Chapter 9: Methods of Separation in Everyday Life

1. Introduction – Why Do We Separate Substances?

In our daily life, we often find two or more substances mixed together. Sometimes we need to separate them because:

We want to obtain a useful component from a mixture.
We want to remove an unwanted component.
We want to make a substance suitable for use or consumption.

Examples

Removing stones from rice or pulses.
Separating husk from grains.
Removing tea leaves from tea.
Separating salt from seawater.
Separating butter from curd.
Removing iron pieces from waste using a magnet.

A mixture contains two or more substances mixed together.

2. Handpicking

Meaning

Handpicking is the method of separating substances by picking them out by hand from a mixture.

It is generally based on differences in:

Size
Colour
Shape

When is handpicking useful?

It is convenient when:

The unwanted particles are present in small quantities.
The particles can be easily seen and picked by hand.

Examples

Removing small stones from rice.
Removing stones from pulses.
Taking out black pepper from vegetable pulao.
Picking green chillies from a dish.
Picking marigold flowers from a mixture of flowers.

3. Threshing

Meaning

Threshing is the process of separating grains from the stalks by beating the harvested crop.

How is it done?

Farmers beat the dried stalks against a hard surface or use machines to separate the grains.

Example

Wheat grains → separated from wheat stalks

Modern threshers

Modern machines called threshers can perform:

Threshing
Winnowing

at the same time.

4. Winnowing

After threshing, grains are mixed with husk. These two components can be separated because they have different weights.

Meaning

Winnowing is the method of separating a lighter component from a heavier component by using wind or blowing air.

Traditional method

A soop (bamboo tray) is traditionally used.

The mixture is placed in the tray and moved in the direction of air or wind.

Heavy grains fall relatively near the place of winnowing.
Lighter husk is blown away by the wind.

Example

Wheat grains + husk → winnowing

Important point

Winnowing depends mainly on the difference in weight of the components.

5. Sieving

Meaning

Sieving is used to separate solid particles of different sizes using a sieve.

The sieve has holes of a suitable size.

Smaller particles pass through the holes.
Larger particles remain on the sieve.

Example: Flour

In flour:

Fine flour particles pass through the sieve.
Bran and larger particles remain on the sieve.

Other examples

Separating pebbles from sand.
Separating stones from construction material.
Separating bran from flour.

Important condition

Sieving works when the components of a solid-solid mixture have different particle sizes.

6. Evaporation

Meaning

Evaporation is the process in which a liquid changes into its vapour.

It can be used to separate a solid dissolved in a liquid.

Example: Salt from seawater

Seawater contains dissolved salts.

The seawater is kept in shallow pits and exposed to:

Sunlight
Air

The water gradually evaporates, leaving behind the dissolved solid materials. Common salt is then obtained and further purified.

Laboratory example

When a salt solution is heated in a china dish:

Salt solution → water evaporates → salt remains

7. Sedimentation

Meaning

Sedimentation is the process in which a heavier, insoluble component settles down at the bottom of a liquid.

Example

If muddy water is kept undisturbed:

Mud particles settle at the bottom.
Water remains above the sediment.

Important words

The solid material that settles at the bottom is called the sediment.

8. Decantation

Meaning

Decantation is the process of removing the liquid by gently tilting the vessel after the heavier insoluble material has settled.

Example

Muddy water:

Muddy water → sedimentation → carefully pour clear water → decantation

Other example

Decantation is also used while:

Washing rice.
Washing pulses.

Limitation

Decantation may not remove all the solid particles. Some particles may remain in the liquid.

9. Filtration

Meaning

Filtration is the method of separating an insoluble solid from a liquid using a filter.

Example: Tea

When tea is poured through a tea strainer:

Tea passes through.
Tea leaves remain in the strainer.

This process is called filtration.

Filtration of muddy water

A piece of cloth can act as a filter because it has tiny pores between its threads.

For finer particles, filter paper can be used.

10. Filter Paper

Filter paper contains very fine pores.

In laboratory filtration:

Muddy water → filter paper → clear water + mud

The mud remains on the filter paper.

Important terms

Residue:
The solid material left on the filter paper.

Filtrate:
The liquid that passes through the filter paper.

For muddy water:

Mud = residue
Water = filtrate

11. Other Filtering Materials

Many materials can be used as filters, depending upon the size of particles that need to be removed.

Examples include:

Cotton
Charcoal
Sand
Cloth
Filter paper

The choice of filter depends on the size of the particles to be removed.

12. Churning

Meaning

Churning is used to separate butter from curd.

Curd is churned using a mathni (churner).

During churning:

Butter, being lighter, floats at the top.
Buttermilk remains behind.

Example

Curd → churning → butter + buttermilk

13. Magnetic Separation

Meaning

Magnetic separation is the method of separating magnetic and non-magnetic substances using a magnet.

Magnetic substances

Substances attracted towards a magnet are called magnetic substances.

Iron is a common example.

Example

A carpenter accidentally mixes iron nails with sawdust.

Instead of handpicking the nails, a magnet can be moved through the mixture.

Iron nails are attracted to the magnet.
Sawdust is not attracted.

Thus, the nails are separated from sawdust.

14. Magnetic Separation in Recycling

Magnets are also used by recyclers to separate iron articles from waste.

In industries, magnets attached to cranes can separate scrap iron from large heaps of waste.

The separated iron can then be:

Recycled
Reused

15. Separation of Oil and Water

Oil does not mix with water.

When the mixture is left undisturbed:

Oil forms a separate layer.
Water forms another layer.

The layers can be separated by decantation.

16. Separation of Salt from Salt Solution

Salt is dissolved in water, so it cannot be separated by ordinary filtration.

The appropriate method discussed in the chapter is evaporation.

Process

Salt + water → heat → water evaporates → salt remains

This is also the basic principle used for obtaining salt from seawater.

17. Separation Based on Different Properties

Different separation methods depend upon different properties of substances.

Method	Property/Difference Used	Example
Handpicking	Size, colour, shape	Stones from rice
Threshing	Attachment of grains to stalks	Grains from stalks
Winnowing	Weight	Husk from grains
Sieving	Particle size	Bran from flour
Evaporation	Volatility/change of state	Salt from salt solution
Sedimentation	Weight/density	Mud from water
Decantation	Settling of insoluble particles/layers	Oil and water
Filtration	Particle size and insolubility	Tea leaves from tea
Churning	Difference in properties/density	Butter from curd
Magnetic separation	Magnetic property	Iron nails from sawdust

18. Why Do We Separate Substances?

The chapter highlights two major purposes:

Purpose 1: To separate two different but useful components

Example:

Curd → butter + buttermilk

Both components can be useful.

Purpose 2: To remove an unwanted component

Example:

Rice + stones → clean rice

The stones are unwanted and are removed.

19. Separation in Everyday Life

We use separation methods every day without always noticing them.

At home

Stones from rice → Handpicking
Bran from flour → Sieving
Tea leaves from tea → Filtration
Rice/pulses washing → Decantation
Butter from curd → Churning

In agriculture

Grains from stalks → Threshing
Husk from grains → Winnowing

At construction sites

Pebbles and stones from sand → Sieving

In industries

Iron scrap from waste → Magnetic separation

From seawater

Salt from seawater → Evaporation

20. Important Activities from the Chapter

Activity 9.1 – Peanuts and Air

Roasted peanuts are rubbed between the palms to remove their skins.

When air is blown over the mixture:

Lighter peanut skins are blown away.
Heavier peanuts remain.

This demonstrates the principle of winnowing.

Activity 9.2 – Salt Solution

Salt is dissolved in water and a few drops of the solution are placed on dark paper.

After drying:

Water disappears.
Salt remains as patches.

This demonstrates evaporation.

Activity 9.3 – Heating Salt Solution

Salt solution is heated in a china dish.

After the water boils away and the dish cools:

Salt is left behind.

This demonstrates separation by evaporation.

Activity 9.4 – Filtration

Muddy water is poured through filter paper placed in a funnel.

Result:

Mud → Residue
Water → Filtrate

This demonstrates filtration.

Activity 9.5 – Water Filter

The chapter asks learners to design a working water filter using low-cost materials.

The activity helps students understand how different filtering materials can remove unwanted particles from water.

21. Separation and the Environment

The chapter also connects separation with environmental awareness.

Fishing nets can trap unwanted materials such as:

Plastic bags
Broken bottles
Food wrappers

This highlights the problem of river and ocean pollution.

Separating recyclable materials from waste can also help in recycling and reuse.

22. Important Special Examples

Ayurveda

Some herbs or plant parts such as roots, leaves, flowers and seeds are dried in shade.

Drying facilitates the evaporation of excess water, leaving the useful plant material.

Tea bags

Tea bags work on the principle of allowing water to pass through while retaining tea leaves. Earlier tea bags were made from materials such as soft cloth; filter paper is commonly used today.

23. Important Definitions – Learn These

Mixture: Two or more substances mixed together.

Handpicking: Separation of components by picking them by hand.

Threshing: Separating grains from stalks by beating them.

Winnowing: Separating lighter particles from heavier particles using wind or air.

Sieving: Separating solid particles of different sizes using a sieve.

Evaporation: Conversion of a liquid into vapour.

Sedimentation: Settling of a heavier insoluble component at the bottom of a liquid.

Decantation: Removing the liquid by carefully tilting the vessel.

Filtration: Separating an insoluble solid from a liquid using a filter.

Churning: Separating butter from curd.

Magnetic separation: Separating magnetic substances from non-magnetic substances using a magnet.

NCERT QUESTIONS/ANSWERS

1. What purpose does handpicking serve in the process of separation?

Answer: (ii) Sorting

Handpicking is used to sort and separate visible unwanted components from a mixture.

2. Which of the following substances are commonly separated using the churning method?

Answer: (iii) Cream from milk

Note: In this chapter, churning is specifically described for obtaining butter from curd.

Match the separation method with its description

Tank 1 – Method Tank 2 – Correct description

Filtration Insoluble particles get filtered as residue

Decantation Mixture of oil and water

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

3. Which factor is usually essential for filtration?

Answer: (iii) Pore size

The size of the pores in the filter determines which particles can pass through and which are retained.

4. True or False

(i) Salt can be separated from salt solution by keeping it under the Sun.

Answer: True (T)

Reason: Water evaporates in sunlight and salt is left behind.

(ii) Handpicking should be used only when the quantity of one component is less.

Answer: True (T)

Handpicking is convenient when the component to be removed is present in a small quantity and can easily be picked by hand.

(iii) A mixture of puffed rice and rice grains can be separated by threshing.

Answer: False (F)

Correct statement: A mixture of puffed rice and rice grains can be separated based on differences in their properties, not by threshing. Threshing is used to separate grains from stalks.

(iv) A mixture of mustard oil and lemon water can be separated by decantation.

Answer: True (T)

Oil and water form separate layers when left undisturbed, so they can be separated by carefully pouring off one layer.

(v) Sieving is used to separate a mixture of rice flour and water.

Answer: False (F)

Correct statement: Filtration is used to separate an insoluble solid from a liquid such as rice flour and water.

5. Match the mixtures with the correct method

Column I – Mixture Answer 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

Final answers:

(i) – (d)

(ii) – (e)

(iii) – (a)

(iv) – (b)

(v) – (c)

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

Answer:

Decantation can be used when the solid particles are heavier and insoluble and settle down at the bottom of the container. The clear liquid can then be carefully poured into another container.

Example: Separating water from settled mud or washing rice and pulses.

Decantation may not completely remove all the solid particles.

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

Answer:

Yes. Nasal hair acts somewhat like a filter. It traps dust and other larger particles from the air before the air enters deeper into the respiratory system.

Thus, it can be related to filtration.

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 generally made from layers of fabric or other filtering materials.

Their role is to filter or trap droplets and particles, reducing the passage of unwanted particles through the mask.

Thus, the working principle of a mask can be related to filtration.

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

Step 1 – Separate potatoes

Use handpicking to remove the potatoes from the mixture.

Step 2 – Add water

Add water to the remaining mixture.

- Salt dissolves in water.

- Sawdust does not dissolve and floats.

Step 3 – Separate sawdust

Carefully remove/separate the floating sawdust, using decantation as appropriate.

Step 4 – Separate salt

The remaining salt solution can be heated.

The water evaporates and salt is left behind.

Sequence:

Potatoes → Handpicking → Sawdust → Separation/decantation → Salt solution → Evaporation → Salt

10. Intelligent Leela – Correct Options

Here is the completed paragraph:

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 boiling, 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.

Correct choices in order:

1. thirsty

2. water

3. unfit

4. filtered

5. muslin cloth

6. boiled

7. boiling

8. filtered

9. fit

The chapter's exercise presents this as an application of sedimentation/filtration and boiling in the context of making muddy water safer for drinking.