Heat transfer by direct contact between solids is called...

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

Answer: (D)

Direct contact allows thermal energy to move from a hotter solid to a cooler one through particle interactions at the interface. This process, called conduction, happens because hotter objects have particles with more kinetic energy, and when they collide with particles in the cooler object, some of that energy is transferred, warming the cooler matter. Metals especially transfer heat well because free electrons rapidly carry energy from the hot region to the cooler region.

Convection, by contrast, involves the bulk movement of a fluid carrying heat, and radiation transfers energy through electromagnetic waves without needing contact or a medium. Reflection isn’t a heat-transfer mechanism; it describes energy bouncing off a surface rather than transferring as heat.