What is Crystallization?
It is a process that separates pure solid from an impure solution in the form of c rystals.
In this case,
- A solution is heated in an open container.
- 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:
- Take some amount of impure copper sulphate solution in a china dish
- Dissolve it in minimum amount of water
- Filter the impurities
- Heat and evaporate the water to get a saturated solution
- Cover the solution with filter paper and leave it undisturbed for 1 day to cool down at room temperature
- Crystals are formed, while impurities are left in the solution
-
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
