A metal spoon in hot soup demonstrates which form of heat transfer?

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

Answer: (A)

Conduction is the transfer of heat through direct contact from a hotter object to a cooler one. In this scenario, the hot soup is in contact with the metal spoon, so energy moves from the soup into the spoon at the interface. The molecules and free electrons in the spoon then carry that energy through the metal, warming the spoon overall. Metals are especially good at this because their free electrons shuttle energy quickly.

Convection would require bulk movement of a fluid, like hot soup circulating or air moving around the spoon, to carry heat—this isn’t the main process here. Radiation would heat the spoon by infrared radiation from the hot liquid without contact, which is possible but not the primary mechanism when there’s direct contact. Diffusion refers to the spread of particles, not the standard way we categorize heat transfer in this situation, so the direct contact energy transfer—conduction—is the best fit.