and animals that live on land are called, habitat., (c) The habitats of plants and animals that live in water are called, habitat., (d) Soil, water and air are the ———— factors of a habitat., (e) Changes in our surroundings that make us respond to them, are, called, ., , 4., , Which of the things in the following list are nonliving?, Plough, Mushroom, Sewing machine, Radio, Boat, Water hyacinth, Earthworm, , 5., , Give an example of a non-living thing, which shows any two characteristics of, living things., , 6., , Which of the non-living things listed below, were once part of a living thing?, Butter, Leather, Soil, Wool, Electric bulb, Cooking oil, Salt, Apple, Rubber, , 7., , List the common characteristics of the living things., , 8., , Explain, why speed is important for survival in the grasslands for animals, that live there. (Hint: There are few trees or places for animals to hide in, grasslands habitats.), , THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS, , 2018-19, , 93

Page 104 :
SUGGESTED PROJECTS AND ACTIVITIES, 1., , Many magazines and newspapers talk about possibility of life outside the, Earth. Read these articles and have a discussion in the class about what, could be defined as life outside Earth., , 2., , Visit a local zoo and find out what special arrangements are made for the, animals that have been brought there from different habitats., , 3., , Find out where are the habitats of the polar bear and the penguin. For each, animal, explain two ways in which it is well adapted to its habitat., , 4., , Find out which animals live in the foot-hills of the Himalayas. Find out if the, types and varieties of animals and plants changes as one goes higher into, the mountain regions of the Himalayas., , 5., , Make a habitat album. Try to obtain pictures of animals and plants that you, have listed in Activity 1 and paste these under different habitat sections in, the album. Draw the leaf shapes and structures for trees found in these, different regions and include these in the album. In addition, draw the, patterns of branching found in trees of these different regions and include, these also in the album., , What is, its, name, and, habitat, , 94, , SCIENCE, , 2018-19

Page 105 :
10, , Motion and Measurement of, Distances, , T, , here was a general discussion, among the children in Paheli and, Boojho's class about the places, they had visited during the summer, vacations. Someone had gone to their, native village by a train, then a bus, and, finally a bullock cart. One student had, travelled by an aeroplane. Another spent, many days of his holidays going on, fishing trips in his uncle's boat., The teacher then asked them to read, newspaper articles that mentioned, about small wheeled vehicles that moved, on the soil of Mars and conducted, experiments. These vehicles were taken, by spacecraft all the way to Mars!, Meanwhile, Paheli had been reading, stories about ancient India and wanted, to know how people travelled from one, place to another in earlier times., , 10.1 STORY, , OF, , imitated the shapes of the animals living, in water. Recall our discussions of this, streamlined shape of fish in Chapters, 8 and 9., Invention of the wheel made a great, change in modes of transport. The, design of the wheel was improved over, thousands of years. Animals were used, to pull carts that moved on wheels., Until the beginning of the 19th, century, people still depended on, animals, boats and ships to transport, them from place to place. The invention, of steam engine led to the development, of new means of transport. Railroads, were made for steam engine driven, carriages and wagons. Later came, , TRANSPORT, , Long ago people did not have any means, of transport. They used to move only on, foot and carry goods on their back. Later, on they began to use animals for, transportation., For transport through water, routes,, boats were used from ancient times. To, begin with, boats were simple logs of, wood in which a hollow cavity could be, made. Later, people learnt to put, together different pieces of wood and, give shapes to the boats. These shapes, , 2018-19, , Fig 10.1 Some means of transportation

Page 106 :
automobiles such as motor cars, trucks, and buses. Motorised boats and ships were, used as means of transport on water. The, early years of 1900 saw the development, of aeroplanes. These were later improved, to carry passengers and goods. Electric, trains, monorail, supersonic aeroplanes, and spacecraft are some of the, contributions of the 20th century., Fig. 10.1 shows some of the different, modes of transport. Place them in the, correct order — from the earliest modes, of transport to the most recent., Are there any of the early modes of, transport that are not in use today?, , 10.2 HOW WIDE IS THIS DESK?, How did people know how far they have, travelled?, How will you know whether you can, walk all the way to your school or whether, you will need to take a bus or a rickshaw, to reach your school? When you need to, purchase something, is it possible for you, to walk to the market? How will you know, the answers to these questions?, It is often important to know how far, a place is, so that we can have an idea, how we are going to reach that place —, walk, take a bus or a train, a ship, an, aeroplane or even a spacecraft!, Sometimes, there are objects whose, length or width we need to know., In Paheli and Boojho's classroom,, there are large desks which are to be, shared by two students. Paheli and, Boojho share one desk, but, frequently, end up objecting that the other is using, a larger share of the desk., , On the teacher's suggestion, they, decided to measure the length of the, desk, make a mark exactly in the middle, of it and draw a line to separate the two, halves of the desk., Both Paheli and Boojho are very fond, of playing gilli danda with their friends., Boojho brought a set of gilli and danda, with him., Here is how they tried to measure, the length of the desk using the danda, and the gilli (Fig. 10.2)., The desk seems to be having a, length equal to two danda lengths and, two lengths of the gilli. Drawing a line, in the middle of the desk leaves each, of them happy with a half of the desk, equal to a danda and a gilli in length., After a few days, the marked line gets, wiped out. Boojho now has a new set, of gilli and danda as he lost his old, one. Here is how, the length of the, desk seems to measure using the gilli, and danda (Fig. 10.3)., , Fig. 10.2 Measuring the length of a desk with, gilli and danda, , Fig. 10.3 Measuring the length of the desk with, a different set of gilli and danda, , 96, , SCIENCE, , 2018-19

Page 107 :
Hello! Now, when measured with the, new set of gilli and danda, the desk, length seems to be about two danda, lengths, one gilli length with a small, length still left out. This is less than one, gilli length. Now what?, What would you suggest Paheli and, Boojho do, to measure the length of the, whole desk? Can they use a cricket, wicket and bails to measure the length, or do you think that this might create, the similar problem?, One thing they could do is to take a, small length of string and mark two points, on it. This will be a string length. They, can measure the width of the desk in, string lengths (Fig. 10.4). How can they, use the string to measure distances less, than the length of a string? They can fold, the string and mark it into, , 1, 1, ,, 2, 4, , and, , 1, 8, , 'string lengths'. Now, perhaps Paheli and, Boojho can measure the exact length of, the desk using the string., You would say that they should use, the scale in their geometry box and solve, their problem? Yes, Of course!, Boojho has been reading about the, way people used to measure distances, , before such standard scales were made, and he has been trying to follow different, methods of measuring distances., There are so many occasions when we, come across a need to measure lengths, and distances. The tailor needs to measure, the length of the cloth to know if it is, enough to stitch a kurta. A carpenter, needs to measure the height and width, of a cupboard to know how much wood, he would need to make its door. The, farmer needs to know the length and, breadth or the area of his land to know, how much seed he can sow and how, much water would be needed for his crops., Suppose, you are asked how tall you, are? You want to tell the length of a, straight line from the top of your head, to the heel of your feet., How long is this room?, How wide is this desk?, How far is it from Delhi to Lucknow?, How far away is the Moon from the, Earth?, All these questions have one thing, in common. They all concern distance, between two places. The two places may, be close enough, like the two ends of a, table or they may be far apart, like, Jammu and Kanyakumari., Let us do a few measurements to see, what exactly we need to do, when we, measure distances or lengths., , 10.3 SOME MEASUREMENTS, Activity 1, Fig. 10.4 Measuring the length of the desk with, string lengths, , Work in groups and each of you do this, activity one by one. Using your foot as a, , MOTION AND MEASUREMENT OF DISTANCES, , 97, , 2018-19

Page 108 :
unit of length, measure the length and, breadth of the classroom. It is possible, that while measuring these you may find, some part remains to be measured as it, is smaller than your foot. Use a string, to measure the length of a part of your, foot as you did before. Record your, observations in Table 10.1., Table 10.1 Measuring length and, breadth of classroom, Name of, student, , Length of the, classroom, , Width of the, classroom, , Activity 2, Work in a group and each of you use, your handspan as a unit to measure, the width of a table or a desk in the, classroom (Fig. 10.5)., , Fig. 10.5 Measuring the width of a table with a, handspan, , Here too, you may find that you, need string lengths equal to your, handspan and then fractions of, this string length to make the, measurement. Record all observations, in Table 10.2., We see that, measurement means the, comparison of an unknown quantity, , Table 10.2 Measuring width of a table, Who measured the, width of the table?, , Number of, handspans, , with some known quantity. This known, fixed quantity is called a unit. The result, of a measurement is expressed in two, parts. One part is a number. The other, part is the unit of the measurement. For, example, if in Activity 1, the length of, the room is found to be 12 lengths of, your foot, then 12 is the number and, 'foot length' is the unit selected for the, measurement., Now, study all the measurements, recorded in Table 10.1 and 10.2. Are all, the measurements for the room using, everybody's foot, equal? Are everybody's, measurement, by handspan, of the, width of the table equal? Perhaps the, results could be different as the length, of your handspan and that of your, friends may not be the same. Similarly,, the length of the foot may be slightly, different for all the students. Therefore,, when you tell your measurement using, your handspan or length of foot as a, unit to others, they will not be able to, understand how big the actual length, is, unless they know the length of your, handspan or foot., We see therefore, that some standard, units of measurement are needed, that, do not change from person to person., , 98, , SCIENCE, , 2018-19

Page 109 :
10.4 STANDARD UNITS, MEASUREMENTS, , OF, , In ancient times, the length of a foot,, the width of a finger, and the distance, of a step were commonly used as, different units of measurements., The people of the Indus valley, civilisation must have used very good, measurements of length because we see, evidence in excavations of perfectly, geometrical constructions., A cubit as the length from the elbow, to the finger tips was used in ancient, Egypt and was also accepted as a unit, of length in other parts of the world., People also used the "foot" as a unit, of length in different parts of the world., The length of the foot used varied, slightly from region to region., People measured a “yard” of cloth by, the distance between the end of the, outstretched arm and their chin. The, Romans measured with their pace, or steps., In ancient India, small length, measurements used were an angul, (finger) or a mutthi (fist). Even today, we, can see flower sellers using their forearm, as a unit of length for garlands in many, towns of India. Many such body parts, continue to be in use as unit of length,, when convenient., However, everyone's body parts could, be of slightly different sizes. This must, , have caused confusion in measurement., In 1790, the French created a standard, unit of measurement called the, metric system., For the sake of uniformity, scientists, all over the world have accepted a set of, standard units of measurement. The, system of units now used is known as, the International System of Units (SI, units). The SI unit of length is a metre., A metre scale is shown in Fig.10.6. Also, shown is the 15 cm scale in your, geometry box., Each metre (m) is divided into 100, equal divisions, called centimetre (cm)., Each centimetre has ten equal divisions,, called millimetre (mm). Thus,, 1 m = 100 cm, 1 cm = 10 mm, For measuring large distances, metre, is not a convenient unit. We define a, larger unit of length. It is called, kilometre (km)., 1 km = 1000 m, Now, we can repeat all our, measurement activities using a, standard scale and measure in SI units., Before we do that, we do need to know, the correct way of measuring lengths, and distances., , 10.5 CORRECT MEASUREMENT, LENGTH, , OF, , In our daily life we use various types of, measuring devices. We use a metre scale, , Fig.10.6 A metre scale and a 15 cm scale, MOTION AND MEASUREMENT OF DISTANCES, , 99, , 2018-19

Page 110 :
for measuring length. A tailor uses a, tape, whereas a cloth merchant uses a, metre rod. For measuring the length of, an object, you must choose a suitable, device. You cannot measure the girth of, a tree or the size of your chest using a, metre scale, for instance. Measuring, tape is more suitable for this. For small, measurements, such as the length of, your pencil, you can use a 15 cm scale, from your geometry box., In taking measurement of a length,, we need to take care of the following:, 1. Place the scale in contact with the, object along its length as shown in, Fig.10.7., 2. In some scales, the ends may be, broken. You may not be able to see, the zero mark clearly (Fig.10.8 (a)]., In such cases, you should avoid, , taking measurements from the zero, mark of the scale. You can use any, other full mark of the scale, say,, 1.0 cm [Fig.10.8 (b)]. Then you must, subtract the reading of this mark, from the reading at the other end., For example, in Fig.10.8 (b) the, reading at one end is 1.0 cm and, at the other end it is 14.3 cm., Therefore, the length of the object is, (14.3-1.0) cm = 13.3 cm., , (a), , (b), Fig. 10.8 (a) Incorrect and (b) correct method of, placing the scale with broken edge, , (a), , (b), Fig. 10.7 Method of placing the scale along the, length to be measured (a) correct and (b) incorrect, , 3. Correct position of the eye is also important for taking measurement., Your eye must be exactly in front of, the point where the measurement is, to be taken as shown in Fig.10.9., Position 'B' is the correct position, of the eye. Note that from position, 'B', the reading is 7.5 cm. From positions 'A' and 'C', the readings may, be different., , 100, , SCIENCE, , 2018-19

Page 111 :
(A), , (B), , (C), , at the results in column 3 where the, measurements are done using a, standard scale. The results may be close, to each other now, but, are they exactly, equal? If not, why do you think there is, a difference? After all, everybody is using, the same scale and not different hand, spans. This could be due to small errors, in taking observations. In higher classes, we will learn about the importance of, knowing and handling such errors in, measurement., , Fig. 10.9 B is the proper position of the eye for, taking reading of the scale, , Activity 3, Measure the height of your classmate, using hand span and then by using a, metre scale. For this, ask your classmate, to stand with his back against a wall., Make a mark on the wall exactly above, his head. Now, measure the distance, from the floor to this mark on the wall, with your handspan and then with a, metre scale. Let all other students measure this length in a similar way. Record, all observations in Table 10.3., Table 10.3 Measurement of height, Who measured Height in, the height?, handspans, , Height in, cm, , Study carefully results obtained by, different students. The results in, column 2 may be different from each, other as the length of the handspan may, be different for different students. Look, , 10.6 MEASURING THE LENGTH, CURVED LINE, , OF A, , We cannot measure the length of a, curved line directly by using a metre, scale. We can use a thread to measure, the length of a curved line., , Activity 4, Use a thread to measure the length of, the curved line AB (Fig.10.10). Put a, knot on the thread near one of its ends., Place this knot on the point A. Now,, place a small portion of the thread along, the line, keeping it taut using your, fingers and thumb. Hold the thread at, this end point with one hand. Using the, other hand, stretch a little more portion, of the thread along the curved line. Go, , A, , B, , Fig.10.10 Measuring the length of a curved line, with a thread, , MOTION AND MEASUREMENT OF DISTANCES, , 101, , 2018-19

Page 112 :
on repeating this process till the other, end B of the curved line is reached., Make a mark on the thread where it, touches the end B. Now stretch the, thread along a metre scale. Measure the, length between the knot in the beginning, and the final mark on the thread. This, gives the length of the curved line AB., We see that we need a lot of care to, ensure that we are measuring distances, and lengths correctly. And, we need, some standard units and devices with, which we measure these distances and, can convey our results to others., , 10.7 MOVING THINGS AROUND, Activity 5, , US, , Think of some objects you have seen, recently. List them in Table 10.4. These, may include a school bag, a mosquito,, a table, people sitting on chairs or people, moving about. The list may also have a, butterfly, a dog, a cow, your hands, a, small baby, a fish in water, a house, a, factory, a piece of stone, a horse, a ball,, a bat, a moving train, a sewing machine,, a wall clock or the hands of a clock., Make your list as large as you can., Which of these are moving? Which, are at rest?, , How did you decide whether an object, is in motion or at rest?, You might have noticed that the bird, is not at the same place after some time,, while the table is at the same place. On, this basis, you may have decided, whether an object is at rest or in motion., Let us look at the motion of an ant, closely., , Activity 6, Select a place where you find ants., Spread a large sheet of white paper on, the ground and keep a little sugar on it., Ants are likely to be attracted to the, sugar and you will find many ants, crawling on the sheet of paper soon. For, any one ant, try and make a small mark, with a pencil near its position when it, has just crawled on to the sheet of paper, (Fig. 10.11). Keep marking its position, after a few seconds as it moves along on, the sheet of paper. After some time,, shake the paper free of the sugar and, the ants. Connect the different points, you have marked, with arrows, to show, the direction in which the ant was, , Table10. 4 Objects at rest and in motion, Objects at rest, , Objects in motion, , House, , A flying bird, , Table, , Second's hand of the, clock, , Clock, Fig. 10.11 Motion of an ant, 102, , SCIENCE, , 2018-19

Page 113 :
moving. Each point you have marked, shows where the ant moved to, in, intervals of a few seconds., Motion seems to be some kind of a, change in the position of an object, with time, isn't it?, In Activity 5, where did you place, objects like a clock, a sewing machine, or an electric fan in your grouping of, objects? Are these objects moving from, one place to other? No? Do you notice, movement in any of their parts? The, blades of the fan or the hands of a, clock— how are they moving? Is their, movement similar to that of an ant or a, train? Let us now look at some types of, motion to help us understand these, differences., , 10.8 TYPES, , OF, , In all these examples we see that the, objects move along a straight line. This, type of motion is called rectilinear, motion., , Activity 7, Take a stone, tie a thread to it and whirl, it with your hand. Observe the motion, of the stone. We see that the stone moves, along a circular path., In this motion, the distance of the, stone from your hand remains the same., This type of motion is called circular, motion., , MOTION, , You may have observed the motion of a, vehicle on a straight road, march-past, of soldiers in a parade or the falling, of a stone (Fig. 10.12). What kind, of motion is this?, Sprinters in a, 100-metre race, also move along a, straight track. Can, you think of more, such examples from, your surroundings?, , (a), , (b), , Fig. 10.13 Some objects in circular motion, , (a), , (b), Fig.10.12 Some examples of rectilinear motion, , (c), , The motion of a point marked on the, blade of an electric fan or the hands of, a clock are examples of circular motion, (Fig. 10.13)., The electric fan or the clock by, themselves are not moving from one, place to another. But, the blades of the, , MOTION AND MEASUREMENT OF DISTANCES, , 103, , 2018-19

Page 114 :
fan rotate and so do, the hands of a, clock. If we mark a, point anywhere on, the blades of a fan or, on the hands of a, clock, the distance of, this point from the, centre of the fan or, the clock, will remain the same as, they rotate., In some cases, an object repeats its, motion after some time. This type of, motion is called periodic motion. Take, the stone tied with a string that you, used in Activity 7. Now, hold the string, in your hand and let the stone hang, from it. This is a pendulum. Pull the, stone to one side with the other hand, and let it go. Now the pendulum is in, motion. It is an example of periodic, motion. A branch of a tree moving to, and fro, motion of a child on a swing,, strings of a guitar or the membrane of, drums (tabla) being played, are all, examples of periodic motion where an, , Boojho is not sure why we say that, the distance of the stone from your, hand is the same when we whirl it, around. Can you help him, understand this? Remember, that the stone is held, with a string., , (a), , (b), , (d), , (c), , (e), , Fig. 10.14 Examples of periodic motion, , object or a part of it repeats its motion after, a fixed interval of time (Fig. 10.14)., Did you observe a sewing machine, as a part of Activity 5? You must have, observed that it remains at the same, location while its wheel moves with a, circular motion. It also has a needle that, moves up and down continuously, as, long as the wheel rotates, isn't it? This, needle is undergoing a periodic motion., Have you observed closely, the, motion of a ball along the ground? Here,, , 104, , SCIENCE, , 2018-19

Page 115 :
the ball is rolling on the ground –, rotating as well as moving forward along, the ground. Thus, the ball undergoes a, rectilinear motion as well as rotational, motion. Can you think of other, examples where objects undergo, combinations of different types of, motion?, We did many measurement activities, and discussed some kinds of motion., We saw that motion is a change in the, , position of an object with time., The change in this position can, be determined through distance, measurements. This allows us to know, how fast or slow a motion is. The, movement of a snail on the ground, a, butterfly flitting from flower to flower, a, river flowing, an aeroplane flying, moon, going around the Earth and blood, flowing inside our bodies show that there, is motion everywhere around us!, , Circular motion, Distance, Measurement, Motion, Periodic motion, Rectilinear, motion, SI units, Units of, measurement, , n, , Different modes of transport are used to go from one place to another., , n, , In ancient times, people used length of a foot, the width of a finger, the, distance of a step as units of measurement. This caused confusion and, a need to develop a uniform system of measurement arose., , n, , Now, we use International System of Units ( SI units). This is accepted, all over the world., , n, , Metre is the unit of length in SI unit., , MOTION AND MEASUREMENT OF DISTANCES, , 105, , 2018-19

Page 116 :
n, , Motion in a straight line is called rectilinear motion., , n, , In circular motion an object moves such that its distance from a fixed, point remains the same., , n, , Motion that repeats itself after some period of time is called periodic motion., , 1., , Give two examples each, of modes of transport used on land, water and air., , 2., , Fill in the blanks:, (i) One metre is ______________ cm., (ii) Five kilometre is ______________ m., (iii)Motion of a child on a swing is ______________., (iv) Motion of the needle of a sewing machine is ______________., (v) Motion of wheel of a bicycle is______________., , 3., , Why can a pace or a footstep not be used as a standard unit of length?, , 4., , Arrange the following lengths in their increasing magnitude:, 1 metre, 1 centimetre, 1 kilometre,1 millimetre., , 5., , The height of a person is 1.65 m. Express it into cm and mm., , 6., , The distance between Radha's home and her school is 3250 m. Express this, distance into km., , 7., , While measuring the length of a knitting needle, the reading of the scale at one, end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?, , 8., , Write the similarities and differences between the motion of a bicycle and a, ceiling fan that has been switched on., , 9., , Why would you not like to use a measuring tape made of an elastic material like, rubber to measure distance? What would be some of the problems you would, meet in telling someone about a distance you measured with such a tape?, , 10. Give two examples of periodic motion., , SUGGESTED PROJECTS AND ACTIVITIES, 1., , Draw a map of your classroom. Roll a ball on the floor. In your map mark the, points where the ball started and where it stopped. Show also the path it, moved along. Did the ball move along a straight line?, , 2., , Using string and a scale, let each student measure the length of his/her foot., Prepare a bar graph of the foot length measurements that have been obtained, for the whole class., , 106, , SCIENCE, , 2018-19

Page 117 :
11, , Light, Shadows and, Reflections, , W, , e see so many objects around, us. On the way to school we, see things like buses, cars,, cycles, trees, animals and sometimes, flowers. How do you think, we see, objects?, Think of the same places at night, time if it were completely dark. What will, you see? Suppose you go inside a, completely dark room. Are you able to, see any objects in the room?, But, when you light a candle or a, torch you can see the objects present in, the room, isn’t it? Without light, things, cannot be seen. Light helps us see, objects., The torch bulb is an object that gives, out light of its own. The Sun, is another, familiar object that gives its own light., During the day, its light allows us to, see objects. Objects like the sun that, give out or emit light of their own are, called luminous objects., What about objects like a chair, a, painting or a shoe? We see these when, light from a luminous object (like the, Sun, a torch or an electric light) falls on, these and then travels towards our eye., , 11.1 T RANSPARENT , O PAQUE, TRANSLUCENT OBJECTS, , all, it is an opaque object. If you are, able to see clearly through an object, it, is allowing light to pass through it and, is transparent. There are some objects, through which we can see, but not very, clearly. Such objects are known as, translucent., , Activity 1, Look around yourself and collect as, many objects as you can — an eraser,, plastic scale, pen, pencil, notebook,, single sheet of paper, tracing paper or a, piece of cloth. Try to look at something, far away, through each of these objects, (Fig. 11.1). Is light from a far away object, able to travel to your eye, through any, of the objects?, Record your observations in a table, as shown in Table 11.1., We see that a given object or material, could be transparent, translucent or, , AND, , Recall our grouping objects as opaque,, transparent or translucent, in Chapter, 4. If we cannot see through an object at, , Fig. 11.1 Observing objects that do or do not, allow light to pass through them, , 2018-19

Page 118 :
Table 11.1, View through the object, possible (fully/ partially/, not at all), , Object/material, , Object is opaque/, transparent/, translucent, , Pencil, Rubber ball, Sheet of writing paper, , Not very sure?, , opaque depending on whether it allows, light to pass through it completely,, partially or not at all., , 11.2 WHAT EXACTLY, , ARE, , SHADOWS?, , Activity 2, Now, one by one hold each of the opaque, objects in the sunlight, slightly above, the ground. What do you see on the, ground? You know that the dark patch, formed by each on the ground is due, to its shadow. Sometimes you can, identify the object by looking at its, shadow (Fig. 11.2)., Spread a sheet of paper on the, ground. Hold a familiar opaque object, at some height, so that its shadow is, formed on the sheet of paper on the, ground. Ask one of your friends to draw, , Fig. 11.2 Sometimes shadow of an object gives, an idea about its shape, , the outline of the shadow while you are, holding the object. Draw outlines of the, shadows of other objects in a similar, way., Now, ask some other friends to, identify the objects from these outlines, of shadows. How many objects are they, able to identify correctly?, Do you observe your shadow in a, dark room or at night when there is no, light? Do you observe a shadow when, there is just a source of light and, nothing else, in a room? It seems we, need a source of light and an opaque, object, to see a shadow. Is there anything, else required?, , Activity 3, This is an activity that you will have to, do in the dark. In the evening, go out in, an open ground with a few friends. Take, a torch and a large sheet of cardboard, with you. Hold the torch close to the, ground and shine it upwards so that its, light falls on your friend's face. You now, have a source of light that is falling on, an opaque object. If there were no trees,, building or any other object behind your, friend, would you see the shadow of, your friend's head? This does not mean, , 108, , SCIENCE, , 2018-19

Page 119 :
a building, or other such surfaces act, as a screen for the shadows you observe, in everyday life., Shadows give us some information, about shapes of objects. Sometimes,, shadows can also mislead us about the, shape of the object. In Fig. 11.4 are a few, shadows that we can create with our, hands and make-believe that they are, shadows of different animals. Have fun!, , Fig. 11.3 A shadow is obtained only on a, screen, , that there is no shadow. After all, the, light from the torch is not able to pass, through his body to the other side., Now, ask another friend to hold the, cardboard sheet behind your friend. Is, the shadow now seen on the cardboard, sheet (Fig. 11.3)?, Thus, the shadow can be seen only, on a screen. The ground, walls of a room,, , Fig 11.4 Shadows of animals hidden in your hand, , Activity 4, Place a chair in the school ground on a, sunny day. What do you observe from, the shadow of the chair?, Does the shadow give an accurate, picture of the shape of the chair? If the, chair is turned around a little, how does, the shape of the shadow change?, Take a thin notebook and look at its, shadow. Then, take a rectangular box, and look at its shadow. Do the two, shadows seem to have a similar shape?, Take flowers or other objects of, different colours and look at their, shadows. A red rose and a yellow rose,, for instance. Do the shadows look, different in colour, when the colours of, the objects are different?, Take a long box and look at its, shadow on the ground. When you move, the box around, you may see that the, size of the shadow changes. When is the, shadow of the box the shortest, when, the long side of the box is pointed, towards the Sun or when the short side, is pointing towards the Sun?, Let us use this long box, to prepare, a simple camera., 109, , LIGHT, SHADOWS AND REFLECTIONS, , 2018-19

Page 120 :
11.3 A PINHOLE CAMERA, You might think that we need a lot of, stuff to make a camera? Not really. If we, just wish to make a simple pin hole, camera., , Activity 5, Take two boxes of cardboard such that, one can slide into another with no gap, in between them. Cut open one side of, each box. On the opposite face of the, larger box, make a small hole in the, middle [Fig. 11.5 (a)]. In the smaller box,, cut out from the middle a square with a, side of about 5 to 6 cm. Cover this open, square in the box with tracing paper, (translucent screen) [Fig. 11.5 (b)]. Slide, the smaller box inside the larger one, with the hole, in such a way that the, side with the tracing paper is inside, [Fig. 11.5 (c)]. Your pinhole camera is, ready for use., Holding the pinhole camera look, through the open face of the smaller, box. You should use a piece of black, cloth to cover your head and the pinhole, camera. Now, try to look at some distant, objects like a tree or a building through, the pinhole camera. Make sure that the, , (a), , objects you wish to look at through your, pinhole camera are in bright sun shine., Move the smaller box forward or, backward till you get a picture on the, tracing paper pasted at the other end., Are these pinhole images different, from their shadows?, Look through your pinhole camera, at the vehicles and people moving on, the road in bright sunlight., Do the pictures seen in the camera, show the colours of the objects on the, other side? Are the images erect or, upside down? Surprise, surprise!, Let us now image the Sun, with our, pinhole camera. We need a slightly, different set up for this. We just need a, large sheet of cardboard with a small, pinhole in the middle. Hold the sheet, up in the Sun and let its shadow fall on, a clear area. Do you see a small circular, image of the Sun in the middle of the, shadow of the cardboard sheet?, Look at these pinhole images of the, Sun when an eclipse is visible from your, location. Adjust your pinhole and, screen to get a clear image before the, eclipse is to occur. Look at the image as, the eclipse begins. You will notice a part, , (b), Fig. 11.5 A sliding pin hole camera, , 110, , (c), , SCIENCE, , 2018-19

Page 121 :
of the image of the Sun gradually, becoming darker as the eclipse starts., Never ever look directly at the Sun., That could be extremely harmful for, the eyes., There is an interesting pinhole, camera in nature. Sometimes, when we, pass under a tree covered with large, number of leaves, we notice small, patches of sunlight under it (Fig. 11.6)., These circular images are, in fact,, pinhole images of the Sun. The gaps, between the leaves, act as the pinholes., These gaps are all kinds of irregular, shapes, but, we can see circular images, of the Sun. Try to locate images of the, , Paheli has another thought. Surely,, all these results that we are seeing,, formation of shadows and pinhole, images are possible only if light moves, in a straight path?, , Activity 6, Let us use a piece of a pipe or a long, rubber tube. Light a candle and fix it, on a table at one end of the room. Now, standing at the other end of the room, look at the candle through the pipe, , (a), , (b), Fig. 11.7 Looking through a pipe pointed, (a) towards and (b) a little away from a candle, Fig. 11.6 A natural pinhole camera. Pinhole, images of the Sun under a tree!, , Sun when an eclipse occurs next. That, could be so much fun!, Boojho has this thought. We saw, upside down images of people on the, road, with our pinhole camera. What, about the images of the Sun? Did we, notice them to be upside down or, anything like that?, , [Fig. 11.7 (a)]. Is the candle visible? Bend, the pipe a little while you are looking at, the candle [Fig. 11.7 (b)]. Is the candle, visible now? Turn the pipe a little to your, right or left. Can you see the candle now?, What do you conclude from this?, This suggests that light travels along, a straight line, isn’t it? That is why,, when opaque objects obstruct it, a, shadow forms., 111, , LIGHT, SHADOWS AND REFLECTIONS, , 2018-19

Page 122 :
11.4 MIRRORS, , REFLECTIONS, , We all use mirrors at home. You look into, the mirror and see your own face inside, the mirror. What you see is a reflection, of your face in the mirror. We also see, reflections of other objects that are in, front of the mirror. Sometimes, we see, reflections of trees, buildings and other, objects in the water of a pond or a lake., , adjust the direction of the torch so that, the patch of light falls on another friend, standing in the room., This activity suggests that a mirror, changes the direction of light that falls, on it., Here is an activity that shows light, travelling along straight lines and, getting reflected from a mirror., , Activity 7, , Activity 8, , This activity should be done at night or, in a dark room. Ask one of your friends, to hold a mirror in his/her hand at one, corner of the room. Stand at another, corner with a torch in your hand. Cover, the glass of torch with your fingers and, switch it on. Adjust your fingers with a, small gap between them so that you can, get a beam of light. Direct the beam of, the torch light onto the mirror that your, friend is holding. Do you see a patch of, light on the other side (Fig. 11.8)? Now,, , Fix a comb on one side of a large thermo, Col sheet and fix a mirror on the other, side as shown in Fig. 11.9. Spread a, dark coloured sheet of paper between, the mirror and the comb. Keep this in, sunlight or send a beam of light from a, torch through the comb., What do you observe? Do you get, a pattern similar to that shown, in Fig. 11.9?, This activity gives us an idea of the, manner in which light travels and gets, reflected from a mirror., , AND, , Fig. 11.9 Light travelling in a straight line and, getting reflected from a mirror, , Fig. 11.8 A mirror reflects a beam of light, 112, , SCIENCE, , 2018-19

Page 123 :
, , Opaque objects do not allow light to pass through them., , , , Transparent objects allow light to pass through them and we can see through, these objects clearly., , , , Translucent objects allow light to pass through them partially., , , , Shadows are formed when an opaque object comes in the path of light., , , , Pinhole camera can be made with simple materials and can be used to, image the Sun and brightly lit objects., , , , Light travels in straight line., , , , Mirror reflection gives us clear images., , 1., , Rearrange the boxes given below to make a sentence that helps us understand, opaque objects., OWS, , AKE, , OPAQ, , UE O, , BJEC, , T SM, , SHAD, , 113, , LIGHT, SHADOWS AND REFLECTIONS, , 2018-19

Page 124 :
2., , Classify the objects or materials given below as opaque, transparent or, translucent and luminous or non-luminous:, Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a, sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot, iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper,, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of, cellophane, a wire mesh, kerosene stove, sun, firefly, moon., , 3., , Can you think of creating a shape that would give a circular shadow if held in, one way and a rectangular shadow if held in another way?, , 4., , In a completely dark room, if you hold up a mirror in front of you, will you see a, reflection of yourself in the mirror?, , SUGGESTED ACTIVITIES, 1., , Make a row of your friends — A, B, C and D, standing in a line. Let one friend, stand in front facing them and holding out a mirror towards them (Fig. 11.10)., Now, each person can tell who they are able to see in the Mirror. A,B, C, or D., If, A is able to see B in the mirror then, can B also see A in the mirror? Similarly,, for any two pairs amongst A,B,C, or D?, If A is not able to see B in the mirror, then, is B able to see A in the mirror?, Similarly, for any two pairs amongst A,B,C, or D?, , Fig. 11.10, This activity tells us something about the way light travels and gets reflected, from mirrors. You will learn more about this in higher classes., 2., , Daayan-Baayan—Take a comb in your right hand and bring it up to your hair, and look at yourself in the mirror. There is your familiar face, grinning at you , Wait, try and find out which is the hand holding the comb, in your mirror, reflection. Is it the right hand or the left? You were holding it in your right hand,, isn't it?, While a pinhole camera seems to be giving us upside down images, a mirror, seems to be turning right hand into left hand and the left into right hand. We, will learn more about this in the higher classes., , 114, , SCIENCE, , 2018-19

Page 125 :
3., , Magic Device—In the chapter on, symmetry in your Mathematics, textbook, you might have made an, interesting device Kaleidoscope, that, uses reflections. Now, let us make, another device, a periscope, that uses, reflections to see around corners! Ask, one of your freinds to stand in the, corridor just out side the entrance to, the classroom with a mirror in hand., Ask another friend also holding a mirror,, to stand in the middle of classroom in, front of the entrance. Now ask your, Fig. 11.11 Seeing around corners!, friends to ajust their mirrors in such a, way that the image of object on the other side of the corridor becomes visible to, you while you are standing inside the class (Fig. 11.11)., You can make a simple periscope by placing two mirrors in a ‘Z’ shaped box as, shown in Fig. 11.12., Mirror 1, , Fig. 11.12 A periscope, , Mirror 2, , THINGS TO THINK ABOUT, 1., , Opaque objects cast shadows, isn't it? Now, if we hold a transparent object in, the Sun, do we see anything on the ground that gives us a hint that we are, holding something in our hand?, , 2., , We saw that changing colour of opaque objects does not change the colour of, their shadows. What happens if we place an opaque object in coloured light?, You can cover the face of a torch with a coloured transparent paper to do this., (Did you ever notice the colours of evening shadows just as the Sun is setting?), , THINGS TO READ, Rudyard Kipling's "Just So Stories" and in particular, the story of "How the Leopard, got its spots" where he mentions stripy, speckly, patchy-blatchy shadows. Here, are a few lines from this story, that has a lot of shadows., ...after ever so many days, they saw a great, high, tall forest full of tree trunks, all 'sclusively speckled and sprottled and spottled, dotted and splashed and, slashed and hatched and cross-hatched with shadows. (Say that quickly aloud,, and you will see how very shadowy the forest must have been.), 'What is this,' said the Leopard, 'that is so 'sclusively dark, and yet so full of, little pieces of light?', 115, , LIGHT, SHADOWS AND REFLECTIONS, , 2018-19

Page 126 :
12, , Electricity and Circuits, , W, , e use electricity for many, purposes to make our tasks, easier. For example, we use, electricity to operate pumps that lift, water from wells or from ground level, to the roof top tank. What are other, purposes for which you use electricity?, List some of them in your notebook., Does your list include the use of, electricity for lighting? Electricity, makes it possible to light our homes,, roads, offices, markets and factories, even after sunset. This helps us to, continue working at night. A power station, provides us with electricity. However, the, supply of electricity may fail or it may not, be available at some places. In such, situations, a torch is sometimes used for, providing light. A torch has a bulb that, lights up when it is switched on. Where, does the torch get electricity from?, , 12.1. ELECTRIC CELL, Electricity to the bulb in a torch is, provided by the electric cell. Electric cells, Caution, , are also used in alarm clocks,, wristwatches, transistor radios, cameras, and many other devices. Have you ever, carefully looked at an electric cell? You, might have noticed that it has a small, metal cap on one side and a metal disc, on the other side (Fig. 12.1). Did you, notice a positive (+) sign and a negative, (–) sign marked on the electric cell? The, , Fig.12.1 An Electric Cell, , metal cap is the positive terminal of the, electric cell. The metal disc is the, negative terminal. All electric cells have, two terminals; a positive terminal and a, negative terminal., An electric cell produces electricity, from the chemicals stored inside it., When the chemicals in the electric cell, are used up, the electric cell stops, , You might have seen the danger sign shown here displayed on poles,, electric substations and many other places. It is to warn people that, electricity can be dangerous if not handled properly. Carelessness in, handling electricity and electric devices can cause severe injuries and, sometimes even death. Hence, you should never attempt to experiment, with the electric wires and sockets. Also remember that the electricity, generated by portable generators is equally dangerous. Use only electric, cells for all activities related to electricity., , 116, , SCIENCE, , 2018-19

Page 127 :
Filament, , Caution: Never join the two terminals, of the electric cell without connecting, them through a switch and a device, like a bulb. If you do so, the chemicals, in the electric cell get used up very fast, and the cell stops working., , Terminals, (a), , (b), , Fig.12.2 (a) Torch bulb and (b) its inside view, , producing electricity. The electric cell, then has to be replaced with a new one., A torch bulb has an outer case of, glass that is fixed on a metallic base [Fig., 12. 2 (a)]. What is inside the glass case, of the bulb?, , Activity 1, Take a torch and look inside its bulb., You can also take out the bulb with the, help of your teacher. What do you, notice? Do you find a thin wire fixed in, the middle of the glass bulb [Fig. 12.2, (b)]? Now switch the torch on and, observe which part of the bulb is, glowing., The thin wire that gives off light is, called the filament of the bulb. The, filament is fixed to two thicker wires,, which also provide support to it, as, shown in Fig. 12.2 (b). One of these thick, wires is connected to the metal case at, the base of the bulb [Fig. 12.2 (b)]. The, other thick wire is connected to the, metal tip at the centre of the base. The, base of the bulb and the metal tip of the, base are the two terminals of the bulb., These two terminals are fixed in such a, , way that they do not touch each other., The electric bulbs used at home also, have a similar design., Thus, both the electric cell and the, bulb have two terminals each. Why do, they have these two terminals?, , 12.2. A BULB CONNECTED, AN ELECTRIC CELL, , TO, , Let us try to make an electric bulb light, up using an electric cell. How do we do, that?, , Activity 2, Take four lengths of electric wire with, differently coloured plastic coverings., Remove a little of the plastic covering, from each length of wire at the ends., This would expose the metal wires at, the ends of each length. Fix the exposed, parts of two wires to the cell and the, other two of the bulb as shown in, Fig. 12.3 and Fig. 12.4., , Fig.12.3 Electric cell with two wires attached to it, , ELECTRICITY AND CIRCUITS, , 117, , 2018-19

Page 128 :
Fig.12.4 Bulb connected to two wires, , You can stick the wires to the bulb, with the tape used by electricians. Use, rubber bands or tape to fix the wires to, the cell., Now, connect the wires fixed to the, bulb with those attached to the cell in, six different ways as have been shown in, Fig. 12.5 (a) to (f). For each arrangement,, find out whether the bulb glows or not., , (a), , (d), , Write 'Yes' or 'No' for each arrangement, in your notebook., Now, carefully look at the, arrangements in which the bulb glows., Compare these with those in which the, bulb does not glow. Can you find the, reason for the difference?, Keep the tip of your pencil on the, wire near one terminal of the electric cell, for the arrangment in Fig. 12.5 (a). Move, the pencil along the wire all the way to, the bulb. Now, from the other terminal, of the bulb, move along the other wire, connected to the cell. Repeat this, exercise for all the other arrangements, in Fig. 12.5. Did the bulb glow for the, arrangements in which you could not, move the pencil from one terminal to, the other?, , (b), , (e), , (c), , (f), , Fig.12.5 Different arrangements of electric cell and bulb, 118, , SCIENCE, , 2018-19

Page 129 :
12.3 AN ELECTRIC CIRCUIT, In Activity 2 you connected one terminal, of the electric cell to the other terminal, through wires passing to and from the, electric bulb. Note that in the, arrangements shown in Fig. 12. 5 (a), and (f), the two terminals of the electric, cell were connected to two terminals of, the bulb. Such an arrangement is an, example of an electric circuit. The electric, circuit provides a complete path for, electricity to pass (current to flow), between the two terminals of the electric, cell. The bulb glows only when current, flows through the circuit., In an electric circuit, the direction of, current is taken to be from the positive, to the negative terminal of the electric, cell as shown in Fig.12.6. When the, , An electric bulb may fuse due to, many reasons. One reason for a bulb to, fuse is a break in its filament. A break, in the filament of an electric bulb means, a break in the path of the current, between the terminals of the electric cell., Therefore, a fused bulb does not light, up as no current passes through its, filament., Can you now explain why the bulb, did not glow when you tried to do so, with the arrangements shown in Fig., 12.5 (b), (c), (d) and (e)?, Now we know how to make a bulb, light up using an electric cell. Would, you like to make a torch for yourself?, , Activity 3, Take a torch bulb and a piece of wire., Remove the plastic covering at the two, ends of the wire as you did before. Wrap, one end of a wire around the base of an, electric bulb as shown in Fig. 12.7. Fix, the other end of the wire to the negative, terminal of an electric cell with a rubber, band. Now, bring the tip of the base of, the bulb, that is, its other terminal in, contact with the positive terminal of the, , Fig.12.6 Direction of current in an electric, circuit, , terminals of the bulb are connected with, that of the electric cell by wires, the, current passes through the filament of, the bulb. This makes the bulb glow., Sometimes an electric bulb does not, glow even if it is connected to the cell., This may happen if the bulb has fused., Look at a fused bulb carefully. Is the, filament inside it intact?, ELECTRICITY AND CIRCUITS, , Fig. 12.7 A home-made torch, 119, , 2018-19

Page 130 :
a drawing pin into the ring at one, end of the safety pin and fix it on the, thermo Col sheet as shown in Fig. 12.8., Make sure that the safety pin can be, rotated freely. Now, fix the other drawing, pin on the thermo Col sheet in a way, that the free end of the safety pin can, touch it. The safety pin fixed in this way, would be your switch in this activity., , Paheli has another, arrangement of the cell, and the bulb. Will the, torch bulb glow in, the following, arrangement?, , cell. Does the bulb glow? Now move the, bulb away from the terminal of the, electric cell. Does the bulb remain, lighted? Is this not similar to what you, do when you switch your torch on or, off?, , 12.4 ELECTRIC SWITCH, , Fig 12.9 An electric circuit with a switch, , We had an arrangement for switching, on or off our home made torch by, moving the base of the bulb away from, the tip of the cell. This was a simple, switch, but, not very easy to use. We, can make another simple and easier, switch to use in our circuit., , Activity 4, You can make a switch using two, drawing pins, a safety pin (or a paper, clip), two wires and a small sheet of, thermo Col or a wooden board. Insert, , Now, make a circuit by connecting, an electric cell and a bulb with this, switch as shown in Fig.12.9. Rotate the, safety pin so that its free end touches, the other drawing pin. What do you, observe? Now, move the safety pin away., Does the bulb continue to glow?, The safety pin covered the gap, between the drawing pins when, you made it touch two of them. In, this position the switch is said to be 'on', (Fig. 12.10). Since the material of the, safety pin allows the current to pass, , Fig. 12.8 A simple switch, , Fig. 12.10 A switch in ‘on’ position, , 120, , SCIENCE, , 2018-19

Page 131 :
through it, the circuit was complete., Hence, the bulb glows., On the other hand, the bulb did not, glow when the safety pin was not in, touch with the other drawing pin. The, circuit was not complete as there was a, gap between the two drawing pins. In, Boojho has drawn the inside, of the torch as in Fig. 12.11., When we close the switch,, the circuit is completed and, the bulb glows. Can you, draw a red line on the figure, indicating the complete circuit?, , Reflector, , this position, the switch is said to be, 'off' as in Fig. 12.9., A switch is a simple device that either, breaks the circuit or completes it. The, switches used in lighting of electric, bulbs and other devices in homes work, on the same principle although their, designs are more complex., , 12.5 E LECTRIC C ONDUCTORS, INSULATORS, , AND, , In all our activities we have used metal, wires to make a circuit. Suppose we use, a cotton thread instead of a metal wire, to make a circuit. Do you think that the, bulb will light up in such a circuit?, What materials can be used in electric, circuits so that the current can pass, through them? Let us find out., , Activity 5, Disconnect the switch from the electric, circuit you used for Activity 4. This would, leave you with two free ends of wires as, shown in Fig. 12.12 (a). Bring the free, ends of the two wires close, to let them, touch each other. Does the bulb light up?, You can now use this arrangement to test, whether any given material allows current, to pass through it or not., , (a), , Fig. 12.11 Inside view of a torch, , (b), , Fig. 12.12 (a) A conduction tester (b) Testing, whether the bulb glows when the tester is in, contact with a key, , ELECTRICITY AND CIRCUITS, , 121, , 2018-19

Page 132 :
Collect samples of different types of, materials such as coins, cork, rubber,, glass, keys, pins, plastic scale, wooden, block, aluminium foil, candle, sewing, needle, thermo Col, paper and pencil, lead. One by one bring the free ends of, the wires of your tester in contact with, two ends of the samples you have, collected [Fig. 12.12 (b)]. Make sure that, the two wires do not touch each other, while you are doing so. Does the bulb, glow in each case?, Make a table in your notebook, similar to Table.12.1, and record your, observations., Table 12.1 Conductors and insulators, Object used in, place of the, switch, , Material, it is, made of, , Bulb, glows?, (Yes/No), , Key, , Metal, , Yes, , Eraser, , Rubber, , No, , Scale, , Plastic, , Matchstick, , Wood, , Glass bangle, , Glass, , Iron nail, , Metal, , What do you find? The bulb does not, glow when the free ends of the wires are, in contact with some of the materials you, have tested. This means that these, materials do not allow the electric current, to pass through them. On the other hand,, some materials allow electric current to, pass through them, which is indicated, by the glowing bulb. Materials which, allow electric current to pass through, them are conductors of electricity., , Insulators do not allow electric current, to pass through them. With the help of, Table 12.1, name the materials that are, conductors of electricity and also those, which are insulators., Conductors ______, ______, _________, Insulator _________, _______, ________, What do you conclude? Which, materials are conductors and which are, insulators? Recall the objects that we, grouped as those having lustre, in, Chapter 4. Are they the conductors? It, now seems easy to understand why, copper, aluminum and other metals are, used for making wires., Let us recall Activity 4 in which we, made an electric circuit with a switch, (Fig.12.9). When the switch was in the, open position, were the two drawing pins, not connected with each other through, the thermo Col sheet? But, thermo Col,, you may have found is an insulator., What about the air between the gap?, Since the bulb does not glow when there, is only air in the gap between the drawing, pins in your switch, it means that air is, also an insulator., Conductors and insulators are, equally important for us. Switches,, electrical plugs and sockets are made of, conductors. On the other hand, rubber, and plastics are used for covering, electrical wires, plug tops, switches and, other parts of electrical appliances,, which people might touch., , 122, , Caution: Your body is a conductor of, electricity. Therefore, be careful when, you handle an electrical appliance., SCIENCE, , 2018-19

Page 133 :
n, , Electric cell is a source of electricity., , n, , An electric cell has two terminals; one is called positive (+ ve) while the, other is negative (– ve)., , n, , An electric bulb has a filament that is connected to its terminals., , n, , An electric bulb glows when electric current passes through it., , n, , In a closed electric circuit, the electric current passes from one terminal of, the electric cell to the other terminal., , n, , Switch is a simple device that is used to either break the electric circuit or, to complete it., , n, , Materials that allow electric current to pass through them are called, conductors., , n, , Materials that do not allow electric current to pass through them are called, insulators., , Bulb, Conductors, Electric cell, Electric circuit, , 1., , Fill in the blanks :, (a) A device that is used to break an electric circuit is called _______________., (b) An electric cell has _______________ terminals., , 2., , Mark 'True' or 'False' for following statements:, (a) Electric current can flow through metals., (b) Instead of metal wires, a jute string can be, used to make a circuit., (c) Electric current can pass through a sheet, of thermo Col., , 3., , Explain why the bulb would not glow in the, arrangement shown in Fig. 12.13., Fig. 12.13, , ELECTRICITY AND CIRCUITS, , 123, , 2018-19

Page 134 :
4., , Complete the drawing shown in Fig 12.14 to, indicate where the free ends of the two wires, should be joined to make the bulb glow., , 5., , What is the purpose of using an electric switch?, Name some electrical gadgets that have switches, built into them., , 6., , Would the bulb glow after completing the circuit, shown in Fig. 12.14 if instead of safety pin we, use an eraser?, , 7., , Fig. 12.14, , Would the bulb glow in the circuit shown in Fig. 12.15?, , Fig. 12.15, 8., , Using the "conduction tester" on an object it was found that the bulb begins to, glow. Is that object a conductor or an insulator? Explain., , 9., , Why should an electrician use rubber gloves while repairing an electric switch, at your home? Explain., , 10. The handles of the tools like screwdrivers and pliers used by electricians for, repair work usually have plastic or rubber covers on them. Can you explain, why?, , SOME SUGGESTED ACTIVITIES, 1. Imagine there were no electric supply for a month. How would that affect your, day to day activities and others in your family? Present your imagination in, the form of a story or a play. If possible stage the play written by you or your, friends in school., 2. For your friends, you may set up a game "How steady is your hand?". You will, need a cell, an electric bulb, a metal key, two iron nails ( about 5 cm in length),, about one and a half metre long thick metal wire (with its plastic insulation, scraped off ) and few pieces of connecting wires. Fix two nails nearly one metre, apart on a wooden board so that these can be used as a hook. Fix the wire, between the nails after inserting it through the loop of the key. Connect one, end of this wire to a bulb and a cell. Connect the other terminal of the cell to, the key with a wire. Ask your friend to move the loop along the straight wire, without touching it. Glowing of the bulb would indicate that the loop of the key, has touched the wire., 3. Read and find out about Alessandro Volta who invented the electric cell. You, may also find out about Thomas Alva Edison who invented the electric bulb., 124, , SCIENCE, , 2018-19

Page 135 :
13, , Fun with Magnets, , P, , aheli and Boojho went to a place, where a lot of waste material was, piled into huge heaps. Something, exciting was happening! A crane was, moving towards the heap of junk. The, long hand of the crane lowered a block, over a heap. It then began to move., Guess, what? Many pieces of iron junk, were sticking to the block, as it moved, away (Fig. 13.1)!, , sticking to the holder. In some pencil, boxes, the lid fits tightly when we close, it even without a locking arrangement., Such stickers, pin holders and pencil, boxes have magnets fitted inside, (Fig. 13.2). If you have any one of these, items, try to locate the magnets hidden, in these., , Fig. 13.2 Some common items that have, magnets inside them, Fig. 13.1 Picking up pieces of iron from waste, , They had just read a very interesting, book on magnets and knew immediately, that there must be a magnet attached, to the end of the crane that was picking, up iron from the junk yard., You might have seen magnets and, have even enjoyed playing with them., Have you seen stickers that remain, attached to iron surfaces like almirahs, or the doors of refrigerators? In some, pin holders, the pins seem to be, , How Magnets Were Discovered, It is said that, there was a shepherd, named Magnes, who lived in ancient, Greece. He used to take his herd of, sheep and goats to the nearby, mountains for grazing. He would take, a stick with him to control his herd. The, stick had a small piece of iron attached, at one end. One day he was surprised, to find that he had to pull hard to, free his stick from a rock on the, , 2018-19

Page 136 :
Fig. 13.4 Magnets of different shapes, , magnets are prepared in different, shapes. For example, bar magnet, horseshoe magnet, cylindrical or a ball-ended, magnet. Fig.13.4 shows a few such, magnets., , Fig.13.3 A natural magnet on a hillside!, , mountainside (Fig. 13.3). It seemed as, if the stick was being attracted by the, rock. The rock was a natural magnet, and it attracted the iron tip of the, shepherd's stick. It is said that this is, how natural magnets were discovered., Such rocks were given the name, magnetite, perhaps after the name of that, shepherd. Magnetite contains iron., Some people believe that magnetite was, first discovered at a place called, Magnesia. The substances having the, property of attracting iron are now known, as magnets. This is how the story goes., In any case, people now have, discovered that certain rocks have the, property of attracting pieces of iron. They, also found that small pieces of these, rocks have some special properties., They named these naturally occurring, materials magnets. Later on the process, of making magnets from pieces of iron, was discovered. These are known as, artificial magnets. Nowadays artificial, , Activity 1, Take a plastic or a paper cup. Fix it on a, stand with the help of a clamp as shown, in Fig. 13.5. Place a magnet inside the, cup and cover it with a paper so that, the magnet is not visible. Attach a, thread to a clip made of iron. Fix the, other end of the thread at the base of, the stand. (Mind you, the trick involved, here, is to keep the length of the thread, sufficiently short.) Bring the clip near, the base of the cup. The clip is raised in, air without support, like a kite., , 126, , Fig. 13.5 Effect of magnet - a paper clip, hanging in air!, SCIENCE, , 2018-19

Page 137 :
13.1 MAGNETIC, MATERIALS, , AND, , NON-MAGNETIC, , Activity 2, Let us walk in the footsteps of Magnes., Only, this time, we will change the, positions of the magnet and the iron., There will be a magnet at the end of our, shepherd's stick. We can attach a small, magnet to a hockey stick, walking stick, or a cricket wicket with a tape or some, glue. Let us now go out on a "Magnes, walk" through the school playground., What does our "Magnes stick" pick up, from the school ground? What about, objects in the classroom?, Collect various objects of day-to-day, use from your surroundings. Test these, with the "Magnes stick". You can also, take a magnet, touch these objects with, it and observe which objects stick to the, magnet. Prepare a table in your, notebook as shown in Table 13.1. and, record your observations., Look at the last column of Table 13.1, and note the objects that are attracted, by a magnet. Now, make a list of, , materials from which these objects are, made. Is there any material common in, all the objects that were attracted by, the magnet?, We understand that magnet attracts, certain materials whereas some do not, get attracted towards magnet. The, materials which get attracted towards, a magnet are magnetic – for example,, iron, nickel or cobalt. The materials, which are not attracted towards a, magnet are non-magnetic. What, materials did you find to be nonmagnetic from Table 13.1? Is soil a, magnetic or a non-magnetic material?, , Boojho has this question for you., A tailor was stitching buttons on, his shirt. The needle has slipped, from his hand on to the floor., Can you help the tailor to, find the needle?, , Table 13.1 Finding the objects attracted by magnet, Material which the object is made of, (Cloth/plastic/ aluminium/ wood/, glass/ iron/ any other, , Attracted by Magnes, stick/ magnet, (Yes/No), , Iron ball, , Iron, , Yes, , Scale, , Plastic, , No, , Shoe, , Leather, , ?, , Name of, the object, , 127, , FUN WITH MAGNETS, , 2018-19

Page 138 :
Activity 3, Rub a magnet in the sand or soil. Pull, out the magnet. Are there some particles, of sand or soil sticking to the magnet?, Now, gently shake the magnet to remove, the particles of sand or soil. Are some, particles still sticking to it? These might, be small pieces of iron (iron filings), picked up from the soil., Through such an activity, we can, find out whether the soil or sand from a, given place contains particles that have, iron. Try this activity near your home,, school or the places you visit on your, holidays. Does the magnet with iron, filings sticking to it, look like any one, of those shown in Fig. 13.6?, Make a table of what you find., (a), , If you fill this table and send it to, Paheli and Boojho, they can compare, the amount of iron filings found in soil, from different parts of the country. They, can share this information with you., , 13.2 POLES, , OF, , MAGNET, , We observed that iron filings (if they are, present) stick to a magnet rubbed in the, soil. Did you observe anything special, about the way they stick to the magnet?, , Activity 4, Spread some iron filings on a sheet of, paper. Now, place a bar magnet on this, sheet. What do you observe? Do the iron, filings stick all over the magnet? Do you, observe that more iron filings get attracted, to some parts of the magnet than others, (Fig. 13.7)? Remove the iron filings, sticking to the magnet and repeat the, , (b), , (c), Fig. 13.6 Magnet with (a) many iron filings, (b) few iron filings and, (c) no iron filings sticking to it., , Fig. 13.7 Iron filings sticking to a bar magnet, , Table 13.2 Magnet rubbed in sand., How many iron filings?, id you find iron, Name of location fD, ilings sticking to, (Colony and, the magnet?, town/ city/, (, M, any/ very few/, village), none), , activity. Do you observe any change in, the pattern with which the iron filings, get attracted by different parts of the, magnet? You can do this activity using, pins or iron nails in place of iron filings, and also with magnets of different shapes., Draw a diagram to show the way iron, filings stick to the magnet. Is your drawing, similar to that shown in Fig. 13.6 (a)?, We find that the iron filings are, attracted more towards the region close, , 128, , SCIENCE, , 2018-19

Page 139 :
Paheli has this puzzle for you., You are given two identical bars, which look as if they might be, made of iron. One of them is a, magnet, while the other is a, simple iron bar. How will, you find out, which one, is a magnet?, , to two ends of a bar magnet. Poles of a, magnet are said to be near these ends., Try and bring a few magnets of different, shapes to the classroom. Check for the, location of the poles on these magnets, using iron filings. Can you now mark the, location of poles in the kind of magnets, shown in Fig. 13.4?, , 13.3 FINDING DIRECTIONS, Magnets were known to people from, ancient times. Many properties of, magnets were also known to them. You, might have read many interesting, stories about the uses of magnets. One, such story is about an emperor in China, named Hoang Ti. It is said that he had, a chariot with a statue of a lady that, could rotate in any direction. It had an, extended arm as if it was showing the, way (Fig. 13.8). The statue had an, interesting property. It would rest in, such a position that its extended arm, always pointed towards South. By, looking at the extended arm of the, statue, the Emperor was able to locate, directions when he went to new places, on his chariot., , Fig. 13.8 The chariot with direction finding statue, , Let us make such a direction finder, for ourselves., , Activity 5, Take a bar magnet. Put a mark on one, of its ends for identification. Now, tie a, thread at the middle of the magnet so, that you may suspend it from a wooden, stand (Fig. 13.9). Make sure that the, magnet can rotate freely. Let it come to, rest. Mark two points on the ground to, show the position of the ends of the, magnet when it comes to rest. Draw a, , Fig. 13.9 A freely suspended bar magnet, always comes to rest in the same direction, 129, , FUN WITH MAGNETS, , 2018-19

Page 140 :
line joining the two points. This line, shows the direction in which the magnet, was pointing in its position of rest. Now,, rotate the magnet by gently pushing one, end in any direction and let it come to, rest. Again, mark the position of the two, ends in its position of rest. Does the, magnet now point in a different, direction? Rotate the magnet in other, directions and note the final direction, in which it comes to rest., Do you find that the magnet always, comes to rest in the same direction?, Now can you guess the mystery behind, the statue in the Emperor's chariot?, Repeat this activity with an iron bar, and a plastic or a wooden scale instead, of a magnet. Do not use light objects for, this activity and avoid doing it where, there are currents of air. Do the other, materials also always come to rest in the, same direction?, We find that a freely suspended bar, magnet always comes to rest in a, particular direction, which is the NorthSouth direction. Use the direction of the, rising sun in the morning to find out, the rough direction towards east, where, you are doing this experiment. If you, stand facing east, to your left will be, North. Using the Sun for finding, directions may not be very exact, but, it, will help to make out the direction, North from the South, on your line., Using this you can figure out which end, of the magnet is pointing to the North, and which points to the South., The end of the magnet that points, towards North is called its North seeking, , In which direction is the main, gate of your school situated from, your classroom?, , end or the North pole of the magnet. The, other end that points towards the South, is called South seeking end or the South, pole of the magnet. All magnets have two, poles whatever their shape may be., Usually, north (N) and south (S) poles, are marked on the magnets., This property of the magnet is very, useful for us. For centuries, travellers, have been making use of this property, of magnets to find directions. It is said, that in olden days, travellers used to find, directions by suspending natural, magnets with a thread, which they, always carried with them., Later on, a device was developed, based on this property of magnets. It is, known as the compass. A compass is, usually a small box with a glass cover, on it. A magnetised needle is pivoted, inside the box, which can rotate freely, (Fig. 13.10). The compass also has a dial, , 130, , Fig. 13.10 A compass, SCIENCE, , 2018-19

Page 141 :
with directions marked on it. The, compass is kept at the place where we, wish to know the directions. Its needle, indicates the north-south direction, when it comes to rest. The compass is, then rotated until the north and south, marked on the dial are at the two ends, of the needle. To identify the north-pole, of the magnetic needle, it is usually, painted in a different colour., , 13.4 MAKE YOUR OWN MAGNET, There are several methods of making, magnets. Let us learn the simplest one., Take a rectangular piece of iron. Place, it on the table. Now take a bar magnet, and place one of its poles near one edge, of the bar of iron. Without lifting the, bar magnet, move it along the length of, the iron bar till you reach the other end., Now, lift the magnet and bring the pole, (the same pole you started with) to the, same point of the iron bar from which, you began (Fig. 13.11). Move the magnet, again along the iron bar in the same, direction as you did before. Repeat this, process about 30-40 times. Bring a pin, or some iron filings near the iron bar to, check whether it has become a magnet., If not, continue the process for some, , more time. Remember that the pole of, the magnet and the direction of its, movement should not change. You can, also use an iron nail, a needle or a blade, and convert them into a magnet., You now know how to make a, magnet. Would you like to make your, own compass?, , Activity 6, Magnetise an iron, needle using a bar, magnet. Now, insert, the, magnetised, needle through a, small piece of cork or, foam. Let the cork, float in water in a, Fig. 13.12 A, bowl or a tub. Make, compass in a cup, sure that the needle, does not touch the water (Fig. 13.12)., Your compass is now ready to work., Make a note of the direction in which, the needle points when the cork is, floating. Rotate the cork, with the needle, fixed in it, in different directions. Note, the direction in which the needle points, when the cork begins to float again, without rotating. Does the needle always, point in the same direction, when the, cork stops rotating?, , 13.5 A TTRACTION AND R EPULSION, BETWEEN MAGNETS, , Fig.13.11 Making your own magnet, , Let us play another interesting game, with magnets. Take two small toy cars, and label them A and B. Place a bar, magnet on top of each car along its, length and fix them with rubber bands, 131, , FUN WITH MAGNETS, , 2018-19

Page 142 :
A, B, Fig. 13.13 Do opposite poles attract each other?, , C, D, Fig. 13.14 Repulsion between similar poles?, , (Fig. 13.13). In car A, keep the south, pole of the magnet towards its front., Place the magnet in opposite direction, in car B. Now, place the two cars close, to one another (Fig. 13.13). What do you, observe? Do the cars remain at their, places? Do the cars run away from each, other? Do they move towards each other, and collide? Record your observations, in a table as shown in Table 13.3. Now,, place the toy cars close to each other, such that the rear side of car A faces, the front side of car B (Fig 13.14). Do, they move as before? Note the direction, in which the cars move now. Next, place, the car A behind car B and note the, direction in which they move in each, case. Repeat the activity by placing cars, , with their rear sides facing each other., Record your observations in each case., What do we find from this activity?, Do two similar poles attract or repel each, other? What about opposite poles — do, they attract or repel each other?, This property of the magnets can also, be observed by suspending a magnet, and bringing one by one the poles of, another magnet near it., , Boojho has this question for you., What will happen if a magnet is, brought near a compass?, , A Few Cautions, Table 13.3, How do the, cars move?, Move towards/, Position of the cars, away from, each other/, not move at all, , Magnets loose their properties if they, are heated, hammered or dropped from, some height (Fig. 13.15). Also, magnets, become weak if they are not stored, properly. To keep them safe, bar, , Front of car A facing, the front of car B, Rear of car A facing, the front of car B, Car A placed behind, car B, Rear of car B facing, rear of car A, , Fig. 13.15 Magnets lose their property on, heating, hammering and droping, , 132, , SCIENCE, , 2018-19

Page 143 :
Fig. 13.16 Store your magnets safely, , magnets should be kept in pairs with, their unlike poles on the same side., They must be separated by a piece of, wood while two pieces of soft iron should, be placed across their ends (Fig. 13.16)., , For horse-shoe magnet, one should keep, a piece of iron across the poles., Keep magnets away from cassettes,, mobiles, television, music system,, compact disks (CDs) and the computer., , Compass, Magnet, Magnetite, North pole, South pole, , , , , , , , , Magnetite is a natural magnet., Magnet attracts materials like iron, nickel, cobalt. These are called magnetic, materials., Materials that are not attracted towards magnet are called non-magnetic., Each magnet has two magnetic poles—North and South., A freely suspended magnet always aligns in N-S direction., Opposite poles of two magnets attract each other whereas similar poles, repel one another., , 133, , FUN WITH MAGNETS, , 2018-19

Page 144 :
1., , Fill in the blanks in the following, (i) Artificial magnets are made in different shapes such as __________,, __________ and ____________., (ii) The Materials which are attracted towards a magnet are called________., (iii) Paper is not a ______ material., (iv) In olden days, sailors used to find direction by suspending a piece of, ___________., (v) A magnet always has __________ poles., , 2., , State whether the following statements are true or false:, (i) A cylindrical magnet has only one pole., (ii) Artificial magnets were discovered in Greece., (iii) Similar poles of a magnet repel each other., (iv) Maximum iron filings stick in the middle of a bar magnet when it is brought, near them., (v) Bar magnets always point towards North-South direction., (vi) A compass can be used to find East-West direction at any place., (vii) Rubber is a magnetic material., , 3., , It was observed that a pencil sharpener gets attracted by both the poles of a, magnet although its body is made of plastic. Name a material that might have, been used to make some part of it., , 4., , Column I shows different positions in which one pole of a magnet is placed near, that of the other. Column II indicates the resulting action between them for, each situation. Fill in the blanks., Column I, , Column II, , N-N, , _________, , N - _________, , Attraction, , S-N, , _________, , _________ - S, , Repulstion, , 5., , Write any two properties of a magnet., , 6., , Where are poles of a bar magnet located?, , 7., , A bar magnet has no markings to indicate its poles. How would you find out, near which end is its north pole located?, , 8., , You are given an iron strip. How will you make it into a magnet?, , 9., , How is a compass used to find directions?, , 10. A magnet was brought from different directions towards a toy boat that has, 134, , SCIENCE, , 2018-19

Page 145 :
been floating in water in a tub. Affect observed in each case is stated in, Column I. Possible reasons for the observed affects are mentioned in, Column II. Match the statements given in Column I with those in Column II., Column I, , Column II, , Boat gets attracted towards the magnet, , Boat is fitted with a magnet with north, pole towards its head, , Boat is not affected by the magnet, , Boat is fitted with a magnet with south, pole towards its head, , Boat moves towards the magnet if north, pole of the magnet is brought near its, head, , Boat has a small magnet fixed along its, length, , Boat moves away from the magnet when, north pole is brought near its head, , Boat is made of magnetic material, , Boat floats without changing its direction, , Boat is made up non-magnetic material, , SOME SUGGESTED ACTIVITIES, 1., , Using a compass, find the direction in which windows and entrance to your, house or classroom open., , 2., , Try to place two equal sized bar magnets one above the other such that their, north poles are on the same side. Note what happens and write your, observations in your note book., , 3., , Few iron nails and screws got mixed with the wooden shavings while a, carpenter was working with them. How can you help him in getting the nails, and screws back from the scrap without wasting his time in searching with, his hands?, , 4., , You can make an intelligent doll, which picks up the things it likes (Fig., 13.17). Take a doll and attach a small magnet in one of its hands. Cover this, hand with small gloves so that the magnet is not visible. Now, your intelligent, doll is ready. Ask your friends to bring different objects near the doll's hand., Knowing the material of the object you can tell in advance whether the doll, would catch it or not., , THINGS TO READ, , Fig. 13.17 An intelligent doll, , ‘Gulliver's Travels’ which has this fantasy of the whole island of Laputa, floating, in air. Could magnets be involved?, 135, , FUN WITH MAGNETS, , 2018-19

Page 146 :
14, , Water, , S, , uppose for some reason your, family gets only one bucket of, water everyday for a week., Imagine what would happen? Would you, be able to cook, clean utensils, wash, clothes or bathe? What are the other, activities you would not be able to do?, What would happen if we do not have, easy access to water for a long period, of time?, Apart from drinking, there are, so many activities for which we use, water (Fig. 14.1). Do you have an idea, about the quantity of water we use in a, single day?, , each activity by you and other family, members. You may use a mug, a glass,, a bucket or any other container to, measure the amount of water used., Table 14.1 Estimation of the, amount of water used by your, family in a day, Activity, , Amount of, water used, , Drinking, Brushing, Bathing, Washing utensils, Washing clothes, Toilets, Cleaning floor, Any other, Total water used in, a day by a family, , Fig. 14.1 Uses of water, , 14.1 HOW MUCH WATER DO, , WE, , USE?, , Activity 1, List all the activities for which you use, water in a day. Some activities are listed, in Table 14.1. Make a similar table in, your notebook. Throughout the day,, measure the amount of water used for, , You now have a rough idea as to how, much water your family uses in a day., Can you estimate the amount of water, used by you for personal cleanliness in, a day. Using this information, calculate, the amount of water needed by your, family in a year. Now, divide this amount, by the number of members of your, family. This will give an idea of the, amount of water needed by one member, of your family in a year. Find the number, of people that live in your village or town., SCIENCE, , 136, , 2018-19

Page 147 :
You may now get an idea of the amount, of water needed by your village or town, in a year., Boojho wonders whether people, living in different regions of our, country get the same amount of, water. Are there regions where, people do not get adequate amount, of water? How do they manage?, , You have listed a number of activities, for which you use water. Do you think,, our water requirement is limited to, activities like these? We use wheat, rice,, pulses, vegetables and many other food, items everyday. We know that some of, the fibres that we use for making fabric, come from plants. Is water not needed, to grow these? Can you think of some, more uses of water? Water is used in, industries for producing almost all the, things that we use. So, we need water, not only for our daily activities but also, for producing many things., , water from a river, spring, pond, well or, a hand pump”. Some others might say,, “We get water from taps”. Have you ever, wondered where water in the taps comes, from? Water that we get from taps is also, drawn from a lake or a river or a well, (Fig. 14.2). It is then supplied through, a network of pipes., , Fig. 14.2 Water in taps comes from rivers,, lakes, borewell or wells, , Each of us may be getting water into, our homes in different ways. But, finally,, all of us get water from the same sources, such as ponds, lakes, rivers and wells., We have discussed some of the, sources of water. Where does the water, come from, to fill these ponds, lakes,, rivers and wells?, , Paheli wants to tell you that, about two glasses of water, are required to produce, each page of a book., , 14.2 WHERE DO WE GET WATER, FROM?, Where do you get the water that you, use? Some of you may say, “We draw, WATER, , Boojho wants you to imagine a, day in your life when water supply, through taps is not available. So,, you have to fetch it yourself from, a far away place. Would you, use the same amount of water, as on any other day?, , 137, , 2018-19

Page 148 :
That is where the water cycle, comes in!, , 14.3 WATER CYCLE, Disappearing Trick of Water, , Fig. 14.3 Oceans cover a major part of the earth, , Do you know that about two thirds, of the Earth is covered with water? Most, of this water is in oceans and seas, (Fig. 14.3)., The water in the oceans and seas has, many salts dissolved in it — the water, is saline. So, it is not fit for drinking, and other domestic, agricultural and, industrial needs. You might have heard, the famous lines of the poem “Rime of, the Ancient Mariner” written by S.T., Coleridge in 1798:, , How many times have you noticed that, water spilled on a floor dries up after, some time? The water seems to disappear., Similarly, water disappears from wet, clothes as they dry up (Fig. 14.4). Water, from wet roads, rooftops and a few other, places also disappears after the rains., Where does this water go?, , “Water water every where, Nor any drop to drink”, , Fig. 14.4 Clothes drying on a clothes-line, , Here the poet has described the, plight of sailors on a ship lost in the, ocean., Yet, oceans play an important role, in supplying the water that we use. Do, you find this surprising? After all, the, water that we use is not salty. Many of, us live in places far away from the, oceans. Does the water supply in these, places also depend on the oceans? How, does the ocean water reach ponds, lakes,, rivers and wells, which supply us water?, How come the water from these sources, is not saline anymore?, , Do you remember Activity 6 in, Chapter 5 in which water with salt, dissolved in it was heated? What did we, find? The water evaporated and the salt, was left behind. This activity gives us, an idea that, on heating, water changes, into its vapour. We also realise from this, activity, that water vapour does not carry, away the salt with it. Water vapours so, formed become a part of the air and, cannot usually be seen. We also found, that heating is essential to convert water, into its vapour. However, we have seen, that water changes into its vapour also, SCIENCE, , 138, , 2018-19

Page 149 :
from the fields, roads, rooftops and, other land areas. We also discussed in, Chapter 5 that to obtain salt, water from, the sea is left in shallow pits to let the, water evaporate. From where does this, water get the heat it needs to evaporate?, Let us find out., , Activity 2, Take two similar plates. Place one of the, plates in sunlight and keep the other, under shade. Now, pour equal amount, of water in each of the plates (Fig. 14.5)., You can use a cap of a bottle to measure, water. Make sure that water does not, spill over. Observe the two plates after, every 15 minutes. Does the water seem, to disappear? From which plate does it, disappear first? What is the source of, heat for this evaporation?, During the daytime, sunlight falls on, the water in oceans, rivers, lakes and, ponds. The fields and other land areas, also receive sunlight. As a result, water, from all these places continuously, changes into vapour. However, the salts, dissolved in the water are left behind., In Activity 2, did you find that water, also disappeared from the plate kept in, , the shade, though it could have taken, more time? Does the heat from the, sunlight reach here? Yes, during the, daytime all the air surrounding us gets, heated. This warm air provides heat for, evaporation of water in the shade. Thus,, evaporation takes place from all open, surfaces of water. As a result, water, vapour gets continuously added to air., However, evaporation of water is a slow, process. That is why we rarely notice its, loss from a bucket full of water. In, sunlight, evaporation takes place faster., On heating water on a burner, its, evaporation takes place even faster. Is, there any other process through which, water vapour gets transferred into air?, , Loss of Water by Plants, You have learnt in Chapter 7 that plants, need water to grow. Plants use a part of, this water to prepare their food and, , Boojho has been reading about, transpiration. He asked himself how much water is lost through, transpiration by wheat plants, that give us one kilogram of, wheat? He found out that this is, nearly 500 litres, that is, roughly, 25 large sized buckets full of, water. Can you now imagine the, amount of water lost by plants, of all the forests, crops and, grasslands together?, , Fig.14.5 Evaporation of water in sunlight and in, shade, WATER, , 139, , 2018-19

Page 150 :
retain some of it in their different parts., Remaining part of this water is released, by the plants into air, as water vapour, through the process of transpiration. Do, you remember observing transpiration, of water by plants in Activity 4 in, Chapter 7?, Water vapour enters the air through, the processes of evaporation and, transpiration. Is it lost for ever? No, we, get it back again, as we will see., , Paheli has noticed dew on leaves of, grass on winter mornings. Did you, notice something similar on leaves, or metal surfaces like iron grills and, gates on a cold morning? Is this, also due to condensation? Do you, see this happening on hot, summer mornings?, , How are clouds formed?, Activity 3, Take a glass half filled with water. Wipe, the glass from the outside with a clean, piece of cloth. Add some ice into the, water. Wait for one or two minutes., Observe the changes that take place on, the outer surface of the glass (Fig.14.6)., From where do water drops appear, on the outer side of the glass? The cold, surface of the glass containing iced water,, cools the air around it, and the water, vapour of the air condenses on the, surface of the glass. We noticed this, process of condensation in Activity 7 in, Chapter 5., , The process of condensation plays an, important role in bringing water back, to the surface of earth. How does it, happen? As we go higher from the, surface of the earth, it gets cooler. When, the air moves up, it gets cooler and, cooler. At sufficient heights, the air, becomes so cool that the water vapour, present in it condenses to form tiny, drops of water called droplets. It is these, tiny droplets that remain floating in air, and appear to us as clouds (Fig. 14.7)., It so happens that many droplets of, water come together to form larger sized, , Ice, , Water, droplets, , Fig. 14.6 Drops of water appear on outer, surface of the glass containing water with ice, , Fig. 14.7 Clouds, SCIENCE, , 140, , 2018-19

Page 151 :
Boojho has noticed fog near the, ground in winter mornings. He, wonders if this is also condensation, of water vapour near the, ground. What do you, think?, , drops of water. Some drops of water, become so heavy that they begin to fall., These falling water-drops are, what we, call rain. In special conditions, it may, also fall as hail or snow., Thus, water in the form of vapour, goes into air by evaporation and, transpiration, forms clouds, and then, comes back to the ground as rain, hail, or snow., , 14.4 BACK, , TO THE, , OCEANS, , What happens to the water that rain and, snow bring to different regions of earth?, Almost all land surfaces are above the, level of oceans. Most of the water that, falls on the land as rain and snow, sooner or later goes back to the oceans., This happens in many ways., Snow in the mountains melts into, water. This water flows down the, mountains in the form of streams and, rivers (Fig. 14.8). Some of the water that, falls on land as rain, also flows in the, form of rivers and streams. Most of the, rivers cover long distances on land and, ultimately fall into a sea or an ocean., However, water of some rivers flows, into lakes., , Fig. 14.8 Rainwater flows down in the form of, streams and rivers, , The rainwater also fills up the lakes, and ponds. A part of the rainwater gets, absorbed by the ground and seems to, disappear in the soil. Some of this water, is brought back to the air by the process, of evaporation and transpiration. The, rest seeps into the ground. Most of this, water becomes available to us as ground, water. Open wells are fed by ground, water. Ground water is the source for, many lakes as well. It is also this ground, water which is drawn by a handpump, or a tubewell. The more handpumps or, tubewells that are used in an area, the, deeper we need to dig to find this ground, water. The loss in the level of ground, water due to over use, is worrisome., Paheli wants to share a concern with, you. In those areas where the land has, little or no vegetation, the rainwater flows, away quickly. Flowing rainwater also, takes the top layer of the soil away with, it. There are few areas where most of the, land is covered with concrete. This, reduces the seepage of rainwater into the, ground which ultimately affects the, availability of ground water., , WATER, , 141, , 2018-19

Page 152 :
We now know that water brought, back to the surface of the earth by rain,, hail or snow, goes back to oceans. Thus,, water from the ocean and surface of the, earth goes into air as vapour; returns, as rain, hail or snow and finally goes, back to the oceans. The circulation of, water in this manner is known as the, water cycle (Fig.14.9). This circulation, of water between ocean and land is a, continuous process. This maintains the, supply of water on land., , 14.5 WHAT, , IF IT, , RAINS HEAVILY?, , The time, duration and the amount of, rainfall varies from place to place. In, some parts of the world it rains, throughout the year while there are, places where it rains only for a few days., , Fig. 14.10 A scene after heavy rains, , In our country, most of the rainfall, occurs during the monsoon season., Rains bring relief especially after hot, summer days. The sowing of many crops, depends on the arrival of monsoon., However, excess of rainfall may lead, to many problems (Fig. 14.10). Heavy, , Fig. 14.9 Water cycle, SCIENCE, , 142, , 2018-19

Page 153 :
heard about droughts occurring in some, parts of our country or the world. Are, you aware of the difficulties faced by, the people living in these areas? What, happens to the animals and the, vegetation in these conditions? Try and, find out about this by talking to your, parents and neighbours and by, reading about it from newspapers, and magazines., , Fig. 14.11 A scene of a flooded area, , rains may lead to rise in the level of water, in rivers, lakes and ponds. The water, may then spread over large areas causing, floods. The crop fields, forests, villages,, and cities may get submerged by water, (Fig. 14.11). In our country, floods cause, extensive damage to crops, domestic, animals, property and human life., During floods, the animals living in, the water also get carried away with the, waters. They often get trapped on land, areas and die when floodwater recedes., Rains also affect the animals living in, the soil., , 14.6 WHAT HAPPENS IF IT DOES NOT, RAIN FOR A LONG PERIOD?, Can you imagine what would happen if, it does not rain in a region for a year or, more? The soil continues to lose water, by evaporation and transpiration. Since, it is not being brought back by rain,, the soil becomes dry. The level of water, in ponds and wells of the region goes, down and some of them may even dry, up. The ground water may also become, scarce. This may lead to drought., In drought conditions, it is difficult, to get food and fodder. You might have, , 14.7 HOW CAN WE CONSERVE WATER?, Only a small fraction of water available, on the Earth is fit for use of plants,, animals and humans. Most of the water, is in the oceans and it cannot be used, directly. When the level of the ground, water decreases drastically, this can not, be used any more. The total amount of, water on Earth remains the same, but,, the water available for use is very limited, and is decreasing with over usage., The demand for water is increasing, day-by-day. The number of people using, water is increasing with rising, population. In many cities, long queues, for collection of water are a common site, (Fig. 14.12). Also, more and more water, is being used for producing food and by, the industries. These factors are leading, , WATER, , Fig. 14.12 A queue for collecting water, 143, , 2018-19

Page 154 :
to shortage of water in many parts of, the world. Hence, it is very important, that water is used carefully. We should, take care not to waste water., , 14.8 RAINWATER HARVESTING, One way of increasing the availability, of water is to collect rainwater and store, it for later use. Collecting rainwater in, this way is called rainwater harvesting., The basic idea behind rainwater, harvesting is “Catch water where it falls”., What happens to the rainwater that, falls in places that are mostly covered, with concrete roads and buildings? It, flows into the drains, isn't it? From there, water goes to rivers or lakes, which could, be far away. A lot of effort will then be, required to get this water back into our, homes as the water did not seep into, the ground., Here two techniques of rainwater, harvesting are discussed, 1. Rooftop rainwater harvesting: In this, system the rainwater is collected from, , Fig. 14.13 Rooftop rainwater harvesting, , the rooftop to a storage tank, through, pipes. This water may contain soil, from the roof and need filtering, before it is used. Instead of collecting, rainwater in the tank, the pipes, can go directly into a pit in the, ground. This then seeps into the, soil to recharge or refill the ground, water (Fig. 14.13)., 2. Another option is to allow water, to go into the ground directly, from the roadside drains that, collect rainwater., , Clouds, , Hail, , Condensation, , Ocean, , Drought, , Rainwater harvesting, , Evaporation, , Snow, , Flood, , Water vapour, , Ground water, , Water cycle, SCIENCE, , 144, , 2018-19

Page 155 :
1., , n, , Water is essential for life., , n, , Water vapour gets added to air by evaporation and transpiration., , n, , The water vapour in the air condenses to form tiny droplets of water, which, appear as clouds. Many tiny water droplets come together and fall down as, rain, snow or hail., , n, , Rain, hail and snow replenish water in rivers, lakes, ponds, wells and soil., , n, , The circulation of water between ocean and land is known as the, water cycle., , n, , Excessive rains may cause floods while lack of it for long periods may, cause droughts., , n, , The amount of usable water on earth is limited so it needs to be used, carefully., , Fill up the blanks in the following:, (a) The process of changing of water into its vapour is called _________________., (b) The process of changing water vapour into water is called _________________., (c) No rainfall for a year or more may lead to _________________ in that region., (d) Excessive rains may cause _________________., , 2., , State for each of the following whether it is due to evaporation or condensation:, (a) Water drops appear on the outer surface of a glass containing cold water., (b) Steam rising from wet clothes while they are ironed., (c) Fog appearing on a cold winter morning., (d) Blackboard dries up after wiping it., (e) Steam rising from a hot girdle when water is sprinkled on it., , 3., , Which of the following statements are “true” ?, (a) Water vapour is present in air only during the monsoon. (, , ), , (b) Water evaporates into air from oceans, rivers and lakes but not from the, soil.( ), (c) The process of water changing into its vapour, is called evaporation.(, (d) The evaporation of water takes place only in sunlight.(, , ), , ), , (e) Water vapour condenses to form tiny droplets of water in the upper layers of, air where it is cooler.( ), , WATER, , 145, , 2018-19

Page 156 :
4., , Suppose you want to dry your school uniform quickly. Would spreading it near, an anghiti or heater help? If yes, how?, , 5., , Take out a cooled bottle of water from refrigerator and keep it on a table. After, some time you notice a droplets of water around it. Why?, , 6., , To clean their spectacles, people often breathe out on glasses to make them, wet. Explain why the glasses become wet., , 7., , How are clouds formed?, , 8., , When does a drought occur?, , SUGGESTED PROJECTS AND ACTIVITIES, 1., , List three activities in which you can save water. For each activity describe, how you would do it., , 2., , Collect pictures relating to floods or droughts from old magazines or, newspapers. Paste them in your notebook and write about the problems that, people would have faced., , 3., , Prepare a poster on ways of saving water and display it on your school notice, board., , 4., , Write a few slogans of your own on the topic ‘Save Water’., , 5., , Can the interlinking of rivers be a solution for mitigation of flood? Discuss., , SCIENCE, , 146, , 2018-19

Page 157 :
15, , Air Around us, , W, , e have learnt in Chapter 9 that, all living things require air., But, have you ever seen air?, You might not have seen air, but, surely, you must have felt its presence in so, many ways. You notice it when the, leaves of the trees rustle or the clothes, hanging on a clothes-line sway. Pages, of an open book begin fluttering, when the fan is switched on. The moving, air makes it possible for you to fly your, kite. Do you remember Activity 3 in, Chapter 5 in which you separated the, sand and sawdust by winnowing?, Winnowing is more effective in moving, air. You may have noticed that during, storms the wind blows at a very high, speed. It may even uproot trees and blow, off the rooftops., Have you ever played with a firki, (Fig. 15.1)?, , Fig. 15.2 Making a simple firki, , Move it a little, back and, forth. Observe, what happens., Does the firki rotate? What makes a firki, rotate — moving air, isn’t it?, Have you seen a weather cock, (Fig. 15.3)? It shows the direction in, which the air is moving at that place., , Fig. 15.3 A weather cock, , 15.1 IS AIR PRESENT EVERYWHERE, AROUND US?, Close your fist — what do you have in, it? Nothing? Try the following activity, to find out., , Fig. 15.1 Different types of firki, , Activity 1, , Activity 2, , Let us make a firki of our own, following, the instructions shown in Fig. 15.2., Hold the stick of the firki and place it, in different directions in an open area., , Take an empty open bottle. Is it really, empty or does it have something inside?, Turn it, upside down. Is something, inside it, now?, , 2018-19

Page 158 :
Fig. 15.4 Experiments with an empty bottle, , Now, dip the open mouth of the bottle, into the bucket filled with water as, shown in Fig. 15.4. Observe the bottle., Does water enter the bottle? Now tilt the, bottle slightly. Does the water now enter, the bottle? Do you see bubbles coming, out of the bottle or hear any bubbly, sound? Can you now guess what was, in the bottle?, Yes! You are right. It is “air”, that was, present in the bottle. The bottle was not, empty at all. In fact, it was filled, completely with air even when you, turned it upside down. That is why you, notice that water does not enter the, bottle when it is pushed in an inverted, position, as there was no space for air, to escape. When the bottle was tilted,, the air was able to come out in the form, of bubbles, and water filled up the empty, space that the air has occupied., This activity shows that air occupies, space. It fills all the space in the bottle., It is present everywhere around us. Air, has no colour and one can see through, it. It is transparent., Our earth is surrounded by a thin, layer of air. This layer extends up to, many kilometres above the surface of, the earth and is called atmosphere. As, we move higher in the atmosphere, the, air gets rarer., , Fig. 15.5 Mountaineers carry oxygen cylinders, with them, , Now can you think, mountaineers, carry oxygen cylinders with them, while, climbing high mountains (Fig. 15.5)?, , 15.2 WHAT, , IS, , AIR MADE, , UP OF?, , Until the eighteenth century, people, thought that air was just one substance., Experiments have proved that it is really, not so. Air is a mixture of many gases., What kind of a mixture is it? Let us find, out about some of the major, components of this mixture, one by one., , Water vapour, We have learnt earlier that air contains, water vapour. We also saw that, when, air comes in contact with a cool surface,, it condenses and drops of water appear, on the cooled surfaces. The presence of, water vapour in air is important for the, water cycle in nature., , Oxygen, Activity 3, In the presence of your teacher, fix two, small candles of the same length on a, SCIENCE, , 148, , 2018-19

Page 159 :
the candle blew out? This indicates the, presence of some component in the air,, which does not support burning. The, major part of air (which does not, support burning candle) is nitrogen., , Glass tumbler, , Carbon dioxide, , Candle, Fig. 15.6 Air has oxygen, , Fig. 15.6 Air has oxygen, , table. Light both the candles. Cover one, of the candles with an inverted glass, tumbler. Observe both the candles, carefully., Do both the candles continue to burn, or go off?, You must have observed that the, candle covered with glass tumbler got, extinguished after some time, whereas, the other candle continued burning., What can be the reason for this?, Think about it., It seems that the candle got, extinguished because the component, inside of the glass tumbler, which, supports burning, is limited. Most of the, component is used up by the burning, candles. However, the other candle is, getting continued supply of air. This, component of air, which supports, burning, is known as oxygen., , Nitrogen, In Activity 3 did you observe that air is, still present in the glass bottle even after, , In a closed room, if there is some, material that is burning, you may, have felt suffocation. This is due to, excess of carbon dioxide that may be, accumulating in the room, as the, burning continues. Carbon dioxide, makes up a small component of the air, around us. Plants and animals consume, oxygen for respiration and produce, carbon dioxide. Plant and animal matter, also consumes oxygen on burning and, produces mainly carbon dioxide and a, few other gases. It is advisable not to, burn dry leaves and discarded remains, of the crop, which pollute our, surroundings., , Dust and smoke, The burning of fuel also produces, smoke. Smoke contains a few gases and, fine dust particles and is often harmful., That is why you see long chimneys in, factories. This takes the harmful smoke, and gases away from our noses, but,, brings it closer to the birds flying up in, the sky!, Dust particles are always present, in air., , Activity 4, Find a sunny room in your school/, home. Close all the doors and windows, with curtains pulled down to make the, , AIR AROUND US, , 149, , 2018-19

Page 160 :
Fig. 15.7 Observing presence of dust in air with, sunlight, , Fig.15.8 Policemen regulating traffic at a crowded, crossing often wear a mask, , room dark. Now, open the door or a, window facing the sun, just a little, in, such a way that it allows sunlight to, enter the room only through a slit., Look carefully at the incoming beam, of sunlight., Do you see some tiny shining, particles moving in the beam of sunlight, (Fig. 15.7)? What are these particles?, During winters you might have, observed similar beam of sunlight filter, through the trees in which dust particles, appear to dance merrily around!, This shows that air also contains, dust particles. The presence of dust, particles in air varies from time to time,, and from place to place., We inhale air when we breathe, through our nostrils. Fine hair and, mucus are present inside the nose to, , prevent dust particles from getting into, the respiratory system., Do you recall being scolded by your, parents when you breathe through your, mouth? If you do that, harmful dust, particles may enter your body., We may conclude, then, that air, contains some gases, water vapour and, dust particles. The gases in air are, mainly nitrogen, oxygen, small amount, of carbon dioxide, and many other, gases. However, there may be some, , Paheli wants to know, why, the transparent glass of, windows, if not wiped off, regularly, appears hazy?, Boojho wants to know, why, during an incident of, fire, one is advised to, wrap a woollen blanket, over a burning object., , Boojho is asking you, why, do you think, the policeman, in Fig. 15.8 is wearing a, mask?, , SCIENCE, , 150, , 2018-19

Page 161 :
carbon dioxide,, water vapour, and other gases, , oxygen, Nitrogen, , Fig.15.9 Composition of air, , variations in the composition of air from, place to place. We see that air contains, mostly nitrogen and oxygen. In fact,, these two gases together make up 99%, of the air. The r emaining 1% is, constituted by carbon dioxide and a few, other gases and water vapour (Fig. 15.9)., , 15.3 H OW DOES O XYGEN B ECOME, AVAILABLE TO ANIMALS AND PLANTS, LIVING IN WATER AND SOIL?, Activity 5, Take some water in a glass or metal, container. Heat it slowly on a tripod, stand. Well before the water begins to, boil, look carefully at the inner surface, , Fig. 15.10 Water contains air, , Here is a question from Paheli, “Will, the tiny air bubbles seen before the, water actually boils, also appear if, we do this activity by reheating, boiled water kept in an air tight, bottle?” If you do not know, the answer you may try doing, it and see for yourself., , of the container. Do you see tiny bubbles, on the inside (Fig. 15.10)?, These bubbles come from the air, dissolved in water. When you heat the, water, to begin with, the air dissolved in, it escapes. As you continue heating, the, water itself turns into vapour and finally, begins to boil. We learnt in Chapters 8, and 9, that the animals living in water, use the dissolved oxygen in water., The organisms that live in soil also, need oxygen to respire, isn’t it? How do, they get the air they need, for, respiration?, , Activity 6, Take a lump of dry soil in a beaker or a, glass. Add water to it and note what, happens (Fig. 15.11). Do you see, bubbles coming out from soil? These, bubbles indicate the presence of air in, the soil., When the water is poured on the, lump of soil, it displaces the air which, is seen in the form of bubbles. The, organisms that live inside the soil and, the plant roots respire in this air. A lot, , AIR AROUND US, , 151, , 2018-19

Page 162 :
Fig. 15.11 Soil has air in it, , and carbon dioxide in the atmosphere, is maintained through respiration in, plants and animals and by the, photosynthesis in plants. This shows, the interdependence of plants and, animals., We can now appreciate, how important, air is for life on earth. Are there any other, uses of air? Have you heard about a, windmill? Look at Fig. 15.12., , of burrows and holes are formed in deep, soil by the animals living in the soil., These burrows also make spaces, available for air to move in and out of, the soil. However, when it rains heavily,, water fills up all the spaces occupied by, the air in the soil. In this situation,, animals living in the soil have to come, out for respiration. Could this be the, reason why earthworms come out of the, soil, only during heavy rains?, Have you ever wondered why all the, oxygen of atmosphere does not get used, up though a large number of organisms, are consuming it? Who is refilling the, oxygen in the atmosphere?, , Fig. 15.12 A windmill, , 15.4 HOW IS THE OXYGEN IN THE, ATMOSPHERE REPLACED?, In Chapter 7, we read about, photosynthesis. In this process, plants, make their own food and oxygen is, produced along with it. Plants also, consume oxygen for respiration, but, they produce more of it than they, consume. That is why we say plants, produce oxygen., It is obvious that animals cannot live, without plants. The balance of oxygen, , The wind makes the windmill, rotate. The windmill is used to draw, water from tubewells and to run flour, mills. Windmills are also used to, generate electricity. Air helps in the, movements of sailing yachts, gliders,, parachutes and aeroplanes. Birds,, bats and insects can fly due to the, presence of air. Air also helps in the, dispersal of seeds and pollen of, flowers of several plants. Air plays an, important role in water cycle., SCIENCE, , 152, , 2018-19

Page 163 :
Atmosphere, Carbon dioxide, Composition of air, Oxygen, Nitrogen, Smoke, Windmill, , n, , Air is found everywhere. We cannot see air, but we can feel it., , n, , Air in motion is called wind., , n, , Air occupies space., , n, , Air is present in water and soil., , n, , Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour and a few, other gases. Some dust particles may also be present in it., , n, , Oxygen supports burning and is necessary for living organisms., , n, , The envelope of air that surrounds the earth is known as atmosphere., , n, , Atmosphere is essential for life on earth., , n, , Aquatic animals use dissolved air in water for respiration., , n, , Plants and animals depend on each other for exchange of oxygen and carbon, dioxide from air., , 1., , What is the composition of air?, , 2., , Which gas in the atmosphere is essential for respiration?, , 3., , How will you prove that air supports burning?, , 4., , How will you show that air is dissolved in water?, , 5., , Why does a lump of cotton wool shrink in water?, , AIR AROUND US, , 153, , 2018-19

Page 164 :
6., , The layer of air around the earth is known as ___________., , 7., , The component of air used by green plants to make their food, is ___________., , 8., , List five activities that are possible due to the presence of air., , 9., , How do plants and animals help each other in the exchange of gases in the, atmosphere?, , SUGGESTED PROJECTS AND ACTIVITIES, 1., , On a clear glass window facing towards an open area, fix a small rectangular, strip of paper. Remove the strip after a few days. Do you notice a difference, between the rectangular section that was left covered with paper and the, rest of the glass window? By repeating this exercise every month, you can, have an idea about the amount of dust present in air around you at different, times of the year., , 2., , Observe the leaves of trees, shrubs or bushes planted by the roadside. Note, whether their leaves have some dust or soot deposited over them. Take similar, observations with the leaves of trees in the school compound or in a garden., Is there any difference in deposition of soot on leaves of trees near the roadside?, What could be the possible reasons for this difference? Take a map of your, city or town and try to identify regions in the map where you have noticed, very thick layer of soot on the plants by the roadside. Compare with results, obtained by other classmates and mark these areas on the map. Perhaps, the results from all the students could be summarised and reported in, newspapers., , SCIENCE, , 154, , 2018-19

Page 165 :
16, , Garbage in, Garbage out, , W, , e throw out so much rubbish, or garbage everyday from our, homes, schools, shops and, offices. The grains, pulses, biscuits, milk, or oil purchased in shops, are packed, in plastic bags or tins. All these, wrapping material go out as garbage., We sometimes buy things that are, rarely used and often thrown into, the garbage., We generate so much garbage in our, day-to-day activities! We often throw, groundnut shells on public places, in, buses or trains, after eating the nuts., We throw away the ticket when we get, off a bus. A child might go on, sharpening pencils just for fun. If we, make mistakes or spill ink on our, notebook, we tear off the sheet and, throw it away. And we also throw away, many domestic wastes such as broken, toys, old clothes, shoes and slippers., What if the garbage is not removed, from our homes and surroundings? How, do you think, this will harm us? When, safai karamcharis take the garbage from, the bins, where does the garbage go and, what happens to it? Is it possible for all, of this garbage to be changed into, something that will not harm us? Can, we contribute towards this in any way?, We will look for answers to these, questions, in this chapter., , A Step towards Cleanliness, , The Prime Minister of India launched, the Swachh Bharat Mission (SBM)., The aim of this mission is to create, an open defecation-free India by, 2 October 2019., Children from Paheli and Boojho’s, school did a project called ‘Dealing with, Garbage’. We will learn about some of, the things they learnt through this, project., , 16.1 DEALING, , WITH, , GARBAGE, , Safai karamcharis collect the garbage in, trucks and take it to a low lying open, area, called a landfill (Fig. 16.1)., There the part of the garbage that, can be reused is separated out from the, one that cannot be used as such. Thus,, , 2018-19, , Fig. 16.1 A landfill

Page 166 :
the garbage has both useful and nonuseful components. The non-useful, component is separated out. It is then, spread over the landfill and then, covered with a layer of soil. Once the, landfill is completely full, it is usually, converted into a park or a play ground., For the next 20 years or so, no building, is constructed on it. To deal with, some of the useful components of, garbage, compost making areas are, developed near the landfill. What is, compost? Let us learn about it, from the, following activity., , Paheli did wonder as to what, could be useful garbage? Why, was it thrown away in the first, place? Is there some garbage that, is not actually garbage?, , Activity 1, Collect the garbage from your house, before it is thrown into the dustbin., Separate it into two groups, so that, they have:, Group 1: Garbage from the kitchen —, like fruit and vegetable peels, egg shells,, waste food, tea leaves. Include, newspapers, dry leaves and paper bags, in this group., Group 2: Pieces of cloth, polythene, bags, broken glass, aluminium wrappers,, nails, old shoes and broken toys., Now divide the contents of each group, into two separate heaps. Label them, , Fig. 16.2 Putting garbage heaps in pits, , as A, B, C and D. Put one heap from, Group 1 and one heap from Group 2, into two separate plastic bags. Tie the, mouth of these two bags tightly. Put all, the four heaps in separate pits and, cover them with soil (Fig. 16.2). You, can also use four pots to bury these, garbage heaps., Remove the soil after four days and, observe the changes in the garbage. A, black colour and no foul smell indicates, that rotting of garbage is complete. Put, the heaps again in the pits and cover, with the soil. Observe again after every, two days and note your observations as, suggested. Did the garbage., (i) rot completely and not smell?, (ii) rot only partially?, (iii) rot almost completely, but still, smells bad?, (iv) not change at all?, Garbage in which heap was seen to, rot and which did not?, Enter options (i), (ii), (iii) or (iv) in, the columns of Table 16.1 based on your, , 156, , SCIENCE, , 2018-19

Page 167 :
Table 16.1 What has happened to, the garbage heaps?, Garbage, heap, , After 4, days, , After 6, days, , After 2, weeks, , A, B, C, D, , observations. If you make any other, observations, do not forget to write all, these down in your notebook. Do not, remove and burn the garbage that did, not rot., If the garbage was found to rot, completely and did not smell, mix it in, the soil where you sow your favourite, plants. This would provide nutrients to, the plants., You must have observed from this, activity that some things in the garbage, rot. They form manure which is used, for the plants. The rotting and, conversion of some materials into, manure is called ‘composting’., In some cities and towns,, municipalities provide separate dustbins, for collecting two kinds of garbage., Usually one is coloured blue and the, other green. The blue bin is for materials, that can be used again — such as, plastics, metals and glass. Did you, notice that these are the materials that, do not rot in the garbage heaps? The, green bins are for collecting kitchen and, other plant or animal wastes. You may, have noticed that this type of wastes rot, completely when buried in the soil. Do, , you see why it is necessary for, us to separate waste into two, groups as we did in Activity 1,, After 4, before we throw it?, weeks, Have you noticed garbage, heaps of dried leaves on the, roadside? Most of the time, these are burnt (Fig. 16.3)., Farmers too often burn the, husk, dried leaves and part of, crop plants in their fields after, harvesting. Burning of these, produces, smoke and gases that are harmful to, our health. We should try to stop such, practices. These wastes could be, converted into useful compost., , Fig. 16.3 Burning of leaves produce harmful, gases, , Here are some of the observations, and thoughts, noted by Paheli and, Boojho, from their project “Dealing, with Garbage”., , GARBAGE IN, GARBAGE OUT, , Boojho noted in his notebook: Do, not burn leaves! You will not be, able to tolerate the fumes!, , 157, , 2018-19

Page 168 :
Paheli made a note in her, notebook: Why has the, government not made, burning of leaves a theft?, Not theft really ☺. She must have, meant “illegal”. She wanted that the, government should make a law against, the burning of leaves and other plant, wastes anywhere in India., , 16.2 VERMICOMPOSTING, We can be friends of plants by supplying, them with compost. We will also be very, good friends to ourselves by making, compost., Talking of friends, do you know that, earthworms are called farmer’s friend?, Let us find out how a type of earthworm, called redworm is used for composting., This method of preparing compost, with the help of redworms is called, vermicomposting. We can try to make, manure by vermicomposting at school., , vegetable wastes including peels of fruits, over this layer of sand., One can also use green leaves, pieces, of dried stalks of plants, husk or pieces, of newspaper or carboard to spread over, the layer of sand. However, shiny or, plastic coated paper should not be used, for this purpose. Dried animal dung, could also be used as a spread over sand, or wire mesh., Sprinkle some water to make this, layer wet. Take care not to use excess of, water. Do not press the layer of waste., Keep this layer loose so that it has, sufficient air and moisture., Now, your pit is ready to welcome the, redworms. Buy some redworms and put, them in your pit (Fig. 16.4). Cover them, loosely with a gunny bag or an old sheet, of cloth or a layer of grass., , Activity 2, Let us dig a pit (about 30 cm deep) or, keep a wooden box at a place, which is, neither too hot nor too cold. What about, a place which does not get direct, sunlight? Let us now make a, comfortable home for our redworms in, the pit or the box., Spread a net or chicken mesh at the, bottom of the pit or the box. You can, also spread 1 or 2 cm thick layer of sand, as an alternative. Now, spread some, , Fig. 16.4 Redworms, , Your redworms need food. You can give, them vegetable and fruit wastes, coffee, and tea remains and weeds from the, fields or garden (Fig. 16.5). It might be, a good idea to bury this food about, 2-3 cm inside the pit. Do not use wastes, , 158, , SCIENCE, , 2018-19

Page 169 :
Fig. 16.5 Food for redworms, , that may contain salt, pickles, oil,, vinegar, meat and milk preparations as, food for your redworms. If you put these, things in the pit, disease-causing small, organisms start growing in the pit. Once, in a few days, gently mix and move the, top layers of your pit., Redworms do not have teeth. They, have a structure called ‘gizzard’, which, helps them in grinding their food., Powdered egg shells or sea shells could, be mixed with the wastes. This would, help redworms in grinding their food. A, redworm can eat food equal to its own, weight, in a day., Redworms do not survive in very hot, or very cold surroundings. They also, need moisture around them. If you take, good care of your worms, in a month’s, time their number will double., Observe the contents of the pit, carefully after 3-4 weeks. Do you now, see loose, soil-like material in the pit?, Your vermicompost is ready (Fig. 16.6)., Put some wastes as food in one corner, of the pit. Most of the worms will shift, , Fig. 16.6 Vermicomposting, , towards this part of the pit, vacating the, other part. Remove the compost from, the vacated part and dry it in the sun, for a few hours. Your vermicompost is, ready for use!, The part left in the pit has most of, the worms in it. You can use these for, preparing more compost or share them, with another user., Use this excellent vermicompost in, your pots, gardens or fields. Is this not, like getting the ‘best out of waste’? Those, of you who have agricultural fields can, try vermicomposting in large pits. You, can save a lot of money that is spent on, buying expensive chemical fertilizers, and manure from the market., , 16.3 THINK, , AND, , THROW, , How much of garbage do you think, is, thrown out by each house everyday? You, can make an estimate by using a bucket, as a measure. Use a 5-10 litre bucket to, collect the garbage from your home for, , GARBAGE IN, GARBAGE OUT, , 159, , 2018-19

Page 170 :
Fig. 16.7 Neighbourhood garbage dump, , a few days. In how many days does the, bucket become full? You know the, number of members in your family. If, you find out the population of your city, or town, can you now estimate the, number of buckets of garbage that may, be generated in a day in your city or, town? We are generating mountains of, garbage everyday, isn’t it (Fig. 16.7)?, Let us read a story about a village, where there is less garbage and more, wisdom. Nanu studies in Class VI. He is, very fond of making paper planes. His, mother is very annoyed when he tears, off sheets from new notebooks to make, aeroplanes, but Nanu does not care., Once Nanu went to his aunt’s village,, along with his mother. He was amazed, at the variety of things his cousin Shyam, had made. Files from old charts,, greeting cards decorated with flowers, made from pencil shavings, mats from, old clothes, baskets from used old, polythene bags were some of the items, Nanu liked. Shyam had even made a, diary from invitation cards!, , One morning Nanu went looking for, his grandmother (Nani). He saw that she, was applying a thick paste on a basket., Nanu asked, “Nani, What are you doing?, What is this paste?”, “This is papier-mâchè, a paste made, of clay and paper in which I have also, mixed some rice husk”, replied Nani., “But, why are you putting it on the, basket?”, asked Nanu., “To make it stronger”, said Nani and, added “would you like to learn this from, me?” Nanu was not very keen and ran, outside to play. He was only interested, in tearing up papers to make planes. In, fact he also started tearing up papers, from Shyam’s files!, Shyam collected all the pieces of, paper Nanu had used, wondering what, to do about him! He just did not listen, to anyone!, It was Nanu’s birthday in a few days., Shyam planned to invite Nanu’s friends., Nanu took out money from his mud pot, and went to the market. He bought some, paper hats for his friends. He asked the, shopkeeper for a polythene bag to keep, the hats, who gave him a paper bag, instead of polythene. Nanu also bought, many other items like biscuits and, toffees. He found it difficult to carry all, of these things as no shopkeeper was, ready to give a polythene bag. Shyam, had told him to carry a cloth bag with, him and he was sorry he did not listen, to him. Somehow, he managed to reach, home with all his purchases (Fig. 16.8)., Nanu’s friends enjoyed the feast on, his birthday and played many games., , 160, , SCIENCE, , 2018-19

Page 171 :
Fig. 16.8 Nanu with bags full of purchases, , All his friends wore the shiny paper hats, Nanu had bought!, Shyam had made beautiful papiermâchè masks for Nanu’s friends. He had, a special gift for Nanu as well. A, photoframe and a greeting card made, from the paste of all the pieces of paper, Nanu had thrown away! It was a new, experience for Nanu. All his friends went, home with their masks. Nanu was too, excited to finish his meal and look at, his gifts., Nanu returned home, after his, holidays were over. How different his, town was from Shyam’s village! There, were no rag pickers in the village as it, was neat and clean. But now he stopped, making faces when he saw the rag, picking children near his house., You might have seen some children,, sorting the garbage near your house or, at other places. Observe the children at, work and find out how they separate, useful material from the garbage. They, are actually helping us., , Talk to one such child and find out:, What do they do with the rubbish, they collect? Where do they take it?, Does he/she go to school? What, about his/her friends?, If they do not go to school, find out, the possible reasons., Can you help this child to read and, write?, Have you ever helped at home to sell, old newspapers, glass and metal, things, plastic bags and your old, notebooks to a garbage dealer? Talk to, him and find out what he does with all, the garbage., Would you like to make paper from, old and discarded paper like Shyam?, Let us learn to do this., , 16.4 RECYCLING, , OF, , PAPER, , You will require pieces of old newspapers,, magazines, used envelopes, notebooks,, or any other paper. Do not use shiny,, plastic coated paper. You will also need, a frame fitted with a wire mesh or a net., You can also use a large sized sieve in, place of a frame., Tear the paper into small pieces. Put, them in a tub or a bucket and pour water, in it. Let the pieces of paper remain, submerged in water for a day. Make a, thick paste of paper by pounding it., Now, spread the wet paste on the wire, mesh fixed to the frame. Pat it gently to, make the thickness of layer of the paste, as uniform as possible. Wait till water, drains off. If required spread an old cloth, or a sheet of newspaper on the paste to, let it soak up the extra water., , GARBAGE IN, GARBAGE OUT, , 161, , 2018-19

Page 172 :
Now, carefully remove the layer of, paste from the frame, spread it on a sheet, of newspaper in the sun. Keep the, corners of the newspaper sheet pressed, by putting some weights so that these, do not curl up., You can add food colour, pieces of, dry leaves or flower petals or pieces of, coloured paper in the paste before, spreading it. It would help you to get a, recycled paper with beautiful patterns, on it., Can we recycle everything, just as we, recycle paper?, , 16.5 PLASTICS – BOON, , OR A, , CURSE?, , Some kind of plastics can be recycled,, but, not all of them. Did you notice, that polythene bags and some plastics, did not rot in Activity 1? You might now, easily understand why polythene bags, create a big problem in garbage disposal., It may be a little difficult to imagine, our life without plastics. Shall we list a, few things we use that are made of, plastics? Toys, shoes, bags, pens,, combs, tooth brushes, buckets, bottles,, and water pipes — the list is very long., Can you name a few parts of a bus, car,, radio, television, refrigerator and a, scooter that are made of plastics?, The use of plastics in itself might not, create so much of a problem. Problems, arise when we use plastics excessively, and are ignorant about ways of, disposing their waste. This is what is, happening all around us! We might even, be acting irresponsibly, knowing well, about its harmful effects., , We often use plastic bags to store, cooked food items. Sometimes these bags, may not be suitable for keeping eatables., Consuming food packed in such plastic, bags could be harmful to our health., Many a time shopkeepers use plastic, bags that have been used earlier for, some other purpose. Sometimes bags, collected by rag pickers are also used, after washing them. Use of such recycled, plastic bags to keep food items could be, harmful for our health. For storing, eatables we must insist on use of plastic, bags that are approved for such a use., All kind of plastics give out harmful, gases, upon heating or burning. These, gases may cause many health problems,, including cancer, in humans. The, government has also laid down, guidelines for recycling of plastics., , Paheli would like to suggest that, containers used for storing, poisonous substances should, be recycled separately and that, such recycled plastics, are not used to make, plastic bags., You must have noticed that people, often fill garbage in plastic bags and, then throw it away. When stray animals, look for food in these bags, they end up, swallowing these. Sometimes, they die, due to this., The plastic bags thrown away, carelessly on roads and other places get, into drains and the sewer system. As a, , 162, , SCIENCE, , 2018-19

Page 173 :
result, drains get choked and the water, spills on the roads. During heavy rains,, it might even create a flood like situation., There is a lot of harm that too much use, of plastics can do!, What can we do to minimise over use, of plastics and deal with garbage?, 1. We make a minimum use of plastic, bags. We re-use the bags whenever it, is possible to do so without any, adverse affects., 2. We insist shopkeepers use paper, bags. We carry a cloth or a jute bag, when we go out for shopping., 3. We do not use plastic bags to store, eatables., 4. We do not throw plastic bags here, and there, after use., 5. We never burn plastic bags and other, plastic items., , 6. We do not put garbage in plastic bags, and throw it away., 7. We use vermicomposting at home and, deal with our kitchen waste usefully., 8. We recycle paper., 9. We use both sides of the paper to, write. We use a slate for rough work., We use blank sheets of paper left in, our notebooks for rough work., 10.We make our family, friends and, others to follow proper practices for, disposing different kinds of wastes., Think about some more ways to, minimise overuse of plastics and, discuss., The most important point to know, and think about is that — more garbage, we generate, more difficult it will be to, get rid of it., , Waste, Let us refuse, plastic., , Garbage, Landfill, Compost, Ver micomposting, Recycling, , n, , Landfill is an area where the garbage collected from a city or town is, dumped. The area is later converted into a park., , n, , Converting plant and animal waste including that from kitchen, into, manure, is called composting., , GARBAGE IN, GARBAGE OUT, , 163, , 2018-19

Page 174 :
1., , n, , The method of making compost from kitchen garbage using redworms is, called vermicomposting., , n, , Paper can be recycled to get useful products., , n, , Plastics cannot be converted into less harmful substances by the process, of composting., , n, , We need to generate less waste and find ways of dealing with the increasing, amount of garbage in our surroundings., , (a) Which kind of garbage is not converted into compost by the redworms?, (b) Have you seen any other organism besides redworms, in your pit? If yes, try, to find out their names. Draw pictures of these., , 2., , Discuss :, (a) Is garbage disposal the responsibility only of the government?, (b) Is it possible to reduce the problems relating to disposal of garbage?, , 3., , (a) What do you do with the left over food at home?, (b) If you and your friends are given the choice of eating in a plastic plate or a, banana leaf platter at a party, which one would you prefer and why?, , 4., , (a) Collect pieces of different kinds of paper. Find out which of these can be, recycled., (b) With the help of a lens look at the pieces of paper you collected for the above, question. Do you see any difference in the material of recycled paper and a, new sheet of paper ?, , 5., , (a) Collect different kinds of packaging material. What was the purpose for which, each one was used? Discuss in groups., (b) Give an example in which packaging could have been reduced?, (c) Write a story on how packaging increases the amount of garbage., , 6., , Do you think it is better to use compost instead of chemical fertilisers? Why?, , ACTIVITIES FOR DEALING WITH GARBAGE, 1., , Collect old and discarded objects and material like glass bottles, plastic bottles,, coconut husk, wool, bed sheets, greeting cards and any other thing. Can you, make something useful out of these, instead of throwing them? Try., , 2., , Prepare a detailed project report on compost making activity you did in school., , 164, , SCIENCE, , 2018-19

Page 175 :
A MATTER OF CONCERN!, In autumn lots of leaves are burnt in cities like Delhi. Some of the gases produced, by burning leaves are similar to the gases released by the vehicles moving on, the roads., Instead of burning, if we make compost from these leaves, we can reduce the, use of chemical fertilizers., The green areas which should have fresh air, actually become full of harmful, gases due to burning of leaves., If you find any one is burning the leaves bring it to notice of municipal authorities, or write to newspapers about it., Generate social pressure against burning of leaves. Ensure that fallen leaves, are not burnt but used for making compost., Write to the ‘Tree Authority’ of your city or state to declare burning of leaves as, an offence., , GARBAGE IN, GARBAGE OUT, , 165, , 2018-19

Page 176 :
2018-19