Which of the following is included among the four heat transfer mechanisms listed?

• A. Evaporation
• B. Condensation
• C. Sublimation
• D. Freezing

Answer: (A)

Heat transfer includes a category for phase changes, in addition to conduction, convection, and radiation. Evaporation is a phase-change process where a liquid becomes vapor, and it involves latent heat—the energy required to change the state without a temperature rise. As heat is supplied to the liquid, molecules at the surface gain enough energy to overcome intermolecular forces and escape as gas, transferring heat to the surroundings in the process. This makes evaporation a clear example of the heat-transfer mechanism that operates during phase changes, which is why it is included among the four mechanisms. The other options—condensation, sublimation, and freezing—are also phase changes and involve latent heat, but evaporation directly exemplifies the phase-change mechanism in the standard four-category framework.