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CONTENT, S. No., , Chapter Name, , Pg. No., , 1., , Matter in Our Surrounding, , 1-8, , 2., , Is Matter Around us Pure ?, , 9 - 20, , 3., , Atoms and Molecules, , 21 - 33, , 4., , Structure of the Atom, , 34 - 43, , 5., , The Fundamental Unit of Life, , 44 - 57, , 6., , Tissue, , 58 - 77, , 7., , Diversity in Living Organism, , 78 - 97, , 8., , Motion, , 98 - 113, , 9., , Force and Laws of Motion, , 114 - 127, , 10., , Gravitation, , 128 - 140, , 11., , Work and Energy, , 141 - 154, , 12., , Sound, , 155 - 170, , 13., , Why do we Fall Ill?, , 171 - 180, , 14., , Natural Resources, , 181 - 192, , 15., , Improvement in Food Resources, , 193 - 205, , 16., , Experiment, , 206 - 272, , 17., , Paper, , 273 - 290, iv
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CHAPTER AT A GLANCE, , Matter In Our Surrounding, , 1
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When we dissolve salt in water, the particles, of salt get into the spaces between particles, of water., Particles are varying and have spaces between them, , DEDQGFVKRZWKHPDJQL¿HGVFKHPDWLFSLFWXUHV, of the three states of matter. The motion of the, particles can be seen and compared in the three states of matter., Dig. Three states of matter, , Matter, The matter is the material of which everything in this universe, in and, around us is made up of in different shapes. It is anything that occupies space and, has mass and offers resistance to any applied force., 3K\VLFDO1DWXUHRI3DUWLFOHV , Matter is made up of particles. The particles of matter are very-very, small., 2, , Science Class - IX
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&KDUDFWHULVWLFVRI3DUWLFOHV , (i), , Particles of matter are continuously moving i.e., they possess, kinetic energy. As the temperature rises, particles moves faster, because kinetic energy of the particles increases., , (ii), , Particles of matter have space between them. When we make, tea, coffee or lemonade (nimbu pani), particles of one type of, matter get into the space between particles of the other. This, shows that there is enough space between particles of matter., , (iii), , Particles of matter attract each other. When we open a water tap,, try to break the stream of water with your ngers, can we do, this ? No, because the stream of water remains together. Particles, of water are held together because of the force of attraction, between them., , •, , The space between the particles and kinetic energy of particles is, PLQLPXPLQVROLGVLQWHUPHGLDWHLQOLTXLGVDQGPD[LPXPLQJDVHV, , •, , The force of attraction between the particles is strongest in solids,, LQWHUPHGLDWHLQOLTXLGVDQGZHDNHVWLQJDVHV, , • 0RYHPHQW RI SDUWLFOHV LV PLQLPXP LQ VROLGV PRUH LQ OLTXLGV DQG, PD[LPXPLQJDVes., , Arrangement of particles in three states of matter, and their movements, , States of Matter, The physical states of a matter are : (i) Solid, (ii) Liquid, (iii) Gas., We can classify our body into three states of matter i.e.,, (i), Bones and teeth are solids., (ii), Blood and water present in our body are liquids., (iii), Air in our lungs is gaseous and also there is 70% of water is in our, body., Matter In Our Surrounding, , 3
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At 100º C, energy of water vapours is much more than the energy of, water at 100º C., So, we can change one state of matter to another state by changing, temperature., , •, , At 25ºC, water is liquid., At 0º C, water is solid (ice)., At 100º C, water is gaseous state (steam)., , (iii), Sublimation : The change of solid directly into vapours on heating, and of vapours into solid on cooling without passing through the intervening, liquid state is called sublimation., ([DPSOH When camphor or ammonium chloride is heated in a China, dish covered by a inverted funnel (with cotton plug in its upper open end), the, vapours of ammonium chloride are converted into solid ammonium chloride on, coming in contact with the cold inner walls of the funnel., , (B), , 6, , Sublimation of Ammonium Chloride, Effect of Change of Pressure :, If we compress a gas in a cylinder, the distance between the particles of, gas is reduced and nally gas is lique ed on lowering temperature., , Science Class - IX
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•, •, , •, , %\DSSO\LQJKLJKSUHVVXUHWKHSDUWLFOHVRIDJDVFDQEHEURXJKWFORVH, together., 6ROLG FDUERQ GLR[LGH GU\ LFH LV FKDQJHG LQWR FDUERQ GLR[LGH JDV, GLUHFWO\ZLWKRXWFKDQJLQJLQWROLTXLGZKHQSUHVVXUHLVUHGXFHGWRRQH, DWPRVSKHULFSUHVVXUH, 7KXV VWDWHV RI PDWWHU LH VROLG OLTXLG JDV DUH GHWHUPLQHG E\, WHPSHUDWXUH SUHVVXUH, , Evaporation : A surface phenomenon in which liquid changes into vapours at, any temperature below its boiling point is called evaporation. Particles on the, surface of a liquid have higher kinetic energy than others, so they break. The, forces of attraction between the particles & escape from the surface of liquid in, the form of vapours., Factors affecting evaporation : Rate of evaporation depends on :, (a), Exposed surface area : On increasing surface area of liquid, rate, of evaporation increases., (b), Increase in temperature : Increases kinetic energy of particles, hence rate of evaporation increases., (c), Humidity : When the humidity of air (degree of dampness of air), is low, evaporation rate is increased. More humidity, less, evaporation., (d), Wind : When wind speed increases, rate of evaporation also, increases., Evaporation always causes cooling : The cooling caused by evaporation is, based on the fact that when a liquid evaporates, it takes latent heat of vaporization, from surroundings which on losing heat get cooled., ([DPSOHV , (i), When we put acetone on our hand, it gets evapourized by taking, heat from our hand and our hand feels cool., (ii), We should wear cotton clothes in summer to keep cool and, comfortable as cotton is good absorber of water, so it absorbs the, sweat from our body and exposes it to air for evaporation of sweat, Matter In Our Surrounding, , 7
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(iii), , thus cools our body., Often people sprinkle water on ground during summer. This, water takes heat from ground and surrounding air to evaporate,, thus making the place cool., , QUESTIONS, 1., 2., 3., 4., 5., 6., , VERY SHORT QUESTIONS (1 Marks), Write different states of matter., Which has more density – liquid or solid ?, What is the melting point of ice ?, Boiling point of alcohol is 78º C. Change it into Kelvin scale ?, Why do gas exert pressure ?, How do we liquefy the gases ?, , 1., 2., 3., 4., 5., , SHORT QUESTIONS (2 Marks), Classify the matter on the basis of physical and chemical characteristics ?, Why solid carbon dioxide is called ‘dry ice’ ?, Why do we keep ether and acetone at cool places ?, Write two factors which will increase rate of evaporation ?, Which gas is supplied in the lique ed form at home and in hospitals ?, SHORT QUESTIONS (3 Marks), Compare the force of attraction between iron, rubber band and chalk ?, Arrange sugar, water and oxygen in the increasing order of force of, attraction between their particles ?, De ne boiling point, melting point and evaporation ?, , 1., 2., 3., , LONG QUESTIONS (5 Marks), Describe the factors affecting evaporation ?, (a) Why do we wear cotton clothes in summers ?, (b) Why do we feel cold, when we keep acetone and ether on our, palm ?, Write three characteristics of particles of matter. Give one example of, each ?, Write the characteristic responsible for :, (a) Smell of perfume spreads in the room., (b) Water takes the shape of the container in which it is kept., , 1., 2., , 3., 4., , 8, , Science Class - IX
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CHAPTER AT A GLANCE, , ‘Pure’ word means that there is no mixing in a substance. But, Is Matter Around Us Pure ?, , 9
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according to scienti c language all things are mixture of so, many substances, not of single one. That’s why they are not pure., E.g., Milk, water, fat, etc., • Pure substances means that all elements have same chemical properties., • A pure substance is made up of same kind of elements., Substance : A substance is a kind of matter that cannot be separated into other, kind of matter by any physical process. A pure substance is made up of same, kind of elements., What is a mixture ?, It is a substance in which two or more substances (element or compound) are, simply mixed together in any proportion. Examples : The air is a mixture of, oxygen, nitrogen, argon, carbon dioxide and water vapour., Types of Mixture : Mixture is of two types :, (i), Homogenous mixture, (ii), Heterogenous mixture, Homogenous Mixture : It has no visible boundaries of separation between the, various constituents, so they are called homogenous mixtures., Example : Sugar in water. It has a uniform composition throughout its, mass., Heterogenous Mixture : These types of mixtures has visible boundaries of, separation between the various constituents., Example : Mixture of sugar and sand. It does not have a uniform, composition throughout its mass., Solution : A solution is a homogenous mixture of two or more substances. E.g.,, Nimboo pani, soda water., Solution : A solution has a solvent and a solute as its components. The component, of the solution that dissolves the other component in it is called the solvent. The, component of the solution that is dissolved in the solvent is called the solute., , Solution, Solute, (Substance dissolved), E.g.,, , 10, , Sugar, , Solvent, (Substance in which dissolved), +, , Science Class - IX, , Water, , , , Sugar solution
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Types of Solution, True, 1. Size of solute, particles smallest., < 10-9 m., , Colloidal, 1. Size of solute particles bigger than, true but smaller than suspension. In, between 10-9 to 10-6 m., , Suspension, 1. Size of particles, biggest. > 10-6 m., , 2. Solute particles, can’t be seen with, naked eye., 3. Homogenous, mixture., , 2. Solute particles can’t be seen with, Naked eye., , 2. Can be seen, with naked eye., , 3. Seems homogenous but actually, heterogenous mixture., , 3. Heterogenous, mixture., , 4. Particles can’t, be separated by, filteration., , 4. Particles can’t be separated by, filteration., , 4. Can be, separated by, filteration., , 5. Transparent, , 5. Translucent, , 5. Opaque, , 6. Stable solutions 6. Stable solutions., – i.e., solute, particles do not, settle on keeping., , 6.Unstable, solution – solute, particles settle, upon keeping., , 7. Do not show, tyndall effect., , 7. Show tyndall effect., , 8. Solution diffuse, rapidly through, filter paper as, well as parchment, paper., 9. e.g., Sugar in, water., , 8. Colloid particles pass through, filter paper but not through, parchment paper., , 7. May or may, not show tyndall, effect., 8. Suspension, particles do not, pass through filter, paper as well as, parchment paper., 9. e.g., Sand/mud, in water., , 9. e.g., Milk, blood., Common examples of colloids :, , Dispersal Phase, (Solute), 1., 2., , Liquid, Solid, , Dispersion, Medium, (Solvent), Gas, Gas, , Type, , Example, , Aerosol, Aerosol, , Fog, cloud, Smoke, , Is Matter Around Us Pure ?, , 11
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3., , Gas, , Shaving, cream, Liquid, Liquid, Emulsion, Milk, face, cream,, emulsion paint, Solid, Liquid, Sol, Mud, digene, Gas, Solid, Foam, Foam, rubber,, sponge, Liquid, Solid, Gel, Jelly, cheese, Solid, Solid, Solid sol, Coloured, gemstones,, glass (milky,, coloured), • Gas in gas is not a colloidal solution – it is called a mixture., , 4., , 5., 6., 7., 8., , Liquid, , Foam, , Concentration of Solution, 1., , Mass by mass percentage, , =, , 2., , Mass by volume percentage, , =, , Methods of Separation of Mixtures, , (1), , Evaporation :, , Basic principle : Out of the two components of a mixture one can, evaporate [i.e., has less boiling point] and other has higher boiling point., Example : Mixture of dye [higher boiling point] and water. Out of water, and dye, water evaporates but dye is left behind in petri dish., , (2), , Centrifugation :, Basic principle : When mixture is rotated very fast, then denser particles, , 12, , Science Class - IX
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are forced at the bottom and lighter particles stay above., , Example : Separating cream from milk., Can you think what is toned and double toned milk ?, Applications :, (a), Used in diagnostic labs for blood and urine tests., (b), Used in dairies and home to separate butter from cream., (c), Used in washing machines dryers to squeeze out water from, clothes., Have you seen dust particles from our clothes settle at the bottom of, washing tub. Do you know why now ?, , (3), , Differential entraction :, , Basic principle : Two immiscible liquids (which do not dissolve in, each other) can be easily separated by putting in a differential entraction funnel/, separating funnel., Example : Water from oil can be separated by rst opening the stop cock, till water is removed in one beaker, then afterwards oil can be collected in a, separate beaker., , Is Matter Around Us Pure ?, , 13
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Applications :, (a), Separation of oil from water., (b), Extraction of iron from its ore. Lighter slag is removed from, above the molten iron., , (4), , Sublimation :, Basic principle : Out of the two components, one will sublime (directly, converts to gas from solid) and other will not., Example : NH4Cl (ammonium chloride) and NaCl common salt mixture can, be easily separated by heating so that NH4Cl sublimes but common salt, remains behind., , Applications :, (a), Camphor, naphthalene, anthracene, NH4Cl can sublime., , (5), , Chromatography :, Basic principle : Coloured components of a mixture can be separated by, using an Absorbent on which they are absorbed at different rates., (Absorption is the process of surface absorption.), , When water/any suitable solvent moves up, the chromatography paper, ink with two different colours separates because both colours are absorbed at, different speeds., 14, , Science Class - IX
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Applications :, (a), To separate colours of a dye., (b), To separate pigments from natural colours like chlorophyll., (c), To separate drugs from blood., (Can you guess what is done when athletes undergo a doping test for, their blood ?), , (6), , Distillation :, , Basic principle : Out of the two components one has a lower boiling, point and other has higher boiling point. This is used to separate two or more, miscible liquids., , Example : When mixture of acetone and water is heated, acetone having, lesser boiling point, boils and moves to delivery tube, within which it condenses, back to liquid with the help of a condenser clamped to it. Thus, acetone is, separated out in a beaker and water is left in the distillation ask., Note : If there are more than two components (liquids) mixed (with, different boiling points) then we use a fractionating column to separate all the, components from each other. This process is done for air, petroleum etc., , Is Matter Around Us Pure ?, , 15
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Petroleum is separated into, SDUDI¿Q ZD[ OXEULFDWLQJ RLO, diesel, kerosene, petrol and, petrol gas by this method., Fractional Distillation of Air :, Air is also separated by this method., , Some of the applications of fractional distillation :, (a), In petroleum re neries, petrochemical and chemical plants,, natural gas processing and cryogenic air separation plants., (b), In oil re neries to separate crude oil into useful substances (or, fractions)., (c), In the process of organic juice., (d), In the separation of oxygen, liquid nitrogen and argon from air., , (7), , Crystallisation :, , Basic principle : To remove impurities from a mixture by rst dissolving, in a suitable solvent and then crystallising out one component., For example : Copper sulphate crystals (impure) are rst dissolved in, sulphuric acid and then heated to saturated solution. Now, this solution, is left overnight. So, only pure copper sulphate crystals are formed, whereas impurities are left behind in the solution. This solution can be, thus ltered so as to get pure copper sulphate crystals on lter paper., Why is crystallisation better than evaporation ?, (i), Some solids decompose or get charred upon heating to dryness, during evaporation. E.g., sugar., (ii), Some impurities remain dissolved in solution after lteration. On, evaporation, these impurities do not evaporate and remain with, the mixture., Applications :, (a), Puri cation of salt from sea water., (b), Separation of crystals [e.g., alum (phitkari, copper sulphate)], from their impure crystals., 16, , Science Class - IX
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:DWHUSXUL¿FDWLRQLQZDWHUWUHDWPHQWSODQWV, , Physical Vs Chemical Changes, Chemical, •, Not easily reversed, •, New product(s) formed, •, Reactants used up, •, Often heat/light/sound/fizzing, occurs, •, Electricity may be produced, •, A precipitate may form, •, E.g., Wood burning, , Physical, •, Easily reversible, •, No new products, •, Often just a state change, •, E.g., ice melting, , Elements, Made of same type of atoms, S. No. Metals, 1., Lustrous, , Non-metals, Non-lustrous, , Metalloids, Metallaoids have, intermediate properties, between metals and, non-metals., , Is Matter Around Us Pure ?, , 17
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2., , Malleable, ductile, , 3., 4., , Sonorous, Good conductors of, heat & electricity, E.g., Gold, iron etc., , 5., , Non-malleable, non- E.g., Boron, germanium,, ductile, silicon, Non-sonorous, Bad conductors, E.g., Oxygen,, phosphorus, , Mixture, 1. Elements or compounds are, simply mixed so no new, substance is formed., , Compound, 1. Substances are reacted together with, each other to make a new substance., , 2. Elements do not combine in a, fixed ratio., , 2. Composition of the components is, fixed i.e., they combine together in a, fixed ratio according to their masses., , 3. A mixture shows the properties 3. Compound doesn’t show the properties, of its components., of component elements., 4. Components can be easily, separated by any mechanical, method which is suitable., , 4. Components can’t be separated, from each other by simple mechanical, methods., , 5. E.g., Mixture of iron and, sulphur., , 5. E.g., Iron and sulphur react to form, iron sulphide., , /DZRI&RQVWDQW3URSRUWLRQV, When a compound is formed two or more elements combine in a xed ratio, according to their masses. For e.g., H2O has H : O = 1 : 8., /DZRI&RQVHUYDWLRQRI0DVV, Mass can neither be created no destroyed in a chemical reaction., , 18, , Science Class - IX
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , Suggest methods used for separation ?, (a), , Husk from wheat, , (b), , Sand from water, , (c), , Stones from daal, , (d), , Camphor powder and common salt powder, , (e), , Butter from milk, , (f), , Pure potash alum from impure potash alum (phitkari), SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , Write basic principles behind :, (a), , Chromatography, , (b), , Crystallisation, , (c), , Distillation, , (d), , Centrifugation, , 2., , Work out a process for separating a mixture of sand, NH4Cl and common, salt ?, , 3., , How can we separate alcohol from water ? Explain the whole process, with diagram ?, , 4., , The municipality water that we get at our homes may still have germs in, it. What can we do for it ?, , 5., , A student was having a beaker full of muddy water. He put a whitish, stone like substance in it and suddenly the mud settled down. What is this, white substance and what do we call this process ?, , Is Matter Around Us Pure ?, , 19
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SHORT ANSWER TYPE QUESTIONS (3 Marks), Explain the techniques used in following diagrams :, , 1., , 2., An athlete underwent a dope test and was found positive for drugs. What, could be the process used to identify that his blood contained those drugs ?, Explain the principle and process., , 20, , Science Class - IX
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CHAPTER AT A GLANCE, , Atoms And Molecules, , 21
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Laws of Chemical Combination, The chemical reaction between two or more substances giving rise to, products is governed by certain laws. These laws are called ‘Laws of Chemical, Combination’., , Law of Conservation of Mass, •, , According to this law, “Mass can neither be created nor destroyed.”, , •, , In a chemical reaction, this law can be understood in the following way :, , “During a chemical reaction total mass of reactants will be equal to total, mass of products.”, •, , For example,, , A, , B o AB, , +, , Reactant, Then,, , Product, , mA + mB = mAB, , where,, , mA = Mass of A, m B = Mass of B, mAB = Mass of AB, , 2H2 (g), , +, , 2 u 2 = 4 gm, , O2 (g), 2 u 16 = 32 gm, , o, , 2H2O (l), 2 u (2 + 16) = 36 gm, , Example : In a reaction 5.3 gm of sodium carbonate reacted with 6 gm of, ethanoic acid. The products were 2.2 gm of CO2, 0.9 gm of H2O and 8.2 gm of, sodium ethanoate. Show that these observation are all in agreement with law of, 22, , Science Class - IX
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conservation of mass., Sodium carbonate + Ethanoic acid o Sodium ethanoate + CO2 + H2O, Solution :, Sodium carbonate Ethanoic acid o Sodium ethanoate CO 2 H 2 O, Reactants, , Products, , Now, according to the law of conservation of mass :, Mass of sodium carbonate + Mass of ethanoic acid = Mass of sodium, ethanoate + Mass of CO2 + Mass of H2O, Putting values of masses from the equation :, 5.3 gm + 6.0 gm = 8.2 gm + 2.2 gm + 0.9 gm, Or, , 11.3 gm, , = 11.3 gm, , Since, LHS = RHS, ? Law of conservation of mass is in agreement with the given values in, equation., Law of Constant Proportion, According to this law, “A pure chemical compound always contain the same, elements combined together in the same proportion by mass irrespective of, the fact from where the sample has been taken or from which procedure has, it been produced.”, For example :, 18 gm of H2O 16 gm of oxygen + 2 gm of hydrogen,, i.e., mH/mO = 2/16 = 1/8, 36 gm of H2O 32 gm of oxygen + 4 gm of hydrogen,, i.e., mH/mO = 4/32 = 1/8, 09 gm of H2O 08 gm of oxygen + 1 gm of hydrogen,, i.e., mH/mO = 1/8, From the above three cases, differently weighing H2O samples were taken but, the ratio of masses of ‘H’ to mass of ‘O’ comes out to be ‘1/8’ is same, proving, law of constant proportion., Likewise, if a sample of ‘H2O’ was taken from anywhere i.e., from well, pond,, lake or anywhere the ratio of masses of ‘H’ to ‘O’ will come out to be same as, ‘1/8’., Example : Hydrogen and oxygen combine in the ratio 1 : 8 by mass to form, Atoms And Molecules, , 23
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water. What mass of oxygen gas would be required to react completely with 3.0, gm of hydrogen gas ?, Solution :, But,, Or, Or, , mH, , 1, , mO, , 8, , Given in equation (For H2O), , mH = 3.0 gm (given), 3, , 1, , mO, , 8, , mO = 24 gm, , ? Mass of oxygen will be 24 gm., Or it will be a sample of 27 gm of H2O where 3 gm of hydrogen is present with, 24 gm of oxygen., , Dalton’s Atomic Theory, Based upon laws of chemical combination, Dalton’s Atomic Theory, provided an explanation for the Law of Conservation of Mass and Law of, Constant Composition., Postulates of Dalton’s atomic theory are as follows :, •, , All matter is made up of very tiny particles called ‘Atoms’., , •, , Atom are indivisible particles, which can’t be created or destroyed in a, chemical reaction. (Proves ‘Law of Conservation of Mass’), , •, , Atoms of an element have identical mass and chemical properties., , •, , Atoms of different elements have different mass and chemical properties., , •, , Atom combine in the ratio of small whole numbers to form compounds., (Proves ‘Law of Constant Proportion’), , •, , The relative number and kinds of atoms are constant in a given compound., , Atom, •, , According to modern atomic theory, an atom is the smallest particle of, an element which takes part in chemical reaction such that during the, chemical reaction, the atom maintain its identity, throughout the chemical, or physical change., , •, , Atoms are very small and hence can’t be seen even through very powerful, microscope., , •, , Atomic radius of smallest atom in hydrogen is 0.37 u 10-10 m, or 0.037 nm., , 24, , Science Class - IX
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1 nm = 109 m, , Such that,, , IUPAC (International Union of Pure & Applied Chemistry) Symbols of, Atoms of Different Elements, Element, , Symbol, , Element, , Symbol, , Aluminium, , Al, , Iodine, , I, , Argon, , Ar, , Iron, , Fe, , Barium, , Ba, , Lead, , Pb, , Calcium, , Ca, , Nitrogen, , N, , Carbon, , C, , Oxygen, , O, , Chlorine, , Cl, , Potassium, , K, , Cobalt, , Co, , Silicon, , Si, , Copper, , Cu, , Silver, , Ag, , Fluorine, , F, , Sulphur, , S, , Gold, , Au, , Zinc, , Zn, , Hydrogen, , H, , Atomic Mass, •, , The mass of an atom of an element is called its atomic mass., , •, , In 1961, IUPAC have accepted ‘atomic mass unit’ (u) to express atomic, and molecular mass of elements and compounds., , Atomic Mass Unit, The atomic mass unit is de ned as the quantity of mass equal to 1/12 of mass, of an atom of carbon-12., 1 amu or u =, , 1, 12, , u Mass of an atom of C12, , 1 u = 1.66 u 10-27 kg, , Likewise,, Atoms And Molecules, , 25
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Element, , Atomic Mass, , Hydrogen, , 1u, , Carbon, , 12 u, , Nitrogen, , 14 u, , Oxygen, , 16 u, , Sodium, , 23 u, , Magnesium, , 24 u, , Sulphur, , 32 u, , Chlorine, , 35.5 u, , Calcium, , 40 u, , How do atoms exist ?, • Atoms of most of the elements are very reactive and does not exist in free, state., •, , Only the atoms of noble gases (such as He, Ne, Ar, Kr, Xe and Rn) are, chemically unreactive and can exist in the free state as single atom., , •, , Atoms of all other elements combine together to form molecules or ions., Atom (Electrically neutral), Ion (electrically charged), , Molecules (electrically neutral), , Molecule, •, , A molecule is a group of two or more atoms which are chemically bonded, with each other., , •, , A molecule is the smallest particle of matter (except element) which is, capable of an independent existence and show all properties of that, substance., , E.g., ‘H2O’ is the smallest particle of water which shows all the properties of, water., •, , A molecule may have atom of same or different elements, depending, upon this, molecule can be categorized into two categories :, , Homoatomic molecules (containing atom of same element) and, Heteroatomic molecules or compounds (containing atoms of different, elements), 26, , Science Class - IX
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Molecules, Homoatomic molecules, , Heteroatomic molecules, , E.g., O2, N2, O3, S8, P4 etc., , E.g., H2O, CO2, NaCl, CaCO3 etc., , Atomicity, The number of atoms present in one molecule of an element is called its, atomicity., Name, , Formula, , Atomicity, , 1. Argon, , Ar, , Monoatomic (1), , 2. Helium, , He, , Monoatomic (1), , 3. Oxygen, , O2, , Diatomic (2), , 4. Hydrogen, , H2, , Diatomic (2), , 5. Phosphorus, , P4, , Tetratomic (4), , 6. Sulphur, , S8, , Polyatomic (8), , Noble gasses constitute, monoatomic molecules, , Chemical formulae, It is the symbolic representation of the composition of a compound., Characteristics of chemical formulae, •, , The valencies or charges on ion must balance., , •, , When a compound is formed of metal and non-metal, symbol of metal, comes rst. E.g., CaO, NaCl, CuO., , •, , When polyatomic ions are used, the ions are enclosed in brackets before, writing the number to show the ratio. E.g., Ca(OH)2, (NH4)2SO4, , Molecular Mass, It is the sum of atomic masses of all the atoms in a molecule of that substance., E.g., Molecular mass of H2O = 2 u Atomic mass of Hydrogen + 1 u, Atomic mass of Oxygen, So, Molecular mass of H2O = 2 u 1 + 1 u 16 = 18 u, Formula Unit Mass, It is the sum of atomic mass of ions and atoms present in formula for a, compound., E.g.,, , In NaCl, Na = 23 a.m.u., , Cl, , = 35.5 a.m.u., , So,, , Formula unit mass = 1 u 23 + 1 u 35.5 = 58.5 u, Atoms And Molecules, , 27
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Rules for writing chemical formulae, (i) We rst write symbols of elements which form compound., (ii) Below the symbol of each element, we should write their valency., (iii) Now cross over the valencies of combining atoms., (iv) With rst atom, we write the valency of second atom (as a subscript)., (v) With second atom, we write the valency of rst atom (subscript)., Examples :, (i) Symbol, , :, , H, , S, , Valencies :, , 1, , 2, , :, , C, , O, , Valencies :, , 4, , 2, , (ii) Symbol, , H2S1 or H2S (Hydrogen sulphide), , C2O4 or CO2 (Carbon dioxide), [Take 2 common, formula by 2], , and, , divide, , the, , and, , divide, , the, , (iii)For Hydrochloric acid (Hydrogen chloride), H, , Cl, , 1, , 1, , H1Cl1 or HCl, , (iv) For Carbon tetrachloride, C, , Cl, , 4, , 1, , C1Cl4 or CCl4, , (v) For Magnesium chloride, Mg, , Cl, , 2, , 1, , MgCl2, , (vi) For aluminium oxide, Al, , O, , 3, , 2, , Al2O3, , (vii)For Calcium oxide, Ca, , O, , 2, , 2, , Ca2O2 or CaO, [Take 2 common, formula by 2], , 28, , Science Class - IX
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(v) Magnesium hydroxide, Mg, , OH, , 2+, , 1–, , Mg(OH) 2, , Molar Mass, The molar mass of a substance is the mass of 1 mole of that substance., It is equal to the 6.022 u 1023 atoms of that element/substance., Example :, (a) Atomic mass of hydrogen (H) is 1 u. Its molar mass is 1 g/mol., (b) Atomic mass of nitrogen is 14 u. So, molar mass of nitrogen (N) is, 14 g/mol., (c) Molar mass of S8, , = Mass of S u 8 = 32 u 8 = 256 g/mol, , (d) Molar mass of HCl = Mass of H + Mass of Cl, = 1 = 35.5 = 36.5 g/mol, Mole concept, A group of 6.022 u 1023 particles (atoms, molecules or ions) of a substance, is called a mole of that substance., 1 mole of atoms, , = 6.022 u 1023 atoms, , 1 mole of molecules, , = 6.022 u 1023 molecules, , 1 mole of oxygen = 6.022 u 1023 oxygen atoms, , Example,, , 6.022 u 1023 is Avogadro Number (L)., •, , 1 mole of atoms of an element has a mass equal to gram atomic mass of, the element., , Important Formulae, (i) Number of moles (n) =, (ii) Number of moles (n) =, n=, (iii), , 30, , m, , N, , M, , N0, , m, , Given mass, , m, , Molar mass, , M, , Given number of particles, Avogadro's number, N, N0, MuN, N0, , Science Class - IX
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Mass of element u 100, , (iv) Percentage of any atom in given compound, , Mass of compound, , Example. Calculate no. of iron atoms in a piece of iron weighing 2.8 gm (At., mass = 54 u)., Solution :, , 1 mole of iron, , = 56 gm (Gram atomic mass of iron), , 1 mole of iron element contains 6.022 u 1023 atoms of iron., So,, , = 6.022 u 1023 atoms, , 56 gm of iron, , 6.022 u 1023, , 2.8 gm of iron, , 56, , u 2.8, , = 3.011 u 1022 atoms, Example. Mass of one molecule of a substance is 5.32 u 10-23 g. What is its, molecular mass ?, Solution :, , Mass of 1 molecule of substance, = 5.32 u 10-23 g, , Mass of 6.022 u 1023 molecules of substance, = 5.32 u 10-23 u 6.022 u 1023, = 32 g, Example. Calculate the mass of 0.5 mole of N2 gas., Solution :, , 1 mole of N2, , Or, , 1 mole of N2, , ?, , 0.5 mole of N2 gas, , = Gram molecular mass of N2, = 28 gm, = 0.5 u 28, = 14 gm of N2, , Example. Calculate the total number of O2 molecules present in 8 gm of O2., Solution : Gram molecular mass of O2, = 6.022 u 1023 O2 molecules, Or, , 32 gm of O2, , Or, , 8 gm of O2, , = 6.022 u 1023 O2 molecules, = 6.022 u 1023 u 8/32 O2 molecules, = 1.51 u 1023 O2 molecules, , Atoms And Molecules, , 31
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS, 1. Write full form of IUPAC., 2. Name the scientist who gave atomic theory of matter., 3. What are building blocks of matter ?, 4. Name two laws of chemical combination., 5. Name the unit in which atomic radius is usually expressed., 6. De ne molecular mass., 7. What is formula unit mass ?, 8. Name the element used as standard for atomic mass scale., SHORT ANSWER TYPE QUESTIONS, 1. What is atomicity ? Explain with two examples., 2. State law of conservation of mass., 3. State law of constant proportion., 4. Calculate molecular mass of H2 and NH3. (At. mass of H = 1 u, N = 14 u), LONG ANSWER TYPE QUESTIONS, 1. Write postulates of Dalton’s atomic theory., 2. What is the difference between molecule of an element and the molecule of, a compound ? Give one example of each., HOTS, 1. In what form does oxygen gas occur in nature ?, 2. In what form do noble gases occur in nature ?, 3. What is the difference between 2H and H2 ?, 32, , Science Class - IX
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NUMERICALS, 1. Calculate the gram atomic mass of one atom of oxygen. (Gram atomic mass, of oxygen = 16 gm), [Ans. 2.66 u 10-23 gm], 2. What would be gram atomic mass of 5 moles of chlorine ?, [Ans. 177.5 gm], 3. Calculate the number of moles present in the following :, (a) 52 gm of He, (b) 12.044 u 1023 He atoms, , [Ans. (a) 13 moles, (b) 2 moles], , Atoms And Molecules, , 33
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CHAPTER AT A GLANCE, , 34, , Science Class - IX
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Contents :, (i), , Discovery of Electron ‘Cathode Rays’, , (ii) Discovery of Protons ‘Anode Rays or Canal Rays’, (iii) Discovery of Neutron, (iv) Atomic Models, (a), , Thomson’s Atomic Model, , (b), , Rutherford’s Atomic Model, , (c), , Bohr’s Atomic Model, , (v) Distribution of Electrons in different shells, (vi) Valence shell & Valency, (vii) Atomic number & Mass number, (viii) Isotopes and their application, (ix) Isobars, , , , John Dalton considered atom to be an indivisible entity, but his concept, had to be discarded at the end of nineteenth century, when scientists through, H[SHULPHQWVZHUHDEOHWR¿QGH[LVWHQFHRIFKDUJHG HOHFWURQVDQGSURWRQV , and neutral particles (neutrons) in the atom. These particles were called the, ‘Sub-atomic Particles’., , Discovery of Electrons – Cathode Rays (By J. J. Thomson), Thomson explained presence of electrons by cathode rays experiment., Facts about Electrons, •, , Charge on electron = 1.6 u 10-19 C (C = Coloumb), (As calculated by Robert E. Millikan), , •, , Mass of electron = 9.1 u 10-31 kg, , Discovery of Protons – Anode Rays/Canal Rays (By E. Goldstein), E. Goldstein by his famous anode rays/canal rays experiment was able to, detect presence of positively charged particles called protons in the atom., Facts about Protons, •, , Charge on proton = + 1.6 u 10-19 C, , •, , Mass of proton = 1.673 u 10-24 gm, i.e.,, , Mass of proton # 1840 u Mass of electron, Structure Of Atom, , 35
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Discovery of Neutrons (By J. Chadwick), •, , J. Chadwick bombarded lighter elements (like lithium, boron etc.) with, D-particles and observed emission of new particles having zero charge, but having mass equal to that of proton., , •, , These particles were called ‘Neutron’ i.e., neutral particle of the atom., , •, , Neutron are absent in Protium isotope of hydrogen atom.(1H1), , •, , Since, mass of electrons are negligible as compared to that of proton, and neutrons hence, sum of masses of protons and neutrons in an atom, will compose its atomic mass., , Atomic Models, •, , From the knowledge of existence of subatomic particles viz., electron,, proton and neutron in an atom, various atomic models were proposed, by different scientists., , •, , Following are some of the atomic models :, , •, , (a), , Thomson’s Model of Atom, , (b), , Rutherford’s Model of Atom, , (c), , Bohr’s Model of Atom, , The most trusted and scienti cally established model of atom which is, adopted these days is ‘Quantum Mechanical Model of Atom’. It will be, dealt in higher classes., , Thomson’s Atomic Model, •, , This model is often called the ‘Water Melon Model’., , •, , In this model, Thomson predicted the presence of electrons inside, positive sphere (made up of protons), just same as seeds of watermelon, are embedded in red edible part of watermelon., , J. J. Thomson’s Model of Atom, •, 36, , Although this model explained neutrality of atom but couldn’t able to, explain other scienti c experiments conducted on atom. Hence it was, Science Class - IX
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discarded., Rutherford’s Atomic Model, •, , In his famous ‘D-ray Scattering Experiment’, Rutherford bombarded, D-ray (Helium nucleus 2He4) upon thin gold foil., , •, , Rutherford made following observations from this experiment :, (i), , Most of D-particles passed through gold foil unde ected., , (ii), , Some of the D-particles de ected by foil by small angles., , (iii) One out of every 12000 particles appeared to rebound., , Rutherford α-ray Scattering Experiment, •, , From his observation, Rutherford draw following conclusions :, (i), , Atom consists of predominantly empty space as most of, D-particles passed through gold foil unde ected., , (ii), , Atom contains centrally placed positively charged nucleus, (carrying positively charged particles), because few D-particles, suffered de ected and very few i.e., one in 12000 bounced, back., , (iii) Since a minute fraction of D-particles suffered de ections and, very few bounced back, this lead to conclusion that most of, the space an atom is empty and the space occupied by nucleus, is negligible compared to this empty space., Size of nucleus was about 105 times that of size of atom., (iv) Whole of the atomic mass concentrated in the nucleus., •, , On the basis of his experiment, Rutherford proposed model of atom, having following features :, (i), , There is positively placed nucleus in an atom. Nearly all the, mass resides in nucleus (Proton + Neutron)., Structure Of Atom, , 37
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(ii), , Electrons revolves round the nucleus in well de ned orbits., , (iii) Size of nucleus is very small compared to the size of atom., Drawbacks of Rutherford’s Model (Unstability of Atom), •, , According to Rutherford, electrons revolve round the nucleus in wellde ned orbits, but electrons being charged particles will lose their, energy and nally will fall into the nucleus. This will make atom highly, unstable., , •, , This was the major drawback of Rutherford which was unexplained by, him., , Bohr’s Atomic Model, •, , To overcome drawbacks of Rutherford’s Model, Neil Bohr in 1912, proposed modi ed model of structure of atom. He made following, assumptions :, (i), , Only certain special orbits known as discrete orbits of electrons, are allowed inside the atom., , (ii), , While revolving in discrete orbits, the electrons do not radiate, energy., , (iii) Energy is emitted or absorbed by an atom only when an, electron moves from one orbit to another., , 38, , Science Class - IX
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Atomic Number, The total number of proton lying in the nucleus of any atom is called the, atomic number., •, , An atomic number is the identity of an atom, changing atomic number, means changing the atom., , •, , Atomic number is denoted by ‘Z’. (Z = nP), , •, , For a neutral atom, no. of protons and electrons are equal., , Mass Number, It is the sum of total number of protons and no. of neutrons lying in the, nucleus of an atom., No. of proton No. of neutrons, •, , It is denoted by ‘A’. (A = nP + nN), , Representation of Atom :, E.g.,, , (E = Symbol of element), , A, ZE, 26, 13 Al, , [ZAl = 13 (nP), A = 13 (nP) + 13 (nN)], , Example. Calculate number of protons, electrons and neutrons for :, (a) 1735Cl, Solution : (a), , (b), , 23, 11 Na, , 35, 17 Cl, , ZCl = 17 (nP), Here, since Cl is neutral, so ne = nP = 17., Now,, , ACl = 35, , Or, , 35 = nP + nN, , Or, , 35 = 17 + nN, , Or, , nN = 35 – 17 = 18, , Distribution Of Electrons In Various Shells, The distribution of electrons in various shells is done in accordance to ‘BohrBury Scheme’., Bohr-Bury Scheme, This scheme can be summarized as follows :, (i), , The lling of electrons in an atom is done in accordance to ‘2n2’, where, ‘n’ is the number of shell and ‘2n2’ represents the total number of, Structure Of Atom, , 39
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electrons that can be accommodated in that particular shell., If n = 1, i.e., K = shell, 2n2 = 2 u 12 = 2 electrons, If n = 2, i.e., L = shell, 2n2 = 2 u 22 = 8 electrons, If n = 3, i.e., M = shell, 2n2 = 2 u 32 = 18 electrons, If n = 4, i.e., N = shell, 2n2 = 2 u 42 = 32 electrons, , Maximum, number, of, electrons that, FDQ EH ¿OOHG, in particular, shell., , (ii) The outermost shell can’t hold more than 8 electrons, while second last, shell can’t have more than 18 electrons, even though they may have, capacity to hold more electrons., For example, in ‘Ca20’, the electron distribution will be :, Ca20 =, , K, , L, , M, , N, , 2, , 8, , 8, , 2, , But, Ca20 = 2, 8, 10 is wrong although ‘M’ shell can contain upto 18, electrons., (iii) The outermost shell can’t hold more than 2 electrons and the, penultimate shell can’t hold more than 8 electrons unless the preceding, inner shell (antepenultimate shell) is lled completely obeying ‘2n2’, rule., Some examples :, (a), , K19 = 2, 8, 8, 1, , (b), , Al13 = 2, 8, 3, , (c), , F9 = 2, 7, , (d), , Ne10 = 2, 8, , (e), , Na11 = 2, 8, 1, , Valence Shell and Valence Electrons, •, , From Bohr-Bury sequence, we know that maximum number of electrons, which can be accommodated in outermost shell is 8., , •, , Every element has an urge to have 8 electrons in its outermost shell, in, achieving 8 electrons an atom can either gain electrons or loose, electrons., , •, , The number of electrons lost or gained by an element in achieving 8, , 40, , Science Class - IX
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electrons in its outermost shell will be called its Valence., For example,, , •, , S. No., , Element, , Electron distribution, , Valence, , 1., , C6, , 2, 4, , 4, , 2., , N7, , 2, 5, , 3, , 3., , O8, , 2, 6, , 2, , 4., , F9, , 2, 7, , 1, , 5., , Ne10, , 2, 8, , 0, , 6., , Na11, , 2, 8, 1, , 1, , 7., , Mg12, , 2, 8, 2, , 2, , 8., , Ca20, , 2, 8, 8, 2, , 2, , For elements like H, He, Li, Be and B, these elements lose their outermost, electron to achieve 2 electrons in their outermost shell. These elements, will have valence in accordance to this act., S. No., , Element, , Electron distribution, , Valence, , 1., , H1, , 1, , 1, , 2., , He2, , 2, , 0, , 3., , Li3, , 2, 1, , 1, , 4., , Be4, , 2, 2, , 2, , 5., , B5, , 2, 3, , 3, , Isotopes :, Isotopes are atoms of same elements having same atomic number and, different mass numbers., E.g., Chlorine has two isotopes of mass numbers 35 and 37 respectively., 35, 17 Cl, , and, , 37, 17 Cl., , Uses of isotopes, (i), , Uranium isotope is used as fuel in nuclear rector., Structure Of Atom, , 41
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(ii) Isotope of cobalt is useful in treatment of cancer., (iii) An isotope of iodine is used in the treatment of goiter., , Isobars, Isobars are the atoms of those elements which have the same mass number, but different atomic numbers are called isobars., mass number and different atomic number., examples., , 40, 20 Ca, , 24, 11 Na, , and, , and, , 40, 18 Ar, , 24, 12 Mg, , have same, are another, , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1. The total number of electrons in Nitrogen is 7. What is its valency ?, 2. What name is given to pair of atoms such as, , 14, 7N, , and, , 15, 7N, , ?, , 3. Name three subatomic particles present in an atom., 4. Name the negatively charged particle present in the atom of all the elements., 5. Which part of atom was discovered by Rutherford’s alpha particle scattering, experiment ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), 1. Why is an atom neutral inspite of the presence of charged particles in it ?, 2. How does a proton differ from an electron ?, 3. Write the distribution of electrons in an atom of element whose atomic, number is 18. What is special about the outermost shell of atom in this, element ?, 4. An element has Z = 7. What is the valency of the element. Also name the, element., LONG ANSWER TYPE QUESTIONS (5 Marks), 1. Differentiate between isotopes and isobars., 2. What is the relationship between the valency of an element and the number, of valence electrons in its atoms ?, 3. Describe Thomson’s model of atom. Which subatomic particle was not, 42, , Science Class - IX
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present in Thomson’s model of atom ?, 4. Describe Rutherford’s model of atom., HOTS, 1. From the symbol, , 31, 15 P, , state :, , (a) mass number of phosphorus., (b) atomic number of phosphorus., (c) electronic con guration of phosphorus., , Structure Of Atom, , 43
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CHAPTER AT A GLANCE, , Study Key Points :, Discovery of Cell, Types of Cell & Organism, Unicellular & Multicellular,, 44, , Science Class - IX
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Prokaryotic & Eukaryotic, Plant Cell & Animal Cell, Cell Shape, Cell Size, Cell, Membrane, Cell wall, Diffusion & Osmosis, Nucleus, Cytoplasm, Endoplasmic, Reticulum, Golgi Apparatus, Mitochondria, Ribosomes, Plastid, Vacuoles,, Lysosomes., , •, •, •, •, •, •, •, , All living forms are composed of microscopic units called as ‘Cells’., A cell is the basic structural and functional unit of all life forms., Study of structure and composition of cell is called as ‘Cytology’., Cell was rst observed by Robert Hooke in a dead cork slice in the year, 1665., First living cell was discovered by A. V. Leeuwenhoek., Its consistency differs under different condition. It exists in sol-gel, states., Protoplasm is an aggregate of various chemicals such as water, ions,, salts and other organic molecules like proteins, carbohydrates, fats,, nucleic acids, vitamins etc., , Cell Theory :, Two biologists, Schleiden and Schwann gave the Cell theory which states that :, (i), All plants and animals are composed of cells., (ii), Cell is the basic unit of life., (iii), All cells arise from pre-existing cells., • Viruses are the exceptions of cell theory., Fundamental Unit Of Life: Cell, , 45
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Types of Cell & Organism :, , On the Basis of Number of Cells :, Characteristics, , Unicellular organism Multicellular organism, , Cell number, , Single cell, , Large number of cells, , Function, , All functions are performed by single cell, , Different cells perform different, specific functions., , Division of labour Not performed, , Cells specified to perform different functions., , Reproduction, , Involves the same, single cell, , Specialised cells, germ cells take, part in reproduction., , Life span, , Short, , Long, , On the Basis of Type of Organization, Prokaryotic Cells, , Eukaryotic Cells, , Very minute in size., , Fairly large in size., , Nuclear region (nucleoid) not, Nuclear material surrounded by a, surrounded by a nuclear membrane. nuclear membrane., Single chromosome present., , More than one chromosome present., , Nucleolus absent., , Nucleolus present., , Membrane bound cell organelles are Membrane bound cell organelles are, absent., present., Cell division by fission or budding, (no mitosis)., , 46, , Science Class - IX, , Cell division by mitosis or meiosis.
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Cell Shape : Cells are of variable shapes and sizes. Their shape is according, to the function. Generally cells are spherical but they may be elongated (nerve, cell), branched (pigmented), discoidal (RBC), spindle-shaped (muscle cell) etc., , Different kinds of cell found in the human body, Cell Size : Size of cell is variable depending upon the type of organism., Some are microscopic while some are visible with naked eyes. Their size may, vary from 0.2 mm to 18 cm., • Size of a typical cell in a multicellular organism ranges from 20-30 mm., Fundamental Unit Of Life: Cell, , 47
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•, •, •, •, , The largest cell is ostrich egg (15 cm in diameter with shell & 8 cm in, diameter without cell)., The longest cell is nerve cell (upto 1 m or more)., Smallest cells so far known are PPLOs e.g., mycoplasma (0.1 mm in, diameter)., Human egg is 0.1 mm in diameter., , Components of Cell, There is an occurrence of division of labour within a cell as they all got certain, speci c components called ‘Cell organelles’. Each of them perform a speci c, function., The three basic components of all the cells are :, (i), Plasma membrane, (ii), Nucleus, (iii), Cytoplasm, , Cell Membrane :, (a), Cell membrane is also called as plasma membrane or plasma, lemma., (b), It is the limiting boundary of each cell which separates the, cytoplasm from its surroundings., (c), It is found in both plant as well as animal cells., (d), It is the outermost covering of a cell in case of animals and lies, below the cell wall in case of plants., (e), It is made up of proteins and lipids where proteins are sandwiched, 48, , Science Class - IX
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(f), (g), , (h), , between bilayer of lipids., Plasma membrane is selectively permeable in nature. It allows or, permits the entry and exit of some materials in and out of the cell., Singer and Nicholson gave the uid mosaic model of plasma, membrane. According to them, it consists of a protein layer, sandwiched between two layers of lipids. It is in quasi uid state., It is 75A thick., It is exible and can be folded, broken and reunited., , Functions of Plasma Membrane :, (a), It regulates the movement of molecules inside and outside the, cell., (b), It helps in maintaining the distinct composition of the cell., (ii), Transportation of molecules across the Plasma Membrane :, This can be done by following ways :, , •, , •, , •, •, •, , Diffusion : Movement of solutes or ions from higher concentration to, lower concentration is called as diffusion. It does not require energy, therefore, it is called as passive transport., Osmosis : The movement of solvent or water from higher concentration, (solvent) to lower concentration (solvent) through a semipermeable, membrane is called as osmosis Or the movement of solvent or water from, lower concentration to higher concentration of solution through a, semipermeable membrane is called as osmosis., Osmosis can also be called as ‘Diffusion of solvents’., Endomosis : Movement of solvent into the cell is called as Endomosis., Exosmosis : Movement of solvent outside the cell is called as Exomosis., , Types of Solutions on the Basis of Concentration, , Fundamental Unit Of Life: Cell, , 49
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(a), , (b), , (c), , Isotonic Solution : When the concentration of the solution, outside the cell is equal to the concentration of cytoplasm of the, cell, it is called as isotonic solution., Hypertonic Solution : When the concentration of the solution, outside the cell is more than the inside the cell. Due to this, cell, looses water and becomes plasmolysed., Hypotonic Solution : When the concentration of the solution, outside the cell is lesser than that of cytoplasm of cell. Due to, this, cell swells up and bursts., , Cell Wall, • It is the outermost covering of the plant cells., • It is absent in animal cells., • Cell wall is rigid, strong, thick, porous and non-living structure. It is, made up of cellulose and hemicelluloses. Cell walls of two adjacent cells, are joined by a layer called middle lamellae., , 50, , Science Class - IX
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Functions of Cell Wall :, (a), It provides de nite shape to the cell., (b), It provides strength to the cell., (c), It is permeable and allows entry of molecules of different sizes., (d), It has the characteristics of repair and regeneration., Nucleus, , •, , Nucleus is the most important cell organelle which directs and controls, all its cellular activities., • It is called as ‘Headquarter of the cell’., • It was discovered by Robert Brown in 1831., • In Eukaryotes, a well-de ned nucleus is present while in Prokaryotes, a, well-de ned nucleus is absent., • Prokaryotes contain a primitive nucleus., • It has double layered covering called as nuclear membrane., • Nuclear membrane has pores which regulate the movement of materials, in & out of the cell., • Besides nuclear membrane, nucleus also contains nucleolus and, chromatin material and the substance lled inside the nucleus is nucleolus., • Chromosomes or chromatin material consists of DNA which stores and, transmits hereditary information for the cell to function, grow and, reproduce., Functions of Nucleus :, (a), It controls all the metabolic activities of the cell and regulates the, cell cycle., (b), It helps in transmission of hereditary characters from parents to, off springs., Fundamental Unit Of Life: Cell, , 51
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Cytoplasm, , •, •, •, , Cytoplasm was discovered by Kolliker in 1862., It is the site of both biosynthetic and catabolic pathways., It can be divided into two parts :, (i), Cytosol : Aqueous soluble part contains various brous proteins, forming cytoskeleton., (ii), Cell organelles : Living part of the cells having de nite shape,, structure and function bounded by plasma membrane., Endoplasmic Reticulum, • It is the network of membranes present in the cytoplasm., • It was discovered by Porter, Claude and Fullam., • These are present in all cells except prokaryotes and mammalian, erythrocytes., , Endoplasmic reticulum is of two types :, Smooth ER, Rough ER, • Made of tubules mainly., • Made of clstemae and vesicles., • Helps in steroid, lipids and, • Helps in protein synthesis., Polysaccharide synthesis., • Ribosomes are absent., • Contains ribosome on its surface., • Helps in membrane biogenesis., Functions of ER :, (a), It is the only organelle which can move within a cell so it serves, as a channel for the transport of materials between various regions, 52, , Science Class - IX
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of cytoplasm and between cytoplasm and nucleus., (b), It also functions as a cytoplasmic framework to provide space for, some of the biochemical activities. It forms endoskeleton of cell., (c), It helps in synthesis of fats, steroids, cholesterol etc., (d), SER plays a crucial role in detoxi cation of drugs and poisonous, by-products., Golgi Apparatus, Golgi apparatus consists of a system of membrane bounded vesicles arranged, parallel to each other in stacks called Cisternae along with some large and spherical, vacuoles. It was discovered by Camilo Golgi. In plants Golgi membrane is, bounded. It is single membrane bounded. It is absent in prokaryotes, mammalian, RBC’s & sieve cells., , Functions of Golgi apparatus :, (a), It helps in formation of lipids., (b), It helps in formation of middle lamellae., (c), It is secretary in nature., (d), It helps in melanin synthesis., (e), Lipids and proteins synthesized in endoplasmic reticulum are, packed at Golgi complex. They provide the site for assembly of, new membrane material., Mitochondria, , Fundamental Unit Of Life: Cell, , 53
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It is a rod shaped structure found in cytoplasm of all eukaryotic cells except, mammalian RBC’s., • These are also absent in prokaryotes., • It was rst seen by Kolliker in insect cells., • Maximum mitochondria are found in metabolically active cells., • It is also called as ‘Power House of the Cell’ or the ‘Storage Battery’., • It is double membranous structure where outer membrane has speci c, proteins while inner membrane is folded inside to form chambers called, Cristae., Functions of Mitochondria :, (a), Its main function is to produce and store the energy in the form of, ATP., (b), , It is the site of Kreb cycle of respiration., , Ribosomes, , Ribosomes are the sites of protein synthesis., All structural and functional proteins (enzymes) coded by the nuclear DNA are, synthesized upon cytoplasmic ribosomes. The DNA codes are transcripted into, messenger RNA (mRNA) molecules in the chromosomes of the nucleus., Functions of Ribosomes :, (a), Ribosomes are the main site of protein synthesis. Synthesized, proteins is transported by endoplasmic reticulum., Plastid, , 54, , Science Class - IX
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•, •, , It is double membranous discoidal structure, found only in plant cells., Besides being discoidal of rhombic in plant cells, they occur in variable, shapes like in algae. They can be ‘U’-shaped, spiral, coiled, ribbonshaped etc., Depending upon the type of pigment present in them, they are of following, three types :, (i), Leucoplast – White, found in underground parts, (ii), Chromoplast – Red, brown, (iii), Chloroplast – Green in colour, found in aerial parts of plants, These are found only in plant cell. It helps in the process of photosynthesis so it, is called the ‘Kitchen of Plants’., Chloroplast have following two parts :, (i), Grana : It constitutes the lamellar system. These are found, layered on top of each other. These stacks are called Grana. Each, granum of the chloroplast is formed by superimposed closed, compartments called Thylakoids., Function : They are the sites of light reaction of photosynthesis as they, contain photosynthetic pigment chlorophyll. In each thylakoid,, Quantasomes are present which are called as Photosynthetic units., (ii), Stroma : It is a granular transparent substance also called as, matrix. Grana are embedded in it. Besides Grana they also, contain lipid droplets, starch grains, ribosomes etc., Function : This is the site of dark reaction of photosynthesis. Also helps, in protein synthesis due to presence of ribosomes., Vacuoles, , •, •, •, , These are membrane bounded regions in the cytoplasm containing water, and other substances., They are bounded by a single membrane called Tonoplast., In animal cells vacuoles are smaller in size and numerous while in plant, Fundamental Unit Of Life: Cell, , 55
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cells a single large vacuole is found which occupies about 90% of the, volume of cell., Functions :, It helps in maintaining osmotic pressure in a cell & stores toxic metabolic, products of plant cell., Lysosome, , • They are tiny sac-like granules containing enzymes of intracellular, digestion., • They are bounded by a single membrane., • They occur in animal cells and a few plant cells., • They do not have a de nite shape or size., Functions :, (a), Their main function is phagy = digestion., (b), They are kind of waste disposal system., (c), They help in digesting foreign materials & cells., Suicidal Bag : During disturbances in cellular metabolism i.e., in case of cell, damage, lysosomes burst and their enzymes are released into the cytoplasm and, they digest their own cell. So they are also called ‘Suicidal Bag’., , •, •, •, •, , Differences between Animal cell and Plant cell, Plant Cell, Animal Cell, Contain chloroplasts for, • No chloroplasts, photosynthesis., Have a cell wall to maintain, • No cell wall, structure and rigidity., Usually do not contain lysosomes and • Contain cilia and/or agella, Peroxisomes., Cells are square and rigid or geometric • Cells are uid and exible,, shaped., many shapes., 56, , Science Class - IX
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•, •, , Limited movement., Have one large central vacuole., , •, •, , Cells can move around., Has small vacuoles., , QUESTIONS, 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., , VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), Name the largest cell of living world ?, Amoeba is a.............organism., Who gave the uid mosaic model of plasma membrane ?, Movement of solvent into the cell is called as................. ., Which cell organelle is called as the ‘Head quarter of cell’ ?, Which cell organelle is called as ‘Power house of cell’ ?, Which cell organelle contains enzymes for ATP production ?, In mitochondria, which portion contains speci c proteins ?, Which cell organelle is called as ‘Digestive bag’ ?, Which organelle controls osomostic pressure in a cell ?, Plastids having coloured pigments are called as............... ., , 1., 2., 3., 4., 5., 6., 7., 8., , SHORT ANSWER TYPE QUESTIONS (2 Marks), What is the composition of protoplasm ?, De ne cell ?, What is the difference between diffusion and osmosis ?, Why plasma membrane is called as selectively permeable membrane ?, De ne Cristae ?, State any two function of Golgi body ?, Name various type of plastids present in a plant cell ?, State the main function of lisosome ?, , 1., 2., , LONG ANSWER TYPE QUESTIONS (5 Marks), Draw a neat and labelled diagram of mitochondria., Differentiate between plant and animal cell with suitable gures., , Fundamental Unit Of Life: Cell, , 57
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CHAPTER AT A GLANCE, , 58, , Science Class - IX
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Key Points : Tissue, Plant Tissue, Meristematic, Apical Meristem, Intercalary, Meristem, Lateral Meristem Permanent, Protective Tissue, Epidermis, Cork,, Parenchyma, Collenchyma, Sclerenchyma, Sclereids, Fibers, Sclerenchyma Fibres,, Complex Permanent Tissue, Xylem, Phloem, Sieve Tubes, Animal Tissue, Epithlial, Tissue, Connective Tissue, Muscular Tissue, Nerve Tissue., , PLANT TISSUE – Meristematic & Permanent, Meristematic Tissue, These are simple living tissues having thin walled compactly arranged immature, cells which are capable of division and formation of new cells., Main features of Meristematic tissues are :, • Thin primary cell wall (cellulosic)., • Intercellular spaces are absent (compact tissue)., • Generally vacuols are absent, dense cytoplasm & prominent nuclei are, present., • Large numbers of cell organelles are present., • Active metabolic state, stored food is absent., • Actively dividing cells are present in growing regions of plants e.g., root &, shoot tips., Classification on the Basis of Origin, (A), Primary (Promeristem), • Derived directly from the meristems of embryo., • They consist of cells derived from primary meristem., • They add to primary growth of plants., Tissue, , 59
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(B), , Secondary, • Formed by permanent tissues., • These are having cells derived from primary permanent tissue., • They usually add to the diameter of plants., Permanent tissue differentiation Secondary meristem, , Classification on the Basis of Location, (A), Apical Meristem, • It is present at the growing tips of stems and roots., • Cell division in this tissue leads to the elongation of stem & root, thus, it is involved in primary growth of the plant., (B), Intercalary Meristem, • It is present behind the apex., • It is the part of apical meristem which is left behind during growth, period., • These are present at the base of leaf & internode region., • These lead to the increase in the length of leaf (Primary) e.g., in grass, stem, bamboo stem, mint stem etc., (C), Lateral Meristem, • It is also called as secondary meristem., • It occurs along the sides of longitudinal axis of the plant., • It gives rise to the vascular tissues., • Causes growth in girth of stem & root., • They are responsible for secondary growth., , PERMANENT TISSUE, •, •, •, 60, , The permanent tissues are composed of those cells which have lost their, capability to divide., They have definite shape, size and thickness. The permanent tissue may, be dead or living., The division & differentiation of the cells of meristematic tissues give rise, Science Class - IX
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to permanent tissues., • In cell differentiation, developing tissue and organs change from simple, to more complex forms to become specialized for specific functions., • The cells of permanent tissue loose the capacity to divide and attain a, permanent shape, size and function., Depending upon the Structure and Composition, the Permanent tissues are, classified into two types :, (A), Simple Permanent Tissues, • These are made up of same type of cells which are similar structurally, and functionally., • They include two types of tissue :, (a), Protective Tissues : These tissues are primarily protective in, function. They consist of :, (i) Epidermis, •, Epidermis forms one cell thick outermost layer of various body, organs of plants such as leaves, flowers, stems and roots., •, Epidermis is covered outside by cuticle. Cuticle is a waterproof layer of waxy substance called as cutin which is secreted, by the epidermal cells., •, Cuticle is very thick in xerophytes., •, Cells of epidermis of leaves are not continuous at some places, due to the presence of small pores called as stomata., •, Each stomata is guarded by a pair of bean-shaped cells called, as guard cells. These are the only epidermal cells which possess, chloroplasts, the rest being colourless., , Tissue, , 61
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Functions of Epidermis, •, The main function of epidermis is to protect the plant from, desiccation and infection., •, Cuticle of epidermis cuts the rate of transpiration and, evaporation of water and prevents wilting., •, Stomata in epidermis allow gaseous exchange to occur during, photosynthesis respiration., •, Stomata also helps in transpiration., (ii) Cork or Phellem, •, In older roots and stems, tissues at the periphery become cork, cells or phellem cells., •, Cork is made up to dead cells with thick walls and do not have, any intercellular spaces., •, The cell walls in cork deposit waxy substance called as suberin., •, The cells of cork become impermeable to water and gases due, to the deposition of suberin., •, The cork cells are without any protoplasm but are filled with, resins or tannins., , Functions of Cork :, •, Cork is protective in function. Cork cells prevent desiccation,, infection and mechanical injury., •, Imperviousness, lightness, toughness, compressibility and, elasticity make the cork commercially valuable., •, Cork is used for insulation, as shock absorber in linoleum., •, Cork is used in the making of a variety of sport goods such as, cricket balls, table tennis, shuttle cocks, wooden paddles etc., (b) Supporting Tissues : These are supportive in function and are of three, types :, 62, , Science Class - IX
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(i), •, •, •, •, •, , Parenchyma : It is the fundamental tissue., Tissue first time evolved in bryophyte., Thin walled cells, oval or spherical in structure., Cell wall mainly composed of cellulose & pectin., Large central vacuole for food & water storage., Primary function is food storage., , •, , Some parenchyma involved in excretory substance storage are, so called as idioblast, storing such as resin, tannin, gums &, oils., In typical parenchyma chlorophyll is absent., Chloroplast containing parenchyma tissue are chlorenchyma, which perform photosynthesis e.g., mesophyll of leaves., In hydrophytic plants aerenchyma (a type of parenchyma, containing air spaces) provides buoyancy., Parenchyma provides turgidity to cells., Collenchyma : It is the living mechanical tissue., , •, •, •, •, (ii), , Tissue, , 63
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•, •, •, , Elongated cells with thick corners., Localized cellulose & pectin thickening., Provides flexibility to plant parts & easy bending of various, parts of plant., •, Present only in herbaceous dicot stem., •, Present at thin margin of leaves., •, Few chloroplasts may be present., •, Gives mechanical strength & elasticity to the growing stems., (iii) Sclerenchyma : (Scleras – hard) Strengthening tissue., , •, •, •, •, 64, , Composed of extremely thick walled cells with little or no, protoplasm., Cells are dead & possess very thick lignified walls., Lignin is water-proof material., Intercellular spaces are absent., Science Class - IX
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Cells of sclerenchyma are of two types :, Sclereids :, • These are also called grit cells or stone cells., • These are small cells, where lumen is so small due to higher thickening, of cell wall, as present in drup fruit (mango, coconut, walnut) in, legume seeds (Macrosclereid)., , Fibers :, • They are very long, narrow, thick, lignified cells. Lumen is large as, compared to sclereids. Generally 1-3 mm long., • In the thick walls of both the fibres and sclereids are present thin, areas called as pits., Sclrenchyma Fibres, • These are used in the manufacture of ropes, mats & certain textile, fibres., • Jute and coir are obtained from the thick bundle of fibres., , Difference between Parenchyma, Collenchyma and Sclerenchyma, Features, , Parenchyma, , Collenchyma, , Sclerenchyma, , Tissue, , 65
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1. Cell shape, , 2. Cell wall, 3. Cytoplasm, 4. Nucleus, , Isodiametric, cells which are, oval, spherical, or polygonal in, shape., Thin cellulosic, cell wall., Abundant, Present (Living, tissue), Large vacuole, Present, , 5. Vacuoles, 6., Intercellular, spaces, 7. Occurrence Basically packing, tissue, all soft, part of plantpith, cortex,, medullary rays., , Circular, oval or, polyhedral., , Variable in shape., Fibres and sclereids., , Uneven thickening, on their cell wall., Present, Present (Living, tissue), Vacuolated, Absent, , Lignified secondary, cell wall present., Absent, Absent (Dead tissue), Absent, Absent, , Dicot hypodermis,, Dicot stems,, bundle sheath,, petiole and, pericycle, seed, pulp, beneath the, epidermis. Absent of fruits., in monocot and, roots., Protection from, 8. Functions Food storage,, Provide tensile, stress and strain,, photosynthesis. strength,, mechanical strength., mechanical, support,, photosynthesis., (B), Complex Permanent Tissues, • It consists of more than one type of cells which work together as a, unit., • It helps in transportation of organic materials, water & minerals., • It is also known as conducting or vascular tissue., • Xylem & phloem together form vascular bundles., Xylem : Also known as wood and is a vascular and mechanical tissue., Thick walled cells are found in the form of tubular passages., , 66, , Science Class - IX
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Xylem consists of four types of cells called as elements :, (i) Tracheids :, • They are elongated angular dead cells (primitive elements) mainly, involved in conduction of water and minerals in gymnosperms., (ii) Vessles : They are advance element (generally found in angiosperms)., • Vessels are cylindrical tube like structures placed one above the other, end to end which form a continuous channel for efficient conduction, of water., (iii) Xylem parenchyma :, • They are small & thick walled parenchymatous cells subjected for, storage of starch (food)., (iv) Xylem sclerenchyma :, • Thy are non-living fibres with thick walls and narrow cavities provide, mechanical support., • Except xylem parenchyma all other xylem elements are dead., • The annual rings present in the trunk of a tree are xylem rings., • By counting the number of annual rings, we can determine the age of, a tree., Phloem : They also consist of both parenchymatous and schlerenc-hymatous cells., , Phloem consists of four types of element :, (i) Sieve tubes :, • Sieve tubes are slender tube like structures made up of elongated,, thin walled cells placed end to end., • The end walls of sieve tube cells are perforated by numerous pores,, called as sieve plates., • Nucleus of sieve cell degenerates at maturity. However, cytoplasm, Tissue, , 67
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•, (ii), •, *, (iii), •, (iv), •, (v), •, •, •, , persists, because of protoplasmic continuation of sieve tube with, companion cell through plasmodesmata., Sieve cells possess slime protein or protein which is concerned with, growth and repair of sieve cells., Companion cells :, Companion cells have dense cytoplasm and prominent nuclei., Sieve cells & companion cells are so called sister cells because they, originate from single mother cell., Phloem fibre :, They give mechanical support to sieve tubes., Phloem parenchyma :, They store food and help in radial conduction of food., Leptome :, Main part of phloem involved in conduction of food, which is sieve, tube., In xylem, only unidirectional movement is possible while in phloem, bidirectional movement can occur., In phloem, except phloem sclerenchyma all elements are living., , Components of Phloem, , Xylem and Phloem, Features, Cells : Living/dead, Cell walls :, Thickness, Material, Permeability, Cross walls, Cytoplasm, Function, 68, , Xylem, Dead, , Phloem, Living, , Thick, Lignin, Impermeable, None, None, Carries water and salts, , Thin, Cellulose, Permeable, Sieve plates, Yes, Carries sugars, , Science Class - IX
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Direction of flow, Special features, , Upwards, Fibres, , Down and up, Companion cells, , ANIMAL TISSUE, , EPITHELIAL TISSUE, •, •, , Always grows on some other types of tissue., Cells of epithelium are set very close to each other and the tissue rests on, a non-cellular basement membrane., • Consists of single layer of cells., • Blood vessels are absent and non-nervous in nature., • It covers all the organs and lines the cavities of hollow organs like stomach., • It is primarily protective in function., Types of Epithelium, , Epithelium tissues are classified as :, (a), Squamous epithelium : Also called pavement epithelium., • Cells arranged end to end like tiles on a floor., Tissue, , 69
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•, •, , (b), , (c), , (d), , Cells are polygonal in surface view., It forms the delicate lining of cavities (mouth, oesophagus, nose,, pericardium, alveoli etc.) blood vessels and covering of the tongue, and skin., • Epithelial cells are arranged in many layers (stratum) to prevent wear, and tear in skin. This pattern is stratified squalors epithelium., Cubical epithelium :, • They are cube like cells that fit closely, cells look like squares in, section, but free surface appears hexagonal., • It is found in kidney tubules, thyroid vesicles & in glands (salivary, glands, sweat glands)., • It forms germinal epithelium of gonads (testes & ovaries)., • It involves in absorption, excretion & secretion. It also provides, mechanical support., Columnar epithelium :, • Columnar means ‘pillar-like’ epithelium. It forms lining of stomach., • Small intestine & colon, forming mucous membranes., • Border of micro villi is present at the free surface end of each cell, which increases absorption efficiency in small intestine., Ciliated epithelium :, • Cells may be cubical or columnar., • On its free surface are present protoplasmic outgrowths called cilia., • It helps in the movement of ova in the fallopian tube., , CONNECTIVE TISSUE, •, , (a), , 70, , The cells of the connective tissue are widely spaced and embedded in, an intercellular matrix., • The mature of matrix decides the function of tissue., • White and yellow fibres are present in the matrix., • Their basic function is to provide support to different organs &, keeping them in place., Fluid or vascular tissue :, , Science Class - IX
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Blood and lymph, • Blood is a connective tissue, fluid matrix of blood is plasma having, wandering or floating cells, called corpuscles, blood helps in the, transportation of various materials such as nutritive substances, gases,, excretory products, hormones etc., Plasma, • Form 55% part of blood. Constitution : 90-91% : water, 7% : protein, (Albumin, fibrinogen, globulin), 0.9% : inorganic salt etc., Corpuscles, • Forms 45% part of blood., RBCs, • They are also called as erthyrocytes, containing red coloured respiratory, pigment called haemoglobin that helps in transportation of oxygen., WBCs (Leucocytes : They are also called as ‘Soldiers of the body’.), • They are irregular, amoeboid, phagocyte cells that protect our body by, engulfing bacterial & other foreign particles. They are of five types :, Monocytes, Lymphocytes, Basophiles, Neutrophiles, Eosinophils., Blood platelets or thrombocytes, • They are spindle shaped cells which are involved in clotting of blood., (b), Skeletal Tissue, , It is hard connective tissue that forms supportive framework of the body. It is of, two types :, , Tissue, , 71
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Bone, • Matrix of bone is very hard because of salts such as calcium phosphate,, CaCO3 (60-70%) etc. and a protein ossein., • Bone cells (osteoblasts) are embedded in this hard matrix., • Matrix is deposited in the form of concentric layers of lamellae formed, round a central canal, the done cells occupy small spaces between the, concentric layers of matrix., • The long bones are usually hollow containing cavity called as marrow, cavity. It is full of bone marrow., , Cartilage, • This tissue is elastic, less harder as compared to bones., • Elasticity is due to presence of chondrin (protein). Cells are called as, chondroblast, which are widely spaced and matrix is reinforced by fibres., • It occurs at joint of bones, in the nose, ear, trachea & larynx., • It provides flexibility and great tensile strength., (c), Connective tissue, It is the most abundant type of connective tissue. It is further divided into, following types :, (i), Yellow fibrous connective tissue, • They are very elastic due to the presence of a network of yellow fibres, in its matrix called as ligament which attaches bone to bone., (ii), White fibrous connective tissue, • They are very little matrix containing abundant white fibres forming, layers., • Bundles of this tissue are called as tendons, which attaches muscles, to the bones., 72, , Science Class - IX
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(d), •, •, , (e), •, •, •, , Aerolar tissue :, It is the most distributed connective tissue in the body., This tissue fills spaces inside organs and is found between the skin &, muscles, around blood vessels, nerves and in the bone marrow., , Adipose tissue :, These are oval and round cells, filled with fat globules., The cells are called as adipocytes., It is found in subcutaneous layer below the skin, around the heart, brain, and below the eyeballs. It acts as an insulator and prevents loss of heat, from the body., , Tissue, , 73
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MUSCULAR TISSUE, •, , Movements are brought about in our body with the help of muscular, tissues., • They are long fibre-like cells called muscle fibres., • They are capable of contraction or relaxation., Types of Muscular Tissue, , (a), •, •, •, •, 74, , Striated muscles, They are also called as voluntary muscles because these are under the, control of one’s will., Muscle fibres or cells are multinucleated and unbranched., Each fibre is enclosed by thin membrane which is called as sarcolemma., Cytoplasm is called as sarcoplasm., These muscles get tired and need rest., Science Class - IX
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(b), •, •, •, •, •, (c), •, •, •, •, •, , Cardiac muscle fibres, They are only involuntary muscles., Only found in the walls of heart., Their structure is in between the striated and non-striated muscles., They are uninucleated and branched. Branches are united by intercalated, disc., In these muscles rhythmic contraction and relaxation occurs throughout, the life., Non-striated muscles, They are involuntary muscles also called as smooth muscles., These muscle fibres are uninucleated and spindle shaped., They are not enclosed by membrane but many fibres are joined together, in bundles., Such muscles are found in the walls of stomach, intestine, urinary bladder,, bronchi, iris of eye etc., Peristaltic movements in alimentary canal are brought about by smooth, muscles., , NERVOUS TISSUE, , •, , They are highly specialized tissue due to which the animals are able to, perceive and respond to the stimuli., , •, , Their functional unit is called as nerve cell or neuron., , •, , Cell body is cyton covered by plasma membrane., , •, , Short hair like extensions rising from cyton are Dendron which are, further subdivided into dendrites., , •, , Axon is long, tail like cylindrical process with fine branches at the end., Axon is covered by a sheath., Tissue, , 75
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•, , Axon of one neuron is very closely placed to the dendrons of another neuron, to carry impulses from one to another neuron in the form of, electrochemical waves. This close proximity is called as synapse., , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , The tissue derived directly from the meristem of embryo is called, as................ ., , 2., , A group of cells with similar structure organized to do a common function, is called as................ ., , 3., , Which plant tissue remains in active metabolic state always ?, , 4., , Sieve tubes and companion cells are found in................tissue. (Xylem/, phloem/collenchyma), , 5., , Long, narrow, dead cells having a thick deposition of lignin in the cell, wall are called................cells. (Parenchyma/cambium/sclerenchyma), , 6., , Which tissue is responsible for transport of water in plants ?, , 7., , The special property of muscle fibres to contract forcefully and return to, relaxed state is called................ . (excitability/contractibility/flexibility), , 8., , A branch of science dealing with the study of bones is called................ ., (Ornithology/physiology/osteology), , 9., , The fluid matrix of blood is called................ . (plasma/lymph/serum), , 10., , Spindle-shaped, non-striated, involuntary muscle fibres present in hollow, internal organs like urinary bladder are called................ . (smooth muscle, fibres/striated muscle fibres/cardiac muscle fibres), SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , Define tissue., , 2., , What do you mean by division of labour ?, , 3., , Name the different elements of xylem and phloem., , 4., , In hydrophytes xylem is less developed. Why ?, , 5., , Write the composition of mammalian blood., , 6., , What is the function of nervous tissue ?, , 7., , State the main features of muscular tissue., 76, , Science Class - IX
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LONG ANSWER TYPE QUESTIONS (5 Marks), 1., , What is tissue ? Explain meristematic plant tissue., , 2., , Mention the role of parenchyma, collenchyma and sclerenchyma., , 3., , Give summarized classification of animal-tissue., , 4., , Describe the structure of neuron with labelled diagram., , Tissue, , 77
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CHAPTER AT A GLANCE, All living organism are grouped on the basis of their similarities and, increasing complexities into different complexities., , 78, , Science Class - IX
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Diversity In Living Organism, , 79, , 1. Unicellular, eukaryotes., 2. Hair like cilia, agella for, movement., 3. Nutrition – Autotrophic or, heterotrophic., , Examples – Unicellular,, algae, diatoms and, protozoans., , 2. No walled (de ned cell, organelles)., , 3. Nutrition-Autotrophic &, Heterotrophic (Autotrophic, – made by self, Hetero –, made by others), , Examples – Bacteria,, Blue-green algae (cyano, bacteria), mycoplasma., , PROTISTA, , 1. No de ned nucleus., , MONERA, (Unicellular Prokaryotes), , 4. Cell made up of cell wall of, tough complex sugar called chitin., Examples – Penicillium, Aspergillus,, Agaricus., , 3. Consume organic decaying, material called saprophytes., , 2. Hetrotrophic nutrition., , 1. Eukaryotic, multicellular., , FUNGI, , PLANTAE, , 5. All the green plants are there., Further divided into ve sub-groups on the, basis of :, (a) Plant body well differentiated or not., (b) Special tissue for the transport of water, are there or not., (c) Beer seeds, whether naked or enclosed, within fruits., Examples – Pinus, algae, funeria, Mangifera, indica., , 4. Cells have cell walls., , 3. Autotrophs – Contain chlorophyll, do, photosynthesis., , 2. Multicellular, , 1. Eukaryotic, , FIVE KINGDOM CLASSIFICATIONS, , 4. Without cell wall.Further, divided into 10 sub-groups on, the basis of extent and type of, body design differentiation., Examples – Tiger, peacock,, ant, insects, shes and soon., , 3. Heterotrophs, , 2. Multicellular, , 1. Eukaryotic, , ANIMALIA
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Biodiversity means the variety of living organisms present on a particular, region. There are about 20 lac organisms known on the earth which differ from, one another in external form, internal structure, mode of nutrition, habitat, etc., Taxonomy : It is a branch of biology which deals with identi cation,, nomenclature and classi cation of organisms. Carolus Lannaeus is called the, father of taxonomy., &ODVVL¿FDWLRQ The method of arranging organisms into groups or sets on, the basis of similarities and differences is called classi cation., ,PSRUWDQFHRI&ODVVL¿FDWLRQ, •, , It makes the study of wide variety of organisms easy and in systematic, manner., , •, , It helps to understand how the different organisms have evolved with, time., , •, , It helps to understand the inter-relationships among different groups of, organisms., , •, , It forms a base for the study of other biological sciences, like biogeography., , %DVLVRI&ODVVL¿FDWLRQ, •, , , , There are certain features or properties used for the classi cation of, living organisms which are known as characteristics. Organisms with, same characteristics are placed in same groups., , &ODVVL¿FDWLRQ6\VWHP, •, , 7ZRNLQJGRPFODVVL¿FDWLRQ Carolus Linnaeus in 1758 classi ed the, living organisms into two groups as plants and animals., , •, , )LYHNLQJGRPFODVVL¿FDWLRQ H. Whittaker in 1959 further classi ed, the organisms into ve kingdoms as Kingdom Monera, Kingdom Protista,, Kingdom Fungi, Kingdom Plantae and Kingdom Animalia., , Note : Carl Woese in 1977 further divided Kingdom Monera into, archaebacteria (or Archae) and Eubacteria (or Bacteria)., +LHUDUFK\RI&ODVVL¿FDWLRQ Linnaeus proposed a classi cation system by, arranging organisms into taxonomic groups at different levels according to the, characteristics they have. The groups or the levels from top to bottom are :, 7KH PDMRU FKDUDFWHULVWLFV FRQVLGHUHG IRU FODVVLI\LQJ DOO RUJDQLVPV LQWR ¿YH, PDMRUNLQJGRPVDUH , 80, , Science Class - IX
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•, , Type of cellular organization, (a) Prokaryotic cells : These are primitive and incomplete cells without, well-de ned nucleus., (b) Eukaryotic cells : These are advanced and complete cells with wellde ned nucleus., , •, , Body organization, (a) Unicellular organisms : These are organisms made up of single cell, with all activities performed by the single cell., (b) Multicellular organisms : These are organisms made up of large, number of cells with different functions performed by different cells., , •, , Mode of obtaining food, (a) Autotrophs : These are the organisms that make their own food by, photosynthesis., (b) Heterotrophs : These are the organisms which depend on other, organisms for food., , Nomenclature : An organism can have different names in different, languages. This creates confusion in naming organism. A scienti c name is, needed which is same in all languages. Binomial nomenclature system given by, Carolus Linnaeus is used naming different organisms., , , )ROORZLQJDUHVRPHFRQYHQWLRQVLQZULWLQJWKHVFLHQWL¿FQDPHV , (1) Genus should be written followed by the species., (2) First letter of the genus should be capital and that of the species should, be in small letter., (3) When printed the name should be written in italics and when written with, hands genus and species should underlined separately., Example : Homo sapiens for humans, Panthera tigris for tiger., , Kingdom I : MONERA, (i) Prokaryotic, unicellular., (ii) Can be autotrophs or heterotrophs., (iii) May or may not have cell wall., (iv) Examples : Anabaena and Bacteria (heterotrophic), Cyano-bacteria or, Diversity In Living Organism, , 81
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Blue-green algae (autotrophic)., , Kingdom II : PROTISTA, (i) Eukaryotic, unicellular., (ii) Can be autotrophic or heterotrophic., (iii) May have cilia, agella or pseudophodia for locomotion., (iv) Examples : Plants like unicellular algae, diatoms; animals like protozoans, (Amoeba, Paramecium, Euglena); fungi like slime molds and water, molds., , Kingdom III : FUNGI, (i) Eukaryotic., (ii) Mostly multicellular but sometimes unicellular (yeast)., (iii) Source of food :, (a) Mostly saprophytes : These organisms use decaying material for, food., (b) Some parasitic : These organisms live inside body of other living, organism to have food and can be disease causing., (c) Symbiotic relation : These are relations between two organisms in, which they live together for bene t of one or both. Lichens are a, symbiotic relation between fungi and cyanobacteria. Here fungi gets, food from cyanobacteria and in return cyanobacteria gets water and, 82, , Science Class - IX
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protection from sunlight through fungi., (iv) Cell wall is made of chitin., (v) Examples : Mushrooms (Agaricus), green mold (Penicillium), smut, (Aspergilus)., , Kingdom IV : PLANTAE, (i) Eukaryotic, multicellular., (ii) Autotrophs., (iii) Cell wall present., Basis of division in Kingdom Plantae, (a) Differentiated body parts : Body is differentiated into leaves,, stems, roots, owers, etc., (b) Presence of vascular tissue : There are two types of vascular tissues, present in the plants :, •, , Xylem : Helps in transport of water., , •, , Phloem : Helps in transport of food., , (c) Reproduction through seeds or spores :, •, , Phanerogam : Plants with seeds are called phanerogam., They contains embryo with stored food and are multicellular., , •, , Cryotogam : Plants with spores are called cryptogam., They contains only naked embryo and are generally unicellular., , (d) Seeds are inside the fruit or naked :, •, , Angiospermae : These are plants with seeds inside the fruit, and bears owers., Diversity In Living Organism, , 83
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•, , Gymnospermae : These are plants with naked seeds and do, not bear owers., , Division 1 : Thallophyta, (i) Basic and elementary plants with undifferentiated body parts., (ii) Generally called algae., (iii), , No vascular tissue present., , (iv) Reproduce through spores., (v) Mainly found in water., (vi) Example : Ulva, Spirogyra, Ulothrix, Cladophora, Chara., , Spirogyra, , Division 2 : Bryophyta, (i) Body structure differentiated but not fully developed., (ii) No vascular tissues present., (iii) Reproduce through spores., (iv) Found on both land and water therefore known as ‘Amphibians of, Plantae Kingdom’., (v) Example : Liverwort (Marchantia, Riccia), Mosses (Funaria), Hornwort, (Dendrocerous)., , 84, , Science Class - IX
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Division 3 : Pteridophyta, (i) Differentiated body structure – leaves, stems, roots, etc., (ii) Vascular tissues present., (iii) Reproduce through spores., (iv) Examples : Marsilea, fern, horsetails., , Division 4. Gymnosperms, (i) Differentiated body parts., (ii) Vascular tissues., (iii) Naked seeds without fruits or owers., (iv) Perennial, evergreen and woody., (v) Examples : Pinus (deodar), Cycus, Ginkgo., , Division 5 : Angiosperms, (i) Also known as ower-bearing plants., (ii) Later on ower becomes fruit., (iii) Seeds are inside the fruit., (iv) Embryos in seeds have structure called cotyledons. They are also called, seed leaves because in many plants they emerge and become green when, they germinate., Diversity In Living Organism, , 85
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Examples, , Bacteria,, Amoeba,, Blue-green Paramecium,, algae, Euglena, , Yeast,, Rhiozpus,, Mushrooms, moulds, , Trees,, Plants,, Shrubs, , Fish, Insects,, Animals, Humans, Birds, , Kingdom V : ANIMALIA, Basis of classi cation of Animalia kingdom :, (i) Symmetry :, (a) Bilateral symmetry : It is when an organism can be divided into, right and left halves, identical but mirror images, by a single vertical, plane., (b) Radial symmetry : It is when an organism is equally spaced around, a central point, like spokes on a bicycle wheel., (ii) Germ layers : In embryonic stages there are different layers of cells, called germ cells. The three different types of germ cells are :, •, , Ectoderm : It is the outermost layer which forms nail, hair,, epidermis, etc., , •, , Endoderm : It is the innermost layer which forms stomach, colon,, urinary, bladder, etc., , •, , Mesoderm : It is the middle layer between ectoderm and endoderm, which forms bones, cartilage, etc., , So, according to the number of germ layers present in embryonic stage,, animal could be :, •, , Diploblastic : Organisms which are derived from two embryonic, germ layers (ecto and endo)., , •, , Triploblastic : Organisms which are derived from all the three, embryonic germ layers., , (iii) Coelom : Body cavity or coelom is important for proper functioning, of various organs. For example, heart which has to contract and expand needs, some cavity or empty space, which is provided by the coelom., Diversity In Living Organism, , 87
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On the basis of presence or absence of coelom, organisms are divided into :, •, , Acoelomates : These are the simple organisms having no body, cavity., , •, , Coelomates : These are complex organisms having true cavity, lined by mesoderm from all sides. These are further sub-divided into, schizocoelomates or protostomes (coelom formed due to splitting, or mesoderm) and enterocoelomates or dueterostomes (coelom, formed from pouches pinched off from endoderm)., , •, , Pseudo coelamate : These are organisms having false coelom. They, have pouches of mesoderm scattered between endoderm and, ectoderm., , (iv) Notochord : It is a long rod like structure, which runs along the body, between nervous tissues and gut and provides place muscle to attach for ease of, movement., Organisms could be :, •, , without notochord, , •, , with notochord, , •, , with notochord in initial embryonic stages and vertebral column in, adult phase, , Phylum 1 : Porifera or Sponges, (i) Cellular level of organization, (ii) Non-motile animals, (iii) Holes on body which led to a canal system for circulation of water and, food, (iv) Hard outside layer called as skeletons, (v) Examples : Sycon, spongilla, euplectelia, , 88, , Science Class - IX
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Phylum 2 : Coelenterata, (i) Tissue level of organization, (ii) No coelom, (iii) Radial symmetry, diploblastic, (iv) Hollow gut, (v) Can move from one place to another, (vi) Examples : Hydra, sea anemone, jelly sh (solitary), corals (colonies), , Phylum 3 : Platyhelminthes, (i) Also called at worms, (ii) No coelom present, (iii) Bilateral symmetry, triploblastic, (iv) Free living or parasite, (v) Digestive cavity has one opening for both ingestion and egestion, (vi) Examples : Planaria (free living), liver uke (parasitic), , Phylum 4 : Mollusca, (i) Coelom present, (ii) Triploblastic, bilateral symmetry, (iii) Soft bodies sometimes covered with shell, (iv) Generally not segmented, Diversity In Living Organism, , 89
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(v) No appendages present, (vi) Muscular foot for movement, (vii) Shell is present, (viii) Kidney like organ for excretion, (ix) Examples : Chiton, octopus, pila, unio, , Phylum 5 : Annelida, (i) Second largest phylum, (ii) Coelom present, (iii) Bilateral, triploblastic, (iv) Segmented (segments specialized for different functions), (v) Water or land, (vi) Extensive organ differentiation, (vii) Examples : Earthworm, leech, nereis, , Phylum 6 : Arthropoda, (i) Largest phylum (consist of 80% of species), (ii) Generally known as insects, (iii) Coelom present, (iv) Bilateral, triploblastic, 90, , Science Class - IX
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(v) Segmented, sometimes fused, (vi) Tough exo-skeleton of chitin, (vii) Joing appendages like feet, antenna, (viii) Examples : Prawn, scorpio, cockroach, house y, butter y, spider, , Phylum 7 : Echinodermata, (i) Spiny skin, marine, (ii) No notochord, (iii) Coelom present, bilateral symmetry, triploblastic, (iv) Endoskeleton of calcium carbonate, (v) Water vascular system for locomotion, (vi) Bilateral symmetry before birth and radial symmetry after birth, (vii) Examples : Antedon, sea cucumber, star sh, echinus, , Phylum 8 : Hemichordata, (i) Small group of marine animals, (ii) Cylindrical, bilateral symmetry, triploblastic, (iii) Coelom present, (iv) Gills for respiration, Diversity In Living Organism, , 91
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(v) Examples : Balanoglossus, , Phylum 9 : Chordata, (i) Bilateral symmetry, triploblastic, (ii) Coelom present, (iii) Notochord, (iv) Gills present at some phase of life, (v) Dorsal nerve chord, (vi) Post anal tail present at some stage of life, for example, present in humans, in embryonic stages, (vii) Sub-divided into two :, (a) Prochordata, •, , Notochord at some stage of life, , •, , Marine, , •, , Examples : Herdemania, amphioxus, , (b) Vertebrata, •, , Notochord converted to vertebral column, , •, , 2, 3, 4 chambered heart, , •, , Organs like kidney for excretion, , •, , Pair appendages, , •, , Examples : Humans (4-chambered), frog (3-chambered),, shes (2-chambered), , Vertebrates are divided into ve classes namely Pisces, Amphibia, Reptilia,, 92, , Science Class - IX
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Aves and Mammalia., •, , Warm blooded organisms : These are organisms which, maintain same body temperature irrespective of outside, temperature. Example : Humans. Human’s body temperature, is approximately 37º., , •, , Cold blooded organisms : These are organisms which change, their body temperature as per surrounding temperature., Example : Frog., , •, , Fishes are divided into two categories on the basis of, skeleton :, , (i), , Fishes with bony skeleton called ERQ\¿VKHV Example : Tuna., , (ii), , Fishes with cartilage skeleton called FDUWLODJLQRXV ¿VKHV, Example : Shark., , (i) Pisces (Fishes), •, , They are shes living in water., , •, , Their skin is covered with scales or plates., , •, , They respire using gills., , •, , They have streamlined body and ns which help them to move in water., , •, , They are cold blooded and their heart has only two chambers., , •, , They lay eggs from which the young ones hatch out., , Some shes have skeleton made of cartilage like Sharks, Rays etc. and some, have skeleton made of bones and cartilage like Tuna, Rohu etc., , (ii) Amphibia (Amphibians), •, , They are found in land and water., , •, , They do not have scales but have mucous glands on their skin., , •, , They are cold blooded and the heart is three chambered., , •, , Respiration is through gills or lungs. They lay eggs in water., Diversity In Living Organism, , 93
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•, , (iii), , Example : Frogs, Toads, Salamanders etc., , Reptilia (Reptiles), , •, , They have scales and breathe through lungs., , •, , They are cold blooded., , •, , Most of them have three chambered heart but crocodiles have four, chambered heart., , •, , They lay eggs with hard covering in water., , •, , Example : Snakes, Turtles, Lizards, Crocodiles etc., , (iv), , Aves (Birds), •, , They are warm blooded animals., , •, , They have four chambered heart., , •, , They breathe through lungs., , •, , They have an outer covering of feathers., , •, , Their two fore limbs are modi ed into wings for ying. They lay eggs., , •, , Example : Crow, Sparrow, Pigeon, Duck, Stork, Ostrich etc., , 94, , Science Class - IX
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(v) Mammalia (Mammals), , S., , •, , They are warm blooded animals., , •, , They have four chambered heart., , •, , They have mammary glands for production of milk to nourish their, young ones., , •, , The skin has hairs and sweat glands. Most of them give birth to their, young ones., , •, , Some of them lay eggs (like Platypus and Echidna)., , •, , Example : Cat, Rat, Dog, Lion, Tiger, Whale, Bat, Humans etc., , Features, , No., 1., Inhabit, , Pisces, , Amphibian, , Reptilia, , Aves, , Mammalia, , Water, , Water and, , Water and, , Water, land, , Land or, , land, , land, , and air, , water, , Lungs, , Lungs, , 2., , Respiratory, , Gills, , Gills, lungs, , Lungs, , 3., , organs, Heart, , 2-cham-, , 3-cham-, , 3-chambered 4-cham-, , bered, , bered, , Maintenance Cold, , Cold, , Cold, , Warm, , Warm, , of body, , blooded, , blooded, , blooded, , blooded, , blooded, , Eggs, , Eggs in, , Eggs with, , Eggs, , Young, , water, , tough, , babies except, , coating on, , platy-pus and, , land, , echidna., , 4., , 4-chambered, , bered, , temperature, 5., , 6., , Youngones, , Skin, , Skin, , Mucus, , Skins, , covered, , glands in, , covered with covered, , sweat glands, , with scales, , skin, , scales, , with, , are present, , feathers, , on the skin, , Skin, , Hair, oil and, , Diversity In Living Organism, , 95
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7., , Special, , Streamlined, , Mammary, , features, , body, , glands which, produces, milk for, children, , 8., , Example : Anabas,, , Salamander, Turtle,, , Ostrich,, , Humans,, , Dog sh,, , Common, , Snakes,, , Sparrow,, , Lion, Tiger,, , Angler sh,, , frog, Toad,, , Lizard,, , Crow,, , Cat, Bat,, , Mandarin, , Hyla (tree, , Flying, , Pigeon,, , Whale, , lizard,, , Tufted, , ray, String, , Crocodile,, , Duck,, , sh, Sea, , Chameleon, , White Stork, , sh, Electric frog), , horse,, Flying sh., , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1. De ne biodiversity., 2. Who wrote the book ‘Origin of Species’., 3. What do you mean by primitive organism and advanced organism ?, 4. Who is known as the father of taxonomy ?, 5. Collect the range of variation that you see around you., 6. Whittaker’s ve kingdom classi cation in detail. The basis of ve kingdom, classi cation., 7. Write the correct sequence of ve kingdom classi cation., 8. Write the examples of Archaebacteria and Eubacteria., 9. What are resting spore and heterocyst ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), 1. What is thallus ?, 2. Why bryophytes are called amphibians of plant kingdom ?, 3. Write the difference between cryptogams and phanerogams., 96, , Science Class - IX
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4. List the difference between monocots and dicots., 5. List the number of phyla that come under animal kingdom., 6. Use the same tips to study the animal kingdom., 7. Explain all the important characteristics of the given phyla :, (a) Platihelminthes, (b) Coelenterates, (c) Annelida, LONG ANSWER TYPE QUESTIONS (5 Marks), 1. Give two examples belonging to members of nematode., 2. What is the cause of elephantiasis ?, 3. What is the most striking feature of phylum arthropoda ?, 4. List the difference between annelids and arthropods., 5. What is notochord and describe its function., 6. Give two examples from phylum protochordata., 7. Bats and whales are classi ed as mammals. Why ?, 8. Circulatory system found in the phylum molusca ?, , Diversity In Living Organism, , 97
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CHAPTER AT A GLANCE, , 98, , Science Class - IX
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direction to explain it., ([DPSOHRamesh travelled 65 km. (Distance is measured by odometer, in vehicles.), •, , Displacement is a vector quantity, direction for its explanation., , requiring both magnitude and, , ([DPSOH Ramesh travelled 65 km south-west from Clock Tower., •, , Displacement can be zero (when initial point and nal point of motion, are same) ([DPSOHcircular motion., , Difference between Distance and Displacement, Distance, Displacement, 1. Length of actual path travelled by an 1. Shortest length between initial point and, object., far point of an object., 2. It is scalar quantity., , 2. It is vector quantity., , 3. It remains positive, can’t be ‘0’ or 3. It can be positive (+ve), negative (-ve), negative., or zero., 4. Distance can be equal to displacement 4. Displacement can be equal to distance or, (in linear path)., its lesser than distance., , Example 1. $ ERG\ WUDYHOV LQ D VHPLFLUFXODU SDWK RI UDGLXV P VWDUWLQJ LWV, PRWLRQIURPSRLQWµ$¶WRSRLQWµ%¶&DOFXODWHWKHGLVWDQFHDQGGLVSODFHPHQW, Solution :, , Total distance travelled by body, S = ?, S = 3.14, R = 10 m, , Given,, , S = SR, , 100, , Science Class - IX
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•, , Non-uniform Motion :, In this type of motion, the body will travel unequal distances in equal, intervals of time., , Non-uniform motion is of two types :, (i), , Accelerated Motion : When motion of a body increases with, time., , (ii), , De-accelerated Motion : When motion of a body decreases with, time., , Speed : The measurement of distance travelled by a body per unit time is called, speed., Speed =, , 102, , Science Class - IX, , Distance travelled, Time taken
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v, , s, t, , •, •, , SI unit = m/s (meter/second), If a body is executing uniform motion, then there will be a constant, speed or uniform motion., , •, , If a body is travelling with non-uniform motion, then the speed will not, remain uniform but have different values throughout the motion of such, body., , •, , For non-uniform motion, average speed will describe one single value, of speed throughout the motion of the body., Average speed =, , Total distance travelled, Total time taken, , Example : :KDWZLOOEHWKHVSHHGRIERG\LQPVDQGNPKULILWWUDYHOVNPV, LQKUV", Solution :, , Distance (V), Time (W), , = 40 km, = 5 hrs., , Speed (in km / hr) =, , =, , Total distance, Total time, 40 km, 5 hrs, , = 8 km/hr, Speed (in m/s), , Ans., , =?, , 40 km = 40 u 1000 m = 40,000 m, 5 hrs = 5 u 60 u 60 sec., =, , =, , 40 u 1000 m, 5 u 60 u 60 s, 80 m, 36 s, , = 2.22 m/s, , Motion, , Ans., , 103
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Conversion Factor, Change from km/hr to m/s, , =, =, , 1000 m, 60 u 60 s, 5, 18, , m/s, , Velocity : It is the speed of a body in given direction., Velocity =, , Displacement, Time, , •, Velocity is a vector quantity. Its value changes when either its magnitude, or direction changes., •, For non-uniform motion in a given line, average velocity will be, calculated in the same way as done in average speed., Average velocity =, , Total displacement, Total time, , •, For uniformly changing velocity, the average velocity can be calculated, as follows :, Avg velocity =, V( avg ) =, , where,, , Initial velocity + Final velocity, 2, u+v, 2, , X initial velocity, v = nal velocity, , SI unit of velocity = ms-1, Velocity =, , Displacement, Time, , ..., , •, , It can be positive (+ve), negative (-ve) or zero., , Example 1 : 'XULQJ¿UVWKDOIRIDMRXUQH\E\DERG\LWWUDYHOZLWKDVSHHGRI, NPKUDQGLQWKHQH[WKDOILWWUDYHOVZLWKDVSHHGRINPKU&DOFXODWHWKH, DYHUDJHVSHHGRIWKHZKROHMRXUQH\, Solution :, Speed during rst half (v), = 40 km/hr, 104, , Science Class - IX
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Graphical Representation of Equation, (i), , Distance-Time Graph : VW graph :, (a), , s/t graph for uniform motion :, , (b), , s/t graph for non-uniform motion :, , (c), , s/t graph for a body at rest :, , v=, , But,, ?, , s2 s1, t2 t1, , V2 = V1, v=, , 0, t2 t1, , Or, , v=0, , Motion, , 107
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(ii), , Velocity-Time Graph : YW graph :, (a), , v/t graph for uniform motion :, , a=, , But,, , (b), , t2 t1, , v2 = v1, a=, , ?, , v2 v1, , 0, t2 t1, , Or, , D=0, , v/t graph for non-uniform motion :, (A), , v/t graph for accelerated (uniform) motion :, , a=, , v2 v1, t2 t1, , In uniformly accelerated motion, there will be equal, increase in velocity in equal interval of time throughout the motion of body., , 108, , Science Class - IX
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Uniform Circular Motion, If a body is moving in a circular path with uniform speed,, then it is said to be executing uniform circular motion., In such a motion the speed may be same throughout the, motion but its velocity (which is tangential) is different at, eact and every point of its motion. Thus, uniform circular, motion is an accelerated motion., , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , Change the speed 6 m/s into km/hr., , 2., , What do speedometer and odometer used for ?, , 3., , What is the other name of negative acceleration ?, , 4., , What does the slope of distance-time graph indicate ?, , 5., , What can you say about the motion of a body if its speed-time graph is a, straight line parallel to the time axis ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , A tortoise moves a distance of 100 m in 15 minutes. What is its average, speed in km/hr ?, , 2., , If a bus travelling at 20 m/s is subjected to a steady deceleration of, 5 m/s2, how long will it take to come to rest ?, , 3., , What is the difference between uniform linear motion and uniform, circular motion ?, , 4., , Explain why the motion of a body which is moving with constant speed, in a circular path is said to be accelerated., LONG ANSWER TYPE QUESTIONS (5 Marks), , 1., , Derive the equations v = X+ DW, V = XW+ ½DW2 and v2 X22DV graphically., , 2., , What is uniform circular motion ? Give two examples which force is, responsible for that., , Motion, , 113
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CHAPTER AT A GLANCE, , Forces and Laws of Motion :, Force : It is the force that enables us to do any work. To do anything, either we, pull or push the object. Therefore, pull or push is called force., Example, to open a door, either we push or pull it. A drawer is pulled to open and
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pushed to close., Effect of Force, (i), , Force can make a stationary body in object. For example, a football can, be set to move by kicking it, i.e., by applying a force., , (ii) Force can stop a moving body. For example, by applying brakes, a, running cycle or a running vehicle can be stopped., (iii) Force can change the direction of a moving object. For example, by, applying force, i.e., by moving handle, the direction of a running bicycle, can be changed. Similarly by moving steering, the direction of a running, vehicle is changed., (iv) Force can change the speed of a moving body. By accelerating, the, speed of a running vehicle can be increased or by applying brakes the, speed of a running vehicle can be decreased., (v) Force can change the shape and size of an object. For example, by, hammering, a block of metal can be turned into a thin sheet. By, hammering, a stone can be broken into pieces., Forces are mainly of two types :, (A) Balanced forces, (B) Unbalanced forces, (A) Balanced Forces, •, , If the resultant of applied forces is equal to zero, it is called balanced, forces., Example, in the tug of war if both the team apply similar magnitude of, forces in opposite directions, rope does not move in either side. This, happens because of balanced forces in which resultant of applied forces, become zero., , •, , Balanced forces do not cause any change of state of an object. Balanced, forces are equal in magnitude and opposite in direction., , •, , Balanced forces can change the shape and size of an object. For example,, when forces are applied from both sides over a balloon, the size and, shape of balloon is changed., Force And Laws Of Motion, , 115
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(B) Unbalanced Forces, •, , If the resultant of applied forces are greater than zero, the forces are, called unbalanced forces. An object in rest can be moved because of, applying balanced forces., , •, , Unbalanced forces can do the following :, * Move a stationary object, * Increase the speed of a moving object, * Decrease the speed of a moving object, * Stop a moving object, * Change the shape and size of an object, , Laws of Motion :, Galileo Galilei : Galileo rst of all said that object move with a constant speed, when no foces act on them. This means if an object is moving on a frictionless, path and no other force is acting upon it, the object would be moving forever., That is, there is no unbalanced force working on the object., •, , But practically it is not possible for any object. Because to attain the, condition of zero, unbalanced force is impossible. Force of friction,, force of air and many other forces are always acting upon an object., , Newton’s Laws of Motion :, Newton studied the ideas of Galileo and gave the three laws of motion. These, laws are known as Newton’s laws of motion., Newton’s First Law of Motion (Law of Inertia) :, Any object remains in the state of rest or in uniform motion along a straight line,, until it is compelled to change the state by applying external force., Explanation : If any object is in the state of rest, then it will remain in rest until, a external force is applied to change its state. Similarly, an object will remain in, motion until any external force is applied over it to change its state. This means, all objects resist to in changing their state. The state of any object can be changed, by applying external forces only., 116, , Science Class - IX
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Newton’s First Law of Motion in Everyday Life :, (a) A person standing in a bus falls backward when bus starts moving, suddenly. This happens because the person and bus both are in rest, while bus is not moving, but as the bus starts moving, the legs of the, person start moving along with bus but rest portion of his body has the, tendency to remain in rest. Because of this, the person falls backward;, if he is not alert., (b) A person standing in a moving bus falls forward if driver applies brakes, suddenly. This happens because when bus is moving, the person, standing in it is also in motion along with bus. But when driver applies, brakes the speed of bus decreases suddenly or bus comes in the state of, rest suddenly, in this condition the legs of the person which are in contact, with the bus come in rest while the rest part of his body have the, tendency to remain in motion. Because of this person falls forward if he, is not alert., (c) Before hanging the wet clothes over laundry line, usually many jerks, are given to the clothes to get them dried quickly. Because of jerks,, droplets of water from the pores of the cloth falls on the ground and, reduced amount of water in clothes dries them quickly. This happens, because when suddenly clothes are made in motion by giving jerks, the, water droplets in it have the tendency to remain in rest and they are, separated from clothes and fall on the ground., (d) When the pile of coin on the carom-board is hit by a striker, coin only, at the bottom moves away leaving rest of the pile of coin at same place., This happens because when the pile is struck with a striker, the coin at, the bottom comes in motion while rest of the coin in the pile has the, tendency to remain in the rest and they vertically falls the carom-board, and remain at same place., Mass and Inertia, •, , The property of an object because of which it resists to get disturb its, state is called inertia. Inertia of an object is measured by its mass. Inertia, is directly proportional to the mass. This means inertia increases with, increase in mass and decreases with decrease in mass. A heavy object, will have more inertia than the lighter one., , •, , In other words, the natural tendency of an object that resists the change, in state of motion or rest of the object is called inertia., Force And Laws Of Motion, , 117
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•, , Since a heavy object has more inertia, thus it is dif cult to push or pull, a heavy box over the ground than the lighter one., , Momentum, •, , Momentum is the power of motion of an object., , •, , The product of velocity and mass is called the momentum. Momentum, is denoted by ‘p’., Therefore,, , Momentum of the object = Mass u Velocity, p=muv, , Or,, , Where, p = momentum, m = mass of the object and v = velocity of the object., Consider the following explanations to understand the momentum :, •, , A person get injured in the case of hitting by a moving object, such as, stone, pebbles or anything because of momentum of the object., , •, , Even a small bullet is able to kill a person when it is red from a gun, because of its momentum due to great velocity., , •, , A person get injured severely when hit by a moving vehicle because of, momentum of vehicle due to mass and velocity., , Momentum and Mass and Velocity, •, , Since momentum is the product of mass and velocity (p = m u v) of, an object. This means momentum is directly proportional to mass and, velocity. Momentum increases with increase of either mass or velocity, of an object., , •, , This means if a lighter and a heavier object is moving with same, velocity, then heavier object will have more momentum than the lighter, one., , •, , If a small object is moving with great velocity, it has tremendous, momentum. And because of momentum, it can harm an object more, severely. For example, a small bullet having a little mass even kills a, person when it is red from a gun., , •, , Usually, road accidents prove more fatal because of high speed than, in slower speed. This happens because vehicles running with high speed, have greater momentum compared to a vehicle running with slower, speed., , Momentum of an object which is in the state of rest :, Let an object with mass ‘m’ is in the rest., Since, object is in rest, therefore, its velocity, v = 0, 118, , Science Class - IX
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Now, we know that, Momentum = mass u velocity, p=mu0=0, , Or, , Thus, the momentum of an object in the rest i.e., non-moving, is equal to zero., Unit of momentum :, SI unit of mass, , = kg, , SI unit of velocity = meter per second i.e., m/s, We know that, , Momentum (p) = m u v, , Therefore,, , p = kg u m/s, , Or, , p = kg m/s, , Therefore, SI unit of momentum, , = kg m/s, , Numerical Problems Based on Momentum, Type I. Calculation of Momentum, Example 1. What will be the momentum of a stone having mass of 10 kg when it, is thrown with a velocity of 2 m/s ?, Solution :, , We know that,, , Mass (m), , = 10 kg, , Velocity (v), , = 2 m/s, , Momentum (p), , =?, , Momentum (p) = Mass (m) u Velocity (v), p = 10 kg u 2 m/s = 20 kg m/s, , Therefore,, Thus, the momentum of the stone, , = 20 kg m/s., , Ans., , Example 2.&DOFXODWHWKHPRPHQWXPRIDEXOOHWRIJZKHQLWLV¿UHGIURPD, gun with a velocity of 100 m/s., Solution : Given,, , Velocity of the bullet (v) = 100 m/s, Mass of the bullet (m) = 25 g = 25/1000 kg = 0.025 kg, Momentum (p) = ?, , Force And Laws Of Motion, , 119
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Since,, , p=muv, , So,, , p = 0.025 u 100 = 2.5 kg m/s, , Thus, momentum of the bullet, , = 2.5 kg m/s., , Ans., , Example 3. Calculate the momentum of a bullet having mass of 25 g is thrown, XVLQJKDQGZLWKDYHORFLW\RIPV, Solution : Given,, , Velocity of the bullet (v) = 0.1 m/s, Mass of the bullet (m) = 25 g = 25/1000 kg = 0.025 kg, Momentum (p) = ?, Momentum (p) = Mass (m) u Velocity (v), , We know that,, Therefore,, , p = 0.025 kg u 0.1 m/s, , Or, , p = 0.0025 kg m/s, , Thus, the momentum of the bullet, , = 0.0025 kg m/s., , Ans., , Example 4. 7KHPDVVRIDJRRGVORUU\LVNJDQGWKHPDVVRIJRRGVORDGHG, on it is 20000 kg. If the lorry is moving with a velocity of 2 m/s, what will be its, momentum ?, Solution : Given,, , Velocity (v) = 2 m/s, , Mass of lorry = 4000 kg, Mass of goods on the lorry = 20000 kg, Therefore,, , Total mass (m) on the lorry = 4000 kg + 20000 kg = 24000 kg, Momentum (p) = ?, Momentum (p) = Mass (m) u Velocity (v), , We know that,, Therefore,, , p = 24000 kg u 2 m/s, , Or, , p = 48000 kg m/s, , Thus, the momentum of the lorry, , = 48000 kg m/s., , Ans., , Example 5. A car having mass of 1000 kg is moving with a velocity of 0.5 m/s., What will be its momentum ?, Solution : Given,, 120, , Velocity of the car (v) = 0.5 m/s, , Science Class - IX
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Mass of the car (m), , = 1000 kg, , Momentum (p) = ?, Momentum (p) = Mass (m) u Velocity (v), , We know that,, Therefore,, , p, , Thus, momentum of the car, , = 1000 kg u 0.5 m/s = 500 kg m/s, = 500 kg m/s., , Ans., , Statement of Second Law, Rate of change of momentum of an object is proportional to applied unbalanced, force in the direction of force., Mathematical expression, Suppose,, , Mass of an object = m kg, Initial velocity of an object = u m/s, Final velocity of an object = v m/s, , So,, , Initial momentum, p1 = mu, Final momentum, p2 = mv, , ?, , Change in momentum, , = Final momentum – Initial momentum, = mv – mu, = m(v – u), , ? Rate of change of momentum, , =, , =, •, , Time taken, , m vu, t, , According to IInd law, this rate of change is momentum is directly, proportional to force., , ?, , , Change in momentum, , , , We know that,, , , , F v, , m vu, , vu, t, , t, , a, , (From Ist equation of motion), , Force And Laws Of Motion, , 121
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So,, , F = kma, , Where k is a constant. Its value = 1., ?, , , , , , , , F = 1 u m u a = ma, = kg m/s2 or Newton, , SI unit, 4'H¿QH1HZWRQ, , Ans. When an acceleration of 1 m/s2 is seen in a body of mass 1 kg, then the, force applied on the body is said to be 1 Newton., Proof of Newton’s First Law of Motion from Second Law, First law states that if external force F = 0, then a moving body keeps moving, with the same velocity, or a body at rest continues to be at rest., So,, , F=0, , We know, , F, , (a), , m vu, t, , A body is moving with initial velocity u, then, , 0, , So,, , m vu, t, , , , v=u, , Thus, nal velocity is also same., (b), , A body is at rest i.e., u = 0., Therefore, from above u = v = 0, So, the body will continue to be at rest., , Third Law of Motion, To every action there is an equal an opposite reaction., Applications :, (i), 122, , Walking is enabled by IIIrd law., Science Class - IX, , v–u=0
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(ii), , A boat moves back when we deboard it., , (iii), , A gun recoils., , (iv), , Rowing of a boat., , Law of Conservation of Momentum, When two (or more) bodies act upon one another, their total momentum remains, constant (or conserved) provided no external forces are acting., Initial momentum = Final momentum, Suppose, two objects A and B each of mass m1 and mass m2 are moving initially, with velocities u1 and u2, strike each other after time t and start moving with, velocities v1 and v2 respectively., , Now,, , Initial momentum of object A = m1u1, Initial momentum of object B = m2u2, Final momentum of object A = m1v1, Final momentum of object B = m2v2, , So,, , Rate of change of momentum in A, F1, , m1v1 m1u1, t, m1 v1 u1, t, , Force And Laws Of Motion, , ...(i), 123
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , Can force be ()ve ? When ?, , 2., , What is the tendency of a body to resist its change of state called ?, , 3., , Inertia is also measured by.................of an object., , 4., , Higher the mass of an object, higher is its................. ., Force, , 5., , Acceleration is determined by.................which is also mass of the object., , 6., , Why does the load from the cage above the seats in a bus falls down, when suddenly brakes are applied ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , Quantity of motion contained in a body is................. ., , 2., , Unit of momentum is................. ., , 3., , De ne 1 Newton., , 4., , Although we know that a moving body keeps moving inde nitely until, an external force is applied on it, then why does a ball stops when we, slide it on ground (without stopping it) ?, , 5., , Why is it dif cult to stop a truck suddenly than a motorbike ?, SHORT ANSWER TYPE QUESTIONS (3 Marks), , 1., 2., 3., , 4., 5., , 126, , When a metro suddenly stops all the passengers fell forward on its oor., Why do this happen ?, We have a huge atmosphere above us that exerts a huge pressure on our, shoulders, head and whole body. Why don’t we get crushed under it ?, A coin of mass 1 kg and a stone of mass 5 kg are thrown down the Eiffel, Tower with an acceleration of 10 m/s2. Which one would reach the, ground early and why ?, Give applications of Ist law of motion i.e., inertia., (a), Friction is measured in.................. ., (b), Distinguish between balanced and unbalance forces., Science Class - IX
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LONG ANSWER TYPE QUESTIONS (5 Marks), 1., , (a), , Derive rst law of Newton from second law., , (b), , Find the force required to stop a car of mass 100 kg with two, passengers each of 50 kg sitting inside, if it is moving at 60 km/, hr speed and takes 5 s to stop., , 2., , Two balls A and B of masses 40 g and 50 g are moving at speeds of 40, m/s and 30 m/s respectively. If after colliding, B stars moving with a, velocity of 25 m/s, what is the velocity of A ?, , 3., , A girl of mass 30 kg jumps on a cart of mass 5 kg with a velocity of 10, m/s. Find the velocity with which she and cart start moving after she, jumps on it., Answers to Long answer type questions, , 1., , (b), , - 2000/3 N, , 2., , 46.25 m/s, , 3. 8.57 m/s, , Force And Laws Of Motion, , 127
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CHAPTER AT A GLANCE, , 128, , Science Class - IX
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Gravitational Force of Earth, If we release a small stone without pushing it from a height, it, accelerates towards earth. The stone is when accelerated towards earth,, means some force is acting on it., The force which pulls the objects towards the centre of the earth is, known as gravitational force of the earth., Here, stone also attracts earth. It means every object in universe attracts, every other object., Newton’s Universal Law of Gravitation, Sir Isaac Newton in 1687 proposed a law about the force of attraction between, the two objects in the universe which is known as Newton’s law of gravitation., , According to this law :, Every mass in this universe attracts every other mass with a force which is, directly proportional to the product of two masses and inversely proportional to, the square of the distance between them., Let masses (m1) and (m2) of two objects are distance (d) apart, then force of, attraction (F) between them, F v m1 u m2, F v, Fv, F=, , 1, d2, m1 u m2, d2, Gm1 u m2, d2, , where G is a constant and is known as Gravitational constant., Value of G = 6.67 u 10-11 Nm2/kg2, G is called universal gravitational constant., If unit of F is in Newton, m is in kg, d is in metre, then unit of G can be calculated, as :, G=, , F ud2, m1 u m2, , so unit be, , Nm 2, kg 2, , Gravitation, , or Nm2/kg2, 129
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Relation between Newton’s third law of motion and Newton’s law of, gravitation, According to Newton’s third law of motion, “Every object exerts equal and, opposite force on other object but in opposite direction.”, According to Newton’s law of gravitation, “Every mass in the universe attracts, the every other mass.”, In case of freely falling stone and earth, stone is attracted towards earth means, earth attracts the stone but according to Newton’s third law of motion, the, stone should also attract the earth and really it is true that stone also attracts the, earth with the same force F = m u a but due to very less mass of the stone, the, acceleration (a) in its velocity is 9.8 m/s2 and acceleration (a) of earth towards, stone is 1.65 u 10-24 m/s2 which is negligible and we cannot feel it., Importance of universal law of gravitation, (i), , The force that binds us to the earth., , (ii) The motion of moon around the earth., (iii) The motion of earth around the sun., (iv) The tides due to moon and the sun., Free fall of an object and acceleration during free fall, When an object is thrown upward, it reaches certain height, then it starts falling, down towards earth. It is because the earth’s gravitational force exerts on it., This fall under the in uence of earth is called ‘free fall of an object’., During this free fall direction do not change but velocity continuously changes, which is called acceleration due to gravity., It is denoted by ‘g’., Its unit is same as acceleration m/s2., , Gravitational Acceleration and its value at the surface of earth, The uniform acceleration produced in a freely falling object due to the, gravitational force of earth, is called acceleration due to gravity. It is represented, by ‘g’ and it always acts towards the centre of the earth., Value of ‘g’ on the surface of earth, The force acting on an object is, F=, Where Me = Mass of earth, 130, , Science Class - IX, , GM e m, R2, , ...(i)
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m = Mass of an object, R = Radius of earth, and if acceleration due to gravity is ‘g’ due to force F then,, F=mug, Equating (i) and (ii), we get, , mug=, , Or, , g=, , ...(ii), , GM e m, R2, GM e, R2, , If G = 6.673 u 10-11 Nm2/kg2, Me = 6 u 1024 kg, R2 = (6.37 u 106)2, Then,, , g=, , 6.6734 u 1011 u 6 u 1024, (6.37 u 106 ) 2, , g = 9.8 m/s2, Relationship and difference between ‘G’ and ‘g’, G = Gravitational constant, g = Acceleration due to gravity, g=, , GM, R2, , Difference between G (Gravitational constant) and, g (Acceleration due to gravity), Gravitation Constant (G), 1. Its value is 6.6734 u 10-11 Nm2/kg2., , Gravitational acceleration (g), 1. Its value is 9.8 m/s2., , 2. Its value remains constant always and 2. Its value varies at various places., everywhere., 3. Its unit is Nm2/kg2., 3. Its unit is m/s2., 4. It is a scalar quantity., , 4. It is a vector quantity., , Example. If two stones of 150 gm and 500 gm are dropped from a height, which, VWRQHZLOOUHDFKWKHVXUIDFHRIHDUWK¿UVWDQGZK\"([SODLQ\RXUDQVZHU, Ans. It was Galileo, who rst time demonstrated and depicted that the acceleration, of an object falling freely towards earth does not depend on the mass of the, object., It can be veri ed by universal law of gravitation. Let an object of mass m, is, allowed to fall from a distance of R, from the centre of the earth., Gravitation, , 131
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Then, the gravitational force,, , F=, , GM e m, R2, , (Me = Mass of the earth), , F=mua, , The force acting on the stone is, So,, , mua=, , Or, , a=, , GM e m, R2, GM e, R2, , So, acceleration in an object falling freely towards earth depends on the mass of, earth and height of the object from the centre of the earth. So stones of mass 150, gm and 500 gm will reach the earth surface together., Equation of motion when an object is falling freely towards earth or thrown, vertically upwards :, Case 1. When an object is falling towards earth with initial velocity (u), then, Velocity (v) after t seconds, v = u + gt, Height covered in t seconds, h = ut + ½gt2, Relation between v and u when t is not mentioned :, v2 = u2 + 2gh, Case 2. When object is falling from rest position means initial velocity u = 0, (zero), then, Velocity (v) after t seconds, v = gt, Height covered in t seconds, h = ½gt2, Relation between v and u when t is not mentioned :, v2 = 2gh, Case 3. When an object is thrown vertically upwards with initial velocity u, the, gravitational acceleration will be negative ( g), then, Velocity (v) after t seconds, v = u gt, Height covered in t seconds, h = ut ½gt2, Relation between v and u when t is not mentioned :, v2 = u2 2gh, Mass, The mass of a body is the quantity of matter contained in it. Mass is a scalar, quantity which has only magnitude but no direction., 132, , Science Class - IX
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SI unit of mass is kilogram which is written in short form as kg., •, Mass of a body is constant and does not change from place to place., •, Mass of a body is usually denoted by the small ‘m’., •, Mass of a body cannot be zero., Weight, The force with which an object is attracted towards the centre of the earth, is, called the weight of the object., Force = m u a, In case of earth,, , a=g, , So,, , F = mu g, , But the force of attraction of earth on an object is called its weight (W). So,, W=mug, So, weight is the force and its SI unit is Newton (N). It depends on ‘g’ and is a, vector quantity., Relation between 1 kg wt and express it into Newton :, W=mug, , We know that, If mass (m) = 1 kg, g = 9.8, , m/s2,, , then, W = 1 kg u 9.8 m/s2, , Or, , 1 kg wt = 9.8N, , So, the gravitational force of earth that acts on an object of mass 1 kg is called, as 1 kg wt., Distinguish between Mass and Weight, Mass, , Weight, , 1. We can measure mass of an object 1. Weight = mass u acceleration or, by its inertia., muJ, 2. The total quantity of matter 2. The gravitational force by which, contained in an object is called mass earth attracts an object is called weight, of an object., of the object., 3. Mass of the object remains constant 3. Weight of the object is different at, at all the places., different places., 4. Measurement of mass is done by 4. Measurement of weight is done by, using a pan or beam balance., using a spring balance., , Gravitation, , 133
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5. Mass does not change even value of 5. Weight of the object becomes zero, g is zero at any place., if g is zero., Factors affecting value of g, Earth is not a perfect sphere. The radius of earth increases when we go from pole, to equator. Therefore, in most of the calculation, we can take g as constant at the, surface of earth or closer to it. But, as we move away from earth, we can use, equation g =, , GM, d2, , for solving problems., , Example. Calculate the value of ‘g’ at a height of 12800 km from the centre of, WKHHDUWK UDGLXVRIHDUWKLVNP 'UDZLWVLQWHUSUHWDWLRQ, Solution : We know that, , g1 =, , GM e, 2, , 2 Re, , , Re = 6400 km, , Weight of the object from the centre of earth = 12800 km = 2Re, ?, , Or, , g2 =, , GM e, 2, , 2 Re, , g1, , G Me, , g2, , Re, , g1, , 2, , u, , 2R e, , 2, , G Me, , 4, , Or, 4g2 = g1, 1, So, the value of gravitational acceleration ‘g’ at a distance of 12800 km from the, centre of the earth is ¼., g2, , The value of gravitational acceleration ‘g’ decreases with increasing height., The weight of an object on moon is one-sixth of the weight on earth., Let mass of an object be m, its weight on earth means the force by which earth, attracts it towards the centre., Now,, , Fe =, , GM e m, R e2, , ...(i), , where G = Gravitational constant, Me = Mass of the earth, m = Mass of object,, Re = Radius of the earth, Weight of an object on moon,, Fm =, 134, , Science Class - IX, , GM m m, R m2, , ...(ii)
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where Mm = Mass of the moon, Rm = Radius of the moon, Dividing equation (i) by equation (ii), we get, Fe, Fm, , =, , GM e m, R e2, , u, , R m2, GM m m, , §R ·, =, u¨ m ¸, Fm M m © R e ¹, Fe, , Me, , 2, , We know that mass of earth is 100 times the mass of the moon., So,, , Me = 100Mm, , And radius of earth is 4 times the radius of moon., So,, , Re = 4Rm, Fe, Fm, , Then,, , Fe, Fm, Fe, Fm, , Hence,, , =, , =, , 100M m, Mm, 100, 1, , u, , § R ·, u¨ m ¸, © 4R m ¹, , 2, , 1, 16, , = 6 times (approx.), , Fe = 6Fm, , Thrust and Pressure, Thrust : The force acting on an object perpendicular to the surface is called, thrust., Pressure : The effect of thrust per unit area is called pressure., Pressure (P) =, SI unit is, , N/m2, , or, , Force (F), Area (A), , Nm-2., , SI unit of pressure is Pascal denoted by ‘Pa’., Factors on which pressure depends, Pressure depends on two factors :, Gravitation, , 135
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(i), , Force applied, , (ii) Area of surface over which force acts, ([DPSOHV , •, , The base of high buildings is made wider so that weight of walls act, over a large surface area and pressure is less., , •, , School bags are having broad strap so that the weight of school bags, fall over a larger area of the shoulder and produce less pressure and, becomes less painful., , •, , The blades of knives are made sharp so very small surface area and on, applying force, it produces large pressure and cuts the object easily., , •, , All liquids and gases are uids and they exert pressure in all directions., , Buoyancy, The upward force experienced by an object when it is immersed into a uid, is called force of buoyancy. It acts in upward direction and it depends on the, density of the uid., •, , Force of gravitational attraction of the earth on the surface of the object, < buoyant force exerted by uid on the surface of the object., , Result : The object oats., •, , Force of gravitational attraction of the earth on the surface of the object, > buoyant force exerted by uid on the surface of the object., , Result : The object sinks., That is why, allpin sinks and boat/ship oats on the surface of water. (Archimedes’, principle), Density, The mass per unit volume is called density of an object. If M is the mass and V, is the volume, then density (d) is, Density (d) =, SI unit = kg/m3, , Mass M, Volume V, , Archimedes’ Principle, It states, when a body is immersed fully or partially in a uid, it experiences a, upward force that is equal to the weight of the uid displaced by it., Applications of Archimedes’ Principle :, (i), 136, , It is used in determining relative density of substances., Science Class - IX
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , State the universal law of gravitation., , 2., , Write the formula to nd the magnitude of the gravitational force between, the earth and an object on the surface of the earth., , 3., , Is value of G constant at all the places ?, , 4., , What is the weight of an object of mass 1 kg ?, , 5., , A body has weight of 10 kg on the surface of earth. What will be its, weight when taken to the centre of the earth ?, Ans : 0, , 6., , What is the value of gravitational acceleration acting on a free falling, object ?, , 7., , What is the value of universal constant G and its unit ?, , 8., , Why do pin sinks in water ?, , 9., , Name a factor on which g depends., , 10., , Name the balance used to measure weight of an object., , Ans : 9.8N, , SHORT ANSWER TYPE QUESTIONS (2 Marks), 1., , Mass of an object is 1600 gm on the earth. What is its mass on the moon, ? Why ?, Ans : 1600 gm, , 2., , Two objects placed in a room, are not pulling each other. Why ?, , 3., , Name the force responsible for the motion of moon around the earth., How can some objects move around the earth ?, , 4., , State Archimedes’ Principle and explain it with example., , 5., , State two factors on which buoyant force depends., LONG ANSWER TYPE QUESTIONS (5 Marks), , 1., , Density of aluminium is 2700 kg m-3. What is its relative density ?, Denisty of water is 1000 kg m-3. De ne relative density., Ans : 2.7, , 2., , A ball is released from a height of 1 metre. What time it will take to reach, the surface of the earth ?, Ans : 0.45 s, , 3., , A ball thrown up, vertically returns to the thrower after 6 s. Find :, (a) the velocity with which it was thrown up., (b) the maximum height it reaches and, (c) its position after 4 s., , 140, , Science Class - IX, , Ans : 29.4 m/s, Ans : 4.9 m, Ans : 39.2 m
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CHAPTER AT A GLANCE, , Work, For doing work, energy is required., •, , In animals, energy is supplied by food they eat., , •, , In machine, energy is supplied by fuel., , Not much work inspite of working hard : Reading, writing, drawing, thinking,, Work And Energy, , 141
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analysing are all energy consuming. But in scienti c manner, no work is done in, above cases., •, , Example : A man is completely exhausted in trying to push a rock, (wall), but work done is zero as wall is stationary., , •, , A man standing still with heavy suitcase may be tired soon but he does, no work in this situation as he is stationary., , Work is said to be done when :, (i), , a moving object comes to rest., , (ii) an object at rest starts moving., (iii) velocity of an object changes., (iv) shape of an object changes., 6FLHQWL¿F&RQFHSWLRQRI:RUN, •, , Work is done when a force produces motion in a body., , •, , Work is said to be done when a force is applied on a body and the body, moves under the in uence of force., , &RQGLWLRQRI:RUN, (i), , Force should be applied on the body., , (ii) Body should be displaced., , 142, , Science Class - IX
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Examples : Work is done when :, (i), , A cyclist is pedaling the cycle., , (ii) A man is lifting load in upward or downward direction., Work is not done when :, (i), , A coolie carrying some load on his head stands stationary., , (ii) A man is applying force on a big rock., Work Done by a Fixed Force, Work done in moving a body is equal to the product of force and displacement, of body in the direction of force., Work = Force u Displacement, W=FuS, Work is a scalar quantity., Unit of Work, Unit of work is Newton metre or Joule., When a force of 1 Newton moves a body through a distance of 1 metre in its own, direction, then the work done is 1 Joule., 1 Joule = 1 Newton u 1 metre, 1 J = 1 Nm, , The amount of work done depends on the following factors :, (i), , Magnitude of force : Greater the force, greater is the amount of work, & vice-versa., , (ii) Displacement : Greater the displacement, greater is the amount of, Work And Energy, , 143
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work & vice-versa., Negative, Positive and Zero Work, Work done by a force can be positive, negative or zero., (i), , Work done is positive when a force acts in the direction of motion of, the body.[ Fig. (a)] (T = 0º)., , Example : A child pulls a toy car with a string horizontally on the ground., Here work done is positive., W =FuS, , (ii) Work done is negative when a force acts opposite to the direction of, motion of the body., Example : When we kick a football lying on the ground, the force of our kick, moves the football. Here direction of force applied & motion of football is same, so work done is positive. But when football slows due to force of friction acting, in a direction opposite to direction of motion of football [Fig. (b)], work done is, negative., , (iii) Work done is zero when a force acts at right angles to the direction of, motion., Example : The moon moves around the earth in circular path. Here force, of gravitation acts on the moon at right angles to the direction of motion of the, moon. So work done is zero., 144, , Science Class - IX
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•, , -ve (negative) sign indicates that work is done against gravity., , Note that if work is done against the direction of motion (gravity), then it is taken, –ve., Example. A coolie lifts a luggage of 15 kg from the ground and put it on his head, 1.5 m above the ground. Calculate the work done by him on the luggage., Solution :, , Mass of luggage (m) = 15 kg, Displacement (S) = 1.5 m, , So,, , Work done, W, , =FuS, = mg u S, , [f = mg], , = 15 u 10 u 1.5, , [g = 10 m/s2], [g = force of gravity], , = 225.0 kg m/s2, = 225 Nm = 225 J, Hence,, , work done, , = 225 J., , Energy, (i), , The sun is the biggest source of energy., , (ii) Most of the energy sources are derived from the sun., (iii) Some energy is received from nucleus of atoms, interior of the earth, and the tides., Work And Energy, , 145
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'H¿QLWLRQ The capacity of doing work is known as energy., The amount of energy possessed by a body is equal to the amount of work it can, do. Working body losses energy, body on which work is done gains energy., Energy is a scalar quantity., Unit : The SI unit of energy is Joule (J) and its bigger unit is kilo joule (kJ)., 1 kJ = 1000 J, The energy required to do 1 Joule of work is called 1 Joule energy., Forms of Energy, Main forms of energy are :, (i), , (ii), , Potential energy, , (iii) Heat energy, , (iv), , Chemical energy, , (v) Electrical energy, , (vi), , Light energy, , (vii) Sound energy, , (viii), , Nuclear energy, , •, , Kinetic energy, , Sum of kinetic energy & potential energy of a body is called mechanical, energy., , Mechanical energy, The energy possessed by a body on account of its motion or position is called, mechanical energy., Kinetic Energy, The energy of a body due to its motion is called kinetic energy., Examples of kinetic energy :, •, , A moving cricket ball, , •, , Running water, , •, , A moving bullet, , •, , Flowing wind, , •, , A moving car, , •, , A running athelete, , •, , A rolling stone, , 146, , Science Class - IX
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•, , Flying aircraft, , Kinetic energy is directly proportional to mass and the square of velocity., Formula for Kinetic Energy, If an object of mass ‘m’ moving with uniform velocity ‘u’, it is displaced through, a distance ‘s’. Constant force ‘f’ acts on it in the direction of displacement. Its, velocity changes from ‘u’ to ‘v’. Then acceleration is ‘a’., Work done, W = f u s, and, , f, , ...(i), , = ma, , ...(ii), , According to third equation of motion, relationship between u, v, s and a is as, follows :, v2 – u2, , = 2as, s, , So,, , v2 u 2, , ...(iii), , 2a, , Now putting the value of f and s from (ii) and (iii) in equation (i),, W, , ma u, m, 2, , v2 u 2, 2a, , u v2 u 2, , 1, 2, , m v2 u 2, , If u = 0 (when body starts moving from rest), W = ½mv2, Or, , EK = ½mv2, , Example. An object of mass 15 kg is moving with uniform velocity of 4 m/sec., What is the kinetic energy possessed by it ?, Work And Energy, , 147
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Solution :, , Mass of the object, m = 15 kg, Velocity of the object, v, EK, , = 4 m/s, = ½mv2, = ½ u 15 kg u 4 ms-1 u 4 ms-1, = 120 J, , The kinetic energy of the object is 120 J., Potential Energy, The energy of a body due to its position or change in shape is known as potential, energy., Examples :, (i), , Water kept in dam : It can rotate turbine to generate electricity due to, its position above the ground., , (ii) Wound up spring of a toy car : It possess potential energy which is, released during unwinding of spring. So toy car moves., (iii) Bent string of bow : Potential energy due to change of its shape, (deformation) released in the form of kinetic energy while shooting an, arrow., , Factors affecting Potential Energy, (i), , P. E. v m, , Mass :, , More the mass of body, greater is the potential energy and vice-versa., (ii) Height above the ground :, P. E., , vh, , (Not depend on the path it follows), , Greater the height above the ground, greater is the P.E. and vice-versa., , , LLL &KDQJHLQVKDSH Greater the stretching, twisting or bending, more is, 148, , Science Class - IX
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the potential energy., Potential Energy of an Object on a Height, If a body of mass ‘m’ is raised to a height ‘h’ above the surface of the earth, the, gravitational pull of the earth (m u g) acts in downward direction. To lift the, body, we have to do work against the force of gravity., Thus,, , Work done, W, , Or, , W, , = Force u Displacement, = m u g u h = mgh, , This work is stored in the body as potential energy (gravitational potential, energy)., Thus,, , Potential energy, EP = m u g u h, , where, , g, , = acceleration due to gravity., , Example. If a body of mass 10 kg is raised to a height of 6 m above the earth,, calculate its potential energy., Solution :, , Potential energy of the body = mgh, Mass of body, Height above the earth, Acceleration due to gravity, , So,, , EP, , = 10 kg, =6m, = 10 m/s2, = 10 u 10 u 6, = 600 J, , Thus, potential energy of the body is 600 Joules., Transformation of Energy, The change of one form of energy to another form of energy is known as, transformation of energy., Work And Energy, , 149
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Example :, (i), , A stone on a certain height has entire potential energy. But when it starts, moving downward, potential energy of stone goes on decreasing as, height goes on decreasing but its kinetic energy goes on increasing, as velocity of stone goes on increasing. At the time stone reaches the, ground, potential energy becomes zero and kinetic energy is maximum., , Thus, its entire potential energy is transformed into kinetic energy., (ii) At hydroelectric power house, the potential energy of water is, transformed into kinetic energy and then into electrical energy., (iii) At thermal power house, chemical energy of coal is changed into heat, energy, which is futher converted into kinetic energy and electrical, energy., (iv) Plants use solar energy to make chemical energy in food by the process, of photosynthesis., /DZRI&RQVHUYDWLRQRI(QHUJ\, •, , Whenever energy changes from one form to another form, the total, amount of energy remains constant., , •, , “Energy can neither be created nor be destroyed.”, , •, , Although some energy may be wasted during conversion, but the total, energy of the system remains the same., , &RQVHUYDWLRQRI(QHUJ\GXULQJ)UHH)DOORID%RG\, •, , A ball of mass ‘m’ at a height ‘h’ has potential energy = mgh., , •, , As ball falls downwards, height ‘h’ decreases, so the potential energy, also decreases., , •, , Kinetic energy at ‘h’ is zero but it is increasing during falling of ball., , •, , The sum of potential energy & kinetic energy of the ball remains the, same at every point during its fall., ½mv2 + mgh, , = Constant, , Kinetic energy + Potential energy = Constant, , 150, , Science Class - IX
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Rate of Doing Work – Power, “Power is de ned as the rate of energy consumption.”, Power, where, , P, , = Power, , W, , = Work done, , t, , = Time taken, , =, , Work done, Time taken, , Or, , P, , W, t, , Unit of Power, SI unit of Power is Watt (W) = 1 Joule/second., 1 Watt, , =, , 1 Joule, 1 second, , Or, , 1W, , 1J, 1s, , Power is one Watt when one Joule work is done in one second., Average Power, , Total work done or total energy used, Total time taken, , Power of Electrical Gadget, The power of an electrical appliance tells us the rate at which electrical energy, is consumed by it., Work And Energy, , 151
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Bigger unit of Power : Bigger unit of power is called Kilowatt or KW., 1 Kilowatt (KW) = 1000 Watt = 1000 W or 1000 J/s, Example. A body does 20 Joules of work in 5 seconds. What is its power ?, Solution :, , Power =, , Work done, Time taken, , Work done = 20 Joules, Time taken = 5 sec., P, , So,, , Power, , 20 J, 5s, , = 4 J/s = 4 W, , Thus, power of the body is 4 Watts., &RPPHUFLDO 8QLW RI (QHUJ\ : Joule is very small unit of energy and it is, inconvenient to use it where a large quantity of energy is involved., For commercial purpose, bigger unit of energy is Kilotwatt hour (KWh)., 1 KWh : 1 KWh is the amount of energy consumed when an electric appliance, having a power rating of 1 Kilowatt is used for 1 hour., Relation between Kilowatt hour and Joule, 1 Kilowatt hour is the amount of energy consumed at the rate of 1 Kilowatt for, 1 hour., 1 Kilowatt hour, , = 1 Kilowatt for 1 hour, = 1000 Watt for 1 hour, = 1000 Watt u 3600 seconds (60 u 60 seconds = 1 hour), = 36,00,000 Joules, , So,, , 1 KWh = 3.6 u 106 J = 1 unit, , Example. A bulb of 60 Watt is used for 6 hrs. daily. How many units (KWh) of, electrical energy are consumed ?, Solution :, , 152, , Power of bulb, , Science Class - IX, , = 60 W =, , 60, 1000, , KW = 0.06 KW
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t, , = 6 hours, , Energy = Power u Time taken = 0.06 u 6 h, = 0.36 KWh = 0.36 units, , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1. De ne the term ‘work’., 2. De ne 1 Joule of work., 3. Give an example in which a force does positive work., 4. Give an example in which a force does negative work., 5. De ne the term energy of a body., 6. Write the units of :, , (a) Work,, , (b) Energy., , 7. De ne Power., 8. De ne 1 Watt energy., 9. De ne 1 Kilowatt hour., SHORT ANSWER TYPE QUESTIONS (2 Marks), 1. What do you undertstand by kinetic energy ? Write its formula., 2. On what factors does the kinetic energy of a body depends ?, 3. What happens to potential energy of a body when its height is doubled ?, (Ans. Doubled), 4. How many joules are there in 1 Kilowatt hour ?, 5. What is conservation of energy ? Explain with an example., SHORT ANSWER TYPE QUESTIONS (3 Marks), 1. What are the quantities on which the amount of work done depend ? How are, they related to work ?, 2. A load of 100 kg is pulled up to 5 m. Calculate the work done., (Ans. 5000 J), (g = 10 m/s2), Work And Energy, , 153
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3. A body of mass m is moving with a velocity 5 ms-1. Its kinetic energy is 25, J. If its velocity is doubled, what is its kinetic energy ?, (Ans. 100 J), LONG ANSWER TYPE QUESTIONS (3 Marks), 1. A boy weighing 50 kg climbs up a vertical height of 100 m. Calculate the, amount of work done by him. How much potential energy he gains ?, (Ans. 4.9 u 104 J), (Given g = 9.8 m/s2), 2. Five electric fans of 120 watts each are used for 4 hours. Calculate the, electrical energy consumed in kilowatt hours., (Ans. 2.4 KWh), 3. The power of an electric heater is 1500 Watt. How much energy it consumes, in 10 hours ?, [Ans. 15 KWh (units)], , 154, , Science Class - IX
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CHAPTER AT A GLANCE, , Sound, (i), , The sensation felt by our ears is called sound., , (ii) Sound is a form of energy which makes us hear., Sound, , 155
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(iii) Law of conservation of energy is also applicable to sound., (iv) Sound travels in form of wave., Production of Sound, Sound is produced when object vibrates or sound is produced by vibrating, objects., •, , The energy required to make an object vibrate and produce sound is, provided by some outside source (like our hand, wind etc.)., , •, , Example : Sound of our voice is produced by vibration of two vocal, cords in our throat [Fig. (a)]., , •, , Sound of a drum or tabla is produced by vibration of its membrane, when struck [Fig. (b)]., , •, , In laboratory experiments, sound is produced by vibrating tuning fork., The vibrations of tuning fork can be shown by touching a small, suspended pith ball (cork ball) with a prong of the sounding tuning, fork. The pith ball is pushed away with a great force., , Sound can be produced by following methods :, (i), , By vibrating string (sitar), , (ii) By vibrating air ( ute), 156, , Science Class - IX
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(iii) By vibrating membrane (table, drum), (iv) By vibrating plates (bicycle bell), (v) By friction in objects, (vi) By scratching or scrubbing the objects etc., Propogation of Sound, •, , The substance through which sound travels is called a medium., , •, , The medium may be solid, liquid or gas., , •, , When an object vibrates, then the air particles around it also start, vibrating in exactly the same way and displaced from their stable, position., , •, , These vibrating air particles exert a force on nearby air particles so they, are also displaced from their rest position and start to vibrate., , •, , This process is continued in the medium till sound reaches our ears., , •, , The disturbance produced by sound travels through the medium (not, the particles of the medium)., , •, , Wave is a disturbance which travels through a medium and carries, energy., , •, , So sound travels in wave form known as mechanical waves., , Sound Waves are Longitudinal Waves, •, , When a body vibrates then it compresses the air surrounding it and, form a area of high density called compression (C)., , •, , Compression is the part of wave in which particles of the medium are, closer to one another forming high pressure., , •, , This compression move away from the vibrating body., , •, , When vibrating body vibrates back a area of low pressure is formed, called rarefaction (R)., , •, , Rarefaction is the area of wave in which particles of the medium are, further apart from one another forming a low pressure or low density, area., Sound, , 157
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•, , When body vibrates back and forth, a series of compression and, rarefaction is formed in air resulting in sound wave., , •, , Propogation of sound wave is propogation of density change., , Sound needs Medium for Propogation, •, , Sound waves are mechanical waves., , •, , It needs material medium for propogation like air, water, steel etc., , •, , It cannot travel in vaccum., , •, , An electric bell is suspended in airtight bell jar connected with vacuum, pump., , •, , When bell jar is full of air, we hear the sound but when air is pumped, out from the bell jar by vacuum pump and we ring the bell, no sound is, heard., , •, , So medium is necessary for propagation of sound., , Experiment to show that sound cannot travel through vacuum, Sound Waves are Longitudinal Waves, (i), , A wave in which the particles of the medium vibrate back and forth in, the same direction in which the wave is moving, is called a longitudinal, wave., •, , 158, , When we push and pull the slinky compression (number of turns, are more or closer) and rarefaction (number of turns are less or, Science Class - IX
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farther) are formed., •, , When a wave travels along with slinky, its each turn moves back, and forth by only a small distance in the direction of wave. So the, wave is longitudinal., , •, , The direction of vibrations of the particles is parallel to the direction, of wave., , (ii) When one end of a slinky is moved up and down rapidly whose other, end is xed, it produces transverse wave., •, , This wave possess along the slinky in horizontal direction, while, turns of slinky (particles) vibrate up and down at right angle to the, direction of wave., , •, , Thus in transverse wave particles of the medium vibrate up and, down at right angles to the direction of wave., , •, , Light waves are transverse waves but they don’t need a material, medium for propagation., , Characteristics of Sound Wave, The characteristics of sound waves are : wavelength, frequency, amplitude, time, period and velocity., •, , When a wave travel in air the density and pressure of air changes from, their mean position., , •, , Compression is shown by crest while rarefaction is shown by trough., , •, , Compression is the region of maximum density or pressure., , •, , Rarefaction is the region of minimum density or pressure., Sound, , 159
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(i) Wavelength :, (a) In sound waves the combined length of a compression and an adjacent, rarefaction is called its wavelength., (b) The distance between the centres of two consecutive compressions or, two consecutive rarefactions is also called its wavelength., (c) It is denoted by the Greek letter lamda O. Its SI unit is metre., , (ii) Frequency :, (a) No. of complete waves produced in one second or number of vibrations, per second is called frequency., (b) Number of compressions or rarefactions passed in one second is also, frequency., , 160, , •, , Frequency of wave is same as the frequency of the vibrating body, which produces the wave., , •, , The SI unit of frequency is hertz (Hz). The symbol of frequency is, v (nu)., , •, , 1 Hertz : One Hz is equal to 1 vibration per second., , •, , Bigger unit of frequency is kilohertz kHz = 1000 Hz., Science Class - IX
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(iii), , Time Period :, , (a) Time taken to complete one vibration is called time period., (b) Time required to pass two consecutive compressions or rarefactions, through a point is called time period., •, , SI unit of time period is second (s). Time period is denoted by T., , •, , The frequency of a wave is the reciprocal of the time period., v, , 1, T, , (iv) Amplitude :, The maximum displacement of the particle of the medium from their original, undisturbed position is called amplitude of the wave., •, , Amplitude is denoted by A and its SI unit is metre (m)., , Sound have characteristics like pitch and loudness and timbre., Pitch : The pitch of sound depends on the frequency of sound (vibration). It, is directly proportional to its frequency. Greater the frequency, higher is the pitch, and lesser the frequency, lower is the pitch., •, , A woman’s voice is shrill having a high pitch while a man’s voice, is at having low pitch., , •, , High pitch sound has large number of compressions and rarefactions, passing a xed point per unit time., , Loudness : The loudness depends on the amplitude of the sound wave., •, , Loudness is the measure of the sound energy reaching the ear, per sec., , •, , Greater the amplitude of sound wave, greater is the energy, louder, the sound; short is the amplitude, less is the energy, soft is the, sound., , •, , Loudness is measured in decibel ‘dB’., Sound, , 161
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Quality or Timbre : The timbre of a sound depends on the shape of sound, wave produced by it. It is the characteristic of musical sound., •, , It helps us to distinguish between two sounds of same pitch &, loudness., , •, , Sound of single (same) frequency is called tone while a mixture of, different frequencies is called note. Noise is unpleasant to hear, while music is pleasant to hear and it is of good quality., , (v) Velocity :, The distance travelled by a wave in one second is called velocity of the wave., Its SI unit is metre per second (ms-1)., Velocity, , Distance travelled, Time taken, , O, , V, , T, , (O is the wavelength of the waves travelled in one time timeperiod T), V, So,, , §1, ¨, ©T, , = Ov, , ·, ¹, , v¸, , Velocity = Wavelength u Frequency, This is the wave equation., , Example. What is the frequency of sound wave whose time period is 0.05, second ?, Solution :, , Frequency, v, , Given, So,, , 1, T, , T = 0.05 s, v, , 1, , 100, , 0.05, , 5, , Hence frequency = 20 Hz., 162, , =, , Science Class - IX, , 20 Hz
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Speed of Sound in Various Mediums, (i), , Speed of sound depends on the nature of material through which it, travels. It is slowest in gases, faster in liquids and fastest in solids., , (ii) Speed of sound increases with the rise in temperature., (iii) Speed of sound increases as humidity of air increases., (iv) Speed of light is faster than speed of sound., (v) In air, speed of sound is 344 ms-1 at 22ºC., Sonic Boom, Some aircrafts, bullets, rockets etc. have ‘supersonic speed’., •, , Supersonic refers to the speed of an object which is greater than the, speed of sound and it produces extremely loud sound waves called, ‘shock waves’ in air., , •, , Sonic boom is an explosive noise caused by shock waves., , •, , It emits tremendous sound energy which can shatter the glass panes of, windows., , 5HÀHFWLRQRI6RXQG, Like light, sound also bounce back when it falls on a hard surface. It is called, re ection of sound. The laws of re ection of light are obeyed during re ection, of sound., (i), , The incident sound wave, the re ected sound wave and normal at the, point of incidence lie in the same plane., , (ii) Angle of re ection of sound is always equal to the angle of incidence of, sound., , 5HÀHFWLRQRI6RXQG, Echo, The repetition of sound caused by the re ection of sound waves is called an, echo., Sound, , 163
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v, , •, , We can hear echo when there is a time gap of 0.1 second in original, sound and echo (re ected sound)., , •, , Echo is produced when sound re ected from a hard surface (i.e., brick, wall, mountain etc.) as soft surface tends to absorb sound., , To calculate the minimum distance to hear an echo :, Speed, , Distance, Time, , Here Speed of sound in air = 344 ms-1 at 22ºC, Time = 0.1 second, 344, , So,, , Distance, 0.1 sec, , Distance = 344 u 0.1 = 34.4 m, , Or, , So, distance between re ecting surface and audience =, 22ºC)., •, , 34.4, 2, , = 17.2 m (at, , Rolling of thunder is due to multiple re ection of sound of thunder, from a number of re ecting surfaces such as clouds and the earth., , Reverberation, (i), , The persistence of sound in a big hall due to repeated re ection of sound, from the walls, ceiling and oor of the hall is called reverberation., , (ii) If it is too long, sound becomes blurred, distorted and confusing., Methods to reduce reverberation in big halls or auditoriums, (i), , Panels made of felt or compressed bre board are put on walls and, ceiling to absorb sound., , (ii) Heavy curtains are put on doors and windows., (iii) Carpets are put on the oor., (iv) Seats are made of material having sound absorbing properties., Difference between Echo and Reverberation, Echo, , Reverberation, , 1. The repetition of sound caused by 1. The persistence of sound in a big hall, re ection of sound wave is called due to repeated or multiple re ections of, echo., sound from the walls, ceiling and oor, of the hall is called reverberation., 164, , Science Class - IX
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2. Echo is produced in a big empty 2. If reverberation is too long, sound, hall. Here is no multiple re ections becomes blurred, distorted and confusing, of sound. Sound is not persistant., due to overlapping of different sound., $SSOLFDWLRQVRI5HÀHFWLRQRI6RXQG, (i), , Megaphone, loudspeakers, bulb horns and trumpets, shehnai etc. are, designed to send sound in a particular direction without spreading, all around. All these instruments have funnel tube which re ects sound, waves repeatedly towards audience. In this amplitude of sound waves, adds up to increase loudness of sound., , (ii) Stethoscope : It is a medical instrument used for listening the sounds, produced in human body mainly in heart and lungs. The sound of the, heartbeats reaches the doctor’s ears by the multiple re ection of the, sound waves in the rubber tube of stethoscope., , (iii) Sound Board : In big halls or auditoriums sound is absorbed by walls,, ceiling, seats etc. So a curved board (sound board) is placed behind the, speakers so that his speech can be heard easily by audiences. The, soundboard works on the multiple re ection of sound., (iv) The ceiling of concert halls are made curved, so that sound after, re ection from ceiling, reaches all the parts of the hall., , Sound, , 165
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Range of Hearing, (i), , Range of hearing in human is 20 Hz to 20000 Hz., •, , Children younger than 5 years and dogs can hear upto 25 KHz., , (ii) The sounds of frequencies lower than 20 Hz are known as ‘infrasonic, sounds’., •, , A vibrating simple pendulum produces infrasonic sounds., , •, , Rhinoceroses communicate each other using frequencies as low as, 5 Hz., , •, , Elephants and whales produces infrasonic waves., , •, , Earthquakes produces infrasonic waves (before shock waves), which some animals can hear and get disturbed., , (iii) The sounds of frequencies higher than 20 KHz are known as ‘ultrasonic, waves’., •, , Dogs, parpoises, dolphins, bats and rats can hear ultrasonic sounds., , •, , Bats and rats can produce ultrasonic sounds., , Hearing Aid, It is battery operated electronic device used by persons who are hard of hearing., Microphone convert sound into electrical signals, than those are ampli ed by, ampli er. Ampli ed signals are send to the speaker of hearing aid. The speaker, converts the ampli ed signal to sound and sends to ear for clear hearing., Applications of Ultrasound, (i), , It is used to detect cracks in metal blocks in industries without damaging, them., , (ii) It is used in industries to clean ‘hard to reach’ parts of objects such as, spiral tubes, odd shaped machines etc., (iii) It is used to investigate the internal organs of human body such as liver,, gall bladder, kidneys, uterus and heart., 166, , Science Class - IX
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(iv) Ecocardiography : These waves are used to re ect the action of heart, and its images are formed. This technique is called echocardiography., (v) Ultrasonography : The technique of obtaining pictures of internal, organs of the body by using echoes of ultrasound waves is called, ultrasonography., (vi) Ultrasound is used to split tiny stones in kidneys into ne grains., SONAR, The word ‘SONAR’ stands for ‘Sound Navigation And Ranging’., •, , SONAR is a device which is used to nd distance, direction and speed, of underwater objects., , •, , SONAR consists of a transmitter and a receptor or detector and installed, at the bottom of a ship., , •, , The transmitter produces and transmits ultrasonic waves., , •, , These waves travel through water and after striking the objects on the, bottom of sea, are re ected back and received by detector., , SONAR, •, , These re ected waves are converted into electric signals by detector., , •, , The sonar device measures the time taken by ultrasound waves to travel, from ship to bottom of sea and back to ship., , Half of this time gives the time taken by the ultrasound waves from ship to, bottom., Let the time interval between transmission and reception of ultrasound signal, is t. Speed of sound through sea water is v, total distance travelled by waves =, 2d. Then, 2d = v u t. This is called echo ranging., Sound, , 167
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The sonar is used to nd the depth of sea, to locate underwater hills, valleys,, submarines, icebergs and sunken ships etc., •, , Bats y in the dark night by emitting high pitched ultrasound waves, which are re ected from the obstacle or prey and returned to bats ear., The nature of re ection tells the bat where the obstacle or prey is and, what it is like., , Structure of Human Ear, •, , The ear consists of three parts : outer ear, middle ear and inner ear., , •, , The ears are the sense organs which help us in hearing sound., , •, , The outer ear is called pinna. It collects the sound from surroundings., , •, , This sound passes through the auditory canal., , •, , At the end of auditory canal, is a thin elastic membrane called ear drum, or tympanic membrane., , •, , The middle ear contains of three bones : hammer, anvil and stirrup, linked with one another. Free end of hammer touches ear drum and that, of stirrup linked with membrane of oval window of inner ear., , •, , The lower part of middle ear has a narrow ‘Eustachian tube’., , •, , The inner ear has a coiled tube called cochlea, which is connected with, oval window. Cochlea is lled with a liquid containing nerve cells., Other side of cochlea is connected to auditory nerve which goes to, brain., , Working :, •, , 168, , When compression of sound wave strikes the ear drum, the pressure on, the outside of ear drum increases and pushes the ear drum inwards., Science Class - IX
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While during rarefaction ear drum moves outwards. Thus, ear drum, starts vibrating back and forth., •, , These vibrations are increased by three bones and middle ear transmits, these ampli ed pressure variations received from sound waves to inner, ear., , •, , In the inner ear the pressure variations are turned into electric signals by, the cochlea., , •, , These electric signals are sent to the brain via auditory nerve and the, brain interprets them as sound., , Working of Human ear, Pinna o Ear canal o Ear drum o Hammer o Anvil o Stirrup o Oval, window o Cochlea o Auditory nerve o Brain, , QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1. Why sound waves are called mechanical waves ?, 2. Which characteristic of sound determine : (a) Pitch, (b) Loudness ?, 3. Write wave formula for velocity of sound., 4. Write the hearing range of human being., 5. What is sound ?, 6. Name the two types of waves which can be generated in a slinky., 7. What is SI unit of frequency ? Write its bigger unit also., 8. How is sound produced ?, 9. In which medium sound travels fastest : air, water or steel ?, 10. Name two devices which work on the re ection of sound., SHORT ANSWER TYPE QUESTIONS (2 Marks), 1. State two laws of re ection of sound., 2. De ne the term wavelength & frequency., 3. De ne the term time period and amplitude., Sound, , 169
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4. Explain why, the ash of lighning reaches us rst and the sound of thunder is, heard a little later ?, 5. What is meant by supersonic speed ?, 6. Why are the ceiling of concert halls made curved ?, SHORT ANSWER TYPE QUESTIONS (3 Marks), 1. What is reverberation ? How can reverberation in a big hall be reduced ?, 2. What is echo ? How is echo formed ? How thunder of clouds is formed ?, 3. Write any three applications of ultrasound., 4. Explain how bats use ultrasound to catch the prey., LONG ANSWER TYPE QUESTIONS (5 Marks), 1. What is SONAR ? Explain its working. Give its uses., 2. A wave is moving in air with a velocity of 340 m/s. Calculate the wavelength, if its frequency is :, (a) 512 vibrations per second, , (b), , 100 Hz., , 3. A sonar station picks up a return signal after 3 seconds. How far away is the, object ? [Speed of sound in water = 1440 m/s], 4. A stone is dropped from the top of a tower 500 m high into a pond of water, at the base of tower. When is the splash heard at the top ? Given g = 10 ms-2, and speed of sound = 340 ms-1., Hints to Long Answer Type Questions, 2. (a) 0.66 metre, , (b), , 3.4 m, , 3. 2160 m, 4. 11.47 s, [Hint : Time taken by stone to reach at pond, t = ?, Use s = ut + ½gt2, 500 =, 0 + ½ u 10t2; so, t2 = 100 or t = 10 sec.], , 170, , Science Class - IX
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CHAPTER AT A GLANCE, , Health is a general condition of a preson’s mind and body. According to, WHO (World Health Organisation) health is a “state of physical, metal and, social well-being of a person”., To make people aware and conscious of keeping healthy and disease-free we, celebrate WORLD HEALTH DAY on 7th April., Why Do We Fall Ill ?, , 171
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•, , ‘Health’ is a state of being well enough to function well physically,, mentally and socially., , •, , Disease : Any disturbance in the structure or function of any organ or, part of body., , •, , The various causes of diseases are pathogens (virus, bacteria), lack of, nutritious diet/balanced diet and lack of public health services., , •, , Acute diseases occur suddenly and lasts for a short duration while, chronic diseases develop slowly and lasts for long period of time., , •, , The diseases/infections can be prevented by life style (exercise, proper, sleep, enough relaxation) modi cation, taking balanced diet, good, personal health and hygiene and also maintaining a clean and healthy, surrounding., , •, , Treatment involves killing of the microbes/pathogens., , Health, •, , Health is a state of physical, mental and social well-being., , •, , The conditions necessary for good health are :, (i) Good physical and social environment., (ii) Good economic conditions., , •, , Good physical and social environment includes clean surroundings,, good sanitation, proper garbage disposal and clean drinking water., , •, , Good economic conditions includes job opportunities for earning to, have nutritious food and to lead a healthy life., , Personal and Community Issues Both Matter for Health, Community Health :, •, , All those activities which people do both individually and in groups for, the development of their society, constitute the community health., , •, , Personal and community health are supplementary to each other., , •, , We protect ourselves by keeping our body clean., , •, , For this, we also require a good and healthy environment in our, surroundings., , •, , We can have this only by the means of community health and, , 172, , Science Class - IX
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development., •, , So, both personal and community health are inter-related., Differences between Being Healthy and Disease-free, Being Healthy, , Being Disease-free, , 1. It is a state of being well enough 1. It is a state of absence from diseases., to function well physically, mentally, and socially., 2. It refers to the individual,, physical and social environment., , 2. It refers only to the individual., , 3. The individual has good health., , 3. The individual may have good, health or poor health., , Disease and Its Causes, What does disease look like ?, •, , When a person is affected by a disease either the functioning or the, appearance of one or more systems of the body will change for the, worse., , •, , These changes give rise to symptoms and signs of disease., , •, , On the basis of the symptoms the physicians look for the signs of a, particular disease and conduct tests to con rm the disease., , Types of Diseases, (i), , Acute Diseases : Acute diseases which last for only very short period, of time and affect body suddenly and quickly. E.g., Cold, cough,, typhoid etc., , (ii) Chronic Diseases : The diseases which last for a long time, even as, much as a life time, are called chronic diseases. E.g., Diabetes,, tuberculosis, elephantiasis etc., Causes of Diseases, Diseases are caused by :, •, , Pathogens like virus, bacteria, fungi, protozoans or worms., , •, , Poor health and under nourishment., , •, , Hereditary and genetic disorder., Why Do We Fall Ill ?, , 173
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•, , Lack of proper treatment of immunization., , •, , Environmental pollution (air, water etc.), , Infectious and Non-infectious Diseases, (i), , Infectious Diseases : The diseases which spread due to infection, by micro-organisms are called infectious diseases. It is communicated, from diseased person to healthy person, caused by some biological, agents/pathogens like viruses, bacteria, fungi, protozoans, fungi worms., , (ii) Non-infectious Diseases : The disease which does not spread by, contact between infected and healthy person through air and water, is, called non-infectious disease. E.g., Arthritis, heart disease., Pictures of Different Micro-organisms, (i) The picture shows SARS viruses coming out, of the surface of an infected cell (see the arrows, for example)., (ii) 500 nanometer = 0.5 micrometer = 0.001, millimeter., (i), , The picture shows Trypanosoma, a protozoan, organism., , (ii) It causes sleeping sickness., (iii) The saucer-shaped substance lying next to, the protozoa, is a red blood cell., (i), , The picture shows Staphylococcus bacteria., , (ii) The Staphylococcus bacteria causes acne., (iii) The scale is indicated at the line at the top left of, the picture. It is 5 micrometers long., (i), , The, given, picture, from the small intestine., , shows, , an, , adult, , (ii) Its technical name is Ascaris Lumbricoides., (iii) The ruler next to it shows 4 centimeter to give an, idea of the scale., 174, , Science Class - IX, , roundworm
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Micro-organisms :, S. No., , Infectious Agents, , Diseases, , 1., , Viruses, , Common cold, in uenza, measles,, chicken pox, AIDS, Hepatitis-B etc., , 2., , Bacteria, , Cholera, typhoid, TB, tetanus,, anthrax, food poisoning etc., , 3., , Fungi, , Skin infections, , 4., , Protozoan, , Malaria,, kala-azar,, amoebic, dysentery, sleeping sickness, , 5., , Worms, , Intestinal infections, elephantiasis, , Antibiotics, •, , Antibiotics blocks biochemical pathways important for bacteria. Hence,, they are effective against them. E.g., Penicillin, tetracycline., , •, , Many bacteria make a cell wall to protect themselves, the antibiotics, (Penicillin) blocks the bacterial process that builds cell wall., , •, , Antibiotics works only against the bacteria and not against the viruses., , Common method of transmission of diseases, (Diseases spread from affected person to healthy person), Why Do We Fall Ill ?, , 175
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Means of Spread of Infectious Diseases, Infectious diseases spread from an infected person to a healthy person through, air, water, food, vectors, physical contact and sexual contact., •, , Through air : By sneezing and coughing, the microbes spread into, air and enter into the body of a healthy person, like common cold,, tuberculosis, pneumonia etc., , •, , Through water : The microbes enter into our body by drinking/eating, polluted and contaminated water/food, like cholera, amoebic, dysentery etc., , •, , Vectors : Some organisms like female anopheles mosquito also work, as a vector of disease, like malaria, dengue, yellow fever etc., , •, , Through sexual contact : Syphilus, AIDS spread by sexual contact, with infected person. AIDS virus can also spread through blood, transfusion and from the mother to her child during pregnancy and, through breast feeding., , $,'6 $FTXLUHG,PPXQR'H¿FLHQF\6\QGURPH, Causes :, AIDS is caused by a retro-virus called HIV (Human Immuno De ciency Virus)., Method of transmission of AIDS :, The transmission of AIDS from an infected to a healthy person takes place :, •, , through sexual contact, , •, , blood transfusion, , •, , use of infected needle or blade etc., , •, , This may also get transmitted from infected mother to her foetus., , Prevention :, •, , Avoid transfusion of infected blood. This can be done by testing whether, the blood is HIV negative or not., , •, , Always use disposable needle and syringe., , •, , Avoid sexual contact with unknown person., , •, , Avoid the same razor used in the salons., , 176, , Science Class - IX
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25*$1±6SHFL¿FDQG7LVVXHVSHFL¿F0DQLIHVWDWLRQV, Disease causing microbes enter the body by different means and goes to different, organs and tissues., (i), , Microbes which enter through the nose are likely to go to the lungs., (Bacteria which cause tuberculosis of lungs)., , (ii) Microbes which enter through the mouth are likely to stay in the gut, (bacteria which causes typhoid) or liver (bacteria which causes, jaundice)., (iii) Virus which causes AIDS enter the body through sexual organs during, sexual contact and spread through the lymph to all parts of the body and, damages the immune system., (iv) Virus which causes Japanese encephalitis (brain fever) enters the body, through mosquito bite and goes and infects the brain., Principles of Treatment :, The treatment of infectious diseases consists of two steps. They are to reduce, the effects of the disease (symptoms) and to kill the microbes which caused, disease., (i), , To reduce the effects of the disease : This can be done by taking, medicines to bring down the effects of the disease like fever, pain or, loose motions etc. and by taking bed rest to conserve our energy., , (ii) To kill the microbes : This can be done by taking suitable antibiotics, and drugs which kills the microbes and the disease is cured., Principles of Prevention, There are two ways of prevention of infectious diseases. They are general ways, and speci c ways., (i), , General ways of prevention : Public hygiene is most important for, prevention of infectious diseases. Proper and suf cient food for, everyone will make people healthy to resist the infection., , Air borne diseases can be prevented by living in conditions that are not, crowded. Water borne diseases can be prevented by providing safe drinking, water. Vector borne diseases can be prevented by providing clean environment., , , LL 6SHFL¿F ZD\V RI SUHYHQWLRQ There are disease speci c measures, which are used to ght them. It is done by Immunisation. This is the, Why Do We Fall Ill ?, , 177
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process of introducing a weakened pathogen inside the body of the, host to fool his/her immune system to produce antibodies against that, particular disease. Not only does our immune system ght the disease, (feeble pathogen), but also keeps a memory of the incident by keeping, those antibodies in blood. Thus, next time even if the disease will strike, the host’s body with full vigor, the body will be able to protect itself with, the help of these antibodies. This is also the basic law followed by, vaccination programmes done for infants., A Few Diseases, Disease, , Pathogen, , Vector (if any), , 1. Malaria, , Protozoa, , Female anopheles, , Recurrent fever, chills, , mosquito, 2. Typhoid, , Bacteria –, , Cockroaches etc., , Salmonella, 3. AIDS, , High fever and intestinal, infections, , Virus – HIV, , –, , Not a disease in itself, it, affects our lymph glands, thereby decreasing our, immunity, , 4. Dengue, , Virus, , Female aedies, , Headache + fever, , egypte mosquito, 5. Worms, , Worms in, , –, , Stomach ache, , –, , Brain fever, , –, , Stomach ache, , intestine, 6. Kala azar, , Protozoa –, Leishmania, , 7. Round, , Ascaris in, , worms, , intestine, , 8. SARS, , Bacteria, , 9. Swine u, , Virus, , Pig + human, , Fever – spreads, , 10. Bird u, , Virus, , Birds, , Fever – spreads, , 11. Ebola, , Ebola virus, , 178, , Science Class - IX, , –, , –, , –, , Fever – spreads
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1. Why is food necessary for us ?, 2. Write the full form of WHO., 3. Name two non-infectious diseases., 4. Write two water-borne diseases., SHORT ANSWER TYPE QUESTIONS (2 Marks), 1. Write the difference between acute and chronic disease., 2. Write the expanded form of AIDS., 3. What is the difference between ‘Being healthy’ and ‘Disease free’ ?, 4. Name two methods for treatment of infectious diseases., SHORT ANSWER TYPE QUESTIONS (3 Marks), 1. How do micro-organisms enter into our body ?, 2. Name four diseases caused by protozoa, virus, bacteria, fungi., 3. What are the different means by which infectious diseases spread ?, 4. What precautions can you take in your school to reduce the incidence of, infectious diseases ?, LONG ANSWER TYPE QUESTIONS (5 Marks), 1. Name ve diseases against which immunization vaccines are available., OR, Name two diseases that can be prevented by using vaccine., 2. Fill in the blanks :, (i), , ..................is a state of physical, mental and social well-being., , (ii) AIDS is a..................(communicable/non-communicable) disease., (iii) Common cold is a..................(acute/chronic) disease., , Why Do We Fall Ill ?, , 179
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(iv) Breathing in polluted air causes..................disease., (v) Small pox is prevented through.................. ., Hints to Long Answer Type Questions, 1. Protozoa – Malaria, Virus – Polio, Bacteria – Pneumonia, TB, Fungi – Skin, disease, 2. (i), , Health, , (ii), , communicable, , (iv) respiratory, , (v), , vaccination, , 180, , Science Class - IX, , (iii), , acute
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CHAPTER AT A GLANCE, , •, , Life on earth depends on resources like soil, water, air and energy from, sun., , •, , Uneven heating of air over land and water-bodies causes winds., , •, , Evaporation of water from water-bodies and subsequent condensation, give us rain., Natural Resources, , 181
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•, , Pollution of air, water and soil affect the quality of life., , •, , We need to conserve our natural resources and use them in a sustainable, manner., , •, , Various nutrients are used again and again in a cycle fashion. This leads, to a certain balance between the various components of the biosphere., , Natural Resources, The resources available on the earth and the energy from the sun are, necessary to meet the basic requirements of all life forms on the earth., The stocks of nature which are useful to mankind are known as natural resources., E.g., air, water, soil, minerals etc., What are these resources on the earth ?, The outermost crust of the earth is called the lithosphere. Water covers, 75% of the earth’s surface. It is also found underground. These comprise the, hydrosphere. The air that covers the whole of the earth like blanket is called the, atmosphere., , Biosphere, All living things on earth together with atmosphere, the hydrosphere and the, lithosphere interact and make life possible is known as biosphere. It may be :, , Biotic components : Plants and animals., Abiotic components : Air, water and soil., , AIR, , •, •, , 182, , Air is a mixture of different gases., Air contains oxygen which is essential to living organisms for, respiration. So it is called breath of life., Science Class - IX
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Role of Atmosphere, •, , Air is a bad conductor of heat. It keeps the average temperature of the, earth constant during the day and even during the course of the, whole year., , •, , Prevents the sudden increase in temperature during day time and during, the night, it slows down the escape of heat into outer space. E.g., At, moon, there is no atmosphere and so the temperature varies from, 190ºC to 110ºC., , The Movement of Air : Winds, •, , During the day, the direction of wind is from sea to land. This is because, the air above the land gets heated faster and starts rising., , •, , During the night, the direction of wind is from land to sea. This is, because at night, both land and sea start to cool., , •, , The movement of air from one region to the other creates winds., , RAIN, •, , Rain is formed by evaporation and condensation of water through water, cycle in which distribution of water takes place. Rain is very important, because it carries out all the agriculture processes in the plants., , •, , So we should conserve rain by contracting dams, pools etc., , Air Pollution, •, , An increase in the content of harmful substance (pollutants) in the air, like carbon dioxide, carbon monoxide, oxides of sulphur, nitrogen,, uoride, lead, nickel, arsenic and dust particles etc. causes air pollution., It may cause :, , In humans : Respiratory and renal problems, high blood pressure, eye, irritation, cancer., In plants : Reduced growth, degeneration of chlorophyll, mottling (patches/, spots of colour) of leaves., Acid Rain, • When fossil fuels are burnt, gases like sulphur dioxide and nitrogen, dioxide (NO2) are released., Natural Resources, , 183
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•, , These gases are dissolving in water form nitric acid and sulphuric acid., , Acid rain kills plant life, pollutes river and streams, , Green House Effect, •, , Carbon dioxide keeps the earth warm much like glass which keeps the, green house warm., , •, , Increase in carbon dioxide (CO2) :, (i) intensi es green house effect., (ii) leads to global warming., (iii) increase in average temperature of earth., (iv) may lead to melting of polar caps., (v) sub-merging number of coastal cities., , Changes in environment affects us and our acitivities change the environment, around us., Environmental Problems Caused by Humans, Depletion of Ozone Layer, •, , Ozone layer is present in the stratosphere which is a part of our, atmosphere from 16 km to 60 km above sea level., , •, , Ozone is an allotrope of oxygen. Its molecule is made up of three, oxygen atoms. Molecular formula is O3., , 184, , Science Class - IX
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•, , Ozone layer absorbs the ultra-violet rays coming from the sun and, protects living being from their harmful effects like skin cancer, cataract, in eyes, weaken immune system., , •, , The decline of ozone layer thickness in Antartica was rst observed in, 1985 and was termed as ozone hole., , Reason of Ozone Depletion, •, , Excessive use of CFCs (Chloro Fluoro Carbon) in refrigeratos, jet, planes, spray cans, re extinguishers., , •, , Nuclear explosion, , Smog, •, , Smog is a type of air pollution., , •, , The word ‘smog’ comes from the blend of two words : Smoke and fog., , •, , Smog can form in any climate where there is a lot of air pollution, especially in cities., , Water : A wonder Liquid, •, , The most unusual natural compound found on earth and which ful lls, almost various demands of different living things., , •, , About three-fourth of the earth surface is 75% are covered with water., , •, , It is present underground, a very large area on the surface (sea, ocean, etc.) and also in the form of water vapour in the atmosphere., , Water Necessary for all Organisms, •, , It maintains a uniform temperature of the body., , •, , All cellular processes take place in a water medium., , •, , All the reactions that take place within our body and within our cells, occur between substances that are dissolved in water., , •, , Water forms the habitat of many plants and animals., , Water Pollution, When water becomes un t for drinking and other uses, then water is said to be, polluted., Causes of Water Pollution, •, , Dumping of wastes from the industries into water bodies., Natural Resources, , 185
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•, , Washing of clothes near water bodies., , •, , Spraying chemical in water eld., , •, , Dumping household wastes into the water bodies., , Various causes of water pollution, (Bathing of humans and animals, disposal of, factory wastes, washing clothes etc.), , Soil, Soil is the portion of the earth surface consisting of disintegrated rock and, decaying organic material. It provides the support for many plants and animals., Creation of Soil : Various Factors, Factor 1. Sun, The sun heats up rocks during the day so that they expand. At night these rocks, cool down and contract. Since all parts of the rocks do not expand and contract, at the same rate, this results in the formation of cracks and ultimately the huge, rocks breaks up into smaller pieces., Factor 2. Water, Fast owing water carries big and small particles of rock downstream. These, rocks rub against other rocks and the resultant abrasion causes the rocks to wear, down into smaller particles., Factor 3. Wind, Wind carries sand from one place to another., , 186, , Science Class - IX
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Living Organisms, Lichen (A slow growing plant), Lichen, moss also grow on surface of rocks. While growing, they release certain, substances that cause the rock surface to powder down and form a thin layer of, soil., , Soil Erosion, Carrying away of upper fertile layer of soil by rain, wind, human activities and, wrong agricultural practice is called soil erosion., Causes, •, , Over grazing of land., , •, , Removal of top soil by wind and water., , •, , Due to lack of trees the upper layer of soil is eroded by air and water., , •, , Leaving land uncultivated for long time., , Biogeochemical Cycles, •, , The ow of substances from non-living to living and back to non-living, is called the cycling of substances., , •, , The cycling of chemical elements like carbon, oxygen, nitrogen,, phosphorus, sulphur and water in the biosphere is called biogeochemical, cycle. It operates through soil, water, air and biotic factors., , Water Cycle, , Water Cycle, Natural Resources, , 187
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•, , The whole process in which water evaporates and falls on the land as, rain and later ows back into the sea via rivers is known as water cycle., , •, , When sun shines, water evaporates continuously from the water, bodies and forms water vapour. This water vapour rises up and goes, into the atmosphere., , •, , The plants absorb water from the soil and use it during the process of, photosynthesis., , They also loose water by the process of transpiration., •, , The water vapour produced by transpiration also goes into the, atmosphere., , •, , The process of respiration and evaporation from the surface of animal, body produces water vapour which goes into the atmosphere., , •, , The evaporation and condensation of water vapour leads to rain. During, winter, the water falls down in the form of dew or snow., , •, , All of the water that falls on the land does not immediately ow back, into the sea. Some of it seeps into the soil and becomes part of the, underground reservoir of fresh water., , •, , The underground water is again taken by plants and water cycle, continues., , Oxygen Cycle, , Oxygen Cycle, 188, , Science Class - IX
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The % of oxygen in air is 21%., •, , The cyclic process by which oxygen element is circulated continuously, through the living and non-living components of the biosphere, constitutes oxygen cycle., , •, , Human beings and animals take oxygen from the atmosphere during, the process of respiration., , The decomposition of dead organisms also takes in oxygen from the, atmosphere., Respiration and decay of dead organisms release CO2 and water., •, , The carbon dioxide and water are used by the green plants during the, process of photosynthesis., , •, , They give out oxygen during this process. This oxygen is again used by, human beings and animals., , Thus, the oxyen cycle keeps repeating in nature., , Carbon Cycle, , Carbon Cycle, 0.03-0.04% carbon is present in the atmosphere in the form of CO2., •, , Carbon cycle maintains the balance of the element carbon in the, atmosphere. Carbon is found in various forms on the earth., , •, , Carbon is present in the atmosphere as carbon dioxide., , •, , Carbon can also occur as carbonates and bicarbonate salts in minerals., Natural Resources, , 189
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•, , Carbon is the essential part of nutrients like carbohydrates, fats, proteins,, nucleic acids and vitamins., , •, , Carbon cycle keeps the level of CO2 constant in the atmosphere., , The Carbon Cycle starts in plants as :, Step I., Plants use CO2 in the atmosphere, convert it into glucose in the presence of, sunlight by the process of photosynthesis. Plants and animals break these, carbohydrates for energy and release CO2 through respiration., Step II., When the plants and animals die, fungi and bacteria decompose the dead remains., This releases the carbon in the remains as carbon dioxide., Step III., Some of the dead plants and animals which get buried under the earth under, certain temperature and pressure get transformed into fossil fuels like coal and, petroleum., On burning these fuels, CO2 is released into the atmosphere., , Nitrogen Cycle, , Nitrates, , Nitrogen Cycle, The sequence in which nitrogen passes from the atmosphere to the soil and, organisms, and then is eventually released back into the atmosphere, is called, nitrogen cycle., •, 190, , Nitrogen makes up 78% of the earth’s atmosphere., Science Class - IX
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•, , Nitrogen is an essential constituent of proteins, nucleic acids like DNA, and RNA, vitamins and chlorophyll., , •, , Plants and animals cannot utilize atmospheric nitrogen readily., , •, , It has to be xed by some organisms called nitrogen xers., , •, , Nitrogen- xing bacteria like Rhizobium live in symbiotic association in, the root nodules of certain leguminous plants., , Root nodules of, leguminous plant, •, , •, , These bacteria convert atmospheric nitrogen into, ammonia which is utilized readily by plants., , •, , Nitrogen- xing bacteria along with free living, bacteria in the soil achieve 90% of nitrogen, xation., , •, , Lightning plays an important role in nitrogen, xation. When lightning occurs, the high, temperature and pressure convert nitrogen and, water into nitrates and nitrites., , •, , Nitrates and nitrites dissolve in water and are, readily used by aquatic plants and animals., , $PPRQL¿FDWLRQ It is the process by which soil bacteria decompose, dead organic matter and release ammonia into soil., •, , 1LWUL¿FDWLRQ It is the process by which ammonia is converted into, nitrites and nitrates., , •, , 'HQLWUL¿FDWLRQ It is the process by which nitrates are converted into, atmospheric nitrogen., , $ÀRZFKDUWWRVKRZWKHLPSRUWDQWVWDJHVRI1LWURJHQ&\FOH, , Natural Resources, , 191
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , What are the resources present on the earth ?, , 2., , Name two gases of air., , 3., , Expand the term CFCs., , 4., , Write the formula of ozone., , 5., , Which acids are present in acid rain ?, , 6., , Name four water borne diseases., , 7., , What are the nitrogen- xing bacteria called ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , Name three types of soil., , 2., , Name the disease that can be caused by UV rays., , 3., , What is the major source of fresh water ?, SHORT ANSWER TYPE QUESTIONS (3 Marks), , 1., , Draw a neat and labelled diagram of water cycle in nature., , 2., , How is green house effect related to global warming ? Explain., , 3., , What are the causes of soil erosion ?, , 4., , Why is water necessary for all organisms ?, LONG ANSWER TYPE QUESTIONS (5 Marks), , 1., , Write the differences between oxygen and ozone., , 2., , Explain the oxygen cycle., OR, What are the factors or processes that make soil ?, , 192, , Science Class - IX
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CHAPTER AT A GLANCE, , Improvement In Food Resources, , 193
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•, , All living organisms need food for health, growth and development., , •, , Food provides nutrients like carbohydrates, fats, protein, vitamins and, minerals., , •, , Both plants and animals are major sources of food., , •, , India has a high population of more than one billion and is still growing., , •, , To feed this growing population we need more than a quarter of a billion, tonnes of grain per year., , •, , This can be done by farming on more land but India is already intensively, FXOWLYDWHG+HQFHLWLVQHFHVVDU\WRLQFUHDVHWKHHI¿FLHQF\RISURGXFWLRQ, for both crops and livestock., , Green Revolution, Green revolution is a programme introduced in many countries to increase food, production by use of modern technology, proper irrigation, improved seeds etc., White Revolution, White revolution is a programme in India to increase production of milk in India., This programme made India self-suf cient in production of milk., , Improvement in Crop Yields, Types of Crops :, (a) Cereals : They include crops like wheat, rice, maize, barley etc. They, provide us carbohydrates., (b) Seeds : Not all seeds of plants are edible like seeds of apple or cherries., Edible seeds include cereals, pulses, oil seeds and nuts. They provide us, fats., (c) Pulses : They include legumes such as gram, pea, black gram, green, gram, lentil. They provide us proteins., (d) Vegetables, spices and fruits : They provide us vitamins & minerals., 194, , Science Class - IX
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They include apple, mango, cherry, banana, water-melon etc., Vegetables like spinach, leafy vegetables, carrot etc., Spices like chilly, black pepper, fodder crops, oats etc., , Crop Season :, Different crops require different conditions (temperature, moisture, etc.),, different photo-periods (duration of sunlight) for their growth and completing, life cycle., The two types of crops seasons are :, (a) Kharif Season : These crops grow during rainy season (June, to October). E.g. of Kharif crops are black gram, green gram,, pigeon pea, rice, paddy, soyabean., (b)Rabi Season : These crops are grown during November to, April. Rabi crops are known as winter crops. E.g., wheat, gram,, peas, mustard, linseed etc., Approaches which enhance the crop yield are as following :, (i), , Crop variety improvement, , (ii), , Crop production improvement, , (iii), , Crop protection improvement, , (A) Crop Variety Improvement : Factors by which variety improvement can be, done are :, •, , Good and healthy seeds, , •, Hybridization : It is the process of crossing between two or more, genetically dissimilar plants to produce a new variety with good properties of, both the crops., Improvement In Food Resources, , 195
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Properties to be possessed by improved seeds, Or, Factors for which variety improvement in crops is done, (a) Higher yield : To increase the productivity of the crop per acre., (b) Improved quality : Quality of crop products vary from crop to crop., (c) Biotic & Abiotic resistances : Crop production reduces due to biotic and, abiotic factors. Varieties resistant to these factors can improve crop production., (d) Wider adaptability : Crops which can grow in different conditions,, will help in setting high production., (e) Desired agronomic traits : Crops which contain desired agronomic, traits (height, branching, leafs), sets high production., (B) Crop Production Improvement : It involves different practices carried out, by farmers to achieve higher standards of crop production. They are :, , (a) Nutrient management, (b) Irrigation, (c) Cropping patterns, (a) Nutrient Management : Like other organisms, plants also require, some elements for their growth. These elements are called nutrients., , 196, , Sources, , Nutrients, , Air, , Carbon, oxygen, , Water, , Hydrogen, oxygen, , Soil, , (i) Macro nutrients : Nitrogen – required by, plants in large amount, phosphorus, potassium,, calcium, magnesium, sulphure., Science Class - IX
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(ii) Micro nutrients : Iron, Mn – required in small, amount, boron, Zn, copper, molybdenum,, chlorine., Manure and Fertilizers, To increase the yield, the soil can be enriched by supplying nutrients in the, form of manure and fertilizers., Manure :, •, , It is a source of organic matter., , •, , It supplies small quantities of nutrient to the soil., , •, , It is prepared by the decomposition of animal excreta and plant waste., , Various forms of Manures :, (A) Compost : The process in which animal excreta (like cow dung),, kitchen waste, plant remains, waste food, sewage waste etc. are, decomposed in pits is known as composting., (B) Vermicompost : Compost prepared by using earthworms to hasten the, process of decomposition of plants and animals refuse is called, vermicompost., (C) Green manure : Some plants like sun hemp, guar etc. are grown and, after sometime mulched by ploughing in the eld. These green plants, turn into green manures. They are rich in nitrogen and phosphorus., Fertilizers :, Fertilizers are prepared in factories. They are made up of chemical substances., They have large amount of nutrients like nitrogen, phosphorus and potassium., Fertilizers are easily absorbed by the plants since they are soluble in water. It, is costly., Difference between Manures and Fertilizers, Manures, 1. These are organic substances., , Fertilizers, 1. These are inorganic substances., , 2. These are made up of natural substanc- 2. These are made of chemical substances., es (decomposition of plant and animal, waste)., 3. These have less amount of nutrient., , 3. These have large amount of nutrients., , Improvement In Food Resources, , 197
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4. These are cheap and are prepared in ru- 4. These are costly and are prepared in, ral homes or elds., factories., 5. Manures are slowly absorbed by the 5. Fertilizers are easily absorbed by the, plants since they are insoluble in water., plants since they are soluble in water., 6. It is dif cult to store and transport., , 6. Their storage and transportation is easy., , (b) Irrigation : The process of supplying water to the crop plants is called, irrigation., , Methods of Irrigation :, (i), , Wells : These are of two types :, Dug wells : In dug wells, water is collected by bullock-operated devices, or by pumps., Tube wells : It makes very deep underground water available for, irrigation. Motor pump is used to lift water., , (ii) Canals : These get water from large rivers., (iii) River lift system : In this system, water is directly taken from rivers, through pumps. This system is useful for irrigation in areas close to, river., (iv) Tanks : These are small storage reservoirs., (v) Rain water harvesting : Rain water harvesting is a accumulation of, water in tanks for later use. This also prevents soil erosion., , 198, , Science Class - IX
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(c) Crop Patterns : Different patterns are used to maximize the production, from crop eld. They are :, , (i), , (i), , Mixed cropping, , (ii), , Inter cropping, , (iii), , Crop rotation, , Mixed cropping : Growing two or more than two crops together on the, same piece of land is called mixed cropping. E.g., wheat and gram,, wheat and mustard, groundnut and sun ower., , (ii) Inter cropping : Two or more crops are grown on the same eld in, a de nite pattern. Few rows of one followed by few rows of the other., E.g., Soyabean + maize, Finger nullet (Bajra) + Cow pea (lobia), (iii) Crop rotation : Crop rotation is policy of growing different crops one, after another on the same eld., • If some crop is grown again and again on the same eld, same, nutrients are extracted from soil again and again. So we should, choose different crops so that all nutrients of soil are used., • Advantages :, (1), , Soil fertility is maintained., , (2), , It controls pests and weeds., , (3), , Several crops can be grown in succession with only one soil, preparation., , (C) Crop Protection Improvement, To protect crops against diseases caused organisms and other harming factors, is called crop protection. Following methods are used to control these, problems :, (a) Pest control during growth, (b) Storage of grains, (a) Pest control during growth : Pest is any destructive organism which, can destroy or harm crops or products obtained from them. Pests are of, many types :, (i), , Weeds : Unwanted plants in the cultivated eld e.g., xanthium., , (ii), , Insects : Insects can harm plants in following ways :, Improvement In Food Resources, , 199
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•, , They cut the root, stem and leaf., , •, , They suck the cell sap from various parts of the plant., , (iii), , Pathogens : Any organism such as bacteria, fungi and viruses, which cause diseases in plants are called pathogens. They are, transmitted through air, water, soil., , (b) Storage of grains : For getting seasonal foods throughout the year, they, are stored in safe storage. But during storage of grains, they can be, destroyed and wasted by various means., (i), , Biotic problem : Due to living organisms like insects, birds,, mites, bacteria, fungi., , (ii), , Abiotic problem : Due to non-living factors such as moisture,, inappropriate temperature etc., , These factors affect quality degradation, loss in weight, change in, colour, poor germinability., Organic Farming, Use of fertilizers and pesticides has their own disadvantages. They cause, pollution, damage soil fertility in long run. Grains, fruits, vegetables obtained, may contain harmful chemical in small amount., Organic farming is a farming system with no or very little use of chemicals, like fertilizers and pesticides., Different ways to protect food grains before they are stored for future use :, (a) Drying : The food grains should be properly dried in the sun., (b) Maintenance of hygiene : The grains must not contain insects. The, godowns should be cleaned well. The cracks in the roof and on the, walls and oor should be sealed completely., (c) Fumigation : Godowns and stores should be properly sprayed with, fumigants. Specially, the seeds should be treated with insecticides and, fungicides., (d) Storage devices : Cleaned and dried grains should be stored in gunny, bags or other proper bags. Airtight, moisture-resistant and temperatureresistant storage devices have been developed by various organizations., These should be used., 200, , Science Class - IX
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ANIMAL HUSBANDRY, Animal husbandry is a scienti c management of domestic animals in an, ef cient manner to obtain food and other useful products from them., Cattle farming : Purpose of cattle farming is :, (a) For getting milk, (b) Ploughing elds, (c) Bull cart for transportation, Types of cattle :, •, , Cow (Bos indicus), , •, , Buffalo (Bos bubalis), , Milch animals : These includes milk producing animals (female cattle)., Draught animals : Those animals which do not produce milk and are used for, agricultural work., Lactation period : The period of milk production between birth of a young one, and the next pregnancy is called lactation period., Care of Cattle, (1) Cleanliness, • Roofed shelter with good ventilation for protection from rain, heat, and cold., • Regular brushing of skin of cattle., • Sloping oor for shelter for avoiding water-logging., (2) Food, • Roughage mainly containing bre, • Concentrates containing proteins, • Food containing micronutrients (vitamins and minerals) for enhanced, milk production, Diseases : Diseases can cause death and reduce milk production., •, , Parasites are small organisms living inside or outside the body of, another organism (host). They derive food from the body of host., , •, , External parasites on skin of cattle cause skin diseases., , •, , Internal parasites like worms cause stomach and intestine problems and, Improvement In Food Resources, , 201
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ukes cause liver problems., •, , Bacteria, virus cause infectious diseases (diseases that can be easily, transmitted from one to another)., , Poultry Farming : Poultry farming is done for eggs and meat. They both provide, protein to our diet., , Broilers : Birds grown for obtaining meat are called broilers. They can be used, after 6-8 weeks from their birth., Layers : Birds grown for obtaining egg are called layers. They can be used after, 20 weeks when sexual maturity has been attempt to lay eggs., Most of the broilers and layers are cross-breed., Breeding is done to enhance following properties in hens :, •, , More and better quality chicks., , •, , Low maintenance., , •, , Breeding is done to produce dwarf broilers (meat-giving birds). Feeding, cost is the biggest expense in poultry farms. Dwarf broilers need less, food and can reduce cost by 30%. Also, they can tolerate more heat., , Fish Production :, , 202, , Science Class - IX
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Fish production is a great source of protein to our diet., Fish production is of two types :, , , )LQQHG ¿VK SURGXFWLRQ7UXH ¿VK SURGXFWLRQ Production and, management of cartilaginous and bony shes such as pomphret, tuna,, cod, catla, prawns, rohu etc., , , , 8Q¿QQHG¿VKSURGXFWLRQ Production of shell- sh such as prawns,, mollusks., , 'HSHQGLQJRQWKHPRGHRIREWDLQLQJ¿VKHV¿VKLQJDUHRIWZRW\SHV , , , &DSWXUH¿VKLQJ Naturally living shes in various water bodies are, captured., , , , &XOWXUH¿VKLQJ Fishes of desired variety are cultivated in con ned, areas with utmost care to get maximum yield. This is also called, aquaculture. Aquaculture can be done in oceans, rivers, lakes, ponds, etc. When it is done in oceans, it is called mariculture., , 0DULQH ¿VKLQJ Marine, reservoirs., , shing includes, , sh production in ponds, rivers,, , •, , Popular marine shes includes pomphret, tuna, sardines, Bombay duck., Some costly shes found in sea like nullets, prawns, seaweed, oysters., , •, , Using satellites, regions of high sh population in sea can be found., Echo-sounders are also used., , ,QODQG¿VKLQJ It includes sh production in fresh water (for example ponds,, rivers, lakes, reservoirs) and brackish water (for example estuaries)., Composite Fish Culture, •, , 5 to 6 varieties in a single sh pond., , •, , They are selected so that they do not compete for food. They should, have different food requirement., , Example :, Catla : Feeds in the upper part of water., Rohu : Feeds in middle part of water., Mrigals, common carps : Feeds at bottom., •, , Advantage : More yield., Problems : Many shes lay eggs during monsoons only, due to which, Improvement In Food Resources, , 203
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number of shes will not grow fast. So hormonal stimulation is used., Using this shes can be made to reproduce any time., Bee-keeping : It is the practice of keeping, caring & management of honeybees, on a large scale for obtaining honey and wax., Many farmers use bee-keeping for additional small income. Also, there are big, farms called apiaries/bee farms., Apiary : The setting up of a number of bee hives in desirable location in a, systematic manner that allows maximum pollen and nectar collection., •, , Some common Indian varieties of bees include apis carana indica, (Indian bee), dorsata (rock bee), ÀRUDO(little bee)., , •, , One Italian variety mellifera is also used in India for commercial large, scale production because of its following advantage :, (a), , High honey collection capacity., , (b), , They reproduce fast., , (c), , They sting less., , (d), , They stay in a bee hive for long., , Honey : It is a dense sweet liquid., •, , It is used in medicines. It is used as sugar., , •, , It is used as a source of energy., , Pasturage : Pasturage is the availability of owers to the bees for nectar and, pollen collection., Or, Pasturage of ora is the type of crop, ower or other plants from which bee, collects nectar and pollent to produce honey., It affects the quality and quantity of honey because different ora produce nectar, and pollen of different types e.g., almond honey of Kashmir is very tasty., , 204, , Science Class - IX
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QUESTIONS, VERY SHORT ANSWER TYPE QUESTIONS (1 Mark), 1., , Why do we need food ?, , 2., , Name some pulses which provide us protein., , 3., , Name the factors to which cultivation practices are related., , 4., , What is the main source of irrigation in India ?, , 5., , What are the two purposes of cattle husbandry ?, SHORT ANSWER TYPE QUESTIONS (2 Marks), , 1., , What is Kharif season ? Name a few Kharif crops., , 2., , What is manure ? How is it prepared ?, , 3., , What are pathogens ? How are they transmitted ?, , 4., , What is hybridization ?, SHORT ANSWER TYPE QUESTIONS (3 Marks), , 1., , What is meant by composite sh culture ?, , 2., , Write advantages of bee-keeping., , 3., , Differentiate between broilers and layers., , 4., , What are the bene ts of mixed cropping ?, LONG ANSWER TYPE QUESTIONS (5 Marks), , 1., , Write the differences between manures and fertilizers., , 2., , What are the ways to protect food grains before they are stored for, future use ?, , Improvement In Food Resources, , 205
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Syllabus of Practicals, Practicals should be conducted alongside the concepts taught in theory, classes. (List of Experiments), 1., , Preparation of :, (a) a true solution of common salt, sugar and alum, (b) a suspension of soil, chalk powder and ne sand in water, (c) a colloidal solution of starch in water and egg albumin/milk in, water and distinction between these on the basis of, , 2., , x, , Transparency, , x, , Filtration criterion, , x, , Stability, , Preparation of, (a) a mixture, (b) a compound, Using iron lings and sulphur powder and distinction between, these on the basis of :, (i) Appearance, i.e., homegeneity and heterogeneity, (ii) Behaviour towards a magnet, (iii) Behaviour towards carbon disulphide as a solvent, (iv) Effect of heat, , 206, , 3., , Separation of the components of mixture of sand, common salt and, ammonium chloride (or camphor)., , 4., , Performing the following reactions and classifying them as, physical or chemical changes :, Science Class - IX
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(a) Iron with copper sulphate solution in water, (b) Burning of magnesium ribbon in air, (c) Zinc with dilute sulphuric acid, (d) Heating of copper sulphate crystals, (d) Sodium sulphate with barium chloride in the form of their, solutions in water, 5., , Preparation of stained temporary mounts of (a) onion peel, (b) human, cheek cells & to record observations and draw their labeled diagrams., , 6., , Identi cation of Parenchyme, Collenchyma and Sclerenchyma tissues, is plants, striped, smooth and cardiac muscle bers and nerve cells in, animals from prepared slides. Drawing of their labeled diagrams., , 7., , Determination of the melting point of ice and the boiling point of water., , 8., , Establishing the relation between the loss in weight of a solid when, fully immersed in, (a) Tap water, (b) Strongly salty water, with the weight of water displaced by it by, taking at least two different solids., , 11. Determination of the speed of a pulse propagated through a stretched, string/slinky., 12. Study of the characteristics of Spirogyra / Agaricus, Moss / Fern, Pinus, (either with male of female cone) and an Angiospermic plant. Drawing, and providing two identifying features of the groups they belong to., 13. Observing the given pictures / charts / models of earthworm, cockroach,, cony sh and bird. For each organiam, drawing of their picture and, recording :, (a) One speci c feature of its phylum., (b) One adaptive feature with reference to its habitat., 14. Veri cation of the law of conservation of mass in a chemical reaction., 15. Study of the external features of root, stem, leaf and ower of monocot, and dicot plants., , Experiment, , 207
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EXPERIMENT NO. 1, Aim :, , To prepare :, , (a) a true solution of common salt, sugar and alum, (b) a suspension of soil, chalk powder and ne sand in water, (c) a colloidal solution of starch in water and egg albumin water and to, distinguish between these on the basis of, (i), , lteration criterion (ii), , transparency, , (iii), , stability, , Appartus required : Ten hard glass test tubes, test tube stand, a China dish, a, glass rod, a tripod stand, funnels, lter paper, torch or ash light., Materials (Chemicals) required : Common salt, sugar, alum, chalk powder,, garden soil, egg albumin, ne sand and distilled water., Procedure :, (a) To prepare true solutions of dry common salt, sugar and alum, Take three test tubes (A, B, C). Pour 10 cc of distilled water in each test tube., Take a pinch of salt and put it in ‘A’ test tube and shake it vigorously after, closing the mouth of test tube. The common salt dissolves completely to, form true solution. Do the same procedure with sugar and alum powder and, put them in test tubes labelled ‘B’ and ‘C’. The result is also same. They all, (salt, sugar and alum) forms true solution with water., E 7RSUHSDUHVXVSHQVLRQVRIVRLOFKDONSRZGHUDQG¿QHVDQGLQZDWHU, Take three test tubes (D, E, F). Pour 10 cc of distilled water in each test, tube and pour a pinch of chalk powder in ‘D’ test tube. Shake it vigorously, after closing the mouth of test tube. The chalk powder does not dissolve, completely to form a suspension. Do the same procedure with garden soil, and sand ( ne sand) in test tubes labelled ‘E’ and ‘F’ respectively. The result, is also same. All three materials form suspension., (c) To prepare colloidal solutions of starch in water and egg albumin in, water, (i), , To prepare a colloidal solution of starch in water, , Take about 1 gm of starch in a China dish. Pour about 20 cc of distilled water, in a China dish. Stir the contents with a glass tube till a milky suspension is, formed. Heat the 50 cc of water to the boiling point on a Bunsen ame, by, placing it on the tripod stand. Stir the contents of the China dish continuously, 208, , Science Class - IX
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and pour it in boiling water. Allow the contents to cool. The product so, formed is colloidal solution of starch in water in test tube ‘G’., (ii) To prepare a colloidal solution of egg albumin in water, Take about ½ cc of egg albumin in a test tube. Pour about 10 cc of distilled, water in the test tube. Shake the contents of the test tube vigorously for 1, minute and the albumin gets suspended to form turbid (light milky) product., The product so formed is the colloidal solution of egg albumin in water., To distinguish a true solution, a suspension and a colloid on the basis of, D WUDQVSDUHQF\, E ¿OWHUDWLRQFULWHULRQ, , F VWDELOLW\, Again take test tube ‘A’, test tube ‘D’ and test tube ‘G’ which are true, solution of salt suspension of chalk powder and colloidal solution of starch, respectively. Now pass laser light through it to see the transparency. Now, lter them all through lter paper and check their stability in test tubes by, allowing its contents to stand for 5 minutes., (a) Transparency, , To distinguish a true solution, a suspension and a colloid on the basis of, transperancy, (b) Filteration criterion, , Experiment, , 209
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(c) Stability : Let the three tubes A, D and G be allowed to stand for 5, minutes., Observations, Test tube ‘A’ :, True solution of, , Transparency, The light rays, , Filteration, Stability, The contents passes No sediments, , passes through it., , through lter paper, , settle down and, , leaving no residue., , the solution, , The ltrate is clear, , remains clear., , Light rays hardly, , and transparent., The contents leave, , The sediments, , pass through, , residue of chalk, , settle down, , contents., , powder on the lter and clear water, , common salt,, sugar, alum, Test tube ‘D’ :, Suspension of, chalk powder, , paper. The ltrate is collects above it., , Test tube ‘G’ :, Colloidal, solution of, , Light rays scatter, , clear., The content passes, , No sediment, , in contents of the, , through lter paper, , settles down, , test tube ‘C’., , leaving no residue, , and there is no, , on the lter paper, , change in its, , and ltrate is, , consistency., , starch, , translucent., Result :, (a) True solutions are transparent, stable, homogenous and they can pass, through lter paper leaving no residue on the lter paper. They do not, scatter light., 210, , Science Class - IX
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(b) Suspensions are opaque, leave residue on the lter paper. They are, unstable. They do not scatter light., (c) Colloids are translucent, leaves no residue on the lter paper and the, ltrate is translucent. They are stable and scatter light., Precautions :, (a) The test tubes should be neat and clean., (b) Wastage of chemicals should be avoided., (c) Mix the contents carefully and stir it thoroughly while preparing various, types of mixtures., (d) Handle burner carefully., (e) Do not taste any material., , Multiple Choice Questions, 1. The particles of colloidal solution can be seen by :, (a) Naked eye, , (b), , Microscope, , (c) Neither by eye or microscope, , (d), , None, , (a) About 108 cm, , (b), , Larger than 105 cm, , (c) Between 107 cm and 105 cm, , (d), , None of these, , (a) True solution, , (b), , A suspension, , (c) A colloidal solution, , (d), , None of these, , 2. The size of colloidal particles is :, , 3. A solution of egg albumin in water is :, , 4. Which of the following is stable when allowed to stand undisturbed for some, time ?, (a) Sugar solution, , (b), , Solution of starch in water, , (c) Milk, , (d), , All the above, , 5. The correct order which describe the true solution, colloidal solution and, suspension in the order of their increasing stability is :, (a) Suspension < Colloidal < True solution, (b) Colloidal solution < True solution < Suspension, (c) True solution < Colloidal solution < Suspension, (d) Colloidal solution < Suspension < True solution, Experiment, , 211
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6. To prepare colloidal solution of starch, we should :, (a) Add starch powder to boiling water and cool, (b) Add starch powder to cold water and boil, (c) Heat starch powder, add it to cold water and then bring to boil, (d) Add starch to cold water & stir, 7. A student was asked to mix the white of an egg with water and stir well. The, student observed that :, (a) A transparent solution is formed, (b) A transparent mixture is formed, (c) Egg white settles down at the bottom, (d) Egg white oats on the surface of the water, 8. Which is incorrect statement about a true solution of common salt in water ?, (a) It is not transparent and is not stable, (b) Its components cannot be separated by ltration, (c) It does not show tyndall effect, (d) Its particles cannot be seen by naked eye, , Answers, 1., , (b), , 2. (c), , 3. (c), , 6., , (d), , 7. (b), , 8. (a)., , 212, , Science Class - IX, , 4. (d), , 5. (a)
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EXPERIMENT NO. 2, Aim :, , To prepare (a) a mixture, (b) a compound, , Using iron llings and sulphur powder and distinguish between these on the, basis of :, (a) appearance i.e., homogeneity and heterogeneity, (b) behaviour towards a magnet, (c) behavior towards carbon disulphide, (d) effect of heat, Theory :, Compound : A pure substance which is composed of two or more elements,, combined chemically in a xed ratio, such that they can be broken into, elements only by chemical means is called a compound., Mixture : When two or more substances (elements, compounds or both) are, mixed together in any proportion do not undergo any change but retain their, individual properties, the resulting mass is called a mixture., Material required : A hard glass test tube, a test tube holder, mortar and pestle,, two watch glasses, a hand lens, a magnet, a rack full of clean test tubes,, Bunsen burner or spirit lamp., Procedure :, (a) Preparation of a mixture of iron and sulphur, Take 7 g of iron llings and 4 g of sulphur and put them in a mortar. Grind, the constituents with pestle thoroughly. The product so obtained is a mixture, of iron and sulphur. Divide the mixture into two halves and place them in two, watch glasses., (b) Preparation of the compound of iron and sulphur (Iron sulphide), Transfer the mixture of one of the watch glasses to a hard glass test tube., Now hold the test tube in the test tube holder. Heat the mixture strongly, on a Bunsen burner till its contents start glowing with a reddish glow. Stop, heating now. Iron reacts with sulphur to form its compound iron sulphide, with the release of heat energy. Again transfer the iron sulphide in watch, glass., Experiment, , 213
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Observation :, Experiment, 1. Action with magnet :, Roll a bar magnet in the, mixture as well as in the, compound., , Observation, , Inference/Result, , Iron particles cling to, the magnet in case of the, mixture, but not in case, of the compound., , Constituents of, a mixture can be, separated by physical, means, but not that of a, compound., , In case of the mixture,, grey particles of iron, and yellow particles, of sulphur can be seen, clearly and they are not, uniform throughout., , Mixtures are, heterogenous in nature,, but compounds are, homogenous in nature., , 2. Observation under, magnifying glass :, Observe the mixture as, well as the compound, under a magnifying, glass by spreading, them thinly on a paper., , In case of the compound,, grey particles are seen, uniformly throughout., 3. Action with carbon, disulphide :, Place a small amount, of the mixture and, compound in separate, test tubes and add 5, cc of carbon disulphide. Shake well., , In case of the mixture,, yellow particles of, sulphur dissolve and grey, particles of iron settle, down., , Constituents of, a mixture can be, separated by physical, means, but not that of a, compound., , In case of the compound,, nothing dissolves., , 4. Effect of heat :, Heat the small amount, of mixture and, compound separately in, two test tubes., , In mixture, sulphur, Mixture shows chemical, & iron melts to form, reactions., compound iron sulphide., Compound do not show, In compound, no change. chemical reaction., , Precautions :, (a) Heat the mixture of iron and sulphur in the hard glass test tube only., (b) While performing various experiments use minimum amount of the, mixture of its compound., 214, , Science Class - IX
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(c) Remove the pieces of broken glass with forceps, not with bare hands., , Multiple Choice Questions, 1. When a mixture of iron llings and sulphur is added to a test tube containing, CS2, what is observed ?, , (a) (i), , (b), , (ii), , (c) (iii), , (d), , (iv), , 2. When iron llings and powdered sulphur are mixed together in a China, dish:, (a) A heterogeneous mixture forms, (b) The constituents present can be seen easily, (c) The constituents can be separated by a magnet, (d) All the above are correct, 3. Which one is not observed when carbon disulphide is added to a mixture of, iron llings and sulphur powder taken in a test tube ?, (a) Sulphur powder dissolves and a yellow solution is formed, (b) Iron llings remain unaffected, Experiment, , 215
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(c) Iron sulphide is formed by the combination of iron of the mixture and, of CS2, (d) Solid sulphur reappears when yellow solution is heated, 4. The smell of H2S is :, (a) pleasant, , (b), , like that of rotten eggs, , (c) like that of burning sulphur, , (d), , none of these, , 5. In the laboratory, what precautions need to be taken with carbon disulphide ?, (a) Kept away from ame, (b) Kept away from carbon, (c) Kept away from distilled water, (d) Kept away from iron sulphide, 6. A student by mistake mixed iron llings and sulphur powder. He wanted to, separate them from each other. The method you would advise him to use is, to dissolve the mixture in :, (a) Boiling water, , (b), , Cold water, , (c) Carbon disulphide, , (d), , Kerosene, , 7. In which of the following mixtures, the separation of the compound may be, done by using a magnet ?, (a) A mixture of ferrous sulphide and copper sulphide, (b) A mixture of iron llings and ferrous sulphide, (c) A mixture of sulphur powder and ferrous sulphide, (d) A mixture of carbon disulphide and ferrous sulphide, 8. A mixture of iron llings and sulphur powder was taken in a test tube and, sulphuric acid was added to it. The observation made was :, (a) Only iron reacts to give hydrogen gas, (b) Only sulphur reacts to give hydrogen sulphide gas, (c) Both iron and sulphur give out hydrogen gas, (d) Both combine to form iron sulphide, , Answers, 1., , (d), , 2. (d), , 3. (c), , 6., , (c), , 7. (b), , 8. (a)., , 216, , Science Class - IX, , 4. (b), , 5. (a)
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EXPERIMENT NO. 3, Aim : To separate the components of a mixture of sand, common salt and, ammonium chloride (or camphor) by sublimation., Materials required : Given mixture of sand, common salt and ammonium, chloride, China dish, wire gauge, tripod stand, funnel, Bunsen burner, cotton,, glass rod, lter paper, beaker, iron stand, watch glass, knife etc., Theory :, (a) Some solid substances on heating directly change into vapours without, going into liquid state. This process of conversion of a solid directly, into vapours is called sublimation., (b) Common salt dissolves in water but sand does not, so we can lter it., (c) The salt can be obtained from salt solution by evaporation., Procedure :, Physical change can be shown as :, , (a) Separation of ammonium chloride from mixture, , Separation of ammonium chloride from mixture, Experiment, , 217
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(i), , Place the mixture in a China dish. Place the China dish on a wire gauge, placed over a tripod stand., , (ii) Heat the China dish with a Bunsen burner/spirit lamp on a medium, ame, till dense white fumes start coming out of the mixture., (iii) Place a glass funnel in an inverted position on the mixture in the China, dish and plug its stem with cotton wool as shown in g. (above)., (iv) Go on heating for 5 minutes., (v) Remove the funnel from the China dish, scrap the ammonium chloride, deposited on its inner sides on a piece of paper., (vi) Go on heating the mixture till dense white fumes coming out of it, stop, completely. Stop heating and allow the mixture to cool., (vii) This mixture consists of sand and common salt., (b) Separation of sand, (i), , Transfer the mixture obtained in step (vii) above in a beaker and add 20, cc of water. Stir it with glass rod., , (ii) Clean the glass funnel and t a cone of lter paper into it. The cone of, lter paper is made by four folding and we take three folds on one side, and one fold on the other side., (iii) Filter the content slowly as shown in g. The clear ltrate of common, salt will collect in the beaker., (iv) Remove the cone from the funnel and place it in the sun. The water, evaporates leaving behind dry sand., Separation of sand from the residue left in the China dish, i.e., sand and, common salt mixture, , (c) Separation of common salt, 218, , Science Class - IX
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Transfer the lterate containing common salt to a China dish. Heat the China, dish on a medium ame. In a few minutes, the water boils off leaving behind, dry common salt in the China dish., Precautions :, (a) All glass apparatus should be clean and dry., (b) Do not heat contents on a high ame., (c) Do not use large amount of mixture or water., (d) Prepare solution in distilled water only., , Multiple Choice Questions, 1. Which of the following is a mixture ?, (a) Ammonium chloride, , (b), , Silicon dioxide, , (c) Air, , (d), , Common salt, , 2. The various constituents of a mixture can be separated by :, (a) Simple physical methods, , (b), , Chemical methods, , (c) Both (a) & (b), , (d), , Neither (a) & (b), , 3. Which of the following is volatile substance ?, (a) Common salt, , (b), , Iron llings, , (c) Camphor, , (d), , Sulphur, , 4. The process by which common salt is separated from its solution in water is:, (a) Sublimation, , (b), , Loading, , (c) Filtration, , (d), , Evaporation, , 5. The process of conversion of a solid substance directly into vapours, is called :, (a) Evaporation, , (b), , Loading, , (c) Sublimation, , (d), , Centrifugation, , 6. The process used to obtain salt from sea water is :, (a) Oxidation, , (b), , Sublimation, , (c) Evaporation, , (d), , Filtration, , Experiment, , 219
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7. Name the odd process amongst the following., (a) Sublimation, , (b), , Evaporation, , (c) Oxidation, , (d), , Dissolution, , 8. The sequence of steps taken for separating the mixture of ammonium, chloride, sand and common salt is :, (a) Filtration, evaporation, sublimation, dissolving in water, (b) Sublimation, dissolving in water, ltration and evaporation, (c) Filtration, dissolving in water, ltration and evaporation, (d) None of the above, , Answers, 1., , (c), , 2. (a), , 3. (c), , 6., , (c), , 7. (c), , 8. (b), , 220, , Science Class - IX, , 4. (d), , 5. (c)
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EXPERIMENT NO. 4, Aim :, , To carry out the following chemical reactions and classify them as, physical or chemical changes :, , (a) Iron nail and copper sulphate solution in water, (b) Burning of magnesium ribbon in air, (c) Zinc with dilute sulphuric acid, (d) Heating of copper sulphate, (e) Sodium sulphate solution with barium chloride in the form of their, solutions in water, Materials required : Test tube stand, re tongs, spirit lamp, iron nail, copper, sulphate solution, 10 cm long magnesium ribbon, a small piece of granulated, zinc, dilute sulphuric acid, sodium sulphate solution, barium chloride, solution., Theory : Chemical reactions are those where two or more elements combine, together to form a substance (or more than one substance) called compound., They do not have their individual properties, cannot be separated by physical, processes and are present in a xed ratio. Physical reactions can be reversible., Procedure :, (a) Experiment with iron nail and copper sulphate solution, Pour about 10 cc of copper sulphate solution in the test tube. Drop a, clear iron nail in the solution and observe for ve to ten minutes., Observations recorded are given below :, (i) Copper sulphate is blue in colour. On placing nail (iron) in it for 5, minutes or more the colour changes from blue to green and light, green., (ii) Iron nail gets coated with reddish/brownish red deposit of copper, metal., Fe (s) + Cu2+SO42 (aq) o Fe2+SO42 (aq) + Cu (s), Experiment, , 221
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When iron nails are kept in CuSO4 solution, (b) Experiment with burning magnesium ribbon in air, Hold one end of a 10 cm long magnesium ribbon and burn it in air on, spirit lamp., Observation : The magnesium ribbon burns with a dazzling white ame to, form a white powdery mass. This white powdery mass continues dropping, from the magnesium ribbon., ', o 2MgO + heat, 2Mg + O2 , , 0DJQHVLXP ULEERQ EXUQV ZLWK D GD]]OLQJ ZKLWH ÀDPH WR IRUP ZKLWH, powdery mass, (c) Experiment with zinc and dilute sulphuric acid, Introduce a small piece of geonulated zinc in a clean test tube. Pour about 5, cc of dilute sulphuric acid in the test tube. Close the mouth of the test tube, with the thumb, till you feel the pressure of gas., Observation : The zinc metal briskly reacts with dilute sulphuric acid. From, the surface of zinc, a large number of tiny bubbles of a gas rise. The contents, of the test tube get hot. The colourless gas evolved is hydrogen, which, explodes with a pop sound when brought near ame., 222, , Science Class - IX
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Zn + H2SO4 (dil.) o ZnSO4 + H2 (g), , H2 gas is produced, when zinc reacts with dil. H2SO4 which burns with, a pop sound, (d) Experiment with copper sulphate on heating, Heat 2 g of blue coloured copper sulphate in a tube on Bunsen ame for, about 2 to 5 minutes., Observations :, (i) Blue coloured copper sulphate crystals crumbled to form white, powdery mass., (ii) Large amount of steamy fumes are given out., (iii) These fumes condense on the cooler part of the test tube., (iv) If few drops of water are added again to white powdery mass, it, regains its blue colour., CuSO4.5H2O o CuSO4 + 5H2O, , Heating of copper sulphate crystals, Experiment, , 223
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(e) Experiment with sodium sulphate and barium chloride solutions, Pour about 5 cc of sodium sulphate in a clean test tube and into this add 5 cc, of barium chloride solution. Shake the contents of the test tube., Observations : A white precipitate is formed, which gradually settles at the, base of the test tube because insoluble barium sulphate is formed., Na2SO4 (aq) + BaCl2 (aq) o BaSO4 (s) + 2NaCl (aq), , White precipitate of BaSO4 gets formed when Na2SO4 solution and, BaCl2 solution react with each other, Precautions :, (a) Test tubes should be clean and dry., (b) Use minimum amount of chemicals., (c) Always hold the test tube with a test tube holder before heating., (d) Use re tongs for holding magnesium ribbon., , Multiple Choice Questions, 1. Copper sulphate colour is :, (a) Reddish brown, , (b), , Blue, , (c) Green, , (d), , Black, , 2. Iron nails are placed in CuSO4 solution and after 10 minutes, its blue colour, disappears and it appears :, (a) Reddish brown, , (b), , Blue, , (c) Greenish, , (d), , Light blue, , 224, , Science Class - IX
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3. The reaction of iron with copper sulphate solution is an example of :, (a) Decomposition reaction, (b) Displacement reaction, (c) Double decomposition reaction, (d) Combination reaction, 4. Iron nails were dipped in CuSO4 solution for 10 minutes. After 10 minutes,, it was observed that :, (a) A reddish brown layer of copper deposits on iron nails, (b) A blue layer of CuSO4 deposits, (c) Iron nails become pale yellow, (d) CuSO4 solution remains blue, 5. Burning of magnesium ribbon in air is an example of :, (a) Displacement reaction, (b) Double decomposition reaction, (c) Combination reaction, (d) All the above, 6. What is the colour of magnesium oxide formed due to the burning of, magnesium ribbon in air ?, (a) White, (b) Red, (c) Black, (d) Blue, 7. The chemical formula of copper sulphate crystals is :, (a) CuSO4.6H2O, (b) CuSO4.10H2O, (c) CuSO4.5H2O, (d) CuSO4.7H2O, Experiment, , 225
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8. Which is not observed when zinc granules are added to dilute sulphuric acid, in a test tube ?, (a) Precipitate at the bottom of the tube, (b) Bubbles of gas escaping from the tube, (c) Gradual decrease in the size of the granules, (d) Heat energy evolved in the reaction, , Answers, 1., , (b), , 2. (b), , 3. (b), , 6., , (a), , 7. (c), , 8. (a)., , 226, , Science Class - IX, , 4. (a), , 5. (c)
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EXPERIMENT NO. 5 (a), Aim :, , To prepare stained temporary mount of onion peel and to record, observations and draw a labelled diagram., , Materials required : Mircoscope, onion, knife, needles, forceps, slide, cover, slip, brush, methylene blue stain, glycerine, glass slide, blotting paper, water, etc., Theory : Onion peel is made up of many rectangular cells. These are plant cells., Each cell has a rigid cell wall made of cellulose. Plant cell has plastids and a, large central vacuole., Procedure :, (a) Take a thin onion scale from an onion., (b) Break it from the concave side to get a transparent and thin piece of, membranous onion peel., (c) Now keep this piece of onion peel in a watch glass containing water., (d) Cut out a small portion of this peel and place it on a glass slide and add, a drop of methylene blue solution for a few seconds., (e) Drain out the stain and mount the onion peel on a drop of glycerine., (f), , Cover the peel gently with cover slip to avoid the entry of air bubbles., , (g) Gently press the cover slip with a needle so as to spread the glycerine, evenly., (h) Remove excess glycerine from the edges of the cover slip using a, blotting paper., , Experiment, , 227
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Under low powerof the Microscope (slide of onion peel), , Observations :, (a) There are large number of brick shaped (rectangular) cells lying side by, side in a membrane., (b) A distinct darkly stained nucleus is present in each cell., (c) A prominent vacuole is seen in the centre and cytoplasm is present on, inner surface of cell wall., Precautions :, (a) Always hold the slide from its edges., (b) Do not put excessive stain on slide., (c) Put the cover slip at 45º angle to avoid the entry of air bubble., (d) Soak excessive water or glycerine on slide with blotting paper., , EXPERIMENT NO. 5 (b), Aim :, , To prepare stained temporary mount of human cheek cells and to record, observations and draw their labelled diagrams., , Materials required : Watch glass, clean glass slide, cover slip, needles, brush,, toothpick, methylene blue solution, blotting paper, high powered microscope., Theory : Human cheek cells are animal cells. They are without cell wall and, have denser cytoplasm. Animal cells do not have large vacuoles. They don’t, have plastids., Procedure :, (a) Take a clear glass slide and in the middle of it pour a drop of distilled, water with the help of a dropper., (b) Take a clean toothpick and use it to scrap the inner wall of cheek gently,, so as to scrap the epithelial tissue., 228, , Science Class - IX
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(c) Mix the scrap on the toothpick in the drop of water placed on the glass, slide., (d) Pour a drop of methylene blue solution on the mixture on the slide and, mix it thoroughly., (e) After 2-3 minutes remove the excess water and methylene blue solution, evenly on the slide by using tip of a blotting paper., (f), , Pour a drop of glycerine on the contents of slide and spread it., , (g) Take a dray and clean cover slip and hold it from its edges with left, hand. Place the cover slip on the slide in such a way that one of its edges, comes in contact with the mounting material i.e., glycerine. Now put, the cover slip without air bubble., (h) Remove the extra material surrounding the slide with the help of, blotting ( lter) paper., (i), , Examine the slide under high power microscope., , Slide of cheek cells under microscope, Observations :, (a) Large number of at cells with irregular boundaries are seen., (b) Each cell has a thin cell membrane (or plasma membrane)., (c) A distinct deeply stained nucleus is seen in each cell., (d) There are no intercellular spaces between the cells., (e) No cell wall is visible., (f), , Space between the plasma membrane and the nucleus is lled with, granules material called cytoplasm., Experiment, , 229
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Inference : The examination of material on the slide suggests that it is an animal, cell, because cell wall and prominent vacuoles also not seen., Precautions :, (a) Scrapping of the cheek cells should be done very carefully so that no, damage is done., (b) The toothpick should be washed thoroughly so that it does not infect the, cheek with any foreign bodies., (c) The slide should be neatly made with no air bubbles and in just the right, amount of glycerine used., (d) Overstaining and understaining should be avoided., (e) Manting should be done in the middle of slide., , Multiple Choice Questions, 1. The outermost layer of a plant cell is :, (a) Cell membrane, , (b), , Cell wall, , (c) Tonoplast, , (d), , Nuclear membrane, , (a) Make the cell turgid, , (b), , nourish the cell, , (c) help in all multiplication, , (d), , highlight the cell organelles, , 2. Cells are stained to :, , 3. Human cheek cells stained in methylene blue and mounted in glycerine were, observed with the help of a compound microscope. The components of the, cells which could be seen are :, (a) Cell wall, cytoplasm, nucleus, (b) Plasma membrane, cytoplasm, nucleus, (c) Plasma membrane, cytoplasm, nucleus, mitochondria, (d) Plasma membrane, cytoplasm, nucleus, mitochondria, lysosomes, 4. Given below are four operations for preparing or temporary mount of human, cheek cells :, (i), , Taking scarping from inner side of the cheek and spreading it on a clean, side., , (ii) Putting a drop of glycerine on the material., (iii) Adding two or three drops of methylene blue., 230, , Science Class - IX
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(iv) Rinsing the mouth with fresh water., The correct sequence of the operations is :, (a) (i), (ii), (iii), (iv), , (b), , (iv), (i), (iii), (ii), , (c) (iv), (i), (ii), (iii), , (d), , (i), (iii), (ii), (iv), , 5. To observe cells in an onion peel, we must prepare the slide by mounting on, it :, (a) Crushed pulp of onion, (b) Dry scale leaf, (c) To make green leaf of onion, (d) Thin layer of eshy leaf of onion should not dry, 6. One of the following is not visible in cheek cells :, (a) Cell membrane, , (b), , Nucleus, , (c) Cell wall, , (d), , Cytoplasm, , 7. In the preparation of a temporary mount of onion peel, the commonly used, stain is :, (a) Safranin, , (b), , Iodine solution, , (c) Methylene blue, , (d), , Glycerine, , 8. The organelle not observed in an animal cell is :, (a) Nucleus, , (b), , Cytoplasm, , (c) Chloroplast, , (d), , Plasma membrane, , Answers, 1., , (b), , 2. (d), , 3. (b), , 6., , (c), , 7. (a), , 8. (c), , 4. (b), , Experiment, , 5. (d), , 231
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EXPERIMENT NO. 6, Aim : To identify parenchyma and sclerenchyma tissues in plants striped, muscle bres and nerve cells in animals from prepared slides and to draw, their labelled diagrams., Materials required : Prepared slides of parenchyma tissues, sclerenchymatous, tissues, striped muscle bres, nerve cells and compound microscope., Theory :, Tissue : A tissue is a group of similar cells having a common origin and held, together by intercellular substances to perform a particular function., Permanent tissues : Some tissues loose their capacity to divide, so they are, called permanent tissues. For example, parenchyma, sclerenchyma in plants, and striped muscle bres and nerve cells in animals., Procedure :, (a) Take a prepared slide and observe it under microscope., (b) Study the slide and write its identifying features. Also, draw diagrams, in your notebook what you see under observation., Observation :, (a) Parenchyma, , Features :, (a) The cells are isodiametric i.e., almost equal in length and width., (b) There are intercellular spaces at the corners for the exchange of gases., 232, , Science Class - IX
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(c) The cells have thin walls., (d) There is a large central vacuole in each cell., (e) A distinct nucleus is present in peripheral cytoplasm., Inference :, (a) Parenchyma tissue is located in soft parts of the stem, leaves, roots,, fruits, owers., (b) They act as packaging material, sometimes photosynthesis also occurs., Observation :, (b) Sclerenchyma, , Features :, (a) Sclerenchymatous cells are dead cells., (b) They have evenly thickened hard cell walls., (c) They have very little or no protoplasm., (d) They have hard ligni ed secondary walls., (e) They can be divided into two types :, (i) Fibres : They are elongated cells with tapering ends., (ii) Sclereids : These are irregular isodiametric cells., Experiment, , 233
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Inference :, This tissue is very widely distributed tissue and occurs in form of distinct, or patches and forms the chief constituents of hard parts of the plant. These, cells, being thick walled and having deposition of lignin give mechanical, strength to the plant., Observation :, , , F 6WULDWHGPXVFOHVRUYROXQWDU\PXVFOHVRUVWULSHGPXVFOH¿EUHV, , 'LDJUDPVKRZLQJVWULDWHGPXVFOH¿EUHVRUVWULSHGPXVFOH¿EUHV, Features :, (a) The bres are long, cylindrical and unbranched., (b) The cells are surrounded by connective tissue., (c) The muscle bres are multinucleated., (d) The nuclei lie towards the periphery of the bres., (e) The cells of this muscle are non-tapering., (f), , Dark and light band appear alternately giving the characteristic striped, or striated appearance., , Inference :, (a) Striped muscle bres are found attached to the bones in different parts, of the body., (b) These bring about skeletal movements., (c) They help in locomotion and maintaining the posture of the body., 234, , Science Class - IX
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Observation :, (d) Nerve tissues :, , Features :, (a) The nerve cell has a larger body called cyton., (b) The cell body (cyton) has a prominent nucleus., (c) Cyton has cytoplasmic projections called dendrites., (d) One of the dendrites is long and is called axon., (e) A group of axons held together by a connective tissue is called a nerve., (f), , The axons are covered with medulary sheath or myelin sheath., , (g) At the nodes of Ranvier, the myelin sheath is absent., (h) The nerve endings are attached to muscles., Inference :, Nerve cell has a large cell body with prominent nucleus such that cyton has, cytoplasmic projections called dendrites and one a long one, called axon., , Experiment, , 235
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Multiple Choice Questions, 1. Unstriated muscles are found in :, (a) Heart, , (b), , Arms and legs, , (c) Urinary bladder, , (d), , All of these, , 2. A permanent slide shows thin walled isodiametric cells with a large vacuole., The slide contains :, (a) collenchymas cells, , (b), , sclerenchyma cells, , (c) parenchyma cells, , (d), , nerve cells, , 3. A gure depicting parts of neuron is given below. The correct identi cations, of the labels 1, 2, 3, 4 respectively is :, , (a) Dendrite, cytoplasm, nissl granules, nerve bres, (b) Cilia, endoplasmic reticulum, nucleoli, nerve bre, (c) Dendrons, cell body, nissl granule, axon, (d) Dendrites, cyton, nucleus, axon, 4. A student Suresh wants to see striated muscles and light and dark muscles., So, he has to see :, , (a) A, , (b), , B, , (c) C, , (d), , D, , 236, , Science Class - IX
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5. Which of the following cells are irregularly thickened at the corners ?, (a) Parenchymatous tissue, , (b), , Collenchymatous tissue, , (c) Sclerenchymatous tissue, , (d), , Meristematic tissue, , (a) Cell body, , (b), , Axon, , (c) Light and dark bonds, , (d), , Dendrites, , 6. Pick the odd one out of the following., , 7. Which one of the following tissues has cells that are having ligni ed thickened, walls ?, (a) Parenchymatous tissue, , (b), , Collenchymatous tissue, , (c) Sclerenchymatous tissue, , (d), , Meristematic tissue, , 8. Plant cells thickened at corners, with non-ligni ed cell walls are :, (a) Parenchyma, , (b), , Collenchyma, , (c) Sclerenchyma, , (d), , None of these, , Answers, 1., , (c), , 2. (c), , 3. (d), , 6., , (c), , 7. (c), , 8. (b)., , 4. (d), , Experiment, , 5. (b), , 237
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EXPERIMENT NO. 7, Aim :, , To determine the melting point of ice and the boiling point of water., , Materials required : A glass beaker (200 cc), a wire gauge, a tripod stand, a, Celsius thermometer, a glass rod, an iron stand, a Bunsen burner or a spirit, lamp, a magnifying glass, distilled water, ice cubes prepared from distilled, water., Theory : When a solid is heated then kinetic energy of the molecules is large, enough to overcome the binding forces and the substance changes its state., Melting point of the solid : The constant temperature, at which a solid, changes completely to its liquid state at a constant pressure of 1 atmosphere,, is called the melting point of the solid., Boiling point of the liquid (water) : The constant temperature, at which a, liquid changes completely to its vapour (gaseous) state at a constant pressure, is called boiling point of the liquid., Procedure :, (a) Melting point of the solid, (i), , Take a beaker and put the small ice pieces (crushed ice) into it (about, 100 g- 150 g)., , (ii) Insert a stirrer into the ice kept in the beaker., (iii) Place the beaker containing ice on the tripod stand with a wire gauze., (iv) Suspend a thermometer vertically in the ice by using an iron stand., (v) Note the temperature of ice before lighting the burner., (vi) Heat the ice pieces. Stir well while heating., (vii) Record the temperature when the ice melts completely., (b) Boiling point of the water, (i), , Take about 50 ml of distilled water in a hard glass test tube., , (ii) Put 2-3 small pieces of pumice stone to avoid bumping., (iii) Fix a cork with bores in the mouth of the test tube and x it in an iron, stand., (iv) Fix a thermometer in one of the bores and a delivery tube in the other, bore., 238, , Science Class - IX
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(v) Heat the boiling tube gently. Keep on moving the ame as otherwise, the tube is likely to break., (vi) Note the temperature when the boiling of water starts. Continue heating, of water till the temperature becomes constant and the water starts, boiling., (vii) Note the constant temperature also., , Observation :, Boiling Point of water, S. No. Time in minutes Boiling point of, , Melting point of ice, S. No. Time in minutes Melting point of, , Water in ºC, , ice in ºC, , 1., , 0, , ................, , 1., , 0, , ................, , 2., , 1, , ................, , 2., , 1, , ................, , 3., , 2, , ................, , 3., , 2, , ................, , 4., , 3, , ................, , 4., , 3, , ................, , 5., , 4, , ................, , 5., , 4, , ................, , Result :, (a) Boiling point of water is ................ºC., (b) The boiling point does not change with time as long as any water is left, for boiling., Experiment, , 239
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(c) Melting point of ice is ................ºC., (d) The melting point of ice does not change with time as long as ice is, present in the mixture of ice and water formed from it., Precautions :, (a) Use a good quality thermometer., (b) Do not record the temperature in half or quarter degrees as the accuracy, of the thermometer is 1 ºC., (c) Record the boiling point or the freezing point only when the mercury, thread is stable at one place for 2 minutes or more., (d) Do not immerse the stem of the thermometer in water or ice. This leads, to expansion or contraction of the stem which results in recording of, wrong temperature., , Multiple Choice Questions, 1. When do ice and water co-exist under atmospheric pressure ?, (a) At 0ºC, , (b), , Below 0ºC, , (c) Above 0ºC, , (d), , At 5ºC, , 2. Renu starts heating pure water in a tube. It will start boiling at :, (a) 173 K, , (b), , 100 K, , (c) 373 K, , (d), , 273 K, , 3. Water in a container is heated uniformly from 0ºC to 100ºC. The volume :, (a) increases continuously, (b) decreases continuously, (c) decreases up to 4ºC and increases further, (d) increases up to 4ºC and decreases further, 4. For the accurate determination of the boiling point of water, we use :, (a) tap water, , (b), , distilled water, , (c) salt solution, , (d), , sugar solution, , 5. Which of the following statements is right with reference to the melting of, ice ?, (a) At melting point only ice exists., (b) At melting point only water exists., 240, , Science Class - IX
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(c) At melting point both ice and water exist., (d) At melting point ice, water and steam exist., 6. Which of the following would you choose to determine the melting point of, ice in your laboratory ?, (a) Dry crushed ice, , (b), , Ice cubes, , (c) Ice added to water, , (d), , Slab of ice, , 7. For determing the melting point of ice we should prefer :, (a) ice made from distilled water, (b) ice made from tap water, (c) dry crushed ice mixed with salt, (d) a mixture of ice and salt, 8. When on heating water starts converting itself into steam, the temperature :, (a) remains constant, , (b), , continuously increases, , (c) decreases, , (d), , cannot be observed, , Answers, 1., , (a), , 2. (c), , 3. (d), , 6., , (a), , 7. (a), , 8. (a)., , 4. (a), , Experiment, , 5. (c), , 241
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EXPERIMENT NO. 8, Aim :, , 7RYHULI\ODZVRIUHÀHFWLRQ, , Material required : Chart paper, glass sheet/cardboard sheet, watch, gum, table,, chalk pieces., Theory : Sound follows laws of re ection like light. These laws are :, (a) Incident angle formed by sound wave, re ection angle are equal to each, other., i = r, (b) Incident ray, re ected sound ray and normal formed at the point of, incidence all lie in the same plane., Procedure :, (i), , Make 2 pipes of 30 cm each and equal diameters from chart paper., , (ii) Put a cardboard/glass sheet between 2 chart pipes or rollers as shown in, picture 1., (iii) Put a clock in front of pipe P1., (iv) Now adjust pipe P2 at different angles and nd when do you hear the, maximum sound., (v) Now mark 2 points each at both the pipes A, B and C, D to mark their, positions., (vi) Remove the pipes and make lines making angle of incidence (between, AB and MN) and re ection angle (CD and MN) and make their values, in the following table AON = i, CON = r., , 242, , Science Class - IX
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Observations :, S., No., 1., , Angle of incidence, i, , $QJOHRIUHÀHFWLRQr, , i r, , 2., 3., 4., , Result/Conclusion :, (a) Angle of incidence is equal to angle of re ection of sound., (b) Incident ray, re ected ray, normal at the point of incidence, all lie in the, same plane., Precautions & sources of error :, (i), , Don’t change the position of pipe P1 until you are able to hear the, maximum sound from P2., , (ii) Keep watch very close to P1., (iii) Glass or cardboard should be of such size that you don’t hear the direct, sound from watch., (iv) Table should not move at all., (v) Both pipes should be of equal lengths and diameters., , MCQs Based on Practical 1, 1. Sound waves are :, (a) Transverse waves, , (b) Longitudinal waves, , (c) Radio waves, , (d) Supersonic waves, , 2. In a stethoscope sound of heartbeats travel through the stethoscope tube :, (a) Along a straight line, (b) As a sonic boom, (c) By beeding along the tube, (d) By undergoing multiple re ection, 3. Find the false statement :, (a) Sound is a form of energy, (b) Sound travels in the form of longitudinal waves, Experiment, , 243
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(c) Sound travels in the form of transverse waves, (d) Sound follows the laws of re ection, 4. Speed of sound depends upon :, (a) Pressure of the medium, (b) Temperature of the medium, (c) Vacuum, (d) None of the above, 5. Nature of re ection of sound depends upon :, (a) Source of sound, , (b) Re ecting surface, , (c) Normal to the re ecting surface, , (d) All of the above, , 6. Which of the following depends on the principle of re ection of sound ?, (a) Stethoscope, , (b) Sound board, , (c) Ultrasound, , (d) All of above, , 7. Speed of sound in air is (at 22ºC) :, (a) 344 ms1, , (b) 344 km hr1, , (c) 344 cms1, , (d) 344 m hr1, , 8. Speed of sound in air is :, (a) More than speed of sound in solids, (b) More than speed of sound in liquids, (c) Less than speed of sound in solids & liquids, (d) Equal to the speed of sound in solids and liquids, Answers, 1. (b), , 2. (d), , 3. (c), , 6. (d), , 7. (a), , 8. (c)., , 244, , Science Class - IX, , 4. (b), , 5. (b)
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EXPERIMENT NO. 9, Aim : 7R¿QGGHQVLW\RIDVROLGZLWKWKHKHOSRIDVSULQJEDODQFHDQGPHDVXULQJ, F\OLQGHU, Materials required : Spring balance, a piece of metal, spring balance, measuring, cylinder, thread, water., Theory : Density is mass per unit volume of a substance. Its unit is kg/m3 or g/, cm3., Density, , Mass, Volume, , Procedure :, (i), , Tie the piece of the metal (or anything else) with a thread and hang it, on a spring balance., , (ii) Find its mass in air., (iii) Fill a measuring cylinder upto half., (iv) Immerse this piece of metal fully in water., (v) Find the volume of displaced water., (vi) Find the volume with different levels of water., , Observations : Mass of the object (x) = .............grams, S., No., , Initial level of, water, V1, , Final level of, water, V2, , Displaced, water, , Experiment, , Volume V2 –, V1 = V, , 245
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Calculations :, , Density, , x, V, , g/cm3, , Result : Density of the solid is found to be............. ., Precautions :, (i), , Metal piece used should be dry., , (ii) Calculate the zero error of spring balance beforehand., (iii) There should be no bubble in water., (iv) Water should not ow out when we put metal piece in it., (v) Lower meniscus of water is read only., , MCQs Based on Practical, , 2, , 1. The spring balance used by one in the laboratory measures :, (a) Mass of body attached only, (b) Weight of body attached only, (c) Weight of spring and the body attached, (d) Mass of the spring and the body attached, 2. The scale used in spring balance reads the mass since it has been :, (a) Elongated, , (b) Compressed, , (c) Clibrated, , (d) Printed corrected, , 3. Density of a substance is a :, (a) Material character, , (b) Temperature variant, , (c) Constant always, , (d) Both (a) and (b), , 4. When a body is oating on the surface of a liquid, the net force experienced, by it is :, (a) Zero, , (b) Weight, , (c) Weight upthrust, , (d) Volume, , 5. A spring balance calibrated in Newton, reads 19.6 N, its mass in grams is :, (a) 2000 g, , (b) 200 g, , (c) 20 g, , (d) 2 g, , 6. The SI unit of density of a substance is :, (a) g/cm3, , (b) kg/m3, , (c) N/m3, , (d) N/cm3, , 246, , Science Class - IX
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7. A balloon lled with hydrogen gas rises up into the air due to the :, (a) Weight of the balloon, (b) Low density of air in the balloon, (c) High density of air, (d) Buoyant force exerted by air on it, 8. A body weights 500 g in air and 400 g in water. The upthrust on the body is :, (a) 100 gwt, , (b) 50 gwt, , (c) 200 gwt, , (d) 100 N, Answers, , 1. (a), , 2. (c), , 3. (d), , 6. (b), , 7. (b), , 8. (a)., , 4. (c), , Experiment, , 5. (a), , 247
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EXPERIMENT NO. 10, Aim : 7RHVWDEOLVKUHODWLRQVKLSEHWZHHQORVVLQZHLJKWRIDVROLGZKHQIXOO\, LPPHUVHG LQ L WDS ZDWHU LL VWURQJO\ VDOW\ ZDWHU ZLWK WKH ZHLJKW RI ZDWHU, GLVSODFHGE\LWE\WDNLQJDWOHDVWGLIIHUHQWVROLGV, Materials required : Spring balance, measuring cylinder, piece of iron, thread,, tap water, brine, piece of wood, over ow jar., Theory : According to Archimedes principle :, “When an object is completely or partially immersed in water, it experiences, a decrease in its weight which is equal to the weight of liquid displaced by the, immersed part of solid.”, Procedure :, (i), , Find weight of an object (glass stopper) in air with the help of spring, balance., , (ii) Keep the over ow jar on a wooden block., (iii) Keep lling the over ow jar till water starts owing., (iv) Keep a measuring cylinder at the nozzle of the jar., (v) Now, put this spring balance hung with glass stopper, fully immersed in, water. Some water will over ow in the measuring cylinder. Find the, amount of water collected in the measuring cylinder., (vi) Note the weight of this glass stopper in water., (vii) Repeat the steps with piece of iron., (viii) Repeat the steps with both the objects in brine (saturated solution of salt, in water)., Observations :, , 248, , Science Class - IX
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Object, , Weight in, air, W1, , Weight in, tap water,, W2, , Decrease in, weight W2 –, W1, , Weight, in brine,, W3, , Decrease, in weight,, W3 – W1, , 1. Glass, stopper, 2. Piece of, iron, Object, , Weight of displaced water, (tap water), , Weight of displaced brine, , Glass stopper, Piece of iron, , Conclusion : Weight of displaced water is equal to the weight of object in tap, water or brine., Precautions :, (i), , Spring balance should be accurate., , (ii) Measuring cylinder taken should be dry., (iii) When the object is immersed in water, the water collected in measuring, cylinder should not over ow (not even a single drop)., (iv) Object immersed in water should not touch the walls of the container., (v) Weight decreased in water should be measured from spring balance, only once the object is stable., (vi) Lower meniscus of colourless solution should be read., , MCQs Based on Practical 3, , 1. In an experiment weight of a solid was measured. Also, weight of displaced, water was also measured in the same experiment. Which law is veri ed, by it ?, (a) Newton’s law, , (b) Archimedes Principle, , (c) Law of gravitation, , (d) Law of solution, , 2. Out of the following sketches, which shows measurement of weight of, displaced water ?, Experiment, , 249
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3. An iron nail sinks in sea water but a ship, which is much heavier keeps, oating. Why ?, (a) Density of sea, (b) Ship is not very heavy, (c) Amount of water displaced by ship is more than the weight of ship, immersed in it, (d) Buoyant force exterted on the ship is less than the weight of ship, 4. To nd the density of powdered salt, what was taken in a eureka ask ?, (a) Water, , (b) Kerosene, , (c) Milk, , (d) Honey, , 5. A boat A oats on water, a ship B’s lower part is immersed in water and a, submarine C is completely immersed in water, because :, (a) A and B are lighter than water, (b) Submarine C is heavier than water, (c) Weight of boat A is equal to the weight of water displaced, weight of B, is less than that of displaced water and weight of C is more than that of, displaced water, (d) Weight of displaced water is equal to the weights of B and C where, weight of displaced water by A is less than that of the weight of A, 6. An experiment which shows decrease in the weight of an object when it is, immersed in water indicates :, (a) Density of a solid, , (b) Flight of a plane, , (c) Stopping a ship in sea, , (d) Sinking of a ship in sea, , 250, , Science Class - IX
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7. In which of the following, the decrease in the weight of an object (when, immersed in water) is equal to the weight displaced :, , 8. If an object is immersed in water in a eureka vessel and then in extremely, salty water in the same eureka vessel, then collected extremely salty water, is...............with respect to collected water., (a) More, (b) Equal, (c) Less, (d) Can’t be decided, Answers, 1. (b), , 2. (d), , 3. (c), , 6. (d), , 7. (c), , 8. (b)., , 4. (b), , Experiment, , 5. (c), , 251
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EXPERIMENT NO. 11, Aim :, , 7R¿QGWKHYHORFLW\RISXOVHSURSDJDWHGWKURXJKDVWUHWFKHGVOLQN\, , Materials required : A slinky, stop watch, meter scale., Procedure :, (i), , Take a slinky and spread it on a table or smooth oor as shown in the, gure., , (ii) Fix its one end at a xed point on wall., (iii) Take the slinky in right hand., (iv) Jerk your hand from right to left., (v) A pulse is generated. Calculate the time taken for 50 pulses., (vi) Let this time taken be T seconds., (vii) Find the distance between two ends of slinky. Let this be D meters., (viii) Speed of pulse =, , D, T/50, , m/s, , (ix) Repeat the same for 5 times and nd the average., Observations :, Length of slinky = ............... m, S. No., , Time for 50 pulses T(s), , 1., 2., 3., 4., 5., , Average = ................m/s, , 252, , Science Class - IX, , Speed
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Precautions :, (i), , Choose a slinky of proper length and ductility., , (ii) Tie one end of slinky properly., (iii) Start the stop watch as you jerk., (iv) Give a jerk to slinky horizontally., , MCQs Based on Practical 11, 1. What kind of waves can be produced in a slinky ?, (a) Transverse waves, , (b) Longitudinal waves, , (c) Both transverse and longitudinal, , (d) None of the above, , 2. Each particle in a wave propagated within a slinky or a thread :, (a) Stays on its place, (b) Vibrates, (c) Doesn’t vibrate, (d) Moves from one end to another, 3. A wave produced for a small interval of time is called :, (a) Pulse, , (b) Wave, , (c) Sound wave, , (d) None of the above, , 4. Thread/slinky used in the experiment should :, (a) Not have small amplitude, (b) Should not be stretched near oor, (c) Not have knots in it, (d) All of the above, 5. A pulse is :, (a) Generated in a small part of the medium, (b) Generated in a large part of the medium, (c) Produced in vaccum, (d) All of above, 6. When the string of a sitar is stretched and left then :, (a) Sitar produces transverse waves and air produces longitudinal waves, (b) Sitar produces longitudinal waves and air produces transverse waves, Experiment, , 253
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(c) Both produce longitudinal waves, (d) Both produce transverse waves, 7. A wave that travels in the form of compression and rarefaction :, (a) Transverse wave, , (b) Longitudinal wave, , (c) Any frequency wave, , (d) Light wave, , 8. Waves produced in water are :, (a) Longitudinal waves, (b) Transverse waves, (c) Half longitudinal half transverse waves, (d) None of the above, Answers, 1. (c), , 2. (b), , 3. (a), , 6. (b), , 7. (b), , 8. (b)., , 254, , Science Class - IX, , 4. (d), , 5. (a)
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EXPERIMENT NO., , 12, , Aim : To study characteristics of Spirogyra/Agaricus, Moss/Fern, Pinus (male, or female cone) and an angiosperm plant and give two identifying features of, groups they belong to., Materials required : Spirogyra, Agaricus, Moss, Fern, Pinus male and female, cone, angiosperm plant., Procedure & Observation :, I., , Spirogyra, &ODVVL¿FDWLRQ , , Division : Thallophyta, Class : Chlorophyta, , Characteristic features :, (i), , It is a lamentous alga which grows in length not in thickness., , (ii) It is slimy to touch., (iii) It has a large vacuole., (iv) It has a series of cells joined end to end., (v) Nucleus is in the centre suspended by cytoplasmic strands., (vi) Pyrenoids are present which store starch (food)., (vii) Chloroplast is ribbon-shaped and are 1-12 in number., Identifying features of the group :, (i) It is mostly found in fresh water but some varieties are found in sea, water and on land., (ii) Presence of chlorophyll in it is as high as in plants., , Experiment, , 255
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II. Agaricus, , , &ODVVL¿FDWLRQ Division : Thallophyta, Class : Fungi, Characteristic features :, (i), , These do not have chloroplast in the thallus., , (ii) It consists of a stalk and umbrella like cap called pileus., (iii) The main body of mushroom appears above ground while vegetative, part lies in the soil in the form of mycelium., (iv) It is a saprophyte., (v) Cell wall is made of a complex sugar chitin., Identifying features of the group :, (i), , Chlorphyll is absent., , (ii) Saprophytic nutrition with intracellular digestion is seen., (iii) Reserve food material is found in the form of fat, oil and glycogen., , III. Moss (Funaria), , , &ODVVL¿FDWLRQ , , Sub kingdom : Cryptogamae, Division : Bryophyta, , Characteristic features :, (i), , The moss plants are commonly found on old walls, ground, moist and, shady places., , (ii) The plant is bisexual, both male reproductive organs (antheridia) and, female reproductive organs (archegonia) are found on the same plant., 256, , Science Class - IX
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(iii) Plant body is called gametophyte and is well-differentiated into rhizome,, stem, leaves., (iv) These plants do not contain vascular bundles to transport materials, from one place to another the leaf body., Identifying features :, (i), , These are non-vascular plants., , (ii) These are called bryophytes of plants kingdom as water is essential for, fertilization., (iii) The plant body is generally thalloid., , IV. Fern (Dryopteris), , , &ODVVL¿FDWLRQ , , Sub kingdom : Cryptogamae, Division : Pteridophyta, , Characteristic features :, (i), , Plant body is a saprophyte which has true roots, stem and leaves with, vascular tissue., , (ii) Reproductive organs are multicellular., (iii) These are found in damp and dark places., (iv) Leaves are quite big and are called fronds., (v) As they have soft, big and beautiful leaves, these plants are used as, ornamental plants., (vi) Immature leaves are coiled like spring., Experiment, , 257
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Identifying features :, (i), , They have vascular tissue for conduction of materials within the parts, of plant., , (ii) Saprophyte is dominant having true roots, stem and leaves., , V. Pinus (With male and female cone), , , &ODVVL¿FDWLRQ , , Division : Pteridophyta, Class : Gymnospermae, , Characteristic features :, (i), , It is a gymnosperm (which have naked seeds)., , (ii) Flowers are not present., (iii) Leaves are needle shaped., Cones are of two types : Male & Female, Male Cone/Staminate :, (i), , These cones are brown coloured, egg shaped., , (ii) These are found in groups/bunches., (iii) Each male cone has larger number of microsporophylls. Each, microsphorophyll has 2 microsporangia., (iv) Each microsporangia has large number of microspores or pollen grains., Female Cone :, (i), , 258, , These are found in between needle shaped leaves in 2-4 in number in, bunches., Science Class - IX
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(ii) In the rst year female cone has megasporophyll which is small and, green-red in colour., (iii) Size of megasporophyll increases in second year. In third year, megasporophylls separate from each other and size of the cone also, increases., , VI. Angiosperm Plant :, , , &ODVVL¿FDWLRQ , , Division : Phanerogam, Class : Angiosperm, , &KDUDFWHULVWLFV , (i), , Plant body is fully differentiated into roots, stem and leaves., , (ii) These are owering plants., (iii) Angiosperms are further divided into two groups viz. Monocots (with, one cotyledon e.g., rice, maize, wheat) and dicots (with two cotyledons, e.g., mustard, mango etc.)., (iv) Dicots have tap root system, reticulate venation whereas monocots, have brous root system with parallel venation., , Experiment, , 259
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MCQs Based on Practical 6, 1. Spirogyra is not found in sea because :, (a) There is a lot of water there, (b) Sea water has a lot of salts, (c) Big sea animals are found in sea, (d) Water is pure, 2. We see trees with needle like leaves in mountaineous regions. These are, called :, (a) Mass, , (b) Conifer, , (c) Algae, , (d) Fungi, , 3. Which of the following statements is true ?, (a) Plants are further sub-divided into algae and fungi, (b) Fern, moss, fungi, bacteria, algae are all owerless plants, (c) Flowered plants may be trees, (d) None of the above, 4. Fungi show a network of multicellular thread like structure called :, (a) Mycelium, , (b) Hyphae, , (c) Sporangium, , (d) Ascocarp, , 5. Plants which produce owers, come in which group ?, (a) Bryophyta, , (b) Pteridophyta, , (c) Gymnosperm, , (d) Angiosperm, , 6. Which of the following grows on dead and decaying organic matter ?, , (a) Mushroom, , (b) Chlamydomonas, , (c) Paramaecium, , (d) Bacteriophage, , 260, , Science Class - IX
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7. A pond seems green because :, (a) It has a lot of sea weeds, , (b) It has algae, , (c) It is polluted, , (d) None of the above, , 8. Pick the odd one out :, (a) Virus, , (b) Yeast, , (c) Fungi, , (d) Mushroom, Answers, , 1. (b), , 2. (b), , 3. (c), , 6. (a), , 7. (b), , 8. (a)., , 4. (a), , Experiment, , 5. (d), , 261
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EXPERIMENT NO. 13, Aim : To observe the given pictures/charts/models of earthworm, cockroach,, ERQ\¿VKELUG, For each organism draw their picture and record of :, D RQHVSHFL¿FIHDWXUHRILWVSK\OXP, E RQHDGDSWLYHIHDWXUHZLWKUHVSHFWWRLWVKDELWDW, Materials required : The specimen of earthworm, cockroach, bony sh and, bird., Procedure :, (i), , Observe the given specimen/chart/model keenly., , (ii) Draw their labelled diagram and write their adaptive features., A. Earthworm :, , , &ODVVL¿FDWLRQ , , Phylum : Annelida, , 6SHFL¿FFKDUDFWHULVWLFIHDWXUHV , (i), , They have bilateral symmetry., , (ii) They are long and body is divided into sections., (iii) They have body length of 6-10 inches., (iv) Some of the anterior body segments concentrate to form head., (v) They mainly eat carbonic compounds (humus) mixed in the soil (moist)., (vi) They have light brown colour., (vii) Exoskeleton is absent., $GDSWDWLRQ$GDSWLYHIHDWXUHV , (i), , Earthworm reside in holes., , (ii) Humus in soil is its main food., , 262, , Science Class - IX
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B. Cockroach :, , , &ODVVL¿FDWLRQ , , Phylum : Arthropoda, , 6SHFL¿FFKDUDFWHULVWLFIHDWXUHV , (i), , They have long body, which is bilaterally symmetrical and segmented., , (ii) They have body length of 5-6 cm., (iii) Colour of their body is red or brownish, therefore they are camou aged, in dark and hence protected from their enemies., (iv) Their whole body is divided into three parts : head, thorax and abdomen., (v) Anterior part of body form a distinct head, bearing compound eyes and, a pair of antennae., (vi) Each body segment usually bears a pair of jointed legs., (vii) Thorax consists of three pairs of jointed legs on its posterior side,, therefore it has been kept in the phylum Arthropoda., (viii) Two pairs of wings are found on anterior side of the thoracic cavity., (ix) Its abdominal portion is divided into ten fragments covered by, exoskeleton of chin., Adaptation/Adaptative features :, (i), , For respiration, it has spiracles., , (ii) Three pairs of segmented or jointed legs help it to run fast., (iii) On its head it has compound eyes and long sensitive antennae, which, help it to move in dark., (iv) It is omnivorous., , & %RQ\¿VK , , , &ODVVL¿FDWLRQ , , Phylum : Chordata, Class : Osteichthyes, Experiment, , 263
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&KDUDFWHULVWLFIHDWXUHV 6SHFL¿F , (i), , They have streamlined body which help them to survive in water., , (ii) They have ns to balance themselves and for locomotion., (iii) Respiration occur through gills., Adaptive features :, (i), , To reduce friction inside water, their body is streamlined., , (ii) To get prevented from decaying in water their body is covered with, scales., (iii) They have air bladder., , D. Birds :, , , &ODVVL¿FDWLRQ , , Phylum : Chordata, Class : Aves, , &KDUDFWHULVWLFIHDWXUHV 6SHFL¿F , (i), , They have streamlined body, which is an adaptive feature to y in air., , (ii) Body is covered with feathers., (iii) Forelimbs are modi ed into wings for ight., (iv) Hind limbs bear four clawed digits and are adapted for walking,, perching or swimming., (v) Bones of endoskeleton are light and spongy., (vi) Muscles which help in ying are well-developed and strong., Adaptive features :, (i), , Body is streamlined., , (ii) Skeleton is light and hollow., 264, , Science Class - IX
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(iii) Body is covered with feathers., (iv) Forelimbs are modi ed into wings., , MCQs Based on Practical 7, 1. What is the scienti c name of cockroach ?, (a) Periplanita Americana, , (b) Rana tigrina, , (c) Australian acacia, , (d) Solanum tuberosum, , 2. Name the scientist who introduced binomial nomenclature., (a) Carolus Linnaeus, , (b) Charles Darwin, , (c) Aristotle, , (d) Robert Brown, , 3. The body of birds is covered with feathers because :, (a) It help them in ying, (b) It keeps the body warm, (c) Both (a) and (b), (d) They get converted into wings later on, 4. Which of the following doesn’t belong to mammalia ?, (a) Bat, , (b) Duck-billed platypus, , (c) Shark, , (d) Whale, , 5. To which class does earthworm belong ?, (a) Unicellular with notochord, (b) Unicellular without notochord, Experiment, , 265
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(c) Multicellular with notochord, (d) Multicellular without notochord, 6. Label A, B, C, D in the following diagram., , (a) Mouth, Segment, Clitellium, Anus, (b) Mouth, Anus, Segment, Clitellium, (c) Mouth, Clitellium, Segment, Anus, (d) Clitellium, Mouth, Segment, Anus, 7. Identify the labelled part A in the following diagram :, , (a) Antennae, , (b) Anal cerci, , (c) Anal style, , (d) Anus, , 8. Immature cockroaches are also called :, (a) Nymph, , (b) Tadpole, , (c) Pupa, , (d) Groove, Answers, , 1. (a), , 2. (a), , 3. (b), , 6. (c), , 7. (c), , 8. (a)., , 266, , Science Class - IX, , 4. (c), , 5. (d)
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EXPERIMENT NO. 14, Aim :, , 7RYHULI\WKHODZRIFRQVHUYDWLRQRIPDVVLQDFKHPLFDOUHDFWLRQ, , Materials required : Physical balance, conical ask, ignition tube, thread, cork, (rubber), barium chloride and sodium sulphate., Principle : Law of Conservation of Mass : Matter is neither created nor, destroyed. Therefore in a chemical reaction the total mass of the substance, remain conserved., Procedure :, (i), , Make aqueous solution of barium chloride and sodium sulphate., , (ii) Barium chloride solution should be taken in an ignition tube and sodium, sulphate solution is taken in a conical ask., (iii) The ignition tube containing barium chloride is hanged with the help, of a thread inside the conical ask having sodium sulphate in it and a, cork is applied on the mouth of the conical ask., (iv) The whole apparatus is now weighed carefully., (v) Now tilt the conical ask in such a way that the two solutions get mixed, well into each other., (vi) After the chemical reaction, a white coloured precipitate is formed in, the conical ask., (vii) Now again weigh the apparatus in the physical balance., Inference : The total mass inside the conical ask remain same even after the, chemical reaction., Result : The mass of the substances don’t change and it remains conserved., Therefore, it can neither be created nor be destroyed., , Experiment, , 267
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MCQs Based on Practical, , 14, , 1. 2 g hydrogen reacts with 16 g oxygen to give 18 g water. Which law is, proven by it ?, (a) Law of conservation of mass, (b) Law of constant proportions, (c) Law of mathematical proportions, (d) None of the above, 2. Ratio between hydrogen and oxygen in water is :, (a) 1 : 8, , (b) 8 : 1, , (c) 1 : 2, , (d) 2 : 1, , 3. Ratio between carbon and oxygen in CO2 is :, (a) 3 : 8, , (b) 8 : 3, , (c) 3 : 4, , (d) 4 : 3, , 4. Dalton proposed :, (a) Liquid is made of small particles called atoms, (b) Atom is indivisible, it can neither be created nor destroyed, (c) All atoms of an element are entirely similar, (d) All of the above, 5. In a chemical reaction, mass can neither be created nor destroyed, what law, is veri ed by it ?, (a) Law of conservation of mass, (b) Law of constant proportions, (c) Law of mathematical proportions, (d) All of the above, 6. A chemical reaction is balanced to satisfy which law ?, (a) Dalton’s atomic theory, (b) Law of constant proportions, (c) Law of mathematical proportions, (d) Law of conservation of mass, 268, , Science Class - IX
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7. 12 g magnesium combines with 16 g oxygen to give 28 g of magnesium, oxide. Which law is proven from it ?, (a) Law of conservation of mass, (b) Law of constant proportions, (c) Law of mathematical proportions, (d) All of the above, 8. 170 g silver nitrate reacts with sodium chloride to give 143.5 g silver chloride, and 85 g sodium nitrate. Wht is the mass of sodium chloride ?, (a) 5.85 g, , (b) 58.5 g, , (c) 385 g, , (d) None of the above, Answers, , 1. (a), , 2. (a), , 3. (a), , 6. (d), , 7. (a), , 8. (b)., , 4. (d), , Experiment, , 5. (a), , 269
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EXPERIMENT NO. 15, Aim : 7RVWXG\WKHH[WHUQDOIHDWXUHVRIURRWVWHPOHDIRIDÀRZHURIDPRQRFRW, DQGGLFRWSODQW, Materials required : A chart showing different parts of a plant or a plant plucked., Theory : Angiosperms with the cotyledon are called monocots and angiosperms, with 2 cotyledons are called dicots., Procedure : Take the plant specimen or chart and observe its parts., Observations :, I. Root :, (i), , Roots in dicots are tap roots LH one main root and many lateral roots, coming out of it., , (ii) Roots in monocots are brous roots LH all are coming out as a tuft., (iii) Roots absorb water and minerals from soil., II. Leaf :, (i), , A leaf is attached to the stem with the help of a structure called petiole., , (ii) Leaves are generally green in colour which do photosynthesis., (iii) The at part of the leaf is called lamina., (iv) Arrangement of veins in leaves is called venation. Monocots have, parallel venation whereas dicots have reticulate venation., III. Stem :, (i), , Stems help in transporting food from leaves to all parts of plant and, water and minerals from soil to all plant parts through root with the help, of vascular bundles viz. xylem and phloem., , IV. Flower :, (i), , Flowers are present in monocots and dicots both., , (ii) Flowers in monocots are generally trimerous whereas those in dicots, are pentamerous., , 270, , Science Class - IX
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(iii) All generally have sepals, petals, stamens and pistils., , 1. That part of a plant on which leaves, owers and fruit are attached is called :, (a) Primary root, , (b) Stem, , (c) Secondary root, , (d) None of these, , 2. Loss of water from different pores of a plant is called :, (a) Transpiration, , (b) Photosynthesis, , (c) Condensation, , (d) Evaporation, , 3. Flower is a modi ed :, (a) Stem, , (b) Root, , (c) Leaf, , (d) Is the basic structure, , 4. Out of which of the following doesn’t show owers ?, (a) Capscium, , (b) Banana, , (c) Lemon, , (d) Sugarcane, , 5. A plant in which stem modi es for storage of food :, (a) Ginger, , (b) Potato, , (c) Onion, , (d) All of these, , 6. Out of which of the following shows exchange of gases :, (a) Stomata, , (b) Lenticels, , (c) Surface of roots, , (d) All of these, Experiment, , 271
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7. Arrangement of veins in a leaf is called :, (a) Venation, , (b) Vascularisation, , (c) Stamen, , (d) Pistil, , 8. Female part of a ower :, (a) Calyx, , (b) Corolla, , (c) Stamen, , (d) Pistil, Answers, , 1. (b), , 2. (a), , 3. (a), , 6. (d), , 7. (a), , 8. (a)., , 272, , Science Class - IX, , 4. (d), , 5. (d)
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SCIENCE, SOLVED QUESTION PAPER, Q. 1. A person travells 6 Km. in a circular path and reaches back on the, starting point. Calculate the displacement., 1, Ans. Displacement is zero because starting point of the journey and ending, point of the jouney is same., Q. 2. Write names of solutions used to stain plant cell and animal cell white, making a slide., 1, Ans. Safranim is used to stain plant cell., Methalene blue is used to stain animal cell., Q. 3. Recognise the phyium of animals on the basis of characteristics given., below. Also write one examples of each., 2, (a) Coelom is lled with blood and legs and jointed., Ans. Phylum-Arthropoda-eg-House y, butter y, spider etc. The animals have, coelom lled with blood and jointed legs., (b) These animal are free living or parasite and these are called at worms., Ans. Platyhelminthes is the phylum of at worms. They are free living or, parasite. example: planaria, liver uke., Q.4. How does endocytosis help is single celled organism like amaeba?, 2, Ans. Amoeba is a unicellular organism. All the processes of living being are, performed in this organism. Plasma membrane is exible. So amoeba, can take its food from surroundings. This process is called endocytosis., Q. 5. Write one word for the following:, (a) A group of cells having structure in which cells are arrnaged in a, special order to perform a work., (b) The process of taking permanent shape and size to perform a special, function., (c) Animal tissue which attaches muscles to bone., (d) Kindly shaped cells surrounding the stomata., Ans. (a) Tissue, (b) Differentiation, (c) Tendors., (d) Guard cells., Q. 6. (a) Explain the law of conservation of energy., (b) Give one example of each energy transformation:, (i) Heat energy to mechanical energy., (ii) Mechanical energy to electric energy., Question Paper, , 279
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Ans., , Q. 7., , Ans., , Q. 8., Ans., , (c) A person is standing from 20 minutes with heavy weight on his head., Does he do any work or not? explain., (a) According to conservation of energy,"Energy can neither be created, nor destroyed''. It can be transformed from one form to it's another, form. Total energy before and after transformation remains the same., (b) (i) Heat is formed by burning of fuel in an engine. This heat energy, is converted into mechanical energy., (ii) In an electric generator. Mechanical energy is converted into, electrical energy., (a) An electric heater of 2000 walt is working for 5 hours. How much, energy it consume?, (b) Convert commercial unit of energy into S.I. unit of energy., (a) Power of electric heater (P) = 2000 w, Time of use (T), = 5 Hr, 2000, Consumed energy (E), = P × t = 2000 × 5 wh =, kw × 5h, 1000, = 10 Kwh., (b) Commercial unit of energy = 1 Kwh, S.I. unit of energy, = 1 Joule, 1 Kwh, = 1000 × 60 × 60 ws = 3.6 × 106 Joules., (a) Draw a diagram showing Rutherford's Drays scattering experiments''., (b) Why rutherford used gold foil in above said experiment?, (a), , (b) Rutherford choose gold foil because they want a very thin layer., Thickness of gold foil is equal to the thickness of 1000 atom put, together., Q. 9. The number of neutrons and protons in the nucle of two atoms A and B, is as follow :, A, B, Proton, 8, 8, Nuetron, 8, 10, 280, , Science Class - IX
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(a), (b), (c), Ans. (a), , Write atomic mass of A and B., Write the relationship between A and B., Write electronic con guration of atom A and B., Both A and B have same number of electrons, so they have same, electonic con guration = 8 = 2, 6, Q. 10. Differentiate the following (Write one difference), (a) Gynmosperm and angiosperm, (b) Birds (Aves) and mammlas., (c) Monocotyletons and dicotyledons plants., Ans. (a) Angiosperm are owering plants in which seeds are found inside the, uits. In gymnosperms seeds are naked., (b) Birds are oviparous animals with dry skin covered by feathers and, wings. Their forelimbs are modi ed into wings. Mammals are, viviparous (except some exceptions) with sweat and oil glands on, their skin., (c) In monocotyledons plants seeds contain only one cotyledon while, in dicotyledons plants seeds contain two cotyledons., Q. 11. What is formula unit mass? How does it calculated ?, Calculate the formula unit mass of a compound Na2S2O3. (Na = 23u, S, = 32u, O = 16u ), Ans. Formula Unit Mass: It is the sum of atomic mass of ions of atoms, present in formula for a compound., Formula unit mass of Na2S2O3 = (2 × Na atomic mass) + (2 × S atomic, mass) + (3 × O atomic mass), = (2 × 23) + (2 × 32) + (3 × 16), = 1584 u., Q. 12. Give Reasons:, (a) When a ball droped from a height, its speed continuously increased., (b) When we stop pedalling a bicycle, its speed slows down., (c) When a tree is shaken vigorously, its fruits and leaves fall down., Ans. (a) When a ball is droped from a height. Its speed continuously, increased due to force of gravity (accelertion due to gravity increase, on coming downwards)., (b) When we stop pedalling a bicycle, its speed slows down due to air, resistance and force of friction between type of bicycle and surface, of road. So retardation force is created which stop the bicycle., (c) When tree is shaken. It moves to and slightly but its fruits and leave, tends to remain at rest due to their inertia and hence detached from, the tree and fall down., Question Paper, , 281
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Q. 13. Cattle farming. poultry and sh farming are included in animal, husbandry. What is the need of animal husbandry., Ans. Management of cattle farming is known as animal husbandry. It includes, various tasks such as giving food to cattles, animals, shelter, breeding,, health, disease control and proper economic utilization. Animal farming, includes cow, buffalo, goat, sheep, camel, poultry, and sheries. Due to, increasing population, demand for milk, eggs, meat etc is also increased., Now farmers take up animal husbandry on commercial basis so it needs, scienti c management practices. cattle farming is done for milk and, agricultural work. By poultry we increase meat an eggs production., sheries is a cheap source of protein food., Q. 14. Give Reason:, (a) Meristematic cell contains dense or abundant cytoplasm a single, large nucleus but no vacuole., (b) In sclerenchyma tissue intercellular space is absent in between the, cells., (c) In xerophytic plants, epidermis is covered with cutin., Ans. (a) Cells of meristems divide continously and help in increasing the, length and girth of the plants, so they have abundant cytoplasm and, prominent nucleus, thin cell wall but no vacuoles. Vacuole is like a, bag which store or liquid substances. Meristematic cells do not have, stared food in them., (b) In sclernchyma tissue intercellular space is absent in berween the, cells because these cells are dead and cell walls are thicked due to, deposition of lignin which acts as cement., (c) In xerophyte plants, epidermis is covered with cutin. Cutin is a layer, which resists transport of water through it. Desert have a little water., Cutin protects cells form dryness and also check transpiration from, leaves., Q. 15. A bike is moving with a velocity of 90 Km/hr. After applying break it, stop in 5 sec. Calculate the force applied by breaks. Mass of motercycle, and rides is 200 Kg., Ans. Mass of motorcycle and rider m = 200 Kg, 5, Initial velocity, u = 90 Km/h–1 = 90 × 18, Final Velocity of motor cycle v = 0, Time, (t) = 5s, 282, , Science Class - IX
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u—v, t, Force, F = ma, 200 × (0 − 25), = –1000 N, F=, 5, Q. 16. With the help of a labelled diagram show nitrogen cycle in nature. Name, Acceleration, , a=, , two molecules essential to life which contain nitrogen. Explain any two, processes involved in the cycling of nitrogen in the environment., Ans. Various steps of nitrogen cycle are :, , Two molecules essential to life which contain nitrogen are:, (i) Nucleic acids, (ii) Some vitamins., Two processes involved in the cycling of nitrogen in the environment, are:, 1. Nitrogen xing bacteria are formed in the roots of legumes. These, bacteria x atmosperic nitrogen in the form of nitrates and nitrites, which can then be used by plants., 2. Fixation of nitrogen by lightning Dutring lightning, the high, temperatures and pressures created in the air convert nitrogen into, oxides of nitrogen. These oxides dissolve in water to give nituie and, nitrogen acids and fall on land along with rain. These are then, utilised by various like forms., Q. 17. (a) Name three diseases against which immunisation vaccines are, available., Question Paper, , 283
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(b) State in brief the principle of immunisation., (c) Why do we not need to immune many infants in our country (below, the age of 5) against Hepatitis A?, Ans. (a) 1. Polio., 2. Measles, 3. Tetanus, (b) When the immune system rst seen an imfections microbe, it responds, against this and then remembers it speci cally. The next time when, that particular microbe or its close relatives enter the body, the immune, system responds more vigorously. This eliminates the infection more, quickly than the rst time around. This is the principle of, immunisation., (c) Because they have already been enposed to hepatitis. A virus through, contaminated water and gone immune to it., Q. 18. What is:, (a) Wave Length, (b) Frequency, (c) Amplitude., Write its S.I. units. Derive the retaltionship between speed, wavelength, and frequency., Ans. (a) Wave Length: The distance berween two consecutive compressions, (C) or two consecutive rare factions (R) is called wavelength. The, wave length is represented by O (Lambda). Its S.I. unit is meter (m)., (b) Frequency: The number of oscillations per unit time is called frequency, of the sound wave. It is represented by v (nu). Its S.I. unit is hertz (Hz)., (c) Amplitude: The maximum displacement of the particles of the medium, from their original undisturbed position, When a wave passes through, a medium is called amplitude. It is represented by the letter A. The SI, unit of amplitude of sound wave is the unit of density., Relationship between speed, wavelength and frequency, Distance travelled m/s is speed, V=, =, 284, , Distance travelled by one complete wave, Time taken to compleete one wave, O, Ts, , Science Class - IX
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⎛1, ⎞, O, = Ov, ⎜⎝ = v⎟⎠, T, T, V = Ov, Wave speed = wave length × frequency, Q. 19. (a) What is the physical state of water at:, (i) 250ºC, (ii) 100ºC, (iii) 0ºC, (b) Convert the following temperature to the celsius selae:, (i) 298 k, (ii) 300 k, (iii) 280 k, Ans. (a), (i) 250ºC, Gas, (ii) 100ºC, Gas, (iii)0ºC, Solid, (b), (i) 298 k = 298 – 273 = 25ºC, (ii) 300 k = 300 – 273 = 27ºC, (iii)280 k = 280 – 273 = 7ºC, Q. 20. A student was given mixture of iron lling and sulphur on heating the, mixture . Observe the following:, (a) What was the colour of compound., (b) Write magnetic effect on the mixture., (c) Write the reaction between carbon disulphite and mixture., (d) On adding dilute sulphuric acid or dilute, hydrochoric acid what will, happen?, Name the gas obtained and write two properties., Ans. (a) When mixture of iron lling and sulphur is reated iron sulphide is, obtained which is black in colour., (b) Iron does not get attracted to a magnet from a mixture of reated iron, llings and sulphur powder., (c) No reaction on carbon disulphide and mixture., (d) On adding dilute hydrochoride acid. The gas obtained is hydrogen, sulphide (H2S)., (i) It is colourless gas., (ii) It smells like rotten eggs., Q. 21. (i) If a man jumps out from a boat, the boat moves backwards. Why?, (ii) Explain our walking in terms of Newton's third law of motion., (iii)A bullet of mass 10 g travelling horizontally with a velocity of 150, ms–1 strikes a stationary wooden block and comes to rest in 0.03 S., Calculate the distance of penetration of the bullet into the block., , V=, , Question Paper, , 285
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Ans. (i) When a man jumps out of a boat to the bank of the river, he applies a, force in the forward direction. Due to the reaction of this boat moves, backward (i.e. away from the bank)., (ii) When we walk on the ground, our foot pushes the ground backward, (action) and in return the ground pushes our foot forward (reaction)., The forward reaction enerted by the ground on our foot makes us walk, forward., 10, (iii)Mass of bullet m = 10 g = 1000 kg= 0.01 kg, Initial velocity, u = 150 ms–1, Final velocity,, v =0, Time taken = 0.03 sec, Then, acceleration., v u (0 150), a = t = 0.03 = –500 ms–2, By third law of motion, v2 – u2 = 2as, v2 u 2 (0)2 − (150)2 −150 × 150, = −2 × 5000, s =, =, 2 × (−5000), 2a, = 2.25 m, , SECTION - B, Q. 1. Mention the type of thermometer that should be used to determine the, melting point of ice in laboratory? What should be the position of bulb in, thermometer?, Ans. Thermometer of range of 0-100 mL is used to determine the melting point, of ice laboratory. Bulb of thermometer should remain the ice cubes., Q. 2. Deepti was asked to prepare four separate mixtures in four beakers A,, B, C, & D by mixing sugar, ne sand, thin paste of starch and chalk powder, respectively in water and then categories each as stable or unstable. What, will be the corred categorization?, Ans. Sugar (stable), ne sand (unstable), thin paste of starch (stable) and chalk, powder (unstable)., Q. 3. Fore limbs of birds are modi ed. Give reasons., Ans. Fore limbs of birds are modi ed into usings for ying. They have an outer, covering of feathers and hollow bones that help them to y., Q.4. Name the technique by which we can prepare a colloidal solution of, starch in water., 286, , Science Class - IX
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Ans. Take about 0.5 gm of starch in a china dish. Pour about 10 mL of distilled, water. stir the contents with a glass tube continuously. Heat the water. In, this way colloidal solution of starch in water is formed., Q. 5. Mention the two precaution to determine the boiling point of water in, laboratory., Ans. (i) The position of bulb should be slightly above the water level., (ii) Stir the water continously in beaker so that temperature should remain, constant., Q. 6. Four students A, B, C, & D in a group take 6m long slinky and produce, a longitudinal wave, they observe that in 10 sec, 4 waves completed. On these, observation the speed of wave in slinky is, (a) 4.8 m/s, (b) 6.4 m/s, (c) 7.2 m/s, (d) 9.6 m/s, Ans. (a) 4.8 m/s, Explanation:, Total distance covered by wave in slinky to cover 4 forth backward motion, S = 4 × 2 × 6 = 48 m, Total time taken (t) = 10 s, Distance, Time, 48 m, =, 10 s, , Speed =, , = 4.8 ms–1, , Question Paper, , 287
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UNSOLVED PAPER, (SECTION - A), Q. 1. Valancy of an element X is 3. Write the chemical formula of its oxide. 1, Q. 2. What is negative work?, , 1, , Q. 3. Why do we keep both snake and turtle in the same class?, , 2, , Q. 4. Why is sound wave is called a longitudinal wave?, , 2, , Q. 5. Describe the microscopic structure of the cell?, , 2, , Q. 6. A sound wave has a frequency 2Hz and wave length 40cm. How, long will it take to travel 1.6 Km., , 3, , Q. 7. De ne potential energy, what are the different types of potential, energy?, , 3, , Q. 8. Compare the properties of electron, proton and neutron?, , 3, , Q. 9. Write the characteristics of kingdom animalia., , 3, , Q. 10. Sound waves of wave length X travel from a medium in which, velocity is V m/s into another medium in which if velocity is 3 m/s is, the wavelength of sound O in the second medium., 3, Q. 11. Why do you fall in the forward direction when a moving bus brakes to a, stop and fall backward when it accelerates from rest., 3, Q. 12. Write a method to seprate different gases of air., , 3, , Q. 13. Classify each of the following as a physical or chemical change., Give reasons., , 3, , (a) Drying of a shirt in the sun., (b) Rising of hot air over a radiator., (c) Buring of kerosene in a lantern., (d) Change in the colour of black tea on adding lemon juice in it., Q. 14. State Newton's second law of motion and derive it mathematically?, , 3, , Q. 15. Raghu switched from traditional to modern farming practices in, which he used large amount of furtilizers and pestiside to gain an, increase in pro t., , 3, , (i) What are the adverse effect of modern farming?, (ii) What is soil pollution?, (iii) What do you think will be effect of modern farming?, (iv) What alternative method could be more bene cial for farming?, 288, , Science Class - IX
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Q. 16. Why does the temperature of a substance remain constant during the, melting point or boiling point?, 5, Q. 17. Draw a plant cell and lebel the parts., (a) synthesize food, (b) Produce energy, (c) Store house of organic substance like protein organic acids., (d) Packages material coming from endoplasmic reticulum., (e) Determine function and development of cell?, Q. 18. (a) What happen to sugar when it is dissolved in water? Where does the, sugar go? What information do you get about the nature of matter, from the dis solution of sugar in wale., (b) Which type of compounds can be puri de by sublimation?, , 5, , Q. 19. (i) State two basis of classifying plants and animals into different, categories., , 5, , (ii) List three characteristics features of fungi?, (iii) Some fungal species live in permanent mutually dependent, relationship with cynobacteria?, Q. 20. What do you mean by work? Give an example of negative work done?, What is the work to be done to increase the velocity from 18 km/hr to 19, km/hr if the mass of the care is 2000 kg., Q. 21.`"Soil is formed by water''. If you agree to this statement then give, reasons for you answers., Q. 22. Which would require a greater force accelerating a 2 kg mass at 5, or a 4 kg mass at 2 ms–2?, , 5, ms–2, 2, , SECTION - B, Q. 23. In experiment to demostrate the boiling point of water. state reason for, following precautions., 2, (a) The bulb of thermometer should not touch the sides of the beaker?, (b) Pumic stone should be added while boiling water., Q. 24. Seena was asked to prepare four seprate mixtures in four beakers A, B,, C, D by mixing sugar, ne sand, thin paste of starch and chalk powder, respectively in water and then categories each as stable or unstable what, will be the correct categorization?, Q. 25. A baby is not able to tell her/his caretakers that she/he is sick. What, would help us to nd out that the baby is sick?, Question Paper, , 2, 289
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Q. 26. A free falling object eventually stops on reaching the ground. What, happens to its kinetic energy., , 2, , Q. 27. A sound wave travels at a speed of 340 m/s. If the wave length of wave, is 1.4 Km. What is the frequency of the wave?, , 290, , Science Class - IX
