Very Short Answer Questions — Topic: Pure Substances & Mixtures
1. What is a pure substance? A substance with fixed composition and distinct properties (element or compound).
2. Give one example of an element. Oxygen (O₂).
3. Give one example of a compound. Water (H₂O).
4. How does a compound differ from a mixture? Compound has fixed composition and chemical bonds; mixture has variable composition and components retain properties.
5. Define mixture. A physical combination of two or more substances that can be separated by physical methods.
Topic: Types of Mixtures
6. What is a homogeneous mixture? A mixture with uniform composition throughout (a solution).
7. Give one example of a homogeneous mixture. Salt dissolved in water.
8. What is a heterogeneous mixture? A mixture with non-uniform composition; components can be seen separately.
9. Give one example of a heterogeneous mixture. Sand in water.
10. What is a suspension? A heterogeneous mixture with large particles that settle on standing (e.g., muddy water).
Topic: Colloids & Solutions
11. Define colloid. A mixture with particle size between solution and suspension; particles do not settle.
12. Give an example of a colloid. Milk.
13. What is a true solution? A homogeneous mixture with molecular or ionic sized particles that do not scatter light.
14. Give an example of a true solution. Sugar dissolved in water.
15. Do colloids show the Tyndall effect? Yes, colloids scatter light and show the Tyndall effect.
Topic: Tyndall Effect & Related Concepts
16. What is the Tyndall effect? Scattering of light by colloidal particles when a beam passes through the mixture.
17. Does a true solution show Tyndall effect? No, true solutions do not show the Tyndall effect.
18. How can you distinguish a colloid from a solution? Shine a beam of light — colloid shows Tyndall effect, solution does not.
19. Give one use of the Tyndall effect. To test whether a mixture is colloid or true solution.
20. Are aerosols colloids? Yes, aerosols (fog, smoke) are colloidal systems with gas dispersing liquid/solid.
Topic: Solute, Solvent & Saturation
21. Define solute. The substance that dissolves in a solvent to form a solution.
22. Define solvent. The substance in which solute dissolves (usually in larger amount).
23. What is a saturated solution? A solution containing the maximum amount of solute that can dissolve at a given temperature.
24. What happens if more solute is added to a saturated solution? The excess solute remains undissolved (precipitate).
25. Give an example of a saturated solution. A sugar solution in which no more sugar can dissolve at that temperature.
Topic: Separation Techniques — Basics
26. Why are mixtures separable by physical methods? Because components retain their physical properties and are not chemically bonded.
27. What property does filtration exploit? Particle size (insoluble solid vs liquid).
28. When is evaporation used? To obtain a solute from its solution by removing the solvent as vapor.
29. What is distillation used for? To separate liquids with different boiling points or to purify solvents.
30. Define fractional distillation. A distillation method using a fractionating column to separate miscible liquids with close boiling points.
Topic: Specific Separation Methods
31. How will you separate sand and water? By filtration.
32. How to separate salt from its solution? By evaporation or crystallization.
33. How to separate a mixture of iron filings and sulfur? Magnetic separation using a magnet to pull out iron.
34. How to separate camphor from salt? Sublimation (camphor sublimes on heating).
35. Which method separates pigments in ink? Paper chromatography.
Topic: Crystallization & Sublimation
36. What is crystallization? Formation of pure crystals from a saturated solution on cooling or evaporation.
37. How is crystallization better than simple evaporation? It yields purer solid crystals while evaporation may give impure residue.
38. What is sublimation? Conversion of a solid directly into vapour without passing through liquid state.
39. Give an example of a substance that sublimes. Camphor, ammonium chloride, iodine.
40. When is sublimation used? To separate substances that sublime from those that do not (e.g., ammonium chloride from sand).
Topic: Miscellaneous Quick Facts
41. Can mixtures have variable composition? Yes, mixtures do not have fixed composition.
42. Are compounds separable by physical methods? No, compounds require chemical methods to separate into elements.
43. Give one example of a colloid in daily life. Butter, milk, fog, whipped cream.
44. What separates blood components in labs? Centrifugation.
45. What property is exploited in chromatography? Differential affinity of components towards stationary and mobile phases.
Topic: Exam-oriented Short Reminders
46. How to identify a true solution in lab? It is transparent and does not show Tyndall effect.
47. Mention one safety tip while doing distillation. Ensure proper cooling and avoid overheating; use clamps and heat-resistant gloves.
48. What should you write when asked for steps to separate a mixture? State stepwise procedure, apparatus, and principle used.
49. Which method to separate oil and water? Separating funnel (decantation/immiscible liquid separation).
50. Why is understanding separation important? It helps obtain pure substances for analysis and practical uses; key exam topic in chemistry.
These Very Short Answer Questions and answers are prepared strictly as per the NCERT syllabus and tailored for CBSE Class 9 board exam practice.