Ferrous sulphate crystals turn white on heating.

1.     Ferrous sulphate crystals contain water of crystallization (FeSO₄.7H₂O).

2.     The crystalline nature and the green colour of the crystals are due to the water of crystallization.

3.     When ferrous sulphate crystals are heated, the water of crystallization is given out.

4.     Anhydrous ferrous sulphate is a white amorphous powder.

5.     Hence, ferrous sulphate crystals turn white on heating.