NCERT Solutions Class 6 Science Chapter 9: Methods of Separation in Everyday Life

Answers to all 10 questions of “Let us enhance our learning” at the end of Chapter 9, Methods of Separation in Everyday Life, in Curiosity, followed by the in-text activities and games. Short notes: Chapter 9 notes.

Question 1

What purpose does handpicking serve in the process of separation? (i) Filtration (ii) Sorting (iii) Evaporation (iv) Decantation

Answer: (ii) Sorting. Handpicking sorts out unwanted pieces, like stones and husk, from a mixture by hand, using differences in size, colour and shape.

Question 2

Which of the following substances are commonly separated using the churning method? (i) Oil from water (ii) Sand from water (iii) Cream from milk (iv) Oxygen from air

Answer: (iii) Cream from milk. Churning fat-rich milk or curd makes the lighter fat (cream or butter) separate and collect at the top. Oil and water are separated by decantation, and sand and water by sedimentation, decantation or filtration.

Question 3

Which factor is usually essential for the filtration? (i) Apparatus size (ii) Presence of air (iii) Pore size (iv) Temperature of the mixture

Answer: (iii) Pore size. A filter holds back particles bigger than its pores and lets the liquid through. That is why a strainer stops tea leaves but not mud, while filter paper, with very fine pores, stops mud too.

Question 4

State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s).

• (i) Salt can be separated from salt solution by keeping it under the Sun. True. The heat of the Sun makes the water evaporate, and the salt is left behind, as in shallow pits of seawater.
• (ii) Handpicking should be used only when the quantity of one component is less. True. Handpicking is convenient only when the pieces to be removed are few and easy to pick. For a large amount, like husk mixed with grains, winnowing is used instead.
• (iii) A mixture of puffed rice and rice grains can be separated by threshing. False. Threshing separates grains from stalks. Correct: A mixture of puffed rice and rice grains can be separated by winnowing, because puffed rice is much lighter and is blown away.
• (iv) A mixture of mustard oil and lemon water can be separated by decantation. True. Oil does not mix with water and forms a separate layer on top, so it can be poured off carefully.
• (v) Sieving is used to separate a mixture of rice flour and water. False. Sieving separates solid particles of different sizes. Correct: A mixture of rice flour and water can be separated by sedimentation and decantation, followed by filtration, because the flour does not dissolve.

Question 5

Match the mixtures in Column I with their method of separation in Column II.

Column I (mixture)	Column II (method)
(i) Gram flour mixed with black gram	(d) Sieving
(ii) Chalk powder mixed with water	(e) Filtration
(iii) Corn mixed with potatoes	(a) Handpicking
(iv) Iron powder mixed with sawdust	(b) Magnetic separation
(v) Oil mixed with water	(c) Decantation

Question 6

In what situations would you use decantation instead of filtration to separate solids from liquids?

Answer: Decantation is better when:

• the solid is heavy and settles quickly, like sand or soil in water, or rice and pulses being washed;
• there is a large amount of liquid and a rough, quick separation is enough;
• the liquid is to be poured off and the solid kept, as when washing rice;
• two liquids do not mix, like oil and water, which no filter can separate.

Filtration is needed when the particles are fine and stay floating, or when every bit of the solid must be removed.

Question 7

Can you relate the presence of nasal hair to any separation process?

Answer: Yes, to filtration. The hairs in our nose act like a filter: they trap dust and other particles in the air we breathe in and let the air pass through to the lungs.

Question 8

During the COVID-19 pandemic, all of us wore masks. Generally, what material are they made of? What is the role of these masks?

Answer: Masks are usually made of layers of cloth, such as cotton, or of special fibre materials. They work as filters: the tiny spaces between their fibres let air pass but stop most of the droplets, dust and germs, protecting both the wearer and the people around.

Question 9

A mixture containing potatoes, salt and sawdust has been given to you. Outline a stepwise procedure for separating each component from this mixture.

Answer:

1. Handpick the potatoes, which are big and easy to see.
2. Put the salt and sawdust into water and stir. The salt dissolves; the sawdust does not.
3. Filter the mixture (or skim off the floating sawdust). The sawdust stays on the filter as residue; dry it.
4. Evaporate the filtrate (salt solution) by heating or keeping it in the Sun. The salt is left behind.

Question 10

Read the story ‘Intelligent Leela’ and tick the most appropriate options. Provide a suitable title.

Answer: The correct choices are: thirsty, water, unfit, filtered, muslin cloth, boiled, cooling, filtered, fit. So the story reads: she went to fetch water before her father felt thirsty; the muddy water was unfit for drinking; she let it settle and then filtered it through muslin cloth; she boiled it for about 10 minutes in a covered pan; after cooling, she filtered it again and made it fit for drinking.

Possible title: Leela Makes Muddy Water Safe (or Clean Water for Father).

In-text activities and questions

Peanut skins and puffed rice (pages 165–166)

• Activity 9.1: Rubbing roasted peanuts loosens their skins. When you blow, the light skins fly away and the heavier peanuts stay. Blowing air separates the lighter part from the heavier part.
• Wheat grains and husk (Fig. 9.4): they do not fall at the same place. The wind blows the husk away, and the grains fall near the farmer, so the wind can separate them.
• Puffed rice mixed with chana dal: blow gently or winnow it; the light puffed rice is carried away from the heavier dal.
• Valli cannot winnow in a closed room: use a fan or blow air over the soop.

The sieve (page 167)

The holes of a sieve are usually all the same size. Sieving will not work if the holes are larger than all the particles, because everything will fall through. The particles that pass through are smaller than the holes, and those that stay are bigger.

What is Sabarmati Ashram famous for? It is linked with the Namak Satyagraha, the Dandi March. Extra: the ashram in Ahmedabad was Mahatma Gandhi’s home for many years, and in 1930 he set out from there on the Dandi March, walking to the sea at Dandi to make salt from seawater in protest against the British law on salt.

Salt from salt water (pages 168–169)

• Water bodies with salt: the seas, and Sambhar Lake in Rajasthan. Extra: Pachpadra and Didwana in Rajasthan are also salt lakes.
• White patches on dark clothes in summer: sweat contains salts dissolved in water; when the sweat evaporates, the salts are left as white patches.
• Activity 9.2: the patches on the black paper are salt. The water evaporated into the air.
• Activity 9.3: heating the salt solution in a china dish boils the water away and leaves salt in the dish.
• Getting back both salt and water: cool the vapour so that it condenses into water in another container; the process is condensation.

Tea, oil and water, and cloth filters (pages 170–172)

• Oil and water: they form two layers when left undisturbed, so the oil can be separated by decantation.
• How many layers of cloth? Try 2, then 4, then 8 layers. More layers make the gaps smaller and the water clearer, but the water flows more slowly. Fold the cloth until the filtrate looks clear.
• Activity 9.5, a water filter model: cut the bottom off a plastic bottle and turn it upside down. Put a piece of cloth or cotton at the neck, then layers of charcoal, fine sand, coarse sand and small pebbles. Pour the pond water in from the top and collect it below. The water will look clearer, but it must still be boiled before drinking.
• Sour milk: it can be used to make paneer. The solid part is separated from the liquid (whey) by straining it through a muslin cloth, which is filtration.

Churning and magnets (pages 173–175)

• Electric appliance for buttermilk: a mixer or blender, which churns the curd.
• The carpenter’s nails: a magnet was used, so the method is magnetic separation.

Activity 9.6: two baskets

Basket 1, to remove a part that is not useful: stones from pulses (1), green chillies from cooked dalia or poha (3), seeds from watermelon (4).

Basket 2, to separate two useful parts: butter from curd (2), sawdust and iron nails from building material (5), marigolds from other flowers (6), pebbles from sand (7), coconut pieces from rice flour (8), oil from water (9), salt from salt solution (10).

Some items can go in either basket if you explain why: for example, oil from water goes in Basket 1 if the water is waste.

Game: Wise Fish

Tank 1 (method)	Tank 2 (matching slip)
Handpicking	larger particles are handpicked
Threshing	beating stalks to remove grains
Winnowing	lighter component is separated by blowing air
Sieving	difference in size of solid particles
Sedimentation	heavier particles settle down
Decantation	mixture of oil and water
Filtration	insoluble particles get filtered as residue
Evaporation	separate salt from seawater
Condensation	conversion of water vapour into its liquid state
Churning	extract butter from curd
Magnetic separation	difference in magnetic properties

Think like a scientist (page 181)

For a mixture of iron nails, sand, black pepper, stones, common salt and water:

1. Pull out the iron nails with a magnet.
2. Handpick the stones and black pepper, which are big and easy to see.
3. Let the sand settle and decant the salty water, then filter it to remove the last of the sand.
4. Evaporate the filtrate to get the salt. To keep the water too, condense the vapour.