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How does latent heat affect a substance during melting, freezing, or vaporization?

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Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy. — phase States of matter.

Latent heat is the energy absorbed or released by a substance during a change in its physical state (phase) that occurs without changing its temperature.1

During these transitions, the substance undergoes the following processes:

Melting and Freezing: The energy associated with melting a solid or freezing a liquid is known as the heat of fusion. To melt a solid, additional heat must be added at a constant temperature to overcome the attractive forces holding the crystal lattice together, allowing particles to move freely in a liquid state.1
Vaporization: The energy required to change a liquid to a vapour at a constant temperature and pressure is called the heat of vaporization. This energy is necessary to break the long-range order of the liquid, enabling the particles to move independently in the gaseous phase.12

Because this energy is used to change the physical state rather than increase kinetic energy, the temperature of the substance remains constant throughout the entire phase change.12