Question

Explain the method that can be used for separating the following mixture:
(i) Sand and husk
(ii) Wheat, sugar and milk
(iii) Water and petrol
(iv) Rice and salt
(v) Sand and salt

Answer 1

Hint: Mixtures are formed by mixing together two or more substances without any chemical reaction. It is possible to separate the different components of a mixture by physical methods of separation like winnowing, sieving, filtration, sedimentation, decantation, etc

Complete step by step solution:
The methods that can be used for to separating the following mixtures:
(i) Sand and husk: Mixture of sand and husk can be separated by winnowing. This method of separation is used to separate the lighter particles from the heavier particle of a mixture by blowing wind. Husks being lighter can be easily separated from the heavier sand particles.

(ii) Wheat, sugar and silk: Silk is lighter than both wheat and sugar and thus, can be separated from wheat and sugar using winnowing. We cannot use the same method for separating wheat from sugar as they are equally heavy. However, they have different particle sizes. Sieving method allows the smaller particles to pass through holes of the sieve while the bigger particles stay on the sieve.

(iii) Water and petrol: Water and petrol are immiscible liquids and can be separated using a separating funnel. Petrol is lighter than water. When the mixture of water and petrol in a separating funnel is allowed to stand for a while, then the layer of petrol floats above the aqueous layer. Water can be collected from the bottom of the separating funnel.

(iv) Rice and salt: Size of rice is bigger than that of salt crystals. Therefore, the mixture of rice and salt can be separated by sieving.

(v) Sand and salt: Salt dissolves in water whereas sand does not dissolve. Thus, the mixture of sand and salt can be separated by dissolving it in water. salt dissolves and sedimentation of sand occurs. Sand can then be separated from the liquid by decantation followed by filtration. Evaporation of the filtrate separates salt.

Note: Physical methods of separation of mixture exploit the differences in physical properties of the various constituents of a mixture like solubility, particle size, weight of particles, etc.