Methods of Separation in Everyday Life
Complete, detailed solutions — every in-text prompt and every exercise question from the chapter, with the original textbook figures.
(Reflective question — a sample answer.)
Yes. Staying connected keeps our relationships with family and friends warm and strong — just like Malli and Valli’s family. We can keep in touch through phone calls, video calls, letters, text messages, and by visiting relatives during holidays and festivals.
Yes. Puffed rice is very light while chana dal is much heavier. So we can use winnowing — blow air across the mixture (or drop it in front of a fan). The light puffed rice is carried away by the air current while the heavier chana dal falls straight down, separating the two.
On rubbing: the thin, papery brown skin loosens and peels off the peanuts.
Can we separate the skin? Yes — the loose skins can be separated from the peanuts.
On blowing: the light peanut skins fly away while the heavier peanuts stay behind. So the removed peanut skins (lighter component) are blown away.
No, the two components do not fall at the same place. The heavier wheat grains fall straight down and form a heap near the platform, while the lighter husk is carried a little away by the wind and settles farther off.
The husk (lighter component) gets blown away.
Yes, the wind can separate the two because they differ in weight. This method is called winnowing.
In a closed room there is no natural breeze, so ordinary winnowing won’t work. We can create an artificial air current using a table fan, hand fan, or hair dryer (or simply by blowing hard). Pour the mixture slowly in front of the moving air — the light husk gets blown aside while the heavier rice grains drop straight down.
(Observation-based — a sample answer.)
Yes. At home, elders often toss rice or pulses in a soop (bamboo tray) or a plate in front of a fan or in a breeze so that the light husk and dust blow away and the clean, heavier grains remain. Separating chaff or dust from grains before cooking is everyday winnowing.
Holes: Yes, the holes of a sieve are usually all of the same (uniform) size.
If holes are larger than the substances: No, sieving will not work — both components would fall through the holes and nothing would be separated. The holes must be bigger than the fine particles (which pass) but smaller than the coarse particles (which stay back).
Size difference: Yes — particles that pass through the sieve are smaller (fine flour) than the particles that remain on the sieve (bran, small stones).
(Observation-based — a sample answer.)
Yes. At construction sites, workers throw sand against a slanting wire-mesh sieve. The fine sand passes through the mesh while the larger pebbles and stones stay back on it. This is sieving, used to separate solids of different sizes.
Yes. In hot weather we sweat, and sweat is a mixture of water with dissolved salts. When the sweat dries on the cloth, the water evaporates into the air but the salt is left behind on the cloth — appearing as white patches.
Yes, white patches appear after the paper dries.
What is left behind is the salt (a solid) — you can feel it by touching the paper. The water has evaporated into the surrounding air as water vapour, leaving the salt behind.
Yes — by combining evaporation with condensation (together called distillation).
Heat the salt solution: the water turns to vapour and rises (leaving the salt behind as residue). If this vapour is then cooled on a colder surface, it condenses back into liquid water. So we recover the salt as well as the pure water.
Yes, the figure answers the question. When water boils, steam rises and touches a cooler surface (like the lid), where it cools and turns back into water droplets. The change of vapour → liquid on cooling is called condensation.
Evaporation followed by condensation lets us recover both the salt and the water — this combined process is distillation.
Oil and water do not mix — oil is lighter and floats, forming a separate layer on top of the water. When left undisturbed the two form two clear layers, so we separate them by decantation: gently tilt/pour so the top oil layer runs off, or drain the lower water. (A separating funnel does this neatly.)
More layers give clearer water. Folding the cloth into several layers makes the effective pores smaller, so more mud and impurities are trapped. Using a fine muslin cloth folded into 3–4 layers works well.
However, cloth cannot remove very fine or dissolved impurities. For those, a filter with even smaller pores — such as filter paper — is needed.
An electric mixer / blender (mixie) — or an electric hand blender / electric churner. It churns the curd, separating the light butter that floats up and leaving buttermilk (chhach) behind.
(Discussion question — a sample answer.)
Soured milk (curd) can be churned to make butter and buttermilk (chhach), or gently heated to make paneer.
Separation methods: churning to obtain butter; and if making paneer, the soft solid is separated from the watery whey by filtration / decantation.
- (i)Filtration
- (ii)Sorting
- (iii)Evaporation
- (iv)Decantation
(ii) Sorting. Handpicking is used to pick out and sort unwanted items — such as small stones or husk — from grains, based on differences in their size, colour and shape. It is convenient only when the particles to be removed are present in small quantity and are large enough to pick by hand.
- (i)Oil from water
- (ii)Sand from water
- (iii)Cream from milk
- (iv)Oxygen from air
(iii) Cream from milk. During churning, the lighter fat (cream/butter) floats to the top and separates from the liquid buttermilk. Oil–water is separated by decantation, sand–water by sedimentation/filtration, and oxygen is not separated from air by churning.
- (i)Apparatus size
- (ii)Presence of air
- (iii)Pore size
- (iv)Temperature of the mixture
(iii) Pore size. Filtration works because the filter’s pores are small enough to hold back the solid particles while letting the liquid pass through. If the pores were larger than the particles, no separation would happen — so pore size is the key factor.
True (i) Salt can be separated from salt solution by keeping it under the Sun.
True. The Sun’s heat evaporates the water, leaving the salt behind (evaporation).
True (ii) Handpicking should be used only when the quantity of one component is less.
True. Handpicking is convenient only when the particles to be removed are few and can be easily picked by hand.
False (iii) A mixture of puffed rice and rice grains can be separated by threshing.
False. Threshing separates grains from stalks. Light puffed rice and heavier rice grains are separated by winnowing (blowing air).
True (iv) A mixture of mustard oil and lemon water can be separated by decantation.
True. Oil and water are immiscible and form separate layers; the lighter oil floats on top and can be poured off by decantation.
False (v) Sieving is used to separate a mixture of rice flour and water.
False. Rice flour in water forms a suspension and the fine flour would slip through a sieve. It is separated by filtration (or sedimentation & decantation). Sieving is only for solid–solid mixtures of different sizes.
| Column I (Mixture) | Column II (Method) | Reason |
|---|---|---|
| (i) Gram flour mixed with black gram | (d) Sieving | Fine flour passes; larger black gram stays on the sieve. |
| (ii) Chalk powder mixed with water | (e) Filtration | Chalk is an insoluble solid suspended in liquid — filtered out. |
| (iii) Corn mixed with potatoes | (a) Handpicking | Both are large and few, differing in size/shape — picked by hand. |
| (iv) Iron powder mixed with sawdust | (b) Magnetic separation | Iron is magnetic and is pulled out by a magnet. |
| (v) Oil mixed with water | (c) Decantation | Immiscible liquids form layers — the oil is poured/tilted off. |
Use decantation when the insoluble solid is heavy and settles quickly to the bottom (sedimentation), leaving a clear liquid on top that can simply be poured off — for example, settled mud/sand in water, tea leaves in tea, or while washing rice and pulses.
It is quick and needs no filter paper. Filtration is chosen instead when the particles are very fine and stay suspended (do not settle) and a cleaner separation is needed.
Yes — nasal hair acts as a natural filter. As we breathe in, the hair traps dust, pollen and germs from the air, stopping them from reaching the lungs while letting the air pass. This is just like filtration, where a filter lets a fluid through but holds back solid particles.
Masks are generally made of layers of cloth or fine non-woven synthetic fabric (such as polypropylene); surgical and N95 masks have fine fibrous filter layers.
Their role is filtration — the fine pores/fibres trap tiny droplets, dust and germs from the air we breathe in and out, reducing the spread of infection.
The mixture has three parts: potatoes (large insoluble solid), salt (soluble solid) and sawdust (light insoluble solid). We combine three methods:
Separating potatoes, salt & sawdust — stepwise
The correct choices are shown in bold:
Before her father felt thirsty, she went to the nearby pond to fetch some water. She noticed the water was muddy and unfit for drinking. To purify it, she kept it for some time and then filtered the muddy water using a piece of muslin cloth. Leela then boiled the water for about 10 minutes in a covered pan. After boiling, she filtered it again and made it fit for drinking.
Methods Leela used: sedimentation & decantation (letting mud settle), filtration (muslin cloth), and boiling to kill germs.
| Method (Tank 1) | Matches with (Tank 2) | |
|---|---|---|
| Filtration | → | insoluble particles get filtered as residue |
| Decantation | → | mixture of oil and water (poured off in layers) |
| Condensation | → | conversion of water vapour into its liquid state |
| Handpicking | → | larger particles are handpicked |
| Churning | → | extract butter from curd |
| Evaporation | → | separate salt from seawater |
| Winnowing | → | lighter component of mixture is separated by blowing air |
| Sedimentation | → | heavier particles settle down |
| Sieving | → | difference in size of solid particles |
| Threshing | → | beating stalks to remove grains |
| Magnetic separation | → | difference in magnetic properties |
A mixture with many components needs several methods used in the right order: