CBSE Class 6 Science Revision Notes Chapter 9: Methods of Separation in Everyday Life

Separation methods help remove unwanted materials or obtain useful components from a mixture. The correct method depends on differences in size, weight, solubility, magnetic properties or physical state.

Mixtures are common in homes, farms, kitchens and industries. Grains may contain stones, wheat stalks hold grains, muddy water contains soil, and salt remains dissolved in seawater. These mixtures cannot all be separated by the same process because their components have different properties.

These CBSE Class 6 Science Revision Notes Chapter 9 follow the current 2026–27 chapter. Revise handpicking, threshing, winnowing, sieving, evaporation, sedimentation, decantation, filtration, churning and magnetic separation. The notes also explain how to choose and combine methods for different mixtures.

Key Takeaways

• Handpicking: Visible solid impurities are removed by hand when present in small amounts.
• Winnowing: Moving air separates lighter husk from heavier grains.
• Filtration: A filter separates an insoluble solid from a liquid.
• Magnetic separation: A magnet removes magnetic materials from non-magnetic substances.

Access Class 6 Science Chapter 9 Methods of Separation Notes in 30 Minutes

Revise the chapter in three parts:

• First 10 minutes: Mixtures, handpicking, threshing, winnowing and sieving
• Next 10 minutes: Evaporation, sedimentation, decantation and filtration
• Final 10 minutes: Churning, magnetic separation and combined separation methods

Need help revising which method works for each mixture?

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Why We Separate Substances in Class 6 Science Chapter 9 Notes

Two or more substances mixed together form a mixture.

A mixture may contain useful components, unwanted substances or both.

Purposes of Separation

Substances are commonly separated for two purposes:

• To remove an unwanted component
• To obtain two or more useful components separately

Examples include:

• Removing stones from rice
• Separating grains from stalks
• Removing husk from wheat
• Obtaining salt from seawater
• Separating tea leaves from tea
• Obtaining butter from curd
• Removing iron nails from sawdust

Basis of Separation

The method selected depends on differences between the components.

A complex mixture may require more than one method.

Handpicking, Threshing and Winnowing Revision Notes

These methods are commonly used to separate agricultural products.

Each one works on a different property.

Handpicking

Handpicking means picking and removing substances from a mixture by hand.

It is suitable when:

• The unwanted material is present in a small quantity.
• Its particles are large enough to be seen.
• It differs in size, colour or shape.
• It can be removed easily by hand.

Examples include:

• Removing stones from rice
• Removing husk from pulses
• Taking black pepper out of pulao
• Removing watermelon seeds
• Picking chillies from cooked food
• Separating potatoes from grains

Handpicking becomes difficult when the unwanted component is too small or present in a large amount.

Threshing

Threshing separates grains from harvested stalks.

Farmers may beat dry stalks against a hard wooden surface. The attached grains loosen and fall away.

Modern threshers perform this work using machines.

Examples include:

• Separating wheat grains from wheat stalks
• Separating paddy grains from harvested plants

The stalks are often dried before threshing because dry grains separate more easily.

Winnowing

Winnowing separates lighter and heavier components using moving air.

Farmers drop the mixture of grains and husk from a height. The lighter husk is carried farther by the wind, while heavier grains fall nearby.

A bamboo tray called a soop is traditionally used for winnowing.

Examples include:

• Separating wheat grains from husk
• Removing peanut skins by blowing
• Separating light chaff from grain

Winnowing requires wind or moving air. It will not work effectively in a completely closed room without airflow.

Handpicking, Threshing and Winnowing Comparison

Threshers may perform threshing and winnowing together.

Sieving in Methods of Separation in Everyday Life Notes

Sieving separates solid particles of different sizes.

A sieve contains holes of equal size. Smaller particles pass through these holes, while larger particles remain above.

Examples of Sieving

• Removing bran from flour
• Removing stones from wheat flour
• Separating pebbles from sand
• Separating fine sand at a construction site
• Separating gram flour from black gram

How Does Sieving Work?

The holes must be:

• Larger than the particles that should pass through
• Smaller than the particles that should remain above

If sieve holes are too large, both components may pass through.

Sieving and Handpicking

Sieving is better when many small particles need separation.

Handpicking is better when a few large impurities can be seen and removed easily.

Evaporation in Class 6 Science Chapter 9 Revision Notes

Evaporation changes a liquid into vapour.

It can separate a solid that is dissolved in a liquid.

Obtaining Salt from Seawater

Seawater contains dissolved salts.

It is kept in shallow pits where sunlight and air cause the water to evaporate. Solid salts remain behind.

Common salt is then obtained through further purification.

Salt Solution Activity

When salt dissolves in water, it may seem to disappear.

Spread a few drops of salt solution on dark paper and let them dry. White salt patches remain after the water evaporates.

This shows that:

• Water changes into vapour.
• Salt does not evaporate with the water.
• The dissolved solid remains behind.

Heating a Salt Solution

A salt solution may also be heated in a suitable dish.

The water boils away, and solid salt remains in the dish.

This activity should be performed under a teacher’s supervision.

Other Uses of Evaporation

Evaporation is used in:

• Obtaining salt from seawater
• Drying medicinal plant parts
• Removing excess water from some materials
• Forming salt patches from sweat on dark clothes

Evaporation recovers the dissolved solid but does not recover the evaporated water in this chapter’s method.

Sedimentation and Decantation Notes

Sedimentation and decantation are often used together.

They are useful when an insoluble solid is mixed with a liquid.

Sedimentation

The settling of a heavier insoluble component at the bottom of a liquid is called sedimentation.

When muddy water is left undisturbed, the heavier mud particles settle at the bottom.

The settled material is called sediment.

Decantation

After sedimentation, the clear upper liquid can be poured gently into another container.

This process is called decantation.

The vessel should be tilted slowly so that the sediment remains at the bottom.

Everyday Examples

Sedimentation and decantation are used in:

• Separating settled tea leaves from tea
• Washing rice and pulses
• Separating mud from water
• Separating oil and water layers
• Pouring clear liquid from settled sand

Oil and Water

Oil and water do not mix.

When left undisturbed, they form separate layers. One layer can be poured away carefully through decantation.

Limitations of Decantation

Decantation may not remove all solid particles.

Very fine particles may remain in the liquid. Filtration can provide better separation.

Filtration in Methods of Separation in Everyday Life

Filtration separates an insoluble solid from a liquid using a filter.

The filter contains pores that allow the liquid to pass while stopping larger solid particles.

Common Examples of Filtration

• Separating tea leaves from tea
• Filtering muddy water through cloth
• Using filter paper in a laboratory
• Draining water through a fishing net
• Using a tea bag
• Passing liquid through cotton, charcoal or sand

Residue and Filtrate

During filtration:

• The solid left on the filter is called the residue.
• The liquid that passes through is called the filtrate.

For muddy water:

• Mud on the filter paper is the residue.
• Water collected below is the filtrate.

Filtration Using Cloth

A cloth contains small pores between its threads.

Liquid passes through these pores, while some solid particles remain behind.

Using several layers may remove more particles because the effective pore size becomes smaller.

Filtration Using Filter Paper

Filter paper has much finer pores than a common strainer or cloth.

To filter muddy water:

1. Fold the filter paper into a cone.
2. Place it inside a funnel.
3. Keep the funnel over a flask.
4. Pour muddy water slowly.
5. Allow the liquid to pass through.

Mud remains as residue. Clearer water collects as filtrate.

Choosing a Filter

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

A filter with pores larger than the particles will not stop them.

Sedimentation, Decantation and Filtration Comparison

Sedimentation and decantation may be used before filtration when the mixture contains a large amount of solid material.

Churning in Methods of Separation Revision Notes

Churning separates butter from curd.

Curd is stirred or rotated using a churner called a mathni.

During churning:

• Butter separates from the curd.
• Butter, being lighter, floats at the top.
• Buttermilk remains below.

Butter can then be collected from the surface.

Modern kitchens may use electric mixers or churners for the same purpose.

Churning is also connected with using sour milk. It may be converted into curd and then used to obtain butter or buttermilk.

Magnetic Separation in Class 6 Science Chapter 9 Notes

Some substances are attracted towards magnets.

These are called magnetic substances.

Iron is a common magnetic substance.

What Is Magnetic Separation?

Separating magnetic and non-magnetic substances using a magnet is called magnetic separation.

Examples include:

• Iron nails from sawdust
• Iron filings from sand
• Scrap iron from waste
• Iron objects from construction material
• Magnetic metal from a mixed heap

The magnet attracts iron while non-magnetic material remains behind.

Industrial Use

Recycling centres use large magnets fitted to cranes.

These magnets lift iron objects from piles of waste. The separated iron can then be recycled and reused.

Magnetic separation is faster than handpicking when many iron pieces are mixed with other materials.

Choosing the Correct Method of Separation

No single method works for every mixture.

The correct choice depends on the properties of the components.

Before choosing a method, ask:

• Are both components solid?
• Is one component dissolved?
• Is one component insoluble?
• Are particle sizes different?
• Is one component lighter?
• Is one component magnetic?
• Can the impurities be seen?
• Is one component present in a small amount?

Combining Separation Methods

A mixture containing several components may require a sequence of methods.

Example: Potatoes, Salt and Sawdust

A possible sequence is:

1. Remove potatoes by handpicking.
2. Add water to the remaining salt and sawdust.
3. Salt dissolves in water, but sawdust does not.
4. Separate sawdust by filtration.
5. Evaporate the filtrate to recover salt.

Example: Iron Nails, Stones, Sand, Pepper, Salt and Water

A possible sequence is:

1. Use a magnet to remove iron nails.
2. Handpick large stones and black pepper.
3. Filter the remaining mixture to remove sand.
4. Evaporate the salt solution to recover salt.

The exact sequence depends on the mixture and the easiest component to remove first.

Why Is Sequence Important?

A good sequence:

• Prevents loss of useful components
• Makes later steps easier
• Reduces unnecessary work
• Uses the strongest property difference first

For example, magnetism can remove iron quickly before handling the remaining mixture.

Class 6 Science Chapter 9 Summary Notes

Important Terms from Methods of Separation

Mixture: Two or more substances mixed together.

Handpicking: Removing visible particles from a mixture by hand.

Threshing: Separating grains from stalks by beating or using a machine.

Winnowing: Using wind or moving air to separate lighter and heavier components.

Sieving: Separating solid particles using a sieve based on size.

Evaporation: Conversion of a liquid into vapour.

Sedimentation: Settling of heavier insoluble particles at the bottom.

Decantation: Removing the upper liquid by gently tilting the container.

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

Residue: Solid left behind on a filter.

Filtrate: Liquid that passes through a filter.

Churning: Separating butter from curd by stirring or rotating it.

Magnetic substance: A material attracted by a magnet.

Magnetic separation: Separating magnetic substances using a magnet.

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