Simply due to intermolecular interactions as polar molecules interact with each other using electrostatic attractions such as dipole-dipole, ion-dipole, dipole-induced dipole and so on, while, for non polar solvent such as hydrocarbons another kind of attraction which also electrostatic attraction which depends on polarizability called dispersion force occurred. In general, the interactions occurred in order to decrease the free energy of the system by loosing energy as heat.
Simply due to intermolecular interactions as polar molecules interact with each other using electrostatic attractions such as dipole-dipole, ion-dipole, dipole-induced dipole and so on, while, for non polar solvent such as hydrocarbons another kind of attraction which also electrostatic attraction which depends on polarizability called dispersion force occurred. In general, the interactions occurred in order to decrease the free energy of the system by loosing energy as heat.