Question

blue copper sulphate solution is treated with iron metal changed to Green why

Answer 1

It is because of a chemical reaction that occurs when copper sulphate solution reacts with iron metal.
Iron displaces copper to form ferrous sulphate and thus the color changes to green.
CuSO4+ Fe----→ FeSO4+Cu

Answer 2

Iron is more conductive then copper. That reason when u put the iron in copper Sulphate solution. The iron take place of the copper. And changes the color of iron into green. Green layer was deposited on the iron. And take place of the copper.