Question

Copper sulphate when heated becomes colourless.give reason

Answer 1

On heating the blue salt of copper sulphate it is seen that it becomes colourless. This is so because the salt strongly looses all the water of crystallization, which leads to the formation of anhydrous copper sulphate which is white in colour. The salt containing water crystallization is called hydrated salts.

anhydrous means without water
so anhydrous copper sulphate means copper sulphate without water.