Question

Why blue colour of copper sulphate crystals disappers on heating?

Answer 1

However, when copper sulphate is heated for some time, the blue colour disappears and it becomes white-gray in colour. This is because the water molecules are lost on heating and copper sulphate pentahydrate is converted to anhydrous copper sulphate.

Answer 2

their blue color is due to water of crystallisation attached to them but when we heat them water gets converted into steam rising up leaving crstals colorless