Question

Ice at 0 degree Celsius appears colder to the mouth than water at 0degree Celsius,why?

Answer 1

because heat is released in the form of latent heat of freezing.

Answer 2

This is all due to Latent Heat of Fusion.

First, heat given to any body can do two things:
Either it can raise temperature is body, or it can change the phase of the body (eg. Liquid to solid)

Latent Heat of Fusion is the heat energy that must be supplied to a mass of 1 gram to convert it from liquid phase to solid phase.

For ice, the latent heat of Fusion is 80 cal/g. That is, you need to supply 80 calories (approx 336 joules) energy to 1gm ice to convert it into water.

Thus, 1 g water at 0° C contains 336 J more energy than ice at 0° C. (And more energy means it is hotter)

So, ice at 0° C appears colder to mouth than water at same temperature.