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.

Given: We need to identify situations where decantation is preferred over filtration.

Concept:
- Decantation is the process of gently pouring out the liquid from a container after the heavier insoluble solid has settled at the bottom (sedimentation).
- Filtration uses a filter medium (like filter paper or cloth) to separate insoluble solids from a liquid.

Situations where decantation is preferred:

1. When the solid particles are heavy and settle quickly at the bottom of the liquid — for example, separating sand or mud from water after it has been allowed to stand undisturbed for some time.

2. When the quantity of solid is large and using filter paper would be slow or impractical.

3. When a filter medium is not available — decantation can be done simply by tilting the vessel carefully.

4. When the solid particles are too coarse to require a fine filter — e.g., separating rice from water after washing.

Conclusion: Decantation is preferred when the insoluble solid is heavier and settles at the bottom easily, making it convenient to pour off the liquid without the need for a filter.

Given: We need to relate nasal hair to a method of separation.

Concept: Filtration is the process of separating insoluble solid particles from a liquid (or gas) using a filter that has fine pores.

Relation:

The nasal hair present inside our nose acts as a natural filter. When we breathe in air, the nasal hair traps dust particles, pollen, germs, and other large impurities present in the air. Only clean, filtered air passes through to the lungs.

This is similar to the process of filtration, where a filter medium (here, nasal hair) allows the fluid (air) to pass through while retaining the solid particles (dust, pollen, etc.).

Conclusion: The nasal hair performs the function of filtration — it filters the air we breathe by trapping harmful particles, just as filter paper traps mud particles while allowing water to pass through.

Given: We need to identify the material of masks and explain their role during COVID-19.

Material of Masks:
Masks used during COVID-19 were generally made of:
- Cloth/cotton (for simple reusable masks)
- Non-woven polypropylene fabric (for surgical masks)
- Multiple layers of fine filter material (for N95 masks)

These materials have very fine pores that act as a filter medium.

Role of Masks:

Masks work on the principle of filtration. The fine pores in the mask material:
1. Trap large respiratory droplets containing the COVID-19 virus that are expelled when an infected person coughs, sneezes, or talks.
2. Prevent the wearer from inhaling virus-laden droplets from the surrounding air.
3. Act as a barrier between the nose/mouth and the external environment.

Conclusion: Masks act as filters — they allow air to pass through but block virus-carrying droplets and particles, thereby reducing the spread of COVID-19. This is an application of the filtration method of separation in everyday life.

Given: A mixture of potatoes, salt, and sawdust.

Properties of components:
- Potatoes — large, solid, visible pieces; insoluble in water.
- Salt — fine solid particles; soluble in water.
- Sawdust — fine, light solid particles; insoluble in water; lighter than water (floats).

Step-by-step Separation Procedure:

Step 1: Handpicking — Separate Potatoes
- The potatoes are large in size and can be easily identified and picked out manually from the mixture.
- Result: Potatoes are separated. The remaining mixture contains salt and sawdust.

Step 2: Add Water and Decantation/Filtration — Separate Sawdust
- Add water to the remaining mixture of salt and sawdust.
- Salt dissolves in water to form a salt solution.
- Sawdust, being insoluble and lighter, floats on the surface of the water.
- Carefully decant (pour off) the floating sawdust, or use filtration — pour the mixture through a filter paper. Sawdust will be retained on the filter paper as residue.
- Result: Sawdust is separated. The filtrate is a salt solution (salt dissolved in water).

Step 3: Evaporation — Separate Salt
- Take the salt solution in a china dish.
- Heat it gently so that the water evaporates completely.
- The solid salt is left behind in the china dish.
- Result: Salt is separated.

Summary Table:

| Step | Method | Component Separated |
|---|---|---|
| 1 | Handpicking | Potatoes |
| 2 | Filtration / Decantation | Sawdust |
| 3 | Evaporation | Salt |

Conclusion: By using a combination of handpicking, filtration/decantation, and evaporation, all three components — potatoes, sawdust, and salt — can be successfully separated from the mixture.

Most Appropriate Options (Correct choices are underlined/bold):

Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty, she went to the nearby pond to fetch some water. After obtaining some water in the container, she noticed that the water was muddy and unfit for drinking. To purify the water, she kept it for some time and then she filtered the muddy water using a piece of muslin cloth. Leela, then, boiled the water for about 10 minutes in a covered pan. After cooling, she filtered it again and made it fit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.

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Reasoning for each choice:

| Blank | Correct Choice | Reason |
|---|---|---|
| thirsty / hungry | thirsty | She went to fetch water, so the need was for thirst. |
| water / grains | water | She went to a pond to fetch water for drinking. |
| fit / unfit | unfit | Muddy water is not safe for drinking. |
| filtered / churned | filtered | Filtration through cloth removes mud particles from water. |
| paper / muslin cloth | muslin cloth | Muslin cloth is a practical filter available in a farm setting; it has fine pores to filter mud. |
| cooled / boiled | boiled | Boiling kills germs and makes water safe to drink. |
| cooling / boiling | cooling | After boiling, the water must be cooled before drinking. |
| filtered / churned | filtered | Filtering again removes any remaining impurities after boiling. |
| fit / unfit | fit | After filtration and boiling, the water becomes safe (fit) for drinking. |

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Suggested Title: *"Leela's Presence of Mind: Purifying Water the Smart Way"*

(Other acceptable titles: *"Smart Leela Saves the Day"* / *"Leela — A Problem Solver"*)