Copper sulphate is Cu SO₄ is a salt of copper.
The anhydrous copper sulphate without any moist or water molecules in it - is a light greenish white powder. When a water drop falls on the anhydrous powder, water molecules are absorbed by the sulphate.
The pentahydrate form CuSO₄ . 5 H₂O of copper sulphate is a beautiful bright shining blue crystalline solid.
Copper sulphate exists in various degrees of hydration ie., different number of molecules of water associated with one molecule of copper sulphate: like trihydrate and heptahydrate - which is green.
Cu SO₄ dissolves in a lot of water (not just drops) giving out heat, and forms [ Cu (H₂O)₆ ]²⁺ and SO₄²⁻ ions.
Cu SO₄ + 5 H₂O ==> ( Cu SO₄. 5 H₂O ) + heat
Cu SO₄ + 6 H₂O ==> Cu (H₂O)₆²⁺ + SO₄²⁻ + heat