How many molecules of water are present in hydrated copper sulphate? What color change can we observe upon its heating?

 One formula unit of hydrated copper sulphate contains five water molecules (5H20). The water molecules which form part of the structure of a crystal are called water of crystallization.

When heated it loses its blue colour and crystal shape to become a powdery white mass.

$CuSO_{4} .5H_{2} O\ \xrightarrow{heat} CuSO_{4} \ +\ 5H_{2}O$

Blue                              White