Short Answer Questions (1–10): Basics of Matter & Pure Substances
1. Define matter.
Matter is anything that has mass and occupies space.
2. What is a pure substance?
A pure substance has a fixed composition and definite properties; it may be an element or a compound.
3. Explain an element with an example.
An element consists of only one kind of atoms and cannot be broken down chemically; e.g., iron (Fe).
4. What is a compound? Give an example.
A compound is formed by chemical combination of elements in fixed ratio; e.g., water (H₂O).
5. How is a compound different from an element?
Elements are simplest forms of matter made of one type of atom; compounds contain two or more elements chemically bonded with new properties.
6. Can a pure substance be separated by physical methods?
No. Pure substances require chemical methods to separate into constituent elements (if compound).
7. Give two everyday examples of compounds.
Water (H₂O) and sodium chloride (NaCl).
8. Why is distilled water considered a pure substance?
Because it contains only water molecules with impurities and dissolved salts removed by distillation.
9. What are fundamental properties of a pure substance?
Fixed melting/boiling points, constant composition, and uniform properties throughout.
10. Name the physical states of matter.
Solid, liquid and gas.
Short Answer Questions (11–20): Mixtures & Their Types
11. Define mixture.
A mixture is a physical combination of two or more substances where each retains its identity and can be separated by physical methods.
12. What is a homogeneous mixture?
A mixture with uniform composition and properties throughout, also called a solution.
13. Give two examples of homogeneous mixtures.
Salt solution and sugar solution.
14. What is a heterogeneous mixture?
A mixture where components are not uniformly distributed and different parts can be visually distinguished.
15. Give two examples of heterogeneous mixtures.
Sand in water and a salad mixture.
16. Define suspension.
A suspension is a heterogeneous mixture with large particles that settle on standing, e.g., muddy water.
17. What is a colloid?
A colloid is a mixture with intermediate particle size whose particles do not settle and scatter light (show Tyndall effect), e.g., milk.
18. How do colloids differ from suspensions?
Colloidal particles do not settle and are smaller; suspension particles are larger and settle on standing.
19. What is meant by solute and solvent?
Solute is the substance dissolved; solvent is the substance in which the solute dissolves (usually present in larger amount).
20. Give one example each of a colloid and a suspension.
Colloid: milk. Suspension: chalk powder in water.
Short Answer Questions (21–30): Properties & Tests
21. What is the Tyndall effect?
Tyndall effect is scattering of light by colloidal particles, making a light beam visible in a colloid but not in a true solution.
22. How can you distinguish between a solution and a colloid?
By Tyndall effect: colloids scatter light (beam visible); true solutions do not.
23. Does a colloid settle on standing?
No, colloidal particles do not settle on standing.
24. What happens when more solute is added to a saturated solution?
The excess solute remains undissolved and may precipitate out.
25. Define dilute and concentrated solutions.
Dilute solution has relatively small amount of solute in solvent; concentrated has large amount of solute.
26. How does temperature affect solubility of solids?
Generally, solubility of solids in liquids increases with temperature, though exceptions exist.
27. Give one laboratory test to show a mixture is colloidal.
Shine a beam of light through the mixture; visible scattering indicates a colloid (Tyndall effect).
28. Can gases form colloids?
Yes; aerosols are colloids where gas disperses liquid or solid particles (e.g., fog, smoke).
29. What is meant by 'pure' in chemistry context?
In chemistry, 'pure' means composed of only one substance with uniform properties and fixed composition.
30. Why are mixtures often preferred in daily life?
Mixtures provide flexibility in composition and combine desirable properties of components, e.g., alloys or food recipes.
Short Answer Questions (31–40): Separation Techniques
31. Why can mixtures be separated by physical methods?
Because components retain their original physical properties and are not chemically bonded.
32. Describe filtration with an example.
Filtration uses a porous medium to separate an insoluble solid from a liquid, e.g., separating sand from water using filter paper.
33. When is evaporation used to separate mixtures?
Evaporation is used to obtain a dissolved solid (solute) by evaporating the solvent, as in obtaining salt from saltwater.
34. What is simple distillation used for?
Simple distillation separates a solvent from a non-volatile solute or liquids with widely different boiling points.
35. Explain fractional distillation briefly.
Fractional distillation separates miscible liquids with closer boiling points using a fractionating column that gives repeated condensation–vaporization cycles.
36. How does chromatography separate substances?
Chromatography separates based on different affinities of components for stationary and mobile phases, causing different travel rates.
37. What is sublimation and when is it used?
Sublimation is the direct transition from solid to gas and is used to separate substances like camphor or ammonium chloride from non-subliming solids.
38. Give one use of centrifugation.
Centrifugation separates fine suspended particles by applying centrifugal force, e.g., separating blood components in laboratories.
39. How is crystallization different from evaporation?
Crystallization yields purer solid by controlled cooling or evaporation to form well-defined crystals; evaporation may leave impure residues.
40. Which method would you use to separate oil and water?
Use a separating funnel or decantation since oil and water are immiscible liquids with different densities.
Short Answer Questions (41–50): Applications & Exam Tips
41. How will you separate a mixture of sand, salt and ammonium chloride?
Sublime ammonium chloride by heating and collect it; dissolve salt in water, filter to remove sand, then evaporate the filtrate to obtain salt.
42. How can iron filings be separated from sand?
Use a magnet to attract and remove iron filings (magnetic separation).
43. Why is paper chromatography useful in analysis?
It separates components of mixtures like inks and pigments and helps identify substances based on their travel distances (Rf values).
44. State one safety precaution during distillation.
Ensure the setup is clamped securely and use cooling water in the condenser; avoid overheating to prevent bumping.
45. What should you mention when answering separation procedure questions in exams?
Mention the step-by-step method, apparatus, principle used, and the reason for choosing that method.
46. Give an example where fractional distillation is industrially important.
Fractional distillation is used in oil refineries to separate crude oil into petrol, diesel, kerosene and other fractions.
47. How do you obtain pure crystals from a solution?
Prepare a saturated solution, allow slow cooling or controlled evaporation so pure crystals form (crystallization), then filter and dry them.
48. What is the role of solubility in separation?
Differences in solubility help choose methods—soluble components can be separated by dissolving and filtering while insoluble ones are filtered directly.
49. Mention one environmental example of a colloid.
Fog is an environmental colloid consisting of tiny water droplets dispersed in air.
50. How can practicing these questions help in board exams?
They strengthen conceptual clarity, improve speed in writing concise answers, and prepare students to tackle NCERT-style questions effectively.
These Short Answer Questions and answers are prepared strictly as per the NCERT syllabus and tailored for CBSE Class 9 board exam standards.