What is meant by water of Crystallisation ? How do you show that copper sulphate crystal contains water of crystallisation ?

Explanation

The water molecules associated with a crystalline substance is called "Water of crystalisation" to show crystalline salts contain water of crystalisation.

Materials required : `CuSO_(4) .5H_(2)O` (Blue vitrial) boiling tube, burner, cork, delivery tube, test tube, clamp stand.
procedure:
1) Take 2g of `CuSO_(4).5H_(2)O` in a boiling tube fitted in a clamp stand.
2) Observe its colour, fit it with cork and delivery tube bent at two right angles which dips into a test tube.
3) Heat crystal in boiling tube.
4) Observe vapours being condensed in test tube.
5) Cool the crystals and add few drops of water into it.
Observation: Water vapour gets condensed in a test tube and colour of blue crystals changes into white. On adding water to anhydrous copper sulphate, it changes into blue again Chemical reaction :
`underset("Blue vitriol")(CuSO_(4).5H_(2)O)overset("heat")tounderset("White")(CuSO_(4)+5H_(2)O)`
Conclusion : Crystalline substance have water of crystalisation which are lost on heating.