Let us have a look at some of the important points in the chapter “IS MATTER AROUND US PURE?” from the class 9th NCERT book. These important points are for quick revision of the chapter. In this we have also included formulas which you will be using while solving the numerical problems.
- Pure substances: have a single type of particle.
- Examples: Elements (e.g., iron, gold) and compounds (e.g., water, sodium chloride).
- Mixtures: contain two or more pure substances.
- Types:
- Homogeneous mixtures: have uniform composition (e.g., air, solutions).
- Heterogeneous mixtures: have non-uniform composition (e.g., soil, sand and iron filings).
- Types:
- Solution: A homogeneous mixture of solute and solvent.
- Components:
- Solute: Substance dissolved (e.g., sugar in water).
- Solvent: Substance in which the solute is dissolved (e.g., water).
- Components:
- Concentration of Solutions:
- Mass by mass percentage: (Mass of solute/Mass of solution) × 100.
- Mass by volume percentage: (Mass of solute/Volume of solution) × 100.
- Volume by volume percentage: (Volume of solute/Volume of solution) × 100.
- Types of Mixtures:
- Suspensions: have visible particles and are unstable (e.g., muddy water).
- Colloids: scatter light (Tyndall effect) and are stable (e.g., milk, fog).
- Elements: cannot be broken down by chemical reactions.
- Categories:
- Metals: Lustrous, malleable, ductile, good conductors of heat and electricity (e.g., gold, copper).
- Non-metals: Varied colors, poor conductors, not lustrous or malleable (e.g., oxygen, chlorine).
- Metalloids: Properties intermediate between metals and non-metals (e.g., silicon, boron).
- Categories:
- Compounds: substances with two or more elements chemically combined in a fixed proportion (e.g., water (H₂O), carbon dioxide (CO₂)).
- Physical changes: do not alter the chemical composition (e.g., melting ice, boiling water).
- Chemical changes: result in new substances (e.g., rusting iron, burning wood).
- Properties of Metals: Malleable, ductile, conduct electricity (e.g., copper used in electrical wires).
- SI units: mass (kg), length (m), volume (m³), pressure (Pa).
- Extra Concepts:
- Milk: Considered an impure substance (mixture).
- Metalloids: Elements with properties of both metals and non-metals (e.g., silicon, germanium).
- Compounds: Formed by chemical reactions between elements (e.g., iron and sulfur forming iron sulfide).
Once you have revised these, lets dive into solving some of the simple and few challenging questions for chapter 2 “Is Matter Around Us Pure”. We have 35 multiple choice questions and match the column question below. You can check out other MCQ questions for class 9 science.
35 MCQ Questions for Class 9 Science: Chapter 2 – Is Matter Around Us Pure?
Question 1. What is the main component of a solution?
a) Solute
b) Solvent
c) Residue
d) Filtrate
Answer:
b) Solvent
Question 2. What kind of mixture is soda water?
a) Heterogeneous
b) Homogeneous
c) Colloid
d) Suspension
Answer:
b) Homogeneous
Question 3. Which process is used to separate a mixture of two miscible liquids?
a) Filtration
b) Distillation
c) Evaporation
d) Decantation
Answer:
b) Distillation
Question 4. A solution that has dissolved as much solute as it is capable of dissolving at a given temperature is called:
a) Unsaturated
b) Saturated
c) Dilute
d) Concentrated
Answer:
b) Saturated
Question 5. What type of mixture is air?
a) Solution
b) Suspension
c) Colloid
d) Compound
Answer:
a) Solution
Question 6. What is the Tyndall effect observed in?
a) Solutions
b) Pure substances
c) Colloids
d) Compounds
Answer:
c) Colloids
Question 7. Which of the following is a chemical change?
a) Dissolving salt in water
b) Boiling of water
c) Rusting of iron
d) Melting of ice
Answer:
c) Rusting of iron
Question 8. How can we separate cream from milk?
a) Filtration
b) Evaporation
c) Centrifugation
d) Decantation
Answer:
c) Centrifugation
Question 9. What is the solubility of a substance?
a) The ability to dissolve in any solvent
b) The temperature at which a substance dissolves
c) The maximum amount of a solute that can be dissolved in a given amount of solvent at a specific temperature
d) The rate at which a solute dissolves in a solvent
Answer:
c) The maximum amount of a solute that can be dissolved in a given amount of solvent at a specific temperature
Question 10. What are elements?
a) Mixtures of two or more substances
b) Substances made of two or more types of atoms
c) Substances that can be broken down into simpler substances by chemical reactions
d) Basic forms of matter that cannot be broken down into simpler substances by chemical reactions
Answer:
d) Basic forms of matter that cannot be broken down into simpler substances by chemical reactions
Question 11. What kind of mixture is milk?
a) Homogeneous
b) Heterogeneous
c) Colloid
d) Suspension
Answer:
c) Colloid
Question 12. What method is used to separate cream from milk?
a) Filtration
b) Evaporation
c) Centrifugation
d) Decantation
Answer:
c) Centrifugation
Question 13. Which of the following will show the Tyndall effect?
a) Salt solution
b) Milk
c) Copper sulphate solution
d) Starch solution
Answer:
b) Milk
Question 14. What is the main property of a colloidal solution?
a) Particles settle down on standing
b) Particles can be seen with the naked eye
c) Particles scatter light
d) Particles do not scatter light
Answer:
c) Particles scatter light
Question 15. What kind of mixture is smoke?
a) Solution
b) Suspension
c) Colloid
d) Compound
Answer:
c) Colloid
Question 16. Which separation technique is used to obtain different gases from air?
a) Distillation
b) Crystallization
c) Fractional distillation
d) Chromatography
Answer:
c) Fractional distillation
Question 17. What is the process of converting a solid directly to a gas?
a) Condensation
b) Evaporation
c) Sublimation
d) Deposition
Answer:
c) Sublimation
Question 18. Which of these is a pure substance?
a) Milk
b) Soil
c) Iron
d) Air
Answer:
c) Iron
Question 19. What type of mixture is soda water?
a) Homogeneous
b) Heterogeneous
c) Colloid
d) Suspension
Answer:
a) Homogeneous
Question 20. Which process is used to separate a mixture of ink and water?
a) Filtration
b) Distillation
c) Evaporation
d) Chromatography
Answer:
d) Chromatography
Question 21. A __________ is a homogeneous mixture of two or more substances.
Fill in the blank.
Answer:
Solution
Question 22. The process of separating grain from chaff is called __________.
Fill in the blank.
Answer:
Winnowing
Question 23. __________ is the only non-metal which exists in a liquid state at room temperature.
Fill in the blank.
Answer:
Bromine
Question 24. The components of a mixture can be separated by __________ means.
Fill in the blank.
Answer:
Physical
Question 25. A saturated solution at a given temperature cannot dissolve more __________.
Fill in the blank.
Answer:
Solute
Question 26. Solutions show the Tyndall effect. (True/False)
True / False
Answer:
False
Question 27. Saltwater is an example of a heterogeneous mixture. (True/False)
True / False
Answer:
False
Question 28. Chromatography is a method for separating dissolved substances from one another. (True/False)
True / False
Answer:
True
Question 29. Distillation is used for separating insoluble substances from a liquid. (True/False)
True / False
Answer:
False
Question 30. Elements can be broken down into simpler substances by chemical reactions. (True/False)
True / False
Answer:
False
Question 31. Which of the following is not classified as an element?
a) Graphite
b) Germanium
c) Silica
d) Silicon
Answer:
c) Silica
Question 32. Which of these statements is true about pure substances?
a) Pure substances have variable composition
b) It may be elements or compounds
c) Pure substances can be separated into simpler substances
d) It contains multiple types of particles
Answer:
b) Pure substances may be elements or compounds
Question 33. Which of the following is not a mixture?
a) Kerosene
b) Air
c) Alcohol
d) Petrol
Answer:
c) Alcohol
Question 34. What best describes a metal?
a) Brittle and poor conductor
b) Malleable and ductile
c) Good insulator
d) Non-magnetic
Answer:
b) It is malleable and ductile
Question 35. Which of these substances normally exists in a liquid state?
a) Bromine and Iodine
b) Mercury and Chlorine
c) Iodine and Mercury
d) Bromine and Mercury
Answer:
d) Bromine and Mercury
Question on Match the Columns
Unmatched Columns – Questions
| Column A | Column B |
|---|---|
| (i) Homogeneous mixture | (a) Mixture of salt and sugar |
| (ii) Heterogeneous mixture | (b) Air |
| (iii) Solution | (c) Oil and water mixture |
| (iv) Colloids | (d) Salt in water |
| (v) Tyndall effect | (e) Fog, clouds, milk |
| (vi) Suspension | (f) Scattering of light in colloids |
Matched Columns – Answer
| Column A | Column B |
|---|---|
| (i) Homogeneous mixture | (b) Air |
| (ii) Heterogeneous mixture | (a) Mixture of salt and sugar |
| (iii) Solution | (d) Salt in water |
| (iv) Colloids | (e) Fog, clouds, milk |
| (v) Tyndall effect | (f) Scattering of light in colloids |
| (vi) Suspension | (c) Oil and water mixture |
MCQ questions from Exemplar Problems
Question 1. Which of the following statements are true for pure substances?
(i) Pure substances contain only one kind of particles
(ii) Pure substances may be compounds or mixtures
(iii) Pure substances have the same composition throughout
(iv) Pure substances can be exemplified by all elements other than nickel
a) (i) and (ii)
b) (i) and (iii)
c) (iii) and (iv)
d) (ii) and (iii)
Answer:
b) (i) and (iii) — A pure substance has only one kind of particles and uniform composition throughout.
Question 2. Rusting of an article made up of iron is called
a) corrosion and it is a physical as well as chemical change
b) dissolution and it is a physical change
c) corrosion and it is a chemical change
d) dissolution and it is a chemical change
Answer:
c) corrosion and it is a chemical change — Rusting forms a new substance (iron oxide), so it is chemical change.
Question 3. A mixture of sulphur and carbon disulphide is
a) heterogeneous and shows Tyndall effect
b) homogeneous and shows Tyndall effect
c) heterogeneous and does not show Tyndall effect
d) homogeneous and does not show Tyndall effect
Answer:
d) homogeneous and does not show Tyndall effect — Sulphur dissolves in carbon disulphide giving a true solution (no Tyndall effect).
Question 4. Tincture of iodine has antiseptic properties. This solution is made by dissolving
a) iodine in potassium iodide
b) iodine in vaseline
c) iodine in water
d) iodine in alcohol
Answer:
d) iodine in alcohol — Tincture iodine is iodine dissolved in alcohol.
Question 5. Which of the following are homogeneous in nature?
(i) ice
(ii) wood
(iii) soil
(iv) air
a) (i) and (iii)
b) (ii) and (iv)
c) (i) and (iv)
d) (iii) and (iv)
Answer:
c) (i) and (iv) — Ice (pure solid water) and air (uniform mixture of gases) are homogeneous; wood and soil are heterogeneous.
Question 6. Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
a) (i), (ii) and (iii)
b) (i), (ii) and (iv)
c) (i), (iii) and (iv)
d) (ii), (iii) and (iv)
Answer:
c) (i), (iii) and (iv) — Melting, bending, and drawing wire change only shape/state; rusting is chemical.
Question 7. Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
a) (i) and (ii)
b) (ii) and (iii)
c) (iii) and (iv)
d) (i) and (iv)
Answer:
a) (i) and (ii) — Decaying and burning produce new substances; sawing and hammering are physical changes.
Question 8. Two substances, A and B were made to react to form a third substance, A2B according to the following reaction: 2A + B → A2B. Which of the following statements concerning this reaction are incorrect?
(i) The product A2B shows the properties of substances A and B
(ii) The product will always have a fixed composition
(iii) The product so formed cannot be classified as a compound
(iv) The product so formed is an element
a) (i), (ii) and (iii)
b) (ii), (iii) and (iv)
c) (i), (iii) and (iv)
d) (ii), (iii) and (iv)
Answer:
c) (i), (iii) and (iv) — A compound does not show properties of its elements, has fixed composition, is classified as a compound, and is not an element.
Question 9. Two chemical species X and Y combine together to form a product P which contains both X and Y: X + Y → P. X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
a) (i), (ii) and (iii)
b) (i), (ii) and (iv)
c) (ii), (iii) and (iv)
d) (i), (iii) and (iv)
Answer:
d) (i), (iii) and (iv) — If X and Y cannot be broken down, they are elements; their combination forms a compound with fixed composition.
