Question

when some zinc granules are placed in copper sulphate solution the solution change its colour

Answer 1

when some zinc granules are placed in copper sulphate solution the solution change its colour., since zinc is more reactive than copper, zinc reacts with copper sulphate (blue) and forms zinc sulphate and copper forms the precipitate..
CUSO4 + ZN = ZNSO4 + CU

Answer 2

Answer: The copper metal will get precipitated out with formation of zinc sulfate.

Explanation:

When Zinc granules are kept in copper sulfate solution the blue color of the copper sulfate solution turns  colorless. This because the zinc is more reactive than the copper metal in reactivity series. This means that zinc metal can easily displace the copper metal from its salt to form aqueous solution of zinc sulfate. This reaction is also an example f displacement reaction.

$Zn(s)+CuSO_4(aq)\rightarrow ZnSO_4(aq)+Cu(s)$