What is Sieving? Where can it be used?

Sieving is a method of separation of mixtures. It is a process by which fine particles are separated from bigger particles by using a sieve.

It is mainly used in flour mills or at construction sites. In a flour mill, impurities like husks and stones are removed from wheat.

Pebbles and stones are removed from sand by sieving.  At home, it is used for cooking purposes. For example, Tea leaves are removed from tea with the help of a sieve.

Principle: The mixture is subjected to horizontal or vertical motion, causing a relative movement between the particles and the sieve. The finer particles pass through the sieve and coarser ones are retained on the sieve surface.

Advantages: 

• Sieving is an easy method of separation as it doesn’t require skills.
• It is a cheap method.
• It takes lesser time.

Disadvantages:

The sieving method cannot be used to separate two substances in a mixture having the same size.

For example, it cannot separate a mixture of chalk powder from flour.

[Note: The size of the pore in the sieve depends on the size of the particles of the constituents to be separated.]