Chemistry: Why Ice Stays at 0°C While Melting

Why does ice sit stubbornly at 0°C while you keep heating it? The answer lies in latent heat of fusion — the energy needed to turn ice into liquid water at a constant temperature. Unlike specific heat capacity, which raises temperature, this energy does something different: it breaks the hydrogen bonds locking H₂O molecules into their rigid lattice, freeing them to slide past one another as a liquid. This matters because it explains a counterintuitive idea: energy can flow into a system without its temperature rising. During melting, the supplied heat is consumed entirely by overcoming intermolecular forces rather than speeding up the molecules. Since temperature reflects average kinetic energy, and that average stays unchanged, the thermometer holds steady at 0°C until every last bond is broken. The relationship E = mL ties this energy to the mass of ice and its specific latent heat, connecting particle-level behaviour to measurable quantities.