1. The document discusses various methods of separating mixtures into pure substances, including handpicking, sieving, magnetic separation, sedimentation, decantation, filtration, evaporation, distillation, and churning. 2. Separation methods work by exploiting differences in properties like particle size, density, melting/boiling points between components of a mixture. Magnetic separation separates out iron filings. Sieving and winnowing separate components by size. 3. Specific techniques are used to separate insoluble solids from liquids, including sedimentation, decantation, coagulation/loading, and filtration. Distillation separates components by selective boiling and condensation.

1. SEPARATION OF SUBSTANCE
SCIENCE (NCERT)
CLASS-VI

2. WHAT IS SEPARATION?
The process by which unwanted or harmful component of
mixture are removed to get a pure substance are called
separation.
1. Remove unwanted or undesirable components.
2. Get a pure sample of substance.
3. Extract useful component from the substance.
4. Remove harmful components.

3. Introduction:
You must have seen that we clean/separate different substances -
we filter tea powder while making tea, we clean rice with water
before using it for cooking and so on. These are the processes we
use commonly to separate substances. In this chapter, we will study
some methods used to separate substances.

4. Pure substance: Many substance around us contain only one type
constituent particles. Elements and compound are pure substance .
Some of the pure substance are iron, copper, water, salt etc.

5. Impure substance: Many substance around us contain more one type
constituent particles. Some of the pure substance are pond water, milk
etc.

6. Impurities: There are unwanted particles present in substance
making it impure.

7. Homogeneous mixtures: Mixture in which the particles of the
substance present cannot be seen are called homogeneous mixtures.
For example, solution of sugar and water, air, cold drinks.

8. Heterogeneous mixtures: Mixture in which particles of the substances
present can be seen easily are called heterogeneous mixtures. For
example, water in oil, dust in air.

9. Need for separation: We carry out the separation of the
components of a mixture or an impure substance with the following
purposes :
(i) To remove the un useful or harmful component.
(ii) To obtain the useful component.
(iii) To remove impurities for getting a pure sample.
Principle of separation
1. The substances present in a mixture retain their original
properties like particle size, density, melting point, boiling point,
volatility, etc.
2. We use the difference in anyone of these properties in the
components of a mixture to separate them.

10. Methods of separation: Hand picking, winnowing, sieving, magnetic
separation, sedimentation, decantation, loading, filtration, evaporation,
sublimation, distillation, churning, etc. are some common methods of
separation.

11. Handpicking :This method is used for separating small particles of
dirt, stone, husk etc. from the grains of wheat, rice, pulses, etc.

12. Threshing
Suppose in a bowl, there are two kinds of fruits. Then you can
easily separate one from the other. But what if the size of the
components in a mixture is much smaller.
The separation techniques of threshing are useful for such smaller
components.
A farmer uses the method of threshing to separate grain from the
stalks. The stalks are beaten to separate the grain seeds. Bullocks or
machines may be useful for threshing.

13. Sieving
You might have seen your mother use a sieve to separate impurities
and bran from flour before using it.
The separation techniques of sieving are mainly used in a flour mill to
separate impurities from wheat before grinding it.
Sieving removes impurities like stones, stalk, and husk that still remain
after threshing and winnowing.
The sieve only removes particles of impurities that are larger than the
pores in the sieve. Therefore, we can design the sieve according to our
need.

14. Winnowing
Winnowing is used to separate lighter components of the mixture from
heavier components by the wind.
These separation techniques are commonly used by farmers to separate
lighter husk particles from the heavier seeds.
The lighter particles are carried away by the wind. The heavier seeds
form a heap near the platform of winnowing. We can use either natural
wind or blow air while winnowing.

15. Magnetic Separation
Iron filings can be separated from a mixture of iron filings and
sand by using a magnet. This process is known as magnetic
separation.

16. Separation of Insoluble Solids from liquids
The following methods are used for separating insoluble solids from
liquids.
Sedimentation
This process is based on the densities of different components of a
mixture. The process of setting down of heavy insoluble particles in a
mixture of water and insoluble substances is called sedimentation.

17. Decantation
The process of pouring out a clear liquid from a vessel (after
sedimentation) without disturbing the sediments (heavy
insoluble settled particles) is called decantation.
The above method has two disadvantages.
(a) It cannot be used for the miscible liquids that dissolve in one
another. For example, petrol mixed in kerosene oil or salt
or sugar solution in water.
(b) During the process of decantation, a small quantity still remains
un separated thus it gets wasted.

18. Coagulation or Loading
Coagulation is the process of improving the settling property of
solids by addition of specific chemicals. When solid particles present
in a mixture are not heavy enough to settle easily, some chemicals can
be added to the mixture to enable the solids to settle.
For example, when alum is added to dirty water, it attaches itself to
the dirt particles and makes several dirt particles stick to each other.
This makes them heavier and helps them to settle down. Alum is
said to be a coagulating agent.

19. Filtration
Filtration is the process of separating suspended solid matter from a
liquid, by causing the latter to pass through the pores of some substance,
called a filter.
The liquid which has passed through the filter is called filtrate. The
filter may be paper, cloth, cotton-wool, glass wool, unglazed
earthenware, sand, or any other porous material.

20. Condensation
Condensation is the change of water from its gaseous form (water
vapor) into liquid water. Condensation generally occurs in the
atmosphere when warm air rises, cools and looses its capacity to
hold water vapor. As a result, excess water vapor condenses to form
cloud droplets

21. Distillation
Distillation is a process of separating the component of substances from
a liquid mixture by selecting evaporation and condensation.

22. Churning (or centrifugation):It is the process of separation of the
lighter particles of a suspended solid from a liquid.
For example: to obtain butter from the curd or milk.

23. Crystallization: The process of crystallization is used for obtaining
pure crystalline substance from impure sample.

24. Saturated Solutions
A solution in which no more substance can be dissolved at a given
temperature is called a saturated solution.

25. RECAPITULATION