To show that iron is more reactive than copper.
Fe + CuSO4(aq) → FeSO4(aq) + Cu(s)
The type of reaction is a displacement reaction. In this process, the highly reactive metal iron replaces the copper in copper sulphate by giving up two electrons, becoming oxidised, and producing a new molecule called ferrous sulphate.
A displacement reaction occurs when an atom or a group of atoms in a molecule is displaced by another atom. A single displacement reaction occurs when an element replaces another element in a compound. Metal can only replace another metal, and a nonmetal can only substitute for another. The other element can only be replaced by a more reactive element in the compound with which it interacts.
For example, when iron is added to a copper sulphate solution, it displaces the copper metal.
A + B-C → A-C + B (General Representation of a displacement Reaction)
The above equation exists when A is more reactive than B. A and B must be either:
Metals' chemical reactivity relates to their respective places in the activity series. Certain metals can displace certain metals from their salts' aqueous solutions. Metal in a higher position in the activity series can displace a metal in a lower position from its aqueous salt solution. Metals are not the only ones affected by the displacement reaction. Nonmetals can also participate in these reactions.
Halogens are one example. The halogen activity sequence is F > Cl > Br > I.