Which term describes the direct heat transfer from one substance to another in contact?

• A. The direct transfer of heat from one substance to another substance that it is touching.
• B. The circulation of heat from a warmer area to a cooler area; boiling, baking...
• C. The cooking of food in steam under pressure
• D. The use of radiation for heat transfer

Answer: (A)

Direct heat transfer through contact is conduction. It happens when two substances touch and energy moves from the hotter one to the cooler one through molecular interaction. In cooking this is why a hot pan can sear and heat food that’s in direct contact with it—think of meat resting on a skillet or a pot transferring heat to soup through the pot bottom. The rate of conduction depends on the temperature difference and the materials’ ability to conduct heat (thermal conductivity): metals like copper and aluminum transfer heat quickly, while materials such as wood or plastic are poor conductors. This differs from convection, which uses moving air or liquid to carry heat, and from radiation, which transfers heat through waves without contact. Steam cooking under pressure involves steam, which primarily transfers heat by convection (and some conduction when contacting food) rather than direct contact alone.