One experiment has been carried out to investigate the specific heat capacity and latent heat of water during heating process. The students observed that the temperature is kept constant during phase change, whereby the temperature showed 0 celcius for a few minutes until all the ice melted. They thought that something went wrong in their experiment. So they asked me. These are my explanation :
During the phase change of a solution, it is the ice that is undergoing the phase change. When a phase change occurs, as in the melting of a solid, the thermal energy goes into separating the molecules, "breaking the intermolecular attractions", so to speak, (hydrogen bonds, in the case of water), and not into changing the temperature of the solution. That is why the temperature constant at melting as well as boiling. The energy is used to weaken the molecular bond, has to work against the atmospheric pressure and used to separate the intermolecular bond between the solvent.