What is conduction?

• A. The transfer of heat through direct contact between substances.
• B. The flow of heat by radiation through empty space.
• C. The mixing of substances at the molecular level.
• D. The transformation of matter between states.

Answer: (A)

Conduction is heat transfer through direct contact between substances. It happens when energy moves from the hotter object to the cooler one via particle interactions and electron movement, with solids typically being the best conductors because their particles are tight and can pass energy efficiently. An everyday example is a metal spoon warming up in hot soup and then feeling warm to the touch as energy travels from the soup, through the spoon, to your hand.

This differs from radiation, which transfers heat through waves across empty space and doesn’t require touch. It also isn’t simply about mixing substances at the molecular level, which describes diffusion, not heat transfer by contact. And it isn’t about changing the state of matter, like melting or boiling, which are phase changes rather than the mechanism of heat transfer by contact.