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Q1. Read the assertion and reason.
Assertion (A): Filter paper is a better choice than ordinary cloth to clean very muddy pond water.
Reason (R): The pores in filter paper are finer than the spaces between woven threads in cloth.
Choose the correct option.
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Q2. Exercise Q9 — A mixture contains potatoes, salt and sawdust. Consider these steps for separating it:
I. Handpick the potatoes from the mixture.
II. Add water and stir; the sawdust floats and is scooped out, salt dissolves.
III. Evaporate the salt solution to recover the salt.
Which are correct steps in this procedure?
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Q3. A bottle holds a mixture of mustard oil and water. The mixture has been left undisturbed for some time. Which separation method is most appropriate, and why?
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Q4. Exercise Q4(i) statement: 'Salt can be separated from salt solution by keeping it under the Sun.' This statement is best judged as
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Q5. Exercise Q5 (matching). Match the mixtures (Column I) with the method (Column II).
I. Gram flour mixed with black gram
II. Chalk powder mixed with water
III. Iron powder mixed with sawdust
The correct order I–II–III is
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Q6. 'Think like a scientist' gives a mixture of iron nails, sand, black pepper, common salt and water. Consider these first steps:
I. Use a magnet to remove the iron nails.
II. Filter the mixture so that sand stays as residue and salt water becomes the filtrate.
III. Begin by evaporating the water from the mixture.
Which are sensible first steps in the chapter's procedure?
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Q7. Read the assertion and reason.
Assertion (A): Threshing and winnowing achieve the same separation in the same step.
Reason (R): Both methods are used by farmers to obtain clean grains from harvested crops.
Choose the correct option.
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Q8. Exercise Q6 asks when decantation, not filtration, separates solids from liquids. Consider these situations:
I. Heavier insoluble solid has settled at the bottom and only a small amount of clear liquid is to be poured off carefully.
II. The liquid contains very fine, suspended particles that do not settle.
III. Filter paper or cloth is not available at the moment of separation.
When would decantation be preferred over filtration?
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Q9. Exercise Q10 'Intelligent Leela' — Leela fetches muddy pond water. She first lets it stand, then filters it through muslin cloth, then boils it for ten minutes in a covered pan, then filters it again. The boiling step in her sequence mainly
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Q10. In Activity 9.3 the teacher heats salt solution in a china dish over a spirit lamp using a wire gauze. After the dish is allowed to cool, salt is felt by touch on the dish. The wire gauze in this set-up mainly
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Q11. Read three claims about Leela's 'filter — boil — filter again' sequence for pond water.
I. The second filtration is needed because boiling can leave a fresh residue (scum) that the first cloth did not catch.
II. Boiling between two filtrations is needed to evaporate dissolved salts from the water.
III. Multi-step procedures are used when a mixture has more than two components or impurities of different sizes.
Which are correct?
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Q12. Read the assertion and reason.
Assertion (A): A mixture having more than two components usually cannot be separated by a single method.
Reason (R): Each separation method works on a single physical property, and components of a mixed sample may differ in many properties.
Choose the correct option.
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Q13. The 'More to know!' box notes that materials other than filter paper can act as filters. Consider these statements:
I. Cotton can serve as a filter for trapping coarse impurities.
II. Charcoal can be used as a filter material in a water-cleaning model.
III. Sand can be used as a filter layer to hold back fine mud particles.
Which are correct?
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Q14. Read the assertion and reason.
Assertion (A): When designing a multi-step separation, the order of methods is often as important as the choice of methods.
Reason (R): Choosing the wrong first step can change a sample so that a later method no longer works on a target component.
Choose the correct option.
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Q15. Exercise Q8 — During the COVID-19 pandemic, masks were widely worn. Most masks are made of layers of cloth or non-woven fibre. The chapter expects students to link the mask to which separation method, and why?
