Class 6
subject - science
chapter - 5
Separation of substances
In our daily life, there are many instances when we notice a substance being separated from a mixture of materials.
Ex ** Tea leaves are separated from the liquid with a strainer.
** Grain is separated from stalks.
** Milk or curd is churned to separate the butter.
The substances to be separated may be particles of different sizes of materials.
These may be in any three States of matter example solid liquid or gas.
Why do we separate substances
Methods of separation
(1) Hand picking :- This method of hand picking can be used for separating slightly larger sized impurities like the piece of dirt, stone and husk from wheat, rice or pulses.
** Hand picking is a convenient method of separating substances.
(2) Threshing :- The process that is used to separate grain from stalk etc is threshing. In this process, stalks are beaten to free The grain seeds.
(3) Winnowing:- Winnowing is used to separate heavier and lighter components of a mixture by wind or by blowing air.
This method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.
(4) Sieving :- Sieving allows the fine flour particles to pass through the holes of the sieve while the bigger impurities remain on sieve.
In a flour mil, impurities like husk and stones are removed from wheat before grinding it.
** Sieving is used when components of a mixture have different size
(5) Magnetic separation :- Process by which magnet is moved over such a mixture, the magnetic material sticks to it and is removed.
Sedimentation :- When the heavier component in a mixture settles after water is added to it, the process is called sedimentation.
Decantation :- When the water along with the dust is removed, the process is called decantation. In this method separating insoluble solids from liquids.
The same principle is used for separating a mixture of two liquids that do not mix with each other.
Ex. Oil and water mixture.
Filtration :- It's separates solid matter and fluid from a mixture with the filter mediam. The liquid that collects in the beaker is called filtrate.
** Fruits and vegetables juices ste usually filtered before drinking to separate the seeds and solid particle of pulp.
** Sedimentation, decantation and filtration separate insoluble solid from liquid.
Separation of water soluble solids --
(1) Evaporation :- The process of conversion of water into its vapour is called evaporation.
The process evaporation takes place continuously where ever water is present.
(2) Condensation :- The process of conversion of water vapour into its liquid form is called condensation.
Saturated solution :- A solution in which no more solute can be dissolved in the solvent.
Churning :- The method which is used for separating lighter particles of its solid suspended in a liquid.
Ex. Button from curd.
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