Question

Based on your experience, when ice melts to liquid water, is the process of endothermic or exothermic? When liquid water freezes to ice at 0°C, is this endothermic or exothermic? (assume that the ice/water is the system in each case.)

Answer 1

When ice melts to liquid water, it is an endothermic process because heat must be absorbed to melt the ice without a change in temperature (Latent heat of fusion).

When liquid water freezes to ice, the process is exothermic because energy is given out for the liquid water to form a more stable ice.