What happens when you heat copper sulphate?
When you heat copper (II) sulfate pentahydrate (the blue crystals) it turns white as the water which is driven off by the heat. The white solid remaining is anhydrous (without water) copper (II) sulfate. If you add water to the anhydrous copper sulfate an exothermic (heat is given off) reaction occurs, you can feel the test-tube getting hot, as the blue copper (II) sulfate pentahydrate is re-formed.
