Figure 16.

Dissolving oil is entropically favorable in hot water, but entropically unfavorable in cold water. For toluene in water.¹⁹⁸ The solvation free energy depends little on temperature. The enthalpy and entropy depend more strongly on temperature, and they compensate. In cold water, the solute induces more ordering than in bulk waters, and the cages have good H-bond and solute interactions.¹⁹⁹ In hot water, insertion of oil breaks potential water–water hydrogen bonds, leading to both higher entropies and higher enthalpies.