MCQs — Topic: Pure Substances & Mixtures (1–6)
1. Which of the following is a pure substance?
Answer: C. Copper
Copper is an element with fixed composition; air, milk and sea water are mixtures.
2. Which of the following is a compound?
Answer: C. Sodium chloride
Sodium chloride (NaCl) is a compound formed by chemical combination of sodium and chlorine in fixed ratio.
3. A substance with uniform composition throughout is called:
Answer: B. Homogeneous mixture
Homogeneous mixtures (solutions) have uniform composition throughout; compounds also are uniform but the general term for mixtures is homogeneous.
4. Which of these is a heterogeneous mixture?
Answer: C. Sand in water
Sand in water is non-uniform and particles can be seen; other options are homogeneous.
5. Which of these statements is true about compounds?
Answer: C. Have fixed composition and distinct properties
Compounds have fixed composition and require chemical methods to separate into elements.
6. Which of the following is correct about mixtures?
Answer: A. Components retain their properties
In mixtures, components retain their identity and properties and can be separated by physical methods; composition is not fixed.
MCQs — Topic: Solutions, Colloids & Suspensions (7–12)
7. Which system will show the Tyndall effect?
Answer: C. Milk
Milk is a colloid and scatters light (Tyndall effect); true solutions like salt or sugar solution do not scatter light.
8. Which of the following will settle down on standing?
Answer: B. Suspension
Suspension has large particles that settle under gravity; colloids do not settle; solutions are homogeneous.
9. Which of these is an example of aerosol?
Answer: B. Fog
Fog is liquid droplets dispersed in gas (air) — an aerosol (colloidal system).
10. Which of the following is NOT true for a true solution?
Answer: B. Shows Tyndall effect
True solutions do not show Tyndall effect because particles are too small to scatter light.
11. Which of the following pairs is correctly matched?
Answer: C. Solution — particles at molecular level
Solutions have molecular/ionic sized particles; colloids do not settle and are not chemically combined.
MCQs — Topic: Solute, Solvent & Saturation (12–18)
12. In a solution, the component present in larger amount is called:
Answer: B. Solvent
Solvent is the medium in which solute dissolves and is usually present in larger amount.
13. A saturated solution is one in which:
Answer: B. Maximum solute has dissolved at given temperature
Saturated solution contains the maximum amount of solute that can dissolve at that temperature; excess remains undissolved.
14. Which factor generally increases solubility of solids in liquids?
Answer: B. Increase in temperature
Most solid solutes dissolve better at higher temperatures (exceptions exist).
15. When some more solute is added to a saturated solution at the same temperature, what happens?
Answer: C. Excess remains undissolved
Saturated solution cannot dissolve more solute at same temperature; excess remains as undissolved solid.
16. Which of the following statements about gas solubility in liquids is true?
Answer: B. Gas solubility decreases with temperature
As temperature rises, dissolved gases escape more readily, reducing solubility.
MCQs — Topic: Separation Techniques (17–26)
17. To separate an insoluble solid from a liquid, which technique is commonly used?
Answer: B. Filtration
Filtration uses porous medium to separate insoluble solids from liquids based on particle size.
18. Which method is suitable for separating a soluble solid from its solution to obtain the solid?
Answer: B. Evaporation
Evaporation removes the solvent leaving behind the dissolved solid; crystallization is preferred for purity.
19. Which technique separates components based on boiling points?
Answer: C. Distillation
Distillation separates liquids by differences in volatility/boiling points.
20. Paper chromatography separates substances based on:
Answer: B. Differential affinity for stationary and mobile phases
Chromatography separates components based on how strongly they interact with stationary phase (paper) vs mobile phase (solvent).
21. Which method would you use to separate camphor from a mixture with salt?
Answer: B. Sublimation
Camphor sublimes (solid to vapour) and can be collected by condensation; salt does not sublime.
22. In laboratory separation of blood components, which technique is preferred?
Answer: B. Centrifugation
Centrifugation uses centrifugal force to separate components based on density differences rapidly.
23. Which of the following is true about crystallization?
Answer: B. It is used to obtain pure crystals from a saturated solution
Crystallization forms pure crystals by controlled cooling or slow evaporation; impurities remain in mother liquor.
24. Fractional distillation is preferred over simple distillation when:
Answer: C. Components have close boiling points
Fractionating column provides repeated vaporization-condensation cycles improving separation for liquids with close boiling points.
MCQs — Topic: Applications & Real-life (27–30)
25. Which industrial process uses fractional distillation extensively?
Answer: B. Oil refining (petroleum)
Crude oil is separated into fractions like petrol, diesel, kerosene using fractional distillation in oil refineries.
26. Which household method can be used to separate a mixture of oil and water?
Answer: C. Separating funnel/decantation
Oil and water are immiscible; they form layers and can be separated by decantation or using a separating funnel.
27. Which technique is best for purifying drinking water contaminated with dissolved salts?
Answer: B. Distillation or reverse osmosis
Distillation removes dissolved salts by vaporizing and condensing pure water; reverse osmosis uses membranes to remove ions.
28. In ink chromatography the ratio of distance travelled by solute to solvent front is called:
Answer: A. Retention factor (Rf)
Rf = distance moved by solute / distance moved by solvent front; used for identification in chromatography.
29. Which among the following is NOT a method of separation?
Answer: C. Melting
Melting changes solid to liquid but does not separate components; other options are separation techniques.
30. Which of the following statements is correct?
Answer: C. Chromatography can separate complex mixtures
Chromatography is versatile for separating complex mixtures; other statements are incorrect (colloids do not pass simple filters, suspensions settle, compounds require chemical methods).
These MCQs and detailed explanations are prepared strictly as per NCERT syllabus and tailored for CBSE Class 9 board exam practice. Practice regularly for speed and accuracy.