Which mechanism transfers heat primarily through direct contact between solids?

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

Answer: (A)

Conduction is the heat transfer that occurs through direct contact between solids. When two solids touch, energy moves from the hotter part to the cooler part by vibrations and interactions between neighboring particles—the process is helped in metals by free electrons that carry energy rapidly from the hot side to the cooler side. This is why you can feel heat move along a metal rod or a skillet warming up its handle where it contacts a hot surface. The other mechanisms work differently: convection needs moving fluids to carry heat, radiation transfers energy as electromagnetic waves without requiring contact, and evaporation involves a liquid changing to vapor, not solid-to-solid contact.