CBSE Class 6 Science Separation of Substances Notes

Topics in the chapter

- Separation of substances
- Types of mixture
- Separation of components of mixtures
- Condensation
- Can water dissolve any amount of a substance?

What is Separation?

The removal of substances from a mixture of two or more substances is known as separation.
Some examples of separation are:
- Separating stones from rice
- Churning milk to obtained butter

Why do we need to separate substances?
- To obtained two different components
- To remove impurities or harmful components
- To group substances of different sizes Separation of substances

Pure substance: The substance which contain only one type of particles.
Examples: Water

Impure substances: The substance which contain more than one kind of particle.
Examples: A plate of rice is mixed with some stones.

Separation of components of mixtures

Mixture of solid with solid

(i) Hand picking
- The component of a solid-solid mixture can be separated by hand picking.
- It is used for separating large size impurities like stones and husk.
- For example: separating grass from mint leaves, separating pebbles from dal.
(ii) Threshing
- The process in which the stalks are beaten to free the grain seeds.
- Threshing is done with the help of bullocks. For large quantity of grains machines are used for threshing.
- This method is used by the farmers to separate the grains from the stalks after harvesting.
(iii) Winnowing
- It is process which is used to separate heavier and lighter components of a mixture by wind or by blowing air.
- This method is used by farmers to separate lighter husk particles from heavier seeds of grain.
(iv) Sieving
- It is a process in which a components of a mixture with different size can be separated by sieve.
- The smaller particles remove out through the pore of sieve and the larger particle is left behind it.
- This method is used to separate wheat bran (the bigger particles) from flour.
(v) Sublimation
- The process in which the solid changes directly into gaseous state on heating is called sublimation.

Mixtures of solids with liquids

(i) Evaporation
- It is a process which is used when we want to get back a substance that has been dissolved. In this process liquid changes into gaseous form on heating.
- Example: Getting salt out of salty water.

(ii) Crystallization
- It is a process which separates a pure solid in the form of crystals from a saturated solution. Separation of solids that do not dissolve in liquids

(i) Sedimentation: The process of separation of 2 components in such a way that the heavier substance settles down.

(ii) Decantation: separation of 2 components which do not mix together.
Example: Water and oil.

(iii) Filtration: The process in which separation of solid from liquid by the filter paper or strainer.
Example: separating mud from water by using filter paper.
Condensation: It is a process by which a substance changes from the gas phase to liquid phase.

Can water dissolve any amount of a substance?

- Water dissolves different amounts of soluble substances in it.
- A saturated solution is one which cannot dissolve more of that substance.
- To dissolves more of a substance in a solution we have to heating it.