DEFINE THE PROCESS OF CRYSTALLISATION?

Crystallization:

• Crystallization is the process of slow precipitation of solid crystals of a substance from a concentrated homogeneous solution. It is basically a separation method in which a substance is transferred from the liquid (i.e. solution) phase to the solid state. The substance is thus obtained in pure crystalline form and has no impurity. It is used by chemists for the purification of solid substances.

Process of crystallization:

Following is an example of using crystallization to obtain pure copper sulphate from an impure sample.

• Take a small amount (5 g) of an impure sample of copper sulphate in a china dish.

• Dissolve the sample in 10 ml of water (we basically have to use minimum amount of water in order to prepare a saturated solution).

• Then, filter it to remove impurities.

• Evaporate the filtrate on a water bath till small crystals are formed indicating that a concentrated solution has been obtained.

• After this, cover the solution with a filter paper and leave it undisturbed at room temperature for the rest of the day.

It will be observed that crystals of pure copper sulphate are obtained and the impurities are left behind in the solution.