Touching a metal spoon in hot soup involves which mechanism?

• A. Conduction
• B. Convection
• C. Radiation
• D. Thermal diffusion

Answer: (A)

Heat transfer by conduction occurs when two objects touch and energy flows from the hotter to the cooler one. A hot soup and a metal spoon are in contact, so energy moves from the soup into the spoon at the surface. The spoon’s high thermal conductivity helps pass that energy quickly along its length, warming the spoon as a whole. This is the dominant mechanism here because it relies on direct contact. Radiation from the soup to the spoon does occur, but contributes less to heating the spoon than conduction through contact. Convection would involve movement of the soup carrying heat to the spoon, which isn’t the main way the spoon gains heat in this situation. Thermal diffusion describes how heat spreads inside a material and, for a solid like metal, is accomplished mainly by conduction, so conduction fits best in this context.