Question 1

Question 1Which 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.(d) Different pigments from an extract of flower petals.(e) Butter from curd.(f) Oil from water.(g) Tea leaves from tea.(h) Iron pins from sand.(i) Wheat grains from husk.(j) Fine mud particles suspended in water.

Accepted Answer

(a) Sodium chloride from its solution in water — Evaporation(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride — Sublimation(c) Small pieces of metal in the engine oil of a car — Filtration(d) Different pigments from an extract of flower petals — Chromatography(e) Butter from curd — Centrifugation(f) Oil from water — By a separating funnel(g) Tea leaves from tea — By using stainer for filtration(h) Iron pins from sand — By using a magnet(i) Wheat grains from husk — Sedimentation/winnowing(j) Fine mud particles suspended in water — Sedimentation/decantation

Question 2

Question 2Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue.

Accepted Answer

Steps for making tea are:Take one cup of water as solvent and boil it for few minutes.When solvent boils, add solutes, i.e., milk, tea leaves, sugar. Boil the solution for a few minutes.Milk is soluble in water. Sugar also dissolves in the solution but tea leaves remain as filtrate.The insoluble residue of tea leaves is filtered using a strainer and the tea is ready.

Question 3

Question 3Pragya 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 solution).Substance DissolvedTemperature in K283293313333353SolubilityPotassium nitrate213262106167Sodium chloride3636363737Potassium chloride3535404654Ammonium chloride2437415566(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?(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.(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?(d) What is the effect of change of temperature on the solubility of a salt?

Accepted Answer

(a) Given,Mass of potassium nitrate required to produce a saturated solution in 100 g of water at 313 K = 62gMass of potassium nitrate required to produce a saturated solution in 50 g of water = ?Required amount = 62100\dfrac{62}{100}10062​ x 50 = 31Hence, 31 g of potassium nitrate is required.(b) The solubility of potassium chloride in water is decreased when the saturated solution of potassium chloride loses heat at 353 K. So, Pragya would observe crystals of potassium chloride, which would have surpassed its solubility at low temperatures.(c) As per the given data :Solubility of potassium nitrate at 293 K = 32 gSolubility of sodium chloride at 293 K = 36 gSolubility of potassium chloride at 293 K = 35 gSolubility of ammonium chloride at 293 K = 37 gWe can observe from this data that ammonium chloride has the highest solubility at 293 K.(d) The solubility of the salt increases with an increase in temperature.

Question 4

Question 4Explain the following, giving examples.(a) Saturated solution(b) Pure substance(c) Colloid(d) Suspension

Accepted Answer

(a) Saturated solution — A saturated solution is one which cannot dissolve more of the solute at a given temperature.Example: Excess carbon leaves off as bubbles from a carbonated water solution saturated with carbon.(b) Pure substance — A substance is said to be pure when it comprises of only one kind of molecules or atoms.Example: Sulphur, diamonds etc.(c) Colloid — A colloid is a heterogeneous mixture in which the size of solute particles is intermediate between true solution and suspension and it shows tyndall effect.Examples: Soap solution, starch solution, milk.(d) Suspension — It is a heterogeneous mixture in which the small particles of a solid are spread throughout a liquid without dissolving in it. Particles of a suspension are visible to the naked eye.Examples: Chalk water mixture, muddy water etc.

Question 5

Question 5Classify each of the following as a homogeneous or heterogeneous mixture.Soda water, wood, air, soil, vinegar, and filtered tea.

Accepted Answer

The given elements are classified below:Soda water — Homogenous mixtureWood — Heterogeneous mixtureAir — Heterogeneous mixtureSoil — Heterogeneous mixtureVinegar — Homogenous mixtureFiltered tea — Homogenous mixture

Question 6

Question 6How would you confirm that a colourless liquid given to you is pure water?

Accepted Answer

We can confirm if a colourless liquid is pure water by boiling it. If it boils at 100°C, then its pure. However, if there is an increase or decrease in the boiling point, then we can say that impurities are added to water.

Question 7

Question 7Which of the following materials fall into the category of 'pure substance'?(a) Ice(b) Milk(c) Iron(d) Hydrochloric acid(e) Calcium oxide(f) Mercury(g) Brick(e) Wood(f) Air

Accepted Answer

Following substances from the above-mentioned list are pure substances:IceIronHydrochloric acidCalcium oxideMercury

Question 8

Question 8Identify the solutions among the following mixtures.(a) Soil(b) Sea water(c) Air(d) Coal(e) Soda water

Accepted Answer

The following are the solutions from the above-mentioned list of mixtures:Sea waterAirSoda water

Question 9

Question 9Which of the following will show the 'Tyndall effect'?(a) Salt solution(b) Milk(c) Copper sulphate solution(d) Starch solution

Accepted Answer

Tyndall effect is shown by:(a) milk(b) starch solution

Question 10

Question 10Classify the following into elements, compounds and mixtures.(a) Sodium(b) Soil(c) Sugar solution(d) Silver(e) Calcium carbonate(f) Tin(g) Silicon(h) Coal(i) Air(j) Soap(k) Methane(l) Carbon dioxide(m) Blood

Accepted Answer

ElementsCompoundsMixtureSodiumCalcium carbonateSoilSilverMethaneSugar solutionTinCarbon dioxideSoapSilicon Coal  Air  Blood

Question 11

Question 11Which of the following are chemical changes?(a) Growth of a plant(b) Rusting of iron(c) Mixing of iron filings and sand(d) Cooking of food(e) Digestion of food(f) Freezing of water(g) Burning of a candle

Accepted Answer

The following are chemical changes :(a) Growth of a plant(b) Rusting of iron(c) Cooking of food(d) Digestion of food(e) Burning of a candle

Question 12

Question 1What is meant by a substance?

Accepted Answer

A substance is a pure single form of matter. It is made up of one kind of atoms or molecules and has definite properties.Example: Copper, oxygen, hydrogen etc.

Question 13

Question 2List the points of difference between homogeneous and heterogeneous mixtures.

Accepted Answer

Differences between homogeneous and heterogeneous mixtures are:Homogeneous mixtureHeterogeneous mixtureHave a uniform composition throughout.Have non-uniform compositions.Particles are completely mixedParticles are separate and can be distinguished with the bare eyes or under a microscope

Question 14

Question 1Differentiate between homogenous and heterogeneous mixtures with examples.

Accepted Answer

Homogeneous mixtureHeterogeneous mixtureHave a uniform composition throughout.Have non-uniform compositions.Particles are completely mixedParticles are separate and can be distinguished with the bare eyes or under a microscopeExamples are salt dissolved in water, sugar dissolved in water, etc.Examples are soil, oil and water, salt and sulphur, etc.

Question 15

Question 2How are sol, solution and suspension different from each other?

Accepted Answer

AttributesSolSolutionSuspensionType of mixtureHeterogeneousHomogeneousHeterogeneousTyndall effectExhibitedNot exhibitedMay or may not be exhibitedAppearanceUsually glassy and clearUnclouded and clearCloudy and opaqueVisibilityVisible with an ultramicroscopeNot visibleVisible with the naked eyeDiffusionDiffuses very slowlyDiffuses rapidlyDo not diffuseStabilityPretty stableHighly stableUnstableSettlingGet settled in centrifugationDo not settleSettle on their ownExampleMilk, blood, smokeSalt solution, sugar solutionSand in water, dusty air

Question 16

Question 3To 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.

Accepted Answer

Given,Mass of solute (NaCl) = 36 gMass of solvent (H2O) = 100 gMass of solution (NaCl + H2O) = 100 + 36 = 136 gConcentration = Mass of soluteMass of solution\dfrac{	ext{Mass of solute}}{	ext{Mass of solution}}Mass of solutionMass of solute​ x 100Concentration = 36136\dfrac{36}{136}13636​ x 100 = 26.47%Hence, the concentration of the solution is 26.47%

Question 17

Question 1Classify the following as chemical or physical changes:Cutting of treesMelting of butter in a panRusting of almirahBoiling of water to form steamPassing of electric current through water and the water breaking down into hydrogen and oxygen gases.Dissolving common salt in waterMaking a fruit salad with raw fruits, andBurning of paper and wood

Accepted Answer

The following is the classification into physical and chemical change:Cutting of trees — Physical changeMelting of butter in a pan — Physical changeRusting of almirah — Chemical changeBoiling of water to form steam — Physical changePassing of electric current through water and the water breaking down into hydrogen and oxygen gases. — Chemical changeDissolving common salt in water — Physical changeMaking a fruit salad with raw fruits — Physical changeBurning of paper and wood — Chemical change

Question 18

Question 2Try segregating the things around you as pure substances and mixtures.

Accepted Answer

Listed below are the classifications based on pure substances and mixtures:Pure substanceMixtureWatersalt solutionDiamondSteelSugarSoilSodium hydroxideBricks

Is Matter Around Us Pure

Exercises

Intext Questions 1

Intext Questions 2

Intext Questions 3