Which statement best describes conduction?

Which statement best describes conduction?

• A. Direct transfer of heat through contact between particles, typically in solids.
• B. Transfer of heat through moving fluids.
• C. Transfer of heat via radiation across empty space.
• D. Transfer of heat by phase change of a substance.

Answer: (A)

Conduction is heat transfer through direct contact between particles. In solids, energy passes from hotter particles to cooler ones by collisions and interactions, and in metals this is aided by free electrons that move rapidly and transfer energy quickly along the material. That’s why a metal rod left in a hot source becomes warm along its length even if only one end touches the heat. This mode is different from convection, where heat moves with moving fluids; and from radiation, which travels through space by electromagnetic waves without requiring direct contact; and from phase-change processes, which involve energy absorbed or released when a substance changes from one phase to another. The statement describing direct transfer of heat through contact between particles, typically in solids, best captures conduction.

Conduction is heat transfer through direct contact between particles. In solids, energy passes from hotter particles to cooler ones by collisions and interactions, and in metals this is aided by free electrons that move rapidly and transfer energy quickly along the material. That’s why a metal rod left in a hot source becomes warm along its length even if only one end touches the heat. This mode is different from convection, where heat moves with moving fluids; and from radiation, which travels through space by electromagnetic waves without requiring direct contact; and from phase-change processes, which involve energy absorbed or released when a substance changes from one phase to another. The statement describing direct transfer of heat through contact between particles, typically in solids, best captures conduction.