MIAT Physics Practice Test 2026 - Free Physics Exam Practice Questions and Study Guide

When a substance undergoes a first-order phase transition at a fixed temperature, the energy you add does not raise the temperature. Instead it goes into latent heat, the energy needed to rearrange the internal structure to switch from one phase to another. This is why the temperature stays constant while melting or boiling occurs—the supplied energy is used to break (or form) the intermolecular bonds that define the phases. For example, melting ice at 0°C uses latent heat of fusion, about 334 kJ per kilogram, to convert solid into liquid; boiling water at 100°C uses latent heat of vaporization, about 2260 kJ per kilogram, to convert liquid into gas. Once the entire material has transformed, any additional energy then increases the temperature of the new phase.