Solvation and interaction between molecules
Solvation involves many different forms of intermolecular interactions: hydrogen bonding, ion dipole moments, van der Waals forces, and other intermolecular forces. Hydrogen bonds, ion dipole moments, and intermolecular forces only occur in polar solvents. The force between ions and ions only occurs in ionic solvents. The thermodynamic solvation reaction only occurs when the Gibbs energy of the solution is reduced, comparing the Gibbs energy separated from the solvent and solid (either gas or liquid). This means that the amount of change in enthalpy minus the change in entropy (multiplied by absolute temperature) is negative, or that the Gibbs free energy of the system is reduced.