Question

State whether the following changes are chemical or physical changes- anhydrous copper sulphate( white in colour) , turns blue, when a drop of water is poured over it

Answer 1

A Physical Change

Anhydrous (laking moisture) $CuSO_4$ is white in colour and hydrated $CuSO_4$ is blue in colour. But when hydrated copper sulphate is heated, it loses it's blueish colour. But when we add a few drops of water, it gets it's colour back.

Thus, the charge is not irresible. Thus, it is a physical change.