Experiment 21: Water of crystallization


  • Study water of crystallization in Copper Sulphate

Materials required:

  • copper sulphate crystals
  • burner
  • test tube


  • Take some crystals of copper sulphate (CuSO4.5H2O) in a test tube
  • Heat these crystals on a burner
  • Note the change in colour of the copper sulphate crystals during the heating. Does it show a bluish white colour? If yes, keep on heating the crystals for some more time. After some time as temperature reaches around 250 °C, the copper sulphate crystals starts appearing white.
  • Stop heating when it becomes complete white
  • Keep the test tube in open atmosphere for some time and allow it to cool. Do you find a change in the colour of copper sulphate crystals



  • Blue crystals of Copper Sulphate turn white


  • Blue crystals of copper sulphate contains water of crystallization


  • Blue crystals of copper sulphate contains water of crystallization. These crystals dehydrate on heating to lose water of crystallisation at a particular temperature and also change their colour. If the dehydrated copper sulphate solid material is allowed to cool in air, then it regains blue colour after gaining water molecules from the atmosphere.

CuSO4 • 5 H20 (bluish) → CuSO4(anhydrous, white) + 5 H2O