Calculate energy in phase changes.
Heating a substance through a phase change takes energy in two distinct forms. Latent heat is absorbed at constant temperature while bonds rearrange — melting ice takes 334 J/g with no temperature rise at all. Sensible heat then raises the temperature at a rate set by the specific heat capacity. Separating the two makes clear why melting dominates: converting ice at 0 C to water at 0 C costs the same energy as heating that water by 80 degrees.
Latent plus sensible heat
Q latent = mass x latent heat; Q sensible = mass x specific heat x delta T; Q total = sum of both
Because all the incoming energy goes into breaking the ordered structure of the solid rather than into molecular kinetic energy. Only once every last crystal has melted does further heating raise the temperature.
Vaporisation must fully separate molecules against their intermolecular attraction, while melting only loosens them. For water that is 2260 J/g against 334 J/g — nearly seven times more, and the reason steam burns are so severe.
Yes, with the sign reversed. The same magnitudes apply to energy released rather than absorbed, which is the principle behind ice-based cooling and steam heating systems.