CBSE Class 6 Science Advanced Chemistry Matter and Its Segregation MCQs Set 02

Answer: (b) Decantation, filtration, evaporation

Explanation:
1. P is a liquid that does not mix with water and floats or sinks as a separate layer, so it can be poured off: decantation.
2. R is small, heavy and insoluble: after the mixture is settled, it is held back on a filter: filtration.
3. Q is dissolved in the water, so it is got back by evaporation.
4. This is option (b).

Teacher's Note:
1. Choose the method by asking whether each part is liquid, insoluble or dissolved.
2. A dissolved solid is always recovered by evaporating the solvent.

Answer: (a) Kidney beans and chick peas

Explanation:
1. Winnowing separates a light part from a heavy part using wind.
2. Wafers are lighter than biscuits, rice flakes are lighter than corn, and sawdust is lighter than sand.
3. Kidney beans and chick peas are about equally heavy, so wind cannot separate them: (a).

Teacher's Note:
1. The two parts must differ clearly in weight.
2. Beans of similar size and weight would be picked out by hand.

Answer: (b) P, R, Q, S

Explanation:
1. Towel P hangs on a rainy day at 22°C. The air is damp and cool, so evaporation is slowest and P takes the longest.
2. Towels R and Q are at 35°C, but they are folded, so less of the cloth is exposed to air. R has more folds than Q, so R dries more slowly than Q.
3. Towel S hangs open on a sunny day at 32°C, so it dries fastest.
4. Order, longest time first: P, R, Q, S, which is option (b).

Teacher's Note:
1. Evaporation is faster with higher temperature, more exposed surface and drier air.
2. Folding hides surface from the air.

Answer: (c) P, Q and R

Explanation:
1. A gas has no fixed volume of its own.
2. It spreads out to fill whatever container it is put in, however big or small.
3. So all of the oxygen can be held by P, Q and R: (c).

Teacher's Note:
1. Compare with a liquid, which has a fixed volume.
2. A gas fills its container; the container's size does not have to equal the gas's old volume.

Answer: (b) 2 and 3

Explanation:
1. Powder 1 is magnetic, so a magnet can separate it from the others.
2. Powder 4 is insoluble, so water can separate it from the soluble powders 2 and 3.
3. Powders 2 and 3 are both soluble in water and both non-magnetic. Neither water nor a magnet can separate them.
4. So the pair 2 and 3 is the hardest to separate: (b).

Teacher's Note:
1. For each pair, look for a property that is different: solubility, magnetism, colour.
2. The fewer differences a pair has, the harder it is to separate.

Answer: (d) a-v, b-iv, c-iii, d-i, e-ii

Explanation:
1. a. Flour and iron powder: the iron is pulled out by a magnet (v).
2. b. Pulses and rice flour: the flour passes through a sieve (iv).
3. c. Kidney beans and lady's fingers: large pieces, so hand picking (iii).
4. d. Coconut oil and water: the oil layer is poured off, decantation (i).
5. e. Sugar dissolved in water: evaporation (ii).
6. This gives a-v, b-iv, c-iii, d-i, e-ii, which is option (d).

Teacher's Note:
1. Match the easy pairs first and cross out options.
2. Dissolved solids need evaporation, never sieving.

Answer: (c) Ice is heavier than water

Explanation:
1. Particles in a gas are far apart, so (A) is correct.
2. A solid keeps both its shape and its volume, so (B) is correct.
3. Ice floats on water, so it is lighter (less dense) than water. Statement (C) is incorrect.
4. Matter can change from solid to liquid to gas and back, so (D) is correct.

Teacher's Note:
1. Ice floats in a glass of water, which is a quick check.
2. Read 'incorrect' carefully in the question.

Answer: (a) P-Sublimation; Q-Magnetic separation; R-Filtration; S-Evaporation

Explanation:
1. P gives camphor from the mixture. Camphor sublimes, so P is sublimation.
2. Q gives iron filings, so Q is magnetic separation.
3. R: water is added. Salt dissolves and sand does not, so sand is removed by filtration.
4. S: salt is recovered from the salt water by evaporation.
5. This is option (a).

Teacher's Note:
1. Follow the product that comes out at each arrow.
2. Camphor, iodine and ammonium chloride are the usual sublimers.

Answer: (b) Winnowing followed by magnetic separation

Explanation:
1. The particles have the same size and colour, so handpicking and sieving will not work.
2. Winnowing blows away the light Y, leaving X and Z.
3. A magnet then pulls out Z, leaving X.
4. So winnowing followed by magnetic separation: (b).

Teacher's Note:
1. List the differing property of each part: weight for Y, magnetism for Z.
2. Use one method for each property.

Answer: (a) i and iii

Explanation:
1. i. When no more salt dissolves the solution is saturated: correct.
2. ii. Milk and water are fully mixed liquids and cannot be filtered apart: wrong.
3. iii. Winnowing separates heavier and lighter parts: correct.
4. iv. Butter is obtained from milk by churning, not sieving: wrong.
5. Only i and iii are correct: (a).

Teacher's Note:
1. Test each match one by one.
2. Churning and centrifugation are used for cream and butter.

Answer: (b) The space in the flask is occupied by air.

Explanation:
1. The stopper seals the flask, so the air inside has no way out.
2. Air takes up space and so there is no room for water to enter.
3. The reason is that the space in the flask is occupied by air: (b).

Teacher's Note:
1. Air is matter: it has mass and occupies space.
2. If the seal were loose, air would escape and water would enter.

Answer: (c) Sand

Explanation:
1. The diagram shows filtration: the solid is held on the filter paper.
2. Salt and sugar dissolve in water, so they would go through the filter paper with the water.
3. Ice crystals melt in water. Sand is insoluble and stays on the paper: (c).

Teacher's Note:
1. Only an insoluble solid can be filtered out of water.
2. The solid on the paper is the residue.

Answer: (c) Element X is a solid and element Y is a gas.

Explanation:
1. In X the particles are packed tightly in a fixed pattern, so X is a solid.
2. In Y the particles are far apart and move about freely, so Y is a gas.
3. (A) and (B) are false because solid particles cannot move freely and a gas can be compressed. (D) is false because X is denser than Y.
4. Hence (c).

Teacher's Note:
1. Count how close the particles are in each box.
2. Tightly packed means solid; widely spread means gas.

Answer: (d) Sieving, evaporation, filtration and separating funnel.

Explanation:
1. W comes from a solid-in-solid mixture, which can be separated by sieving.
2. X comes from a soluble solid in a liquid, so it is recovered by evaporation.
3. Y comes from an insoluble solid in a liquid, so it is separated by filtration.
4. Z comes from immiscible liquids, which are separated using a separating funnel.
5. In (a), filtration is used for a soluble solid; in (b), sedimentation is used for a solid-solid mixture; in (c), winnowing is used for an insoluble solid in a liquid. All three are wrong, so only (d) fits.

Teacher's Note:
1. Work from the end of the flowchart: a dissolved solid needs evaporation, an insoluble solid needs filtration.
2. Immiscible liquids always go with the separating funnel.

Answer: (d) None of these

Explanation:
1. The three boxes are a solid (particles fixed in a pattern), a liquid (particles close but free) and a gas (particles far apart).
2. Energy is given out when matter changes to a state with less energy: freezing (liquid to solid, II), deposition (gas to solid, IV) and condensation (gas to liquid, VI).
3. So the processes that give out energy are II, IV and VI. I, III and V (melting, sublimation and evaporation) take in energy.
4. No option lists II, IV and VI, so the answer is none of these.

Teacher's Note:
1. Heating makes a state change forwards (solid to liquid to gas); cooling makes it go backwards.
2. Check the direction of every arrow before choosing.

Answer: (c) II, III and IV only

Explanation:
1. I is wrong: salt does not evaporate with water; only the water evaporates.
2. If too much salt was taken (II) or too little water was used (IV), the water became saturated and the extra salt could not dissolve.
3. That undissolved salt stayed with the sand and was thrown away (III).
4. So II, III and IV are the possible reasons: (c).

Teacher's Note:
1. Salt remains behind when water evaporates.
2. Think about a saturated solution: extra solute stays undissolved.