Which term is defined as heat transfer through direct contact with a surface?

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

Answer: (A)

Direct contact heat transfer is conduction. It occurs when thermal energy moves from one object to another through direct molecular interaction at their interface. For example, touching a hot metal spoon transfers heat from the spoon to your hand by conduction. This mechanism is most effective in solids where particles are closely packed, though it also happens in liquids and gases. In contrast, convection involves heat carried by moving fluids, radiation travels as energy waves through space or a medium without touching, and evaporation involves a liquid changing to a vapor at a surface, which is a phase-change process. So the term defined by heat transfer through direct contact with a surface is conduction.