text: The above equations of state suggest methods to experimentally measure changes in the thermodynamic potentials using physically measurable parameters. For example the free energy expressions
  and
  can be integrated at constant temperature and quantities to obtain:
  can be integrated:
  :<math>
  \Delta H = \int_{S1}^{S2}T\,\mathrm{d}S = \Delta Q\,\,\,\,
  :<math>
  \Delta U = \int_{S1}^{S2}T\,\mathrm{d}S = \Delta Q\,\,\,\,
  Note that these measurements are made at constant {N } and are therefore not applicable to situations in which chemical reactions take place.