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NCERT solutions for class 9 science chapter 2 Is Matter around us pure, , Q 1. What is meant by a substance?, , ut, e, , Answer:, Substance-, , A substance is a matter which consists of a single type of particles and has specific, , tit, , properties. For example tin, sulphur, pure sugar (sucrose) etc., , In, s, , Q 2. List the points of differences between homogeneous and heterogeneous mixtures., Answer:, , sh, , The differences between homogeneous and heterogeneous mixturesHETEROGENOUS, , 1. It has uniform compositions., , 1. It does not have a uniform, , ka, , HOMOGENEOUS, , composition, , separation., , 2. Visible boundaries of, , 3. It consists of only one, , separation, , phase., , 3. They consist of more than, , examples- sugar + water =, , one phase., , sugar solution, , examples- sugar +sand = sugar, , Aa, , 2. No visible boundaries of, , + sand
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NCERT free solutions for class 9 science chapter 2 Is Matter around us, , ut, e, , pure?, Topic 2.2 What is a solution?, , tit, , Q 1. Differentiate between homogeneous and heterogeneous mixtures with examples., Answer:, , In, s, , Homogeneous Mixture: It is a mixture in which different constituents are mixed, uniformly and these constituents cannot be easily separated., , But,, , sh, , Example: Sugar solution, soda, water, soft drinks, vinegar, air, etc., , Heterogeneous mixtures: It is a mixture in which different constituents are not mixed, , ka, , uniformly and the constituents can be easily seen and can be easily separated., Example: Sugar and sand mixture, milk, ink, paint, wood, blood, etc., , Aa, , Q 2. How are sol, solution and suspension different from each other?, Answer:, , Difference between sol, solution and suspension are given below:, Sol(Colloids), , Suspension, , Solution
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1. Heterogeneous mixture, , 1.Homogeneous mixture, , 2. We cannot see the size, , 2. Particles are visible by, , 2. the particles are not visible to, , of the particle with a naked, , the human naked eye, , a naked eye., , eye., , ut, e, , 1. Heterogeneous mixture, , 3. They can scatter the, , 3. scatters the beam of, , beam of light passing, , light passing through, , through them, , them, , 4. Solute particles cannot, , 4. Solute particles can be, , 4. solute particles cannot be, , separated by filtration, , separated by filtration and, , tit, , sh, , and sedimentation., , light., , In, s, , be separated by filtration, , 3. unable to scatter the beam of, , sedimentation., , ka, , Q 3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of, water at 293 K. Find its concentration at this temperature., , Aa, , Answer:, , Given that,, , Mass of solute (sodium chloride) = 36 g =, Mss of water (as a solvent) = 100 g =, Therefore, the total mass of solution = 100 + 36 = 136 g =
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According to question,, Concentration =, , ut, e, , %, Hence the concentration of the solution at 293 K is 26.47%, , CBSE NCERT solutions for class 9 science chapter 2 Is Matter around us, , tit, , pure?, , In, s, , Topic 2.3 Separating the components of a mixture, , Q 1. How will you separate a mixture containing kerosene and petrol (difference in their, boiling points is more than 25ºC), which are miscible with each other?, , sh, , Answer:, , The mixture of kerosene and petrol which are miscible with each other can be, , ka, , separated by the distillation method., , Take the mixture in a distillation flask and fit it with the thermometer. Heat the mixture, slowly. As the boiling point of petrol is lower than that of kerosene, so, petrol vaporizes, , Aa, , first. It condenses in the condenser and is collected from the outlet., And thus kerosene is left in the flask., , Q 2. Name the technique to separate
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(i) butter from curd,, (ii) salt from sea-water, (iii) camphor from salt., , ut, e, , Answer:, The following techniques are used to separates them-, , tit, , (i) Centrifugation method, , (iii) Sublimation., , In, s, , (ii) Evaporation and, , Q 3. What type of mixtures are separated by the technique of crystallisation?, , sh, , Answer:, , The crystallization technique is used to purify solids., In this method, pure solids can be separated in the form of its crystals from the solution., , ka, , For example- salts from seawater can be separated by this method., , NCERT textbook solutions for class 9 science chapter 2 Is Matter around, , Aa, , us pure?, , Topic 2.4 Physical and Chemical changes, Q 1. Classify the following as chemical or physical changes:, • cutting of trees,
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• melting of butter in a pan,, • rusting of almirah,, , ut, e, , • boiling of water to form steam,, , hydrogen and oxygen gases,, • dissolving common salt in water,, , In, s, , • making a fruit salad with raw fruits, and, , tit, , • passing of electric current, through water and the water breaking down into, , • burning of paper and wood, Answer:, , sh, , Physical changescutting of trees, , •, , melting of butter in a pan, , •, , boiling of water to form steam, , •, , dissolving common salt in water, , •, , making a fruit salad with raw fruits, , Aa, , ka, , •, , Chemical changes-, , •, , rusting of almirah,, , •, , passing of electric current, through water and the water breaking down into hydrogen and, oxygen gases,, , •, , burning of paper and wood
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Q 2. Try segregating the things around you as pure substances or mixtures., Answer:, , ut, e, , Pure substance - Water, sugar and gold, Mixtures- plastics papers, air and milk, , NCERT solutions for class 9 science chapter 2 Is Matter around us, , tit, , pure?: Solved Exercise Questions, , In, s, , Q 1. Which separation techniques will you apply for the separation of the following?, (a) Sodium chloride from its solution in water., , (b) Ammonium chloride from a mixture containing sodium chloride and ammonium, chloride., , (c) Small pieces of metal in the engine oil of a car., , sh, , (d) Different pigments from an extract of flower petals., (e) Butter from curd., , ka, , (f) Oil from water., , (g) Tea leaves from tea., (h) Iron pins from sand., , Aa, , (i) Wheat grains from husk., , (j) Fine mud particles suspended in water., , Answer:, , The following separation techniques are used to separate-
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a) Sodium chloride from its solution in water. by Evaporation, method, b) Ammonium chloride from a mixture containing sodium chloride and ammonium, chloride. by Sublimation, , ut, e, , c) Small pieces of metal in the engine oil of a car. by filtration., , d) Different pigments from an extract of flower petals. by chromatography,, , In, s, , f) Oil from water. by separation funnel, , tit, , e) Butter from curd. by centrifugation,, , g) Tea leaves from tea. by filtration,, , h) Iron pins from sand. by magnetic separation,, , sh, , i) Wheat grains from husk. by winnowing or sedimentation,, , j) Fine mud particles suspended in water. by decantation and filtration ., , ka, , Q 2. Write the steps you would use for making tea. Use the words solution, solvent,, solute, dissolve, soluble, insoluble, filtrate and residue., , Aa, , Answer:, , The steps for making a tea1. Use water as a solvent and boil it for few minutes., 2. Now, add some tea leaves and sugar and milk (if you want) as a solute., 3. Again, boil it for few minutes so that sugar will dissolve in it.
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4. At last filter the solution. Collect the filtrate in a cup. The insoluble tea leaves left, behind as a residue., Q 3. (a) Pragya tested the solubility of three different substances at different, temperatures and collected the data as given below (results are given in the following, , solution)., , ut, e, , table, as grams of a substance dissolved in 100 grams of water to form a saturated, , What mass of potassium nitrate would be needed to produce a saturated solution of, , Temperature in K, , In, s, , Substance Dissolved, , tit, , potassium nitrate in 50 grams of water at 313 K?, , 293, , 313, , 333, , 353, , Potassium Nitrate, , 21, , 32, , 62, , 106, , 167, , Sodium Chloride, , 36, , 36, , 36, , 37, , 37, , ka, , sh, , 283, , 35, , 35, , 40, , 46, , 54, , Ammonium Chloride, , 24, , 37, , 41, , 55, , 66, , Aa, , Potassium Chloride
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Answer:, We have,, , Therefore, according to question,, Mass of potassium nitrate in 50 g of water at 313K, , ut, e, , Mass of potassium nitrate = 62g in 100 g of water, , tit, , Q 3.(b) Pragya tested the solubility of three different substances at different, , temperatures and collected the data as given below (results are given in the following, , In, s, , table, as grams of a substance dissolved in 100 grams of water to form a saturated, solution)., , Pragya makes a saturated solution of potassium chloride in water at 353 K and, leaves the solution to cool at room temperature. What would she observe as the, , ka, , sh, , solution cools? Explain., , Aa, , Substance Dissolved, , Temperature in K, , 283, , 293, , 313, , 333, , 353, , Potassium Nitrate, , 21, , 32, , 62, , 106, , 167, , Sodium Chloride, , 36, , 36, , 36, , 37, , 37
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35, , 35, , 40, , 46, , 54, , Ammonium Chloride, , 24, , 37, , 41, , 55, , 66, , ut, e, , Potassium Chloride, , tit, , Answer:, , chloride will be obtained., , In, s, , Pragya will observe that, on cooling the saturated solution, the crystals of potassium, , Q 3. (C) Pragya tested the solubility of three different substances at different, temperatures and collected the data as given below (results are given in the following, , solution)., , sh, , table, as grams of a substance dissolved in 100 grams of water to form a saturated, , Find the solubility of each salt at 293 K. Which salt has the highest solubility at this, , Aa, , ka, , temperature?, , Substance Dissolved, , Potassium Nitrate, , Temperature in K, , 283, , 293, , 313, , 333, , 353, , 21, , 32, , 62, , 106, , 167
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36, , 36, , 36, , 37, , 37, , Potassium Chloride, , 35, , 35, , 40, , 46, , 54, , Ammonium Chloride, , 24, , 37, , 41, , 55, , 66, , tit, , ut, e, , Sodium Chloride, , In, s, , Answer:, The solubility of each salt at 293K is, Potassium nitrate = 32g, , •, , Sodium chloride = 36g, , •, , Potassium chloride = 35 g, , •, , Ammonium chloride = 37g, , sh, , •, , ka, , Q 3. (d) Pragya tested the solubility of three different substances at different, temperatures and collected the data as given below (results are given in the following, table, as grams of a substance dissolved in 100 grams of water to form a saturated, , Aa, , solution)., , What is the effect of change of temperature on the solubility of a salt?
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Substance Dissolved, , Temperature in K, , 293, , 313, , 333, , 353, , Potassium Nitrate, , 21, , 32, , 62, , 106, , 167, , Sodium Chloride, , 36, , 36, , 36, , 37, , 37, , Potassium Chloride, , 35, , 35, , 40, , 46, , 54, , Ammonium Chloride, , 24, , 37, , 41, , 55, , 66, , tit, , In, s, , sh, , Answer:, , ut, e, , 283, , ka, , Solubility is directly proportional to the temperature., Therefore, on increasing temperature, the solubility of salt increases., , Aa, , Q 4.(a) Explain the following giving examples., saturated solution, , Answer:, , Saturated solution - In a given solvent, when no more solute can be dissolved in a, solution at a given temperature is called a saturated solution.
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Q 4.(b) Explain the following giving examples, pure substance, , ut, e, , Answer:, Pure substance -, , A pure substance is a matter which consists of a single type of particles and has, , In, s, , Q 4.(c) Explain the following giving examples., , tit, , specific properties. For examples tin, sulphur, pure sugar (sucrose) etc., , colloid, Answer:, , sh, , colloid -, , A colloid is a solution in which the solute particle is bigger in size as compare to the true, solution. It is a heterogeneous mixture. Because of the small size of colloidal particles,, , ka, , we cannot see them with naked eyes. For example milk and blood., Q 4.(d) Explain the following giving examples., , Aa, , (d) suspension, , Answer:, , Suspension-, , It is a heterogeneous solution in which the solute particles do not dissolve in solvent but, remain suspended throughout the bulk of the medium. Particles are visible by naked, eyes. Chalk-water is an example of this type of solution.
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Q 5. Classify each of the following as a homogeneous or heterogeneous mixture., soda water, wood, air, soil, vinegar, filtered tea., , The mixture of following are homogeneous in nature-, , ut, e, , Answer :, , Soda water, vinegar, and filtered tea. as there are no separation boundaries in their, , tit, , solution., , Heterogeneous - Wood, air and soil. As we can easily see the separation boundaries., , In, s, , Q 6. How would you confirm that a colourless liquid given to you is pure water?, Answer:, , By boiling the give colourless water we can check that it is pure or not. If it is pure then, at atmospheric pressure., , sh, , the water boils at 100, , This is because the melting and boiling point of pure substance doesn't change., , ka, , Q 7. Which of the following materials fall in the category of a “pure substance”?, , Aa, , (a) Ice, , (b) Milk, (c) Iron, , (d) Hydrochloric acid, (e) Calcium oxide
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(f) Mercury, (g) Brick, , ut, e, , (h) Wood, (i) Air, Answer:, , tit, , A pure substance is a matter which consists of a single type of particles and has, specific properties-, , Ice, , •, , Iron, , •, , Hydrochloric acid, , •, , calcium oxide and, , •, , mercury, , sh, , •, , In, s, , Therefore, the following given substances are '' pure substance " -, , ka, , Q 8. Identify the solutions among the following mixtures., , Aa, , (a) Soil, , (b) Seawater, (c) Air, , (d) Coal, , (e) Soda water
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Answer:, A solution is a homogeneous mixture of two or more than two substances., So, according to the definition, out of the given seawater, air and soda water are, , ut, e, , examples of solutions., , Q 9. Which of the following will show the “Tyndall effect”?, , tit, , (a) Salt solution, , In, s, , (b) Milk, (c) Copper sulphate solution, (d) Starch solution., , sh, , Answer:, , Tyndall effect is shown by the colloidal solution and suspension and it is not shown by a, , ka, , true solution., , Therefore, in the above-given solution only milk and starch solution will be able to, , Aa, , scatter the light and hence show Tyndall effect., Q 10. Classify the following into elements, compounds, and mixtures., (a) Sodium, (b) Soil, (c) Sugar solution
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(d) Silver, (e) Calcium carbonate, , ut, e, , (f) Tin, (g) Silicon, (h) Coal, , tit, , (i) Air, , (k) Methane, , (m) Blood, Answer:, , sh, , (l) Carbon dioxide, , In, s, , (j) Soap, , ka, , Elements cannot be broken down into any simpler substance. and the compounds have, fixed composition can be broken down into elements by chemical or electrochemical, , Aa, , reaction. Mixtures have no fixed composition they are either homogeneous or, heterogeneous., , Therefore, Sodium, Silver, Tin, and Silicon are elements., Q 11. Which of the following are chemical changes?, (a) Growth of a plant
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(b) Rusting of iron, (c) Mixing of iron filings and sand, , ut, e, , (d) Cooking of food, (e) Digestion of food, (f) Freezing of water, , tit, , (g) Burning of a candle., , In, s, , Answer:, , Out of given following are the examples of chemical changesGrowth of plants, , •, , Rusting of iron, , •, , cooking of food, , •, , Digestion of food, , •, , Burning of candle, , Aa, , ka, , sh, , •
