Crystallization

What is Crystallization?

It is a process that separates pure solid from an impure solution in the form of crystals.

In this case, 

1. A solution is heated in an open container. 
2. Then it is left to cool .

After some time, pure solids are formed in the form of crystals.

                                                                                                                                                                                                                                                        Application or Uses of Crystallization

• Separation of Salt from Sea Water
• Separation of Crystals of Alum from impure samples
• Separation of Pure Copper Sulphate from impure Sample

Procedure:

1. Take some amount of impure copper sulphate solution in a china dish
2. Dissolve it in minimum amount of water
3. Filter the impurities
4. Heat and evaporate the water to get  a saturated solution
5. Cover the solution with filter paper and leave it undisturbed for 1 day to cool down at room temperature
6. Pour the cooled solution through a filter paper, to obtain the crystals

Why is Crystallization a better technique than Evaporation?

• During evaporation, we heat the solid.
  While heating, some solids get decomposed
  Also, some solids get charred (burnt)
  Example - Sugar

• Some impurities may remain dissolved even after filtration
  These may contaminate solid during the process of evaporation.

Hence, it is better to use crystallization instead of evaporation and filtering