Which of the following is NOT a mode of heat transfer?

The correct answer is that evaporation is not considered a mode of heat transfer in the traditional sense of the term. Instead, evaporation is a phase change process where a liquid turns into a vapor as it gains energy, primarily through heat. While evaporation does involve heat energy, it functions differently from the primary modes of heat transfer.

Convection, radiation, and conduction are the three primary modes of heat transfer:

• Convection involves the movement of heat through fluids (liquids and gases), where warmer areas rise and cooler areas sink, creating a current that transfers heat.

• Conduction is the transfer of heat through direct contact between materials, where energy is passed from molecule to molecule.

• Radiation is the transfer of heat in the form of electromagnetic waves, allowing heat to be transferred through a vacuum without the need for a medium.

In contrast, evaporation is about changing the state of a substance and is thus categorized separately from the fundamental methods of transferring thermal energy. This distinction is important for understanding thermodynamic processes as a whole.