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SAI International School
Subject-Chemistry

Ch-Is Matter around us pure?
Topic-Separation techniques introduction, Evaporation, centrifugation
LESSON NOTE

Separation of mixtures:
1. Mixtures containing two solids

 Handpicking  Sieving
 Threshing  Magnetic Separation
 Winnowing  Sublimation
2. Mixtures containing a solid and a liquid
 Insoluble solid and a liquid
a) Sedimentation c) Filtration
b) Decantation d) Centrifugation
 Soluble solid and a liquid
a) Evaporation d) Distillation
b) Crystallisation
c) Chromatography
3. Mixtures containing two liquids
 Immiscible liquids
a) Separating funnel
 Miscible liquids
a) Fractional distillation
1. Hand Picking:This method involves simply picking out all the unwanted
substances by hand and separating them from useful ones. The separated
substances may be an impurity that has to throw away or maybe that both the
separated substances are useful. For example – if you separate black grapes
from green ones from a mixture of the two.
2. Threshing:This method is mostly done during the harvesting of crops. Normally,
the stalks of the wheat are dried once it is harvested. The grain is then separated
from the stalks and grounded into the floor by beating the dry stalks to shake off
the dried grains.
3. Winnowing: When the grains are collected from the process of threshing, it
needs to be cleared out of husks and chaffs before it is turned into flour. Normally
the separation of the mixture is carried out with the help of wind or blowing air.
The husk and chaff are blown away by the strong wind when the farmers drop
the mixture from a certain height to the ground. The heavier grains are collected
at one place.
4. Sieving: It is done to separate mixtures that contain substances mostly of
different sizes. The mixture is passed through the pores of the sieve. All the
smaller substances pass through easily while the bigger components of the
mixture are retained.