In melting ice, added heat breaks more hydrogen bonds rather than increasing the speed of molecular motion, so the temperature of the ice-water mixture remains at a constant 32F until all the ice melts. That is why ice keeps drinks cold: Added heats goes into melting the ice, not raising the temperature. Once all the ice has melted, added heat again makes the molecular move faster and so raises the water temperature.

Some of the heat energy, however, until goes into breaking hydrogen bonds that than increasing the speed of molecular motion. It therefore takes a large amount of heat to raise the temperature.