I know that during melting, there is no temperature change as the heat
energy is used to do work against potential bond energy but why doesn't
temperature change when freezing?
Freezing is the opposite process of melting. If the temperature does not
increase as the ice melts, the temperature will not decrease as water
freezes.
Melting and freezing are entropy changes. Entropy measure the amount of
disorder in a system. A system, like ice, which has less freedom of
motion, has less disorder. A system, like liquid water, which has more
freedom of motion, has more disorder.
So water has more entropy than ice.
Ice is a very ordered arrangement of H2O molecules in a crystalline
form. As heat energy is added to ice, the energy is used the break the
bonds between the H2O molecules in the ice crystals. So, the temperature
remains constant. You might say that the energy that is added to the
ice is used to increase the entropy of the system, instead of increasing
the temperature of the system.
