When aluminium is dipped into copper sulphate solution, a chemical reaction takes place in which aluminium displaces copper from the solution and forms aluminium sulphate. The reaction can be represented as follows:

$$2Al(s) + 3CuSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Cu(s)$$

In this reaction, aluminium atoms lose three electrons each to form aluminium ions (Al3+), while copper ions (Cu2+) gain two electrons each to form copper atoms (Cu). The aluminium atoms react with sulphate ions (SO4 2-) from the copper sulphate solution to form aluminium sulphate, while the copper atoms are deposited on the surface of the aluminium metal.