The dominant mode of heat transfer that requires direct contact between substances is conduction.

• A. False
• B. Conduction
• C. True
• D. Radiation

Answer: (C)

Conduction is heat transfer through direct contact, moving energy from the hotter region to the cooler region by particle interactions and, in metals, by free electrons passing energy along. When a hot object touches a cooler one, its particles collide with the neighbors, transferring some of their kinetic energy and warming the cooler body. Metals especially feel this quickly because electrons can zip around and carry energy rapidly from the hot area to the cooler area. Radiation, by contrast, transfers energy through electromagnetic waves and doesn’t require contact, while convection relies on the movement of fluid. Because conduction fundamentally needs contact between substances to move energy, the statement is true.