Which term describes the energy required for a phase change without a temperature change?

• A. Latent heat
• B. Sensible heat
• C. Kinetic energy
• D. Potential energy

Answer: (A)

During a phase change at a constant temperature, energy goes into altering the substance’s internal structure and the forces between its molecules rather than raising its temperature. This energy is called latent heat because it is “hidden” in the change of phase. For example, melting ice at 0°C requires latent heat of fusion, and boiling water at its boiling point requires latent heat of vaporization. Sensible heat is the energy that changes temperature, while kinetic energy relates to the motion of particles and potential energy to the position or arrangement of those particles. So the energy needed for a phase change without a temperature change is latent heat.