Why it is necessary to separate …

The mixtures are separated into their components for the following reasons:

1. To remove an undesirable component - Tea is made by boiling tea leaves in water and then adding milk and sugar. After the tea has been made, the used tea leaves become the undesirable component of the mixture 'tea' and are removed from it by using a tea strainer. 

2. To remove a harmful component - Foodgrains like rice, wheat, pulses etc. usually contain small pieces of stones and some insects etc. These are harmful to us and are hence removed from the foodgrains before using them.

3. To obtain a pure sample of a substance - Tap water contains some dissolved salts in it so it is an impure mixture. This water is made free of dissolved salts or impurities by the process of distillation and as a result, we get a pure sample of water.

4. To obtain a useful component - Milk is a mixture from which useful component 'butter' is separated.