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

• A. Condensation
• B. Conduction
• C. Convection
• D. Radiation

Answer: (A)

Condensation is a phase-change process, not a mode of heat transfer. The modes of heat transfer describe how energy moves: conduction through solids and fluids by molecular contact, convection with fluid flow, and radiation by electromagnetic waves. Condensation happens when water vapor loses enough energy to become liquid, releasing latent heat to the surroundings. Heat transfer can accompany condensation, but the change of state itself isn’t a transport mechanism. In practical terms, you see condensation when humid air contacts a cooler surface and the vapor dew points, forming liquid droplets as energy leaves the vapor. So condensation doesn’t fit as a mode of heat transfer, which is why it’s the correct choice for NOT being one.