Burning of paper and wood ? Chemical change<\/li>\n<\/ul>\nQuestion 7.
\nTry segregating the things around you as pure substances or mixtures.
\nAnswer:
\nPure substance: Water, salt, sugar
\nMixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food<\/p>\n
Question 8.
\nWhat type of mixtures is separated by the technique of crystallization?
\nAnswer:
\nBy the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from the sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.<\/p>\n
Class 9 Science Chapter 2 Is Matter Around Us Pure Textbook Questions and Answers<\/h3>\n
Question 1.
\nWhich separation techniques will you apply for the separation of the following?
\n(a) Sodium chloride from its solution in water.
\n(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
\n(c) Small pieces of metal in the engine oil of a car.
\n(d) Different pigments from an extract of flower petals.
\n(e) Butter from curd.
\n(f) Oil from water.
\n(g) Tea leaves from tea.
\n(h) Iron pins from sand.
\n(i) Wheat grains from husk.
\n(j) Fine mud particles suspended in water.
\nAnswer:
\n(a) Sodium chloride from its solution in water ? Evaporation
\n(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride ? Sublimation
\n(c) Small pieces of metal in the engine oil of a car ? Centrifugation or filtration or decantation
\n(d) Different pigments from an extract of flower petals ? Chromatography
\n(e) Butter from curd ? Centrifugation
\n(f) Oil from water ? Using separating funnel
\n(g) Tea leaves from tea ? Filtration
\n(h) Iron pins from sand ? Magnetic separation
\n(i) Wheat grains from husk ? Winnowing
\n(j) Fine mud particles suspended in water ? Centrifugation<\/p>\n
<\/p>\n
Question 2.
\nWrite the steps you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
\nAnswer:
\nFirst, water is taken as a solvent in a saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer as residue. Sugar is added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea.<\/p>\n
Question 3.
\nPragya 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 substance dissolved in 100 grams of water to form a saturated solution).
\n
\n(a) What mass of potassium nitrate would be needed to produce a saturated solution of
\npotassium nitrate in 50 grams of water at 313 K?
\n(b) 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 solution cools? Explain.
\n(c) Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
\n(d) What is the effect of change of temperature on the solubility of a salt?
\nAnswer:
\n(a) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need
\n\\(\\frac{62 \\times 50}{100}\\) = 31 grams of potassium nitrate
\n(b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with decrease in temperature.<\/p>\n
(c) (i) Solubility of Potassium nitrate at 293 K is 32 grams.
\n(ii) Solubility of Sodium chloride at 293 K is 36 grams.
\n(iii) Solubility of Potassium chloride at 293 K is 35 grams.
\n(iv) Solubility of Ammonium chloride at 293 K is 37 grams.
\nThe solubility of Ammonium chloride is highest at this temperature.<\/p>\n
(d) The solubility of salt increases with increase in temperature.<\/p>\n
Question 4.
\nExplain the following giving examples:
\n(a) Saturated solution
\n(b) Pure substance
\n(c) Colloid
\n(d) Suspension
\nAnswer:
\n(a) Saturated solution: A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature. The solution cannot dissolve beyond that amount of solute at that temperature. Any more solute added will settle down at the bottom of the container as a precipitate.<\/p>\n
Suppose 500 g of a solvent can dissolve a maximum of 150 g of a particular solute at 40\u00b0C. Then, the solution obtained by dissolving 150 g of that solute in 500 g of that solvent at 300 K is said to be a saturated solution at 300 K.<\/p>\n
(b) Pure substance: A pure substance is a substance consisting of a single type of particles i. e., all constituent particles of the substance have the same chemical properties.
\nFor example, salt, sugar, water are pure substances.<\/p>\n
(c) Colloid: A colloid is a heterogeneous mixture. The size of the solutes in this mixture is so small that they cannot be seen individually with naked eyes, and seems to be distributed uniformly throughout the mixture. The solute particles do not settle down when the mixture is left undisturbed. This means that colloids are quite stable. Colloids cannot be separated by the process of filtration. They can be separated by centrifugation. Colloids show the Tyndall effect. For example, milk, butter, foam, fog, smoke, clouds.<\/p>\n
(d) Suspension: Suspensions are heterogeneous mixtures. The solute particles in this mixture remain suspended throughout the bulk of the medium. The particles can be seen with naked eyes. Suspension shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. This means that suspensions are unstable. Suspensions can be separated by the method of filtration. For example, mixtures of chalk powder and water, wheat flour and water.<\/p>\n
<\/p>\n
Question 5.
\nClassify each of the following as a homogeneous or heterogeneous mixture. Soda water, wood, air, soil, vinegar, filtered tea
\nAnswer:
\nHomogeneous mixtures: Soda water, air, vinegar
\nHeterogeneous mixtures: Wood, soil, filtered tea<\/p>\n
Question 6.
\nHow would you confirm that a colourless liquid given to you is pure water?
\nAnswer:
\nEvery liquid has a characteristic boiling point. Pure water has a boiling point of 100\u00b0C (373 K) at 1 atmospheric pressure. If the given colourless liquid boils at even slightly above or below 100\u00b0C, then the given liquid is not pure water. It must boil at sharp 100\u00b0C. Thus, by observing the boiling point, we can confirm whether a given colourless liquid is pure water or not.<\/p>\n
Question 7.
\nWhich of the following materials fall in the category of a “pure substance”?
\n(a) Ice
\n(b) Milk
\n(c) Iron
\n(d) Hydrochloric Acid
\n(e) Calcium oxide
\n(f) Mercury
\n(g) Brick
\n(h) Wood
\n(i) Air
\nAnswer:
\nThe following materials fall in the category of a “pure substance”:
\n(a) Ice
\n(c) Iron
\n(d) Hydrochloric acid
\n(e) Calcium oxide
\n(f) Mercury<\/p>\n
Question 8.
\nIdentify the solutions among the following mixtures:
\n(a) Soil
\n(b) Sea water
\n(c) Air
\n(d) Coal
\n(e) Soda water
\nAnswer:
\nThe following mixtures are solutions:
\n(b) Sea water
\n(c) Air
\n(e) Soda water<\/p>\n
Question 9.
\nWhich of the following will show the “Tyndall effect”?
\n(a) Salt solution
\n(b) Milk
\n(c) Copper sulphate solution
\n(d) Starch solution
\nAnswer:
\nMilk and starch solution will show the “Tyndall effect”.<\/p>\n
Question 10.
\nClassify the following into elements, compounds and mixtures:
\n(a) Sodium
\n(b) Soil
\n(c) Sugar solution
\n(d) Silver
\n(e) Calcium carbonate
\n(f) Tin
\n(g) Silicon
\n(h) Coal
\n(i) Air
\n(j) Soap
\n(k) Methane
\n(l) Carbon dioxide
\n(m) Blood
\nAnswer:
\nElements:
\n(a) Sodium
\n(d) Silver
\n(f) Tin
\n(g) Silicon<\/p>\n
Compounds:
\n(e) Calcium carbonate
\n(k) Methane
\n(l) Carbon dioxide<\/p>\n
Mixtures:
\n(b) Soil
\n(c) Sugar solution
\n(h) Coal
\n(i) Air
\n(j) Soap
\n(m) Blood<\/p>\n
<\/p>\n
Question 11.
\nWhich of the following are chemical changes?
\n(a) Growth of a plant
\n(b) Rusting of iron
\n(c) Mixing of iron fillings and sand
\n(d) Cooking of food
\n(e) Digestion of food
\n(f) Freezing of water
\n(g) Burning of candle
\nAnswer:
\nThe following changes are chemical changes:
\n(a) Growth of a plant
\n(b) Rusting of iron
\n(d) Cooking of food
\n(e) Digestion of food
\n(g) Burning of candle<\/p>\n
Class 9 Science Chapter 2 Is Matter Around Us Pure Additional Important Questions and Answers<\/h3>\n
Multiple Choice Questions <\/span>
\nChoose the correct option:<\/span><\/p>\nQuestion 1.
\nWhich of the following statements are true for pure substances?
\n(i) Pure substances contain only one kind of particles
\n(ii) Pure substances may be compounds or mixtures
\n(iii) Pure substances have the same com-position throughout
\n(iv) Pure substances can be exemplified by all elements other than nickel
\n(a) (i) and (ii)
\n(b) (i) and (iii)
\n(c) (iii) and (iv)
\n(d) (ii)and (iii)
\nAnswer:
\n(b) (i) and (iii)<\/p>\n
Question 2.
\nRusting of an article made up of iron is called
\n(a) corrosion and it is a physical as well as chemical chang
\n(b) dissolution and it is a physical change
\n(c) corrosion and it is a chemical change
\n(d) dissolution and it is a chemical change
\nAnswer:
\n(c) corrosion and it is a chemical change<\/p>\n
Question 3.
\nA mixture of sulphur and carbon disulphide is
\n(a) heterogeneous and shows Tyndall effect
\n(b) homogeneous and shows Tyndall effeet
\n(c) heterogeneous and does not show Tyndall effect
\n(d) homogeneous and does not show Tyndall effect
\nAnswer:
\n(d) homogeneous and does not show Tyndall effect<\/p>\n
<\/p>\n
Question 4.
\nTincture of iodine has antiseptic properties. This solution is made by dissolving
\n(a) iodine in potassium iodide
\n(b) iodine in vaseline
\n(c) iodine in water
\n(d) iodine in alcohol
\nAnswer:
\n(d) iodine in alcohol<\/p>\n
Question 5.
\nWhich of the following are homogeneous in nature?
\n(i) ice
\n(ii) wood
\n(iii) soil
\n(iv) air
\n(a) (i) and (iii)
\n(b) (ii) and (iv)
\n(c) (i) and (iv)
\n(d) (iii) and (iv)
\nAnswer:
\n(c) (i) and (iv)<\/p>\n
Question 6.
\nWhich of the following are physical changes?
\n(i) Melting of iron metal
\n(ii) Rusting of iron
\n(iii) Bending of an iron rod
\n(iv) Drawing a wire of iron metal
\n(a) (i), (ii) and (iii)
\n(b) (i), (ii) and (iv)
\n(c) (i), (iii) and (iv)
\n(d) (ii), (iii) and (iv)
\nAnswer:
\n(c) (i), (iii) and (iv)<\/p>\n
Question 7.
\nWhich of the following are chemical changes?
\n(i) Decaying of wood
\n(ii) Burning of wood
\n(iii) Sawing of wood
\n(iv) Hammering of a nail into a piece of wood
\n(a) (i) and (ii)
\n(b) (ii) and (iii)
\n(c) (iii) and (iv)
\n(d) (i) and (iv)
\nAnswer:
\n(a) (i) and (ii)<\/p>\n
<\/p>\n
Very Short Answer Type Questions<\/span><\/p>\nQuestion 1.
\nDefine solvent.
\nAnswer:
\nThe component of the solution that dissolves the other component in it is called the solvent.<\/p>\n
Question 2.
\nDefine solute.
\nAnswer:
\nThe component of the solution that is dissolved in the solvent is called solute.<\/p>\n
Question 3.
\nWhat is \u2019tincture of iodine’?
\nAnswer:
\nA solution of iodine in alcohol is known as tincture of iodine. It has iodine (splid) as the solute and alcohol (liquid) as the solvent.<\/p>\n
Question 4.
\nWhat are alloys?
\nAnswer:
\nThe homogeneous mixture of two or more metals or a metal and non-metal is called an alloy. E.g., steel is an alloy of iron and carbon.<\/p>\n
Question 5.
\nGive one example of gas in liquid , solution.
\nAnswer:
\nCold-drinks, carbon dioxide gas as solute is mixed with water as a solvent.<\/p>\n
Question 6.
\nHow can a solution be dilute or concentrated?
\nAnswer:
\nThe amount of solute dissolved in a solvent decides whether the solution is dilute or concentrated.<\/p>\n
Question 7.
\nWhat is “concentration of a solution”?
\nAnswer:
\nThe concentration of a solution is the amount of solute present in a given amount of solution or the amount of solute dissolved in a given mass or volume of solvent.<\/p>\n
Question 8.
\nState the difference between aqueous and non-aqueous solution.
\nAnswer:
\nAqueous solutions have water as solvent and non-aqueous solutions do not have water as solvent.<\/p>\n
<\/p>\n
Question 9.
\nWhat is “solubility” of a solute?
\nAnswer:
\nThe amount of the solute present in the saturated solution at the given temperature is called its solubility.<\/p>\n
Question 10.
\nWhat is saturated solution?
\nAnswer:
\nThe maximum amount of solute that ‘ can be dissolved in a solvent at given temperature is called saturated solution, where no more solute can dissolve further.<\/p>\n
Question 11.
\nWhat is unsaturated solution?
\nAnswer:
\nIf the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.<\/p>\n
Question 12.
\nHow can you convert saturated solution into unsaturated or vice-versa?
\nAnswer:
\nSaturated solution on heating becomes unsaturated and unsaturated solution on cooling becomes saturated.<\/p>\n
Question 13.
\nWhy water is called universal solvent?
\nAnswer:
\nWater can dissolve large number of substances in it.<\/p>\n
Question 14.
\nWhat is Tyndall effect?
\nAnswer:
\nThe scattering of light by colloidal particles is known as Tyndall effect.<\/p>\n
Question 15.
\nHow can we separate colloidal mixtures?
\nAnswer:
\nBy centrifugation, in a centrifuge machine the colloidal solution is kept in a test tube, rotated very fast and due to centrifugal force’ the colloidal particles are separated.<\/p>\n
Question 16.
\nWhat is emulsion?
\nAnswer:
\nWhen both the dispersed phase and dispersing medium is liquid, it is called emulsion. E.g., milk, face cream.<\/p>\n
Question 17.
\nWhat is aerosol?
\nAnswer:
\nWhen the solid or liquid is dispersed in a gas if Is called aerosol. E.g., smoke, fog. .<\/p>\n
Question 18.
\nWhat is the principle for separation of immiscible liquids?
\nAnswer:
\nThe principle of separating immiscible liquids into layers depends on their densities. The less denser liquid collects at the top and more denser liquid at- the bottom.<\/p>\n
Question 19.
\nWhat is chromatography?
\nAnswer:
\nChromatography is the technique used for separation of those solutes that dissolve in the same solvent.<\/p>\n
<\/p>\n
Question 20.
\nWhat is distillation?
\nAnswer:
\nDistillation is the separation technique of two miscible liquids that boils without decomposition and have sufficient difference in their boiling points.<\/p>\n
Question 21.
\nHow can you separate two liquids that have less than 25 K difference of boiling points?
\nAnswer:
\nTo separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, is fractional distillation.<\/p>\n
Question 22.
\nWhat is condenser?
\nAnswer:
\nIt is an apparatus used to convert gas into liquid by cooling it.<\/p>\n
Question 23.
\nWhat is crystallisation?
\nAnswer:
\nWhen a saturated solution is heated and allowed to cool slowly, crystal of the solute dissolved in die saturated solution are separated from it. It is used to purify solids.<\/p>\n
Question 24.
\nHow will you separate miscible and immiscible liquids?
\nAnswer:
\nMiscible liquid can be separated by distillation and immiscible liquids can be separated by using separating funnel.<\/p>\n
Short Answer Type questions<\/span><\/p>\nQuestion 1.
\nWhy is mixture called impure substance?
\nAnswer:
\nMixture consists of different components which retain their properties and can be easily separated by physical processes, hence it is called as impure substance.<\/p>\n
Question 2.
\nGive the differences between mixture and compound.
\nAnswer:
\nMixture:<\/p>\n
\n- Constituents combine in any rato to form mixture.<\/li>\n
- Constituents retain their properties.<\/li>\n
- Constituents can be separated by physical processes.<\/li>\n<\/ol>\n
Compound:<\/p>\n
\n- Constituents combine in fixed ratio to form a compound.<\/li>\n
- Constituents do not retain their properties<\/li>\n
- Constituents cannot be separated by physical processes.<\/li>\n<\/ol>\n
<\/p>\n
Question 3.
\nDistinguish between a physical change and chemical change.
\nAnswer:
\nPhysical Change:<\/p>\n
\n- No new substance is formed.<\/li>\n
- It is a reversible change.<\/li>\n
- The properties of constituents are retained.<\/li>\n
- No new substance is formed.<\/li>\n<\/ol>\n
Chemical Change:<\/p>\n
\n- New substance is formed.<\/li>\n
- It is irreversible change.<\/li>\n
- The properties of constituents are not retained.<\/li>\n
- Completely new substance is formed.<\/li>\n<\/ol>\n
Question 4.
\nState the properties of a solution.
\nAnswer:
\nProperties of a solution are:<\/p>\n
\n- A solution is a homogeneous mixture.<\/li>\n
- Particles of a solution are smaller than 1 nm and cannot be seen by naked eyes.<\/li>\n
- Do not scatter beam of light.<\/li>\n
- Solute particles cannot be separated from the mixture by the process of filtration and thus, solution is stable.<\/li>\n<\/ol>\n
Question 5.
\nState the properties of a suspension.
\nAnswer:
\nProperties of a suspension:<\/p>\n
\n- Suspension is a heterogeneous mixture having particle size greater than 100 nm.<\/li>\n
- The particles of a suspension can be seen by naked eyes.<\/li>\n
- Particles can scatter a beam of light.<\/li>\n
- It is unstable.<\/li>\n<\/ul>\n
Question 6.
\nWhat is a colloidal solution?
\nAnswer:
\nIt is a heterogeneous solution which appears to be homogeneous, particles size is very small and so cannot be seen with naked eyes but it is stable. E.g., milk and blood.<\/p>\n
<\/p>\n
Question 7.
\nState the properties of colloidal solution.
\nAnswer:
\nProperties of colloidal solution.<\/p>\n