Revision Notes of Ch 5 Separation of Substances Class 6th Science
- 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.