Crystallization

What is Crystallization?

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

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. Crystals are formed, while impurities are left in the solution
7. Pour the cooled solution through a filter paper, to obtain the crystals and dry.
   

We will obtain pure crystals of Copper Sulphate on the filter paper

Why is Crystallization a better technique than Evaporation?

• During evaporation, we heat the solid. While heating, some solids get decomposed or charred (burnt)
  Example - Sugar.
  This is not a problem in Crystallisation
  
  
• In evaporation, some impurities remain dissolved even after filtration.  These may contaminate solid during the process of evaporation.
  These impurities get removed in cyrstallisation