Copper sulphate pentahydrate contain 5 moles of water per one mole of copper (II) sulphate. Its formula is written as CuSO4.5H2O and has blue colour due to water of hydration. It can be converted into anhydrous copper sulphate when heated strongly. When heated, it loses two water molecules at ~63°C followed by two more at ~109°C and the final water molecule at ~200°C and turns to white coloured anhydrous copper sulphate. This above process can be reversed. When water is added to white coloured anhydrous copper sulphate, its colour changes to blue, indicating that the blue coloured copper sulphate pentahydrate is regenerated. So, it is a reversible chemical change.
This video explains the reversible chemical change occurs during the heating of hydrated copper sulphate