For any substance, why does temperature remain constant during change of state?

1 Answer
Jun 28, 2017

Answer:

Because a condition of #"phase equilibrium"# applies during change of state.

Explanation:

For the thermodynamic processes......

#H_2O(s)rightleftharpoonsH_2O(l)# at #0# #""^@C# and....

#H_2O(l)rightleftharpoonsH_2O(g)# at #100# #""^@C# .....

.........these occur under equilibrium conditions. Energy has to be supplied to break the (strong) bonds between the molecules of the condensed phase; for water, this so-called #"latent heat of fusion"# or #"latent heat of vaporization"# are quite large and reflects the degree of INTERMOLECULAR force between the individual molecules (i.e. a consequence of hydrogen bonding).