Methods of Separation in Everyday Life

Correct Option: (ii) Sorting

Handpicking is used to manually sort and pick out unwanted or desired components from a mixture based on differences in size, colour, and shape. For example, removing small stones from pulses by hand is a form of sorting. It does not involve any liquid separation (filtration/decantation) or heating (evaporation).

Correct Option: (iii) Cream from milk

Churning is the process of vigorously stirring or agitating a liquid to separate components of different densities. Curd is churned to separate butter (cream/fat) from it. This is a traditional method widely used in Indian households. The other options involve different separation methods such as decantation, sedimentation, or industrial processes.

Correct Option: (iii) Pore size

Filtration works on the principle that a filter (such as filter paper, cloth, or sand) has pores of a specific size. Particles larger than the pore size are retained as residue, while smaller particles and the liquid pass through as filtrate. The pore size determines what gets separated, making it the most essential factor in filtration.

(i) True [T]

When salt solution is kept under the Sun, the water evaporates due to heat from sunlight, leaving behind the solid salt. This is the principle of evaporation used in salt pans.

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(ii) True [T]

Handpicking is a slow, manual process. It is practical and efficient only when the quantity of the component to be removed is small (e.g., removing a few stones from pulses). If the quantity is large, it becomes very time-consuming and impractical.

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(iii) False [F]

Reason: Threshing is the process of beating stalks to separate grains from them. Puffed rice and rice grains are already separated from their stalks; they are both solid components of different sizes and densities.

Correction: A mixture of puffed rice and rice grains can be separated by winnowing (since puffed rice is lighter and gets blown away by air/wind) or by sieving (based on difference in size).

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(iv) True [T]

Mustard oil and lemon water are two immiscible liquids (they do not dissolve in each other). Oil, being lighter, forms a separate layer on top of water. By carefully tilting the vessel, the water layer can be poured out, separating the two liquids. This process is called decantation.

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(v) False [F]

Reason: Sieving is used to separate solid mixtures based on differences in particle size. Rice flour particles are extremely fine and would pass through the pores of a sieve along with water; sieving cannot separate a dissolved or suspended solid from a liquid effectively in this case.

Correction: A mixture of rice flour and water can be separated by filtration (using filter paper or a fine cloth to retain the flour particles while water passes through).

Given: Mixtures in Column I are to be matched with appropriate separation methods in Column II.

Concept Used: Each separation method is chosen based on the physical properties of the components — size, magnetic nature, solubility, density, etc.

| Column I | Column II |
|---|---|
| (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 |

Reasoning:
- (i) → (d) Sieving: Gram flour has very fine particles while black gram is larger; a sieve separates them based on particle size.
- (ii) → (e) Filtration: Chalk powder is insoluble in water; it can be separated using filter paper which retains chalk as residue.
- (iii) → (a) Handpicking: Corn and potatoes are large, easily distinguishable objects that can be manually sorted.
- (iv) → (b) Magnetic separation: Iron powder is magnetic; a magnet attracts and separates it from non-magnetic sawdust.
- (v) → (c) Decantation: Oil and water are immiscible; oil floats on water and can be separated by carefully pouring (decanting) the water layer.