Question

What do you observe when iron nail are added to copper sulphate solution

Answer 1

When the iron nail is dipped in copper sulphate solution{blue in colour}, the chemical properties of the solution changes and the solution becomes iron sulphatesolution{green in colour}. It is a chemical change
Here is the required reaction:
Copper Sulphate + Iron - - - - > Iron Sulphate + Copper
CUSO​4 + FE - - - - > FESO4 + CU
It is a displacement reaction that is a type chemical reaction
Hope It Helps You!!!  : )

Answer 2

When iron nail is dipped in copper sulphate there takes reaction between them and copper sulphate charges its colour from blue to light green. This shows iron is more reactive then copper, it can replace copper from CuSO4. CuSO4 is in blue colour and FeSO4 is in light  green colour