If the molar enthalpy of solution of positive, the solubility increases with increasing temperature. If it is negative, the solubility decreases, in agreement with Le Chatelier's principle. Le Chatelier's principle is a favorite for the MCAT. (If a chemical system at equilibrium experiences a change in concentration, temperature, or total pressure; the equilibrium will shift in order to minimize that change.)

Although a positive entropy change would be expected with the dissociation in water of ions (similar to sublimation), the opposite occurs due to the imposition of order by the ions on the surrounding water molecules through the formation of hydration spheres. Dissolving an electrolyte in water decreases entropy. This would not be true for dissolving a nonpolar substance in a nonpolar solvent. This distinction has been important in at least one MCAT question in the past.