When an iron bar is dipped into a solution of copper(II)sulfate one will observe copper metal forming on the surface of the iron and a color change in the solution from blue to green. This is an example of a single replacement reaction in which copper replaces or displaces iron. Here's the equation:
`Fe_((s))+ CuSO_4_(aq_) -> Cu_((s)) + FeSO_4_(aq)`
Copper is lower on the activity series than iron, which means that it has a lower tendency to be oxidized. Since it's in its oxidized form, Cu2+ and iron is in the reduced form Fe, electrons will be transferred from iron to copper. Copper will be reduced to Cu metal, plating onto the surface of the iron. Iron will be oxidized to Fe2+, forming a soluble green complex ion in water.