To prove that iron is more reactive than copper:
Steps:
Take a solution of copper sulphate (blue).
Add some iron nails to it.
Leave it for about an hour.
Observations:
A brown coating is formed on the surface of iron
The color of copper sulphate solution has turned from blue to light green.
Conclusion:
Due to high reactivity of iron, it displaces copper and forms iron sulfate solution (light green).
(Iron)Fe+(Copper sulphate)CuSO4
→(Iron sulphate)FeSO4+(Copper) Cu