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


  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

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
    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



  1. Class 9
  2. Chapter 2 Class 9 - Is Matter Around Us Pure

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.