Zinc displacing copper. Strip of zinc (Zn) metal half-submerged in an aqueous solution (blue) of copper (II) sulphate (CuSO4). Solid copper (Cu, brown) is being deposited as the copper ions are replaced in the solution by zinc ions. This is known as a displacement or substitution reaction. The zinc is said to be more reactive than copper, and can be placed above it in a reactivity series.