An ideal solution is formed when the intermolecular attractive forces between the solute and solvent molecules (A-B) are nearly equal to those between the pure component molecules (A-A and B-B). In such solutions, there is no change in enthalpy ($\Delta_{mix}H = 0$) or volume ($\Delta_{mix}V = 0$) upon mixing, meaning the volume of the solution is the sum of the volumes of the components . Deviations from this equality in forces lead to non-ideal behaviour (positive or negative deviations) .