CBSE Class 9 Chemistry Is Matter Around Us Pure Worksheet

Very Short Answer Type Questions

Question. Name the types of mixtures.
Answer : Homogeneous mixture and heterogeneous mixture.

Question. Define dispersion medium.
Answer :  It is the component which is present in excess and acts as a medium in which colloidal particles are dispersed.

Question. A colloid which have liquid as dispersed phase and solid as dispersion medium called-
Answer : Gel.

Question. The component of solution that is present in smaller proportion
Answer : Solute.

Question. Name a metal which is liquid at room temperature.
Answer : Mercury.

Question. An element made up of only one type of—
Answer : Atom.

Question : How would you confirm that a colorless liquid given to you is pure water?
Answer : If the given colorless liquid boils at 100°C sharp, it is pure water, otherwise not.

Question: Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water
Answer : Sea water, air and soda water: Homogeneous mixture Coal, Soil: Heterogeneous solution.

Short / Long Answer Type Questions

Question. (i) State the principle of the process of centrifugation.
(ii) List any three applications of centrifugation.
Answer :
 (i) Centrifugation is the process of separating suspended particles from a liquid like colloids by churning the liquid at a high speed. The principle is that denser particles are forced to the bottom and lighter stay at the top when spun rapidly.
(ii) Applications of centrifugation :
(a) Used in dairies and homes to separate cream from milk or butter from cream.
(b) Used in washing machines to squeeze out water from clothes.
(c) Used in laboratories to separate colloidal particles from their solutions.
(d) Used in diagnostic labs for blood and urine test.

Question. Why is water considered as compound?
Answer :  Water is considered as compound because :
(i) Water is composed of two elements : hydrogen and oxygen.
(ii) The ratio of hydrogen and oxygen by mass in any sample of pure water is the same.
(iii) The properties of water are different from its constituent elements : hydrogen and oxygen.
(iv) Water can be decomposed by chemical means only

Question. Write characteristics of compounds.
Answer : Characteristics of compounds :
(i) Compounds are the substances formed by chemical combination of two or more elements.
(ii) The constituent elements are present in a fixed ratio.
(iii) A chemical reaction takes place during the  formation of a compound.
(iv) Properties of a compound are different to those of its elements.
(v) Constituent elements cannot be separated by physical processes.

Question : Name the technique to separate
(i) Butter from curd
(ii) Salt from sea water
(iii) Camphor from salt
Answer :
(i) By using centrifugation method, butter can be separated from curd.
(ii) By using evaporation method, salt from sea water can be separated .
Water vaporises on evaporation leaving behind the salt.
(iii) Camphor from salt can be separated by sublimation method. On subliming camphor will be converted into vapour leaving behind the salt.

Question : Classify the following as chemical or physical changes
(a) Cutting of trees,
(b) Melting of butter in a pan,
(c) Rusting of almirah,
(d) Boiling of water to form steam,
(e) Passing of electric current, through water and the water breaking down into hydrogen and oxygen gases,
(f) Dissolving common salt in water,
(g) Making a fruit salad with raw fruits, and
(h) Burning of paper and wood
Answer :
Physical Change :
Cutting 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
Chemical Change :
Rusting of almirah.
Passing of electric current, through water and the water breaking down into hydrogen and oxygen gases.
Burning of paper and wood.

Question : Write the steps you would use for making tea. Use the words solution, solvent,solute, dissolve, soluble, insoluble, filtrate and residue.
Answer : Method of preparation of tea
(i) Take some water (solvent) in a pan and heat it.
(ii) Add some sugar (solute) and boil to dissolve the sugar completely the obtained homogeneous mixture is called solution.
(iii) Add tea leaves (or tea) in the solution and boil the mixture.
(iv) Now add milk and boil again.
(v) Filter the mixture through the tea stainer and collect the filtrate or soluble substances, i.e., tea in a cup. The insoluble tea leaves left behind as residue in the 8 trainer.

Question : Explain the following giving examples.
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) Suspension
Answer :
(a) Saturated solution: A solution in which no more amount of solute can be dissolved at a particular temperature is called saturated solution.
Example: when sugar is dissolved repeatedly in a given amount of water, a condition is reached at which further dissolution of sugar is not possible in that amount of water at room temperature.
(b) Pure substance: A substance made up of single type of particles (atoms and/or molecules) is called pure substance. All elements and compounds are said to be pure, Example: water, sugar etc.
(c) Colloid:A heterogeneous mixture in which the solute particle size is too small to be seen with the naked eye, but is big enough to scatter light is known as Colloid. There are two phases in colloidal solution Dispersed phase: solute particles are said to be dispersed phase Dispersion medium: the medium in which solute particles are spread is called the dispersion medium.
Example: Milk, clouds etc., are the example of colloid.
(d) Suspension: A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of suspension are visible to the naked eye.
Example: Mixture of sand, Water and Muddy water etc.

Question : Classify 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
Answer : Elements : Sodium, silver, tin and silicon
Compounds : Calcium carbonate, methane, and carbon dioxide Mixtures : Soil, sugar solution, coal, air, soap and blood.

Exam Questions NCERT Class 9 Science Chapter 2 Is Matter Around Us Pure

Question. What are two types of matter on the basis of composition?
Ans : Pure substance and mixture.

Question. What is the principle of separation?
Ans : The difference in physical or chemical properties of components of mixture is the basis of separation.

Question. Give chemical name of chalk and quicklime.
Ans : (i) Chalk : Calcium Carbonate
(ii) Quicklime : Calcium Oxide

Question. Milk of Magnesia is a-
Ans : True solution.

Question. Name of process used to separate liquids which have difference in boiling points of less than 25°C—
Ans : Fractional distillation.

Question. Name two metals which are highly malleable and ductile.
Ans : Gold and silver.

Question. Melting of wax is a physical change but burning of wax is a chemical change. Explain.
Ans : (i) Melting of wax changes the state of wax from solid to liquid. No new substance is formed. The chemical nature of solid wax and liquid wax is the same. Hence, melting of wax is a physical change.
(ii) Burning of wax gives new gaseous products. Both the physical and chemical changes are taking place. Hence, burning of wax is a chemical change.

Question. Name the process by which pure copper sulphate can be obtained from its impure sample.
Ans : Crystallization.

Question. Define the term heterogeneous.
Ans : A substance that does not have the same properties throughout the mixture is called heterogeneous.

Question. Define Chromatography.
Ans : The process of separation of different dissolved constituents of a mixture by absorbing them over an appropriate absorber is called, Chromatography.

Very Short Answer Type Question

Question. Name the process by which all dyes present in black ink be recovered.
Answer : Chromatography.

Question. How can you test the purity of a given substance?
Answer : A pure substance always has the same taste, colour or texture at particular temperature and pressure and fixed melting or boiling point. For example : Pure water boils at 100°C but if it has some impurities then water boils at a temperature above 100°C.

Question. What is decantation? Explain.
Answer : Decantation is the process of separating insoluble solids from liquids. A suspension of solid particles in a liquid is allowed to stand for sometime. Insoluble solid particles settle down at the bottom due to their weight. This is called sedimentation. The clear liquid is then transferred into another container, without disturbing the settled particles. In other words, clear liquid is decanted and separated from solid.

Question. Hydrogen is considered as element. Why?
Answer : Hydrogen have one type of element and it cannot be broken by physical or chemical process, so it is considered as element.

Question. Classify the elements.
Answer : (1) Metals, (2) Non-metals, and (3) Metalloids.

Question. Give an example of a liquid and liquid type solution.
Answer : Vinegar is a mixture of acetic acid and water.

Question. A system which have same properties throughout is called-
Answer : Homogeneous.

Short / Long Answer Type Question

Question : Classify each of the following as a homogeneous or heterogeneous mixture. Soda water, wood, air, soil, vinegar, filtered tea.
Answer : Homogeneous mixtures: Air, soda water, vinegar, filtered tea.
Heterogeneous mixtures: Wood, soil,

Question : Which of the following materials fall in the category of a "pure substance"?
(a) Ice (b) Milk (c) Iron
(d) Hydrochloric acid (e) Calcium oxide (f) Mercury
(g) Brick (h)Wood (i) Air
Answer : Ice, iron, calcium oxide, mercury are pure substance as they have definite composition.
Milk is a colloid, so it is a heterogeneous mixture.
Hydrochloric acid is also a mixture of hydrogen chloride gas and water.

Question : Which of the following will show "Tyndall effect"?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution
Answer : Milk and starch solution will show "Tyndall effect" as both of these are colloids.

Question : Which 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
Answer : Growth of a plant, rusting of iron, cooking of food, digestion of food, burning of a candle are chemical changes, because here the chemical composition of substance changes.

Question : How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?
Answer : Simple distillation is the method which can separate the mixture of kerosene and petrol (b.p. differ by more than 25°C).
Method:In a distillation flask, a mixture of kerosene and petrol is taken as shown in figure. The mixture is heated slowly and the temperature is recorded with the help of thermometer. Petrol (b.p. = 70° C to 1200 ° C) vaporizes first and the temperature becomes constant for some time (till all petrol evaporates from the mixture).
Vapours of petrol are condensed and collected in another container while the kerosene remains in the distillation flask. As soon as the temperature starts’ rising again, the heating is stopped and both the components are collected separately.

Question : What types of mixtures are separated by the technique of crystallisation?
Answer : Crystallisation method can be used for the purification of those mixtures which Contain insoluble and/or soluble impurities.
Have crystalline nature.
Cannot be separated by filtration as some impurities are soluble.

Question : Try segregating the things around you as pure substances or mixtures.
(a) Wood
(b) Coal
(c) Milk
(d) Sugar
(e) Common salt
(f) Soap
(g) Soil
(h) Rubber
Answer :
(a) Mixture
(b) Mixture
(c) Mixture
(d) Pure substance
(e) Pure substance
(f) Compound/mixture
(g) Mixture
(h) Pure substance

Question : 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.
(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.
Answer :
(a) Evaporation
(b) Sublimation
(c) Filtration
(d) Chromatography.
(e) centrifugal machine or churning the curd by hand.
(f) Decantation
(g) Filtration.
(h) Magnetic Separation.
(i) Winnowing.
(j) Coagulation and decantation:

Question : 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 substance dissolved in 100 grams of water to form a saturated solution).
(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?
Answer :
(a) Mass of potassium nitrate needed to produce its saturated solution in 100 g of water at 313 K = 62 g
Mass of potassium nitrate needed to produce its saturated solution in 50 g of water at 313
K = 62/100 x 50g = 31g
(b) Crystals of potassium chloride are formed. This happens as solubility of solid decreases with decreasing the temperature.
(c) Solubility of each salt at 293 K
Potassium nitrate 32 g per 100 g water
Sodium chloride 36 g per 100 g water
Potassium chloride 35 g per 100 g water
Ammonium chloride 37 g per 100 g water
Note:Solubility of a solid is that amount in gram which can be dissolved in 100 g of water (solvent) to make saturated solution at a particular temperature.
Ammonium chloride has the maximum solubility (37 g per 100 g of water) at 293 K.
(d) Solubility of a (solid) salt decreases with decrease in temperature while it increases with rise in temperature.

Question. Brass is a
(a) Compound
(b) Element
(c) Homogeneous mixture
(d) Heterogeneous mixture

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(Q.1) Name the process which can be used to recover sugar from an aqueous sugar solution .

(Q.2) What happens when a saturated solution is heated ?

(Q.3) Name the process you would use to separate a mixture of water and alcohol.

(Q.4) Give an example of an aqueous solution in which gas is dissolved.

(Q.5) What is the cause of Tyndall effect as shown by colloid ?

(Q.6) Give two examples of colloidal solution .

(Q.7) Name the technique to separate -
(a) Salt from sea water
(b) Butter from curd

(Q.8) When a paper is burnt it is considered a chemical change because
(A) The change is permanent.
(B) There is no change in mass.
(C) The chemical composition changes.
(D) Both (1) and (3)

(Q.9) An aqueous solution at room temperature was heated and some more solute was added to it. It was observed that after sometime solution could not dissolve any more of the solute. The solution now formed is called
(A) Saturated solution.
(B) Super saturated solution.
(C) Unsaturated solution.
(D) Homogeneous solution.

(Q.10) A mixture of iron filings and sulphur powder can be separated using
(A) A magnet
(B) Handpicking
(C) Carbon disulphide solution
(D) Both (1) and (3)

(Q.11) A mixture of chalk powder and water can be separated using the technique of filtration because
(A) Chalk powder remains suspended in water.
(B) They form a miscible solution.
(C) The mixture can easily pass through filter paper
(D) Water acts as a good solvent.

(Q.12) The necessary condition for separation of the components of a mixture regarding the boiling points of the components of a mixture of two or more miscible liquids is
(A) Their boiling points should be same
(B) Their boiling points should be less than 373 K.
(C) Their boiling points should differ by 25 K.
(D) The boiling point of one of the component should be 373 K.

(Q.13) To check whether a given aqueous salt solution is saturated or unsaturated, we will
(A) Heat the solution
(B) Cool the solution
(C) Add more water to the solution
(D) Add more salt to the solution.

(Q.14) A mixture of salt and iodine is heated in a china dish. A few minutes later it is observed that
(A) The mixture starts melting.
(B) Salt is left behind in the dish.
(C) Iodine is left behind.
(D) Nothing happens.

(Q.15) Crystallization is considered better than evaporation for obtaining pure crystal of sugar because
(A) On heating sugar can burn.
(B) Sugar particles will evaporate.
(C) Sugar particles will decompose.
(D) Sugar particles will melt.

(Q.16) Which is the only metal that exists in liquid state at room temperature?
(A) Sodium
(B) Mercury
(C) Germanium
(D) Gallium

(Q.17) Why is inter-conversion of states of matter considered physical change?
(A) Because state changes from one form to another.
(B) Because a change in temperature is required.
(C) Because the chemical composition of the substance remains unchanged.
(D) Because they have same physical properties.

(Q.18) Separating cream from milk is done using
(A) filtration
(B) Centrifugation machine
(C) Evaporation
(D) Boiling

(Q.19) The dispersed phase of a colloid is similar to __________ of a solution.
(A) Solute
(B) Solvent
(C) Solubility
(D) Concentration

(Q.20) A mixture
(A) Has a fixed composition.
(B) Does not have a fixed melting point.
(C) Has a fixed melting point.
(D) Is a pure substance.

(Q.21) When a suspension is left undisturbed for some time
(A) Some larger solute particles settle down at the bottom.
(B) All the solute particles settle down.
(C) It absorbs the light rays passing through it.
(D) It turns into a true solution.

(Q.22) The concentration of solute particles remains same throughout in
(A) Homogeneous mixture
(B) Heterogeneous mixture
(C) Suspension
(D) Both (1) and (2)

(Q.23) Tyndall effect and Brownian movement are exhibited by
(A) True solution
(B) Colloid
(C) Suspension
(D) Suspension and colloid both

(Q.24) S and Fe are heated together to prepare FeS. Composition in the ratio S:Fe by mass is
(A) 4:7
(B) 3:7
(C) 4:8
(D) 3:8

(Q.25) The size of particles in a true solution is less than
(A) 10^-10m
(B) 10^-8m
(C) 10^-7m
(D) 10^-9m

(Q.26) The necessary condition to be specified while expressing solubility is
(A) Temperature
(B) Pressure
(C) Boiling point
(D) Atomic number of solute

(Q.27) The principle behind fractional distillation technique in separation of two liquids is
(A) Difference in Melting point
(B) Difference in Boiling point
(C) Difference in Concentration
(D) Difference in Solubility

(Q.28) Sulphur and sand mixture can be separated by the addition of which of the following solvent
(A) Carbon disulphide
(B) Water
(C) Alcohol
(D) Sulphuric acid

(Q.29) Solubility of a gas in a liquid increases on
(A) Increasing temperature.
(B) Decreasing pressure.
(C) Increasing pressure.
(D) No effect of temperature and pressure.

(Q.30) The non-metal which is liquid at room temperature is -
(A) Chlorine
(B) Bromine
(C) Iodine
(D) Fluorine

(Q.31) Soap solution is an example of
(A) Sol
(B) Foam
(C) Emulsion
(D) Gel

(Q.32) Solvent in air is
(A) Nitrogen
(B) Oxygen
(C) Carbon Dioxide
(D) Argon

(Q.33) Dispersed phase and dispersion medium in a jelly are ___and__, respectively.
(A) Solid, liquid
(B) Liquid, solid
(C) Solid, solid
(D) Liquid, Liquid

(Q.34) Which out of the following will show tyndall effect?
(A) Smoke
(B) Salt solution
(C) Alloys
(D) Aerated drinks

(Q.35) Which of the following gas will boil first during fractional distillation of air?
(A) Oxygen
(B) Nitrogen
(C) Argon
(D) None of the above

(Q.36) What type of solution are alloys?
(A) Solids in liquids
(B) Liquids in solids
(C) Solids in solids
(D) Liquids in liquids

(Q.37) Size of the particles of a solution is less than:
(A) 10^-8m
(B) 10^-9m
(C) 10^-7 m
(D) 10^-10 m

(Q.38) Colloid having liquid dispersed in liquid is called:
(A) Sol
(B) Gel
(C) Emulsion
(D) Aerosol

(Q.39) Separation technique used for two or more miscible liquids having difference in their boiling points
(A) Centrifugation
(B) Evaporation
(C) Chromatography
(D) Fractional distillation

(Q.40) Name the metal that is liquid at room temperature.
(A) Sodium
(B) Mercury
(C) Potassium
(D) Magnesium

(Q.41) Metals are ductile. This means:
(A) Metals can be drawn into wires
(B) Metals can be hammered into sheets
(C) Metals produce ringing sound
(D) Metals are good conductors

(Q.42) Which of the following is a poor conductor of heat and electricity?
(A) Sodium
(B) Silver
(C) Gold
(D) Carbon