Page 50 - ICSE Chemistry 8

SEPARATION OF MIXTURES

Mixtures are combina ons of two or more pure substances that come in several forms. Most of the
mixtures can be separated depending on their nature. For instance, a few iron nails sunk in the sand
can be separated using a magnet. This is possible because iron nails and sand have diff erent proper es.
Similarly, table salt is available to us as a mixture in seawater. The
Thinking Fountain
salt that is useful to us can be obtained from the mixture by the Give some examples of mixtures
method of evapora on and is refi ned in order to remove harmful found at home that need to be
components so that it can be used for cooking. separated before they are used.
State the methods used to separate
The process of separa ng the components of a mixture is called
these mixtures.
separa on of mixture.

Separa on of mixtures becomes essen al due to the following reasons.
• To obtain a useful component from a mixture
• To obtain a pure sample of a substance and to enhance purity of a substance

• To remove harmful and undesirable impuri es
Principle of Separation of Mixtures

In a mixture, each component retains its individual iden ty and proper es. The basis of separa on of a
mixture is the fact that each component has diff erent physical and chemical proper es. These components
are either elements or compounds. The techniques used for separa ng mixtures rely on the diff erences in
the physical proper es of the components.

Let’s study in detail the various techniques used for separa on of mixtures.
Separating Solid-Solid Mixtures

Handpicking
The method in which components of a mixture can be separated by
picking them with one’s hand is called handpicking.

The principle on which the technique is based is the visible diff erence
in size, shape or colour of the components of a mixture. Due to this, it
becomes easy to pick small stones present in pulses or rice.

Sieving Fig. 3.1: Handpicking
The method in which the components of a mixture are separated
using a sieve is called sieving.

The principle of the technique is the diff erence in size of the
components of a mixture. When we place a mixture on a sieve and
shake it, the component with a smaller size falls down through the
holes of the sieve, whereas the component with a larger size remains
on the sieve. A sieve is used to remove small stones from sand at
construc on sites. Sieving is also used to separate impuri es from
fl our. Fig. 3.2: Sieving

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