2.27 describe the use of anhydrous copper(II) sulphate in the chemical test for water

Anhydrous copper(II) sulphate will turn from white to blue if water is present.

To test for water, all you need to do is add anhydrous copper(II) sulphate, which is a white powder, to the substance you are testing. If the anhydrous copper(II) sulphate turns from white to blue, water is present.

This is a reversible reaction, meaning if you heat the blue powder, it will turn white again. This is because the water has 'left' (it's evaporated)

NOTE: anhydrous means without water, hydrated means with. Therefore, if water is present, anhydrous copper(II) sulphate will turn to hydrated copper(II) sulphate.

NOTE NOTE: this does not show pure water, just that the substance contains water molecules