The thermal denaturation of DNA involves heating DNA, leading to breaking bonds, specifically hydrogen bonds and hydrophobic stacking attractions between the bases. Thus, thermal denaturation is an endothermic process that absorbs heat, making the net enthalpy change positive, ∆H thermal > 0. Thermal denaturation has been proved to be endothermic by measurement of the temperature dependence of ln K. (See, for example, ). Gibbs free energy change, in this case, is positive, ∆G > 0.