Class 9 Science Chapter 2 Important Questions

Class 9 Science Chapter 2 Important Questions of Is Matter Around Us Pure? Class 9 Science Chapter 2 Extra Questions contains all long and short answers questions with solutions and explanations.

All the questions based on elements, compounds and mixtures are taken for the description of the chapter 2 of class ix science. These sets of questions include all the basic and important questions which are crucial for the school tests and final term exams. These revision questions of high school science ensure scoring good marks in exams and clearing all doubts in chapter 2 of 9th science. UP Board students also use the same NCERT Textbooks as the CBSE Students. So, these questions are important for UP Board students also.

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Class 9 Science Chapter 2 Important Extra Questions for 2020-2021

Class: 9Science
Contents:Important Questions and Answers
Chapter: 2Is Matter Around Us Pure?

9th Science Chapter 2 Extra Question Answers for 2020-2021

Important Extra Questions for class 9 science chapter 2 Is Matter Around Us Pure is given below. Proper answers of each question is also given just below the questions. We have tried to cover entire chapter 2 of class 9 science NCERT at our level best. If someone want to add some more questions in this section, please send us the questions with answer. We will include the questions, if it is up to marks and useful for the students.

Class 9 Science Chapter 2 Important Extra Questions Set – 1

What is meant by a pure substance?

A pure substance is one which made up of only one kind of particle either atoms or molecules. For example, oxygen, carbon etc.

To make a saturated solution 36g of sodium chloride is dissolved in 100g of water at 293K. Find its concentration at this time temperature.

Mass of sodium chloride = 36g
Mass of water = 100g
Total mass of the solution = (36 + 100) g = 136g
Concentration (mass percentage) of solution = (Mass of NaCl )/(Mass of solution ) × 100
= 36g/(136g ) × 100
= 26. 47g

Which separation technique will you apply to separate containing kerosene and petrol (difference in their boiling points is more than 250C) which are miscible with each other?

The miscible mixture of kerosene and petrol can be separated by fractional distillation. On heating the distillation flask, petrol having lower boiling points than kerosene, distils our first.

Name the technique to separate (i) butter and curd (ii) salt and water (iii) camphor from salt.

(i) Centrifugation
(ii) Evaporation
(iii) Sublimation

How can you change a saturated solution to an unsaturated solution without adding any more solvent to it?

By heating the saturated solution, it becomes unsaturated.

Difference between Homogenous and Heterogeneous Mixtures.

Homogenous Mixtures.Heterogeneous Mixtures.
1. The composition remains uniform throughout.1. The composition does not remain uniform throughout.
2. The components of the mixture cannot be separated by visible boundaries.2. The components of the mixture can be separated by visible boundaries.
3. Example: A mixture of salt and water, ethanol and water.3. Examples: A mixture of sand, sugar, chalk and water.

Class 9 Science Chapter 2 Important Extra Questions Set – 2

Sucrose crystals obtained from sugarcane and beetroot are mixed together. Will it to be a passing pure substance or a mixture? Give reason for the same.

It is a pure substance because chemical composition of sugar crystals is same irrespective of its source.

Based on which factor a solution is said to diluted, concentration or saturated?

A solution is said to be diluted, concentrated or saturated on the basis of the amount of solute dissolved in the solution.

Identify solute and solvent in tincture of iodine.

Iodine is the solute and alcohol is the solvent.

What is mass per cent of a solution?

It is defined as the mass in grams of the solute present in one hundred grams of a solution.

What are the two components of a colloidal solution?

The two components of a colloidal solution are dispersed phase and dispersing medium.

Classify the following as chemical or physical changes
    1. Cutting of trees
    2. Melting of butter in a pan
    3. Rusting of almirah,
    4. Boiling of water to form steam,
    5. Dissolving common salt in water
    6. Making a fruit salad with raw fruits and
    7. Burning of paper and wood.
    1. Physical change
    2. Physical change
    3. Chemical change
    4. Physical change
    5. Chemical change
    6. Physical change
    7. Physical change
    8. Chemical change

Class 9 Science Chapter 2 Important Extra Questions Set – 3

In what respect does not true solution differ from a colloidal solution?

A true solution is homogeneous whereas a colloidal solution is heterogenous.

Two liquids A and B are miscible with each other at room temperature. Which separation technique will you apply to separate the mixture of A and B if the difference in their boiling points is 270C?

We can separate two miscible liquids by fractional distillation, if both the liquids have difference in their boiling points. So the mixture of liquid of A and B can be separated by fractional distillation.

Define crystallisation.

It is a process that separate a pure solid in the form of its crystals from a solution.

Why is crystallisation technique considered better than simply evaporation to purify solids?

Crystallisation is considered better than simply evaporation because
(i) some solids decompose or get charred on heating to dryness.
(ii) some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.

Why is water called universal solvent?

Water is known as universal solvent because it has the ability to dissolve wide variety of substances.

How do colloid, solution and suspension differ from each other?

1. It is homogenous in nature.1. Heterogeneous in nature.1. Heterogeneous in nature.
2. Particle size is less than 10-7 cm.2. Colloidal particle size is between 10^-4 to 10^-7 cm.2. Particle size is 10^-3 to 10^-5.
3. It does not scatter light.3. It scatters a beam of light.3. It scatters a beam of light.
4. True solution pass through filter paper.4. They also pass through a filter paper.4. Suspended particles do not pass through filter paper.

Class 9 Science Chapter 2 Important Extra Questions Set – 4

Which of the are physical changes? Melting of iron metal, rusting of iron, bending of iron rod, drawing a wire of iron metal.

Melting of iron metal, bending of iron rod and drawing a wire of iron metal are physical changes because there is no change in the chemical composition of iron, only its form is changing.

Name two elements which exist in liquid state at room temperature.

Gallium and mercury exist in liquid state at room temperature.

An unknown substance A on thermal decomposition produces B and C What is an element, a compound or a mixture?

Unknown substance A should be a compound because elements and mixture do not decompose.

Identify the elements from the following substances sulphur, brine, hydrochloride acid, water, neon, paper, sugar.

The elements are sulphur and neon.

Sea water can be classified as homogenous as well as heterogeneous mixture; Comment.

Sea water is a mixture of salts and water which cannot be separated except by evaporation. Therefore, sea water is considered homogenous.
Sea water also contains mud, decayed plants, etc., other than salts and water, so it is heterogeneous also.

Differences between an Element and a Compound.
1. An element is made up of same kind of atoms.1. A compound is obtained from different kinds of atoms.
2. An element cannot split by physical or chemical methods.2. A compound can be split into new substances by chemical method.

Class 9 Science Chapter 2 Important Extra Questions Set – 5

Why is it not possible to distinguish particles of a solute from the solvent in solution?

A true solution is homogenous in nature. The solute and solvent particles are very small. They cannot be distinguishing even under a microscope.

Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do.

Particle size in a suspension is large than those in a colloidal solution. Also molecular interaction in a suspension is not strong enough to keep the particles suspended and hence they settle down.

Identify colloids and true solution from the following: Pond water, frog, aluminium paints, vinegar and glucose solution.

True solution are vinegar and glucose solution. Colloids are frog, aluminium paint.

Give two examples each for (i) Aerosol, (ii) Emulsion.

(i) Aerosol: Clouds smoke
(ii) Emulsion: Milk, face cream

Smoke and fog both are aerosols. In what way are they different?

Both fog and smoke have gas as the dispersion medium. The only difference is that the dispersed phase in fog is liquid and in smoke it is a solid.

Properties of Colloid
    • It is a heterogeneous mixture.
    • Size of particle is too small to be seen by naked eye.
    • They do not settle down when left undisturbed.
    • They scatter light passing through them making its path visible.
    • They cannot be separated by the process of filtration.

Class 9 Science Chapter 2 Important Extra Questions Set – 6

What do you understand by the term distillation? Give its one application.

Distillation is used to get back acetone. We know that boiling point of water is 1000C and since acetone is more volatile it will separate our first.

Define chromatography and give its one application.

Chromatography is a technique used for the separation of a mixture of solutes brought about by distribution of dissolved material between two immiscible phases, one of which is mobile phase and the other part is stationary phase. It is useful in forensic science to detect and identify trace amounts of substances in the contents of bladder or stomach.

Is water an element or a compound? Give one reason in support of your statement.

Water is a compound because of the following reasons:
(i) It is compound of two different elements, hydrogen and oxygen which cannot be separated by physical methods. They can be separated only by electrolysis.
(ii) The physical and chemical properties of hydrogen and oxygen are entirely different from the properties of water.

Suggest separation technique (s) one would need to employ to separate the following mixtures: (a) Mercury and water, (b) Potassium chloride and ammonium chloride, (c) Common salt water and sand, (d) Kerosene oil, water and salt

(a) Separation by using separating funnel.
(b) Sublimation
(c) Filtration to separate sand followed by evaporation/distillation.
(d) Separation by using separating funnel to separate kerosene oil followed by evaporation or distillation.

What would you observe when? (a) a saturated solution of potassium chloride prepared at 600C is allowed to cool at room temperature? (b) an aqueous sugar solution is heated to dryness? (c) a mixture of iron filings and Sulphur powder is heated strongly?

(a) Solid potassium chloride will separate out.
(b) Initially the water will evaporate ad then sugar will get charred.
(c) Iron suplhide will be formed.

Name the process associated with the following
    1. Dry ice is kept at room temperature and at one atmospheric pressure.
    2. A potassium permanganate crystal is in a beaker and water is poured into a beaker wit stirring.
    3. An acetone bottle is left open and the bottle becomes empty.
    4. Milk is churned to separate cream from it.
    5. Setting of sand when a mixture of sand and water is left undisturbed for some time.
    6. Fine beam of light entering through a small hole in a dark room, illuminates the particles its paths.
    1. Sublimation
    2. Dissolution/ diffusion
    3. Evaporation/ diffusion
    4. Centrifugation
    5. Sedimentation
    6. Scattering of light.

Class 9 Science Chapter 2 Important Extra Questions Set – 7

On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide. (a) Is this a physical or a chemical change? (b) Can you prepare one acidic and one basic solution by using the products formed in above process? If so, write the chemical equation involved.

(a) Chemical change.
(b) Acidic and basic solution can be prepared by dissolving the products of the above process water.
CaO + H2O → Ca(OH)2 (basic solution)
CO2 + H2O → H2CO3 (acidic solution)

Classify the following into metals, non-metals and metalloids: (i) Germanium (ii) Boron (iii) Diamond (iv) Iodine (v) Copper (vi) Helium

Metal – Copper
Non Metals – Diamond, iodine and helium
Metalloids – Germanium, boron.

Distinguish between physical change and chemical change.

Physical change:
(i) In a physical change, one physical properties such as colour, physical state, density, volume, etc. change; chemical properties remain unchanged.
(ii) No new substance is formed in a physical change.
(iii) Very little or no energy in the form of heat, light or sound is usually absorbed or given out in a physical change.
(iv) A physical change is a temporary change.
(v) The original form of a substance can be regained by simply physical methods.
(vi) A physical change is reversible.
Chemical change:
(i) In a chemical change, the chemical composition and chemical properties undergo a changes.
(ii) A new substance is formed in a chemical change.
(iii) A chemical change is always accompanied by absorption or evolution of energy.
(iv) A chemical change is a permanent change.
(v) Original substance cannot be obtained by simply physical methods.
(vi) A chemical change is irreversible.

Distinguish between metals and non-metals.

(a) Metals: (i) They have lustre (sheen).
(ii) They are malleable and ductile.
(iii) They have high density and high melting and boiling points.
(iv) Except mercury and gallium all other metals are solid at room temperature.
(v) They are sonorous.
(vi) They are good conductors of heat and electricity.
(vii) They are generally hard (except sodium or potassium).
(viii) They have high tensile strength.
(b) Non-metal: (i) They are non-lustrous.
(ii)The are neither malleable nor ductile.
(iii) They have low density and low melting and boiling points.
(iv) Non- metals may exist in solid, liquid or gaseous states at room temperature.
(v) They are not sonorous.
(vi) They are poor conductors of heat and electricity.
(vii) Non-metals are generally soft. (except diamond)
(viii) They have low tensile strength.

Distinguish between compounds and mixtures.

(a) Compound: (i) Compounds are formed as a result of chemical reactions between two or more elements or compounds.
(ii) The components of a compound are always present in a definite ratio by the mass.
(iii) The properties of a compound are entirely different from its constituents.
(iv) Compounds are always homogenous in nature.
(v) Compound formation is accompanied by absorption or evolution of light, heat or electrical energy.
(vii)Melting and boiling points of a compound are usually sharp are fixed.
(viii) The constituents of a compound cannot be separated by physical by physical or mechanical means. They can however be separated by chemical methods.
(b) Mixtures: (i) Mixtures are formed by simply mixing two or more constituents. There are no chemical reactions between the constituents.
(ii) The properties of a mixture are same as those of its constituents.
(iii) The components of a mixture may be present in any ratio.
(iv) Mixture are usually heterogeneous (except in solution)
(v) Heat, light or electrical energy may not be evolved or absorbed during the formation of a mixture.
(vii) The components of a mixture can be easily separated by physical methods.

Difference between a True Solution and a Colloidal

True SolutionColloidal
1. A true solution is a homogenous mixture of two or more substances.1. A colloidal solution is a heterogeneous mixture of two substance.
2. The size of the particles is less than one nanometer.2. The range of particle size is between one nanometer to 1000 nanometer.
3. It is always transparent.3. It is transparent.
4. The particle cannot be seen even with microscope.4. The particle of a colloidal solution can be seen with microscope.
5. It does not show Tyndall effect.5. It shows Tyndall effect.

Class 9 Science Chapter 2 Important Extra Questions Set – 8

Define Element?

Robert Boyle discovered element in 1661 an element is a basic form of matter that cannot be broken down into simpler substance by chemical reaction.

What is Tyndall effect?

The scattering of a beam of light is called Tyndall effect this happens due to the scattering of light by the particles of dust and seen when the light passes through a dense forest.

Write the principal of evaporation method?

The principle of evaporation method is that a volatile component is separated by its non-volatile component.

What is fractional distillation method or which method is used to separate gases from air?

The method which is used to separate the component of a mixture in which the components have difference less than 25K in their boiling points is called fractional distillation method. It is used to separate different gases from air.

What is a concentration of a solution?

The concentration of a solution is the amount of a solute that present in the given amount of a solution.
Concentration of solution = (amount of solute )/(amount of solution)

Classify the following Physical and Chemical Changes with reason
    1. Drying of a shirt in the sun.
    2. Rising of hot air over a radiator.
    3. Burning of kerosene in a lantern.
    4. Change in the colour of black tea on adding lemon juice to it.
    5. Churning of milk cream to get butter.
    1. It is a physical change because water is converted from its liquid state to gaseous state because the sun’s heat.
    2. It is a physical change because water in the radiator is converted from a liquid state to gaseous state.
    3. It is a chemical change because combustion of kerosene occurs and new products are formed.
    4. It is a chemical change because there is a reaction between the citric acid in the lemon and the compounds of tea resulting in formation of new product.
    5. It is a physical change because the cream suspended in the milk is separated by churning.
One Word Questions

Non- metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable and are coloured.

    1. Name a lustrous non-metal.
    2. Name a non-metal which exists as a liquid at room temperature.
    3. The allotropic form of a non-metal is a good conductor of electricity. Name the allotrop.
    4. Name a non-metal which is known a to form the largest number of compound.
    5. Name a non-metal other than carbon which shows allotropy.
    6. Name a nonmetal which is required for combustion.
Answers of One Word Questions
    1. Iodine
    2. Bromine
    3. Graphite
    4. Carbon
    5. Sulphur
    6. Oxygen

You are provided with a mixture containing sand, iron filings, ammonium chloride and sodium chloride. Describe the procedure you would use o separate these constituent from the mixture.


(i) Removing iron filings from the mixture by magnetic separation. Take the mixture in a Petri dish and roll a bar magnet over it. Iron filings will get attach to the magnet and thus separate from the mixture.
(ii) Removing ammonium chloride by sublimation
Transfer the remaining mixture into china dish and heat it. On heating, ammonium chloride sublime and solidifies on condensation. The mixture containing sand and sodium chloride left behind in the china dish.
(iii) Removing sand by filtration
Make a solution of sand and sodium chloride in water. Filter the solution. Sodium chloride will dissolve in water and sand is left as residue on the filter paper.
(iv) Evaporate the filtrate to dryness to get sodium chloride or by crystallisation.

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