MP Board Solutions Class 9 Science Chapter 2 – Is Matter Around Us Pure

Is Matter Around Us Pure – Important Questions with Answers

1. Define solution with example.
Answer: A homogeneous mixture of substances.
Example: Salt in water.

2. Differentiate homogeneous and heterogeneous mixtures.
Answer:

• Homogeneous mixtures are uniform (e.g., sugar solution).

• Heterogeneous mixtures are non-uniform (e.g., oil and water).

3. Define colloid with example.
Answer: A mixture with medium-sized particles that don’t settle.
Example: Milk.

4. What is the Tyndall effect? Give one example.
Answer: Light scattering by colloidal particles.
Example: Fog.

5. Name two methods to separate mixtures.
Answer: Filtration and evaporation.

6. What is distillation? When is it used?
Answer: Distillation separates liquids based on boiling points.
Used to obtain pure water from salt water.

7. Explain chromatography with one application.
Answer: It separates mixture components based on movement on a medium.
Application: Separating ink pigments.

8. Difference among solution, colloid, and suspension.
Answer:

• Solution: Clear, particles <1 nm, no settling.

• Colloid: Cloudy, particles 1–1000 nm, no settling, shows Tyndall effect.

• Suspension: Particles >1000 nm, settle on standing.

9. Define alloy and state whether it is pure.
Answer: Homogeneous mix of metals; not a pure substance.

10. Why can mixtures be separated physically but compounds cannot?
Answer: Mixtures are physically combined; compounds are chemically bonded.

11. Define solute and solvent.
Answer: Solute is dissolved substance; solvent dissolves the solute.

12. Why is water called a universal solvent?
Answer: Because many substances dissolve in water.

13. Define suspension. Give a characteristic.
Answer: A heterogeneous mixture whose particles settle on standing; visible particles.

14. Differentiate filtration and centrifugation.
Answer: Filtration uses gravity; centrifugation uses centrifugal force for separation.

15. When is evaporation used?
Answer: To separate a non-volatile solute and remove the solvent.

16. When is distillation preferred over evaporation?
Answer: To collect both liquid and solute, especially when solvents have different boiling points.

17. What is precipitation? Give example.
Answer: Formation of an insoluble solid.
Example: Mixing solutions of barium chloride and sulfuric acid produces barium sulfate precipitate.

18. Define crystallization.
Answer: Recovery of pure crystals from a saturated solution by evaporation.

19. What is chromatography used for in food testing?
Answer: To detect food dyes and adulterants.

20. Define purity test for any substance.
Answer: Checking fixed melting or boiling point indicates purity.

21. What are isomers? Give an example.
Answer: Compounds with same formula but different structures.
Example: Ethanol (C₂H₅OH) and dimethyl ether (CH₃OCH₃).

22. What is the composition of air?
Answer: Approx. 78 % nitrogen, 21 % oxygen, 1 % other gases.

23. Is tap water pure? Why not?
Answer: No; it contains dissolved impurities and minerals.

24. What is molecular mass?
Answer: Sum of atomic masses in a molecule.

25. Define chromatography and mention two types.
Answer: Technique to separate mixtures.
Types: Paper chromatography and thin-layer chromatography.