If boiling of water involves change in internal energy, then why does the temperature remain constant?

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Laci Conrad · Accepted Answer

Temperature characterizes the average energy of atoms/molecules, as per Boltzmann distribution:  w  (      p    ,      q    )  ∝      e          −                        H          (                      p                    ,                      q                    )                                      k            B                    T                      ,where the potential energy may contain interactions, i.e., it is not simply a sum of potential energies of separate atom/molecules in external field. Further, one can then prove the equipartition theorem that the average energy per degree of freedom is       k    B    T      /    2However, there is nothing in these statements about the temperature being the kinetic energy. This is the case when we consider an ideal gas, in which (by its definition) the interactions between the atoms/molecules are neglected and all the energy is the kinetic one.Thus, the reason why the boiling water is not increasing its temperature, is because the energy goes into overcoming the potential keeping the molecules close to each other in the liquid phase.

If boiling of water involves change in internal energy, then why does the temperature remain constant?

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