What is the direct transfer of heat from one substance to another that it is touching?

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

Answer: (C)

Direct transfer of heat through direct touch between substances is conduction. When two objects touch and have different temperatures, energy moves from the hotter object to the cooler one by interactions at the interface and through the materials themselves. The more energetic particles in the hot object collide with cooler particles, passing some of their energy along and warming the cooler object until temperatures even out or the contact ends. Metals are especially good conductors because free electrons can quickly shuttle energy from one region to another. This is different from convection, which uses moving fluids to transport heat, and from radiation, which transfers heat via electromagnetic waves without needing contact. The term “contact” describes touching, but it isn’t the name of the heat-transfer mechanism.