1) The document discusses various methods for separating substances from mixtures, including handpicking, threshing, sieving, winnowing, sedimentation, decantation, filtration, evaporation, and condensation. 2) Key separation methods include threshing grains from stalks, sieving to separate particles of different sizes, and winnowing to separate lighter and heavier particles using wind. 3) More advanced techniques involve sedimentation, decantation, and filtration to separate solids and liquids, or evaporation and condensation to separate soluble solids like salt from water.

1. VIDYA BHARTI EDUCATIONAL INSTITUTIONS
SCIENCE NOTES CLASS 6TH
SEPRATION OF SUBSTANCES
In the day to day life, there are times when one needs to separate a useful
substance from a mixture. This is done by using various methods of
separation of substance.
Mixture: A substance which is composed of two or more substances; in which
each component retains its unique property; is called mixture. Air is a mixture
of gases. Water which we drink is a mixture of pure water and many other
substances.
Pure Substance: A substance is called pure when each particle of the
substance has the same unique property. For example; distilled water is pure
water as each drop of it contains nothing but water.
Need for separation of substances: Taking out useful substances from a
mixture is usually the main reason for separation of substances. Sometimes,
we also need to separate substances when we need to use different
components in different ways.
Separating solid from a mixture of solids:
Handpicking: It is the simplest method of separation of substances. This
method is used only when unwanted material is in small quantity. Moreover,
shape, size, or colour of the unwanted material is different from that of the
useful materials. For example; pebbles, broken grains and insects are
separated from rice, wheat and pulses; by handpicking.
Threshing: Threshing is used for separating seeds from the harvested stalks.
Manual Threshing: When the quantity is small, threshing is done manually.
Small bundles of the harvested stalks are thrashed on a hard surface. This
helps in separating the grains.
Threshing by Animals: For larger quantities, threshing is done in the
traditional way; by using animals. For this, stalks are spread around a pole.
Several bullocks are tied to the pole and are made to walk over the harvested
stalks. Trampling by hooves of the animals helps in separating grains.
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2. VIDYA BHARTI EDUCATIONAL INSTITUTIONS
SCIENCE NOTES CLASS 6TH
SEPRATION OF SUBSTANCES
Threshing Machine: Now-a-days, threshing machines are used for the
purpose. It can be powered by either a diesel engine or an electric motor. It
helps in saving time and labour.
Sieving: When the size of particle it too small to be picked by hand or when
the quantity is too large, sieving is used for separating substances. A sieve;
having holes of proper size is used. The bigger particles are retained by the
sieve whereas the smaller ones pass through it. For example; this method is
used for separating bran from flour, sand from gravel, pearls of different sizes,
etc.
Winnowing: The process of separation of lighter particles from heavier
particles; with the help of wind; is called winnowing. This method is used for
separating grains from husk. Farmers drop the mixture of wheat and husk
from a height. The husk is carried by the wind and form a heap at a small
distance away. The wheat grains being heavier fall vertically to form a
separate heap.
Combine Harvester: Modern farming involves use of a machine; called
combine harvester. This machine harvests, threshes and winnows in a single
operation. Combine harvesters are used in developed countries; like the USA.
In India, such machines can be seen in the farms of Punjab.
Sedimentation, Decantation And Filtration:
These methods are usually used in combination. They are used for separating
soluble and insoluble solids from a mixture of solids and liquid.
Sedimentation: Insoluble particles settle down at the bottom and the process is
called sedimentation. For example; muddy water contains soil and sand in
water. Soil and sand; being insoluble in water; settle down at bottom if water is
allowed to stand for some time.
Decantation: This process is used after sedimentation. The upper layer; which
contains water is slowly poured out from the container. It leaves the sediment
behind.
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HEAD OFFICE: 131/12 KRISHNA COLONY, STREET NO 4, NEAR SHIV MANDIR, GURGAON

3. VIDYA BHARTI EDUCATIONAL INSTITUTIONS
SCIENCE NOTES CLASS 6TH
SEPRATION OF SUBSTANCES
Filtration: This method is used for separating fine insoluble solid particles from
the liquid. In this process, the mixture is passed through a filter. The solid
particles do not pass through the filter and clear liquid is collected.
Evaporation: The process of conversion of water into its vapour is called
evaporation.
Condensation: The process of conversation of water vapour into its liquid
called condensation.
Evaporation and condensation are used for separating a soluble solid from
water. For example; salt can be separated from a solution of salt and water;
by using the combination of evaporation and condensation.
Salt is prepared from sea water by evaporation and condensation. Sea water
is collected in shallow pits and allowed to evaporate. The water evaporates
and crystals of salt are obtained in the pits. The salt is then sent to factories
for further purification.
Saturated Solution: When a solution of a liquid and solid has enough of the
solid and it cannot take any more solid; the solution is called saturated
solution. On the other hand, when more solid can be dissolved in the given
solution; it is called unsaturated solution.
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HEAD OFFICE: 131/12 KRISHNA COLONY, STREET NO 4, NEAR SHIV MANDIR, GURGAON