Class 6 chapter 9

 

Class 6 Science

Chapter 9: Methods of Separation in Everyday Life

1. Introduction

A mixture contains two or more substances mixed together. Separation is the process of removing different components of a mixture.

Different methods of separation are used depending on the size, shape, colour, weight, and other properties of the substances.

2. Handpicking

• Handpicking is a method of separating unwanted substances by hand.
• It is used when unwanted particles differ in size, colour, or shape.
• It is suitable for mixtures containing a small amount of impurities.

Examples: Removing stones from rice and separating rotten fruits from fresh fruits.

3. Threshing

• Threshing is the process of separating grains from the stalks of harvested crops.
• It is done by beating harvested crops or using machines called threshers.

Example: Separating wheat grains from wheat stalks.

4. Winnowing

• Winnowing is the process of separating lighter particles from heavier particles using wind or moving air.
• The lighter husk is blown away, while the heavier grains fall down.

Example: Separating husk from wheat grains.

5. Sieving

• Sieving is the process of separating particles of different sizes using a sieve.
• Smaller particles pass through the holes, while larger particles remain on the sieve.

Examples: Separating bran from flour and removing stones from sand.

6. Evaporation

• Evaporation is the process in which a liquid changes into vapour.
• It is used to obtain a dissolved solid from a solution.
• Heat or sunlight increases the rate of evaporation.

Examples: Obtaining salt from seawater and salt solution.

7. Sedimentation

• Sedimentation is the process in which heavier, insoluble particles settle down at the bottom of a liquid.
• The settled particles are called sediment.

Example: Mud settling at the bottom of muddy water.

8. Decantation

• Decantation is the process of carefully pouring off the clear liquid without disturbing the settled particles.
• It is used to separate a liquid from sediment or to separate two liquids that do not mix.

Examples: Pouring clear water from muddy water and separating oil from water.

9. Filtration

• Filtration is the process of separating insoluble solid particles from a liquid using a filter.
• The liquid that passes through the filter is called the filtrate.
• The solid left behind on the filter is called the residue.

Examples: Separating tea leaves from tea using a strainer and filtering water using cloth or filter paper.

Designing a Simple Water Filter

• Take a plastic bottle and cut its bottom.
• Place cotton, sand, and gravel in layers inside the bottle.
• Pour muddy water through the filter.
• The water collected below will be clearer.

Note: This filter does not make water safe for drinking. Proper purification is required.

10. Churning

• Churning is the process of separating butter from curd or cream by stirring it rapidly.
• Butter separates from the liquid portion called buttermilk.

Example: Separating butter from curd using a churner.

11. Magnetic Separation

• Magnetic separation is the process of separating magnetic substances from non-magnetic substances using a magnet.
• It is useful when one component of a mixture is attracted by a magnet.

Examples: Separating iron nails from sawdust and iron filings from sand.

12. Quick Revision

Method	Example
Handpicking	Stones from rice
Threshing	Grains from stalks
Winnowing	Husk from grains
Sieving	Bran from flour
Evaporation	Salt from seawater
Sedimentation	Mud settling in water
Decantation	Clear water from muddy water
Filtration	Tea leaves from tea
Churning	Butter from curd
Magnetic Separation	Iron nails from sawdust

Important Point

The method of separation depends on the properties of the substances present in the mixture.