Which process transfers heat by direct contact between substances?

Which process transfers heat by direct contact between substances?

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

Answer: (A)

Conduction is heat transfer through direct contact between substances. When two objects touch, the particles in the hotter object vibrate more and transfer some of that kinetic energy to the cooler object through collisions and molecular interactions. This is why a metal spoon left in hot soup becomes warm—the heat moves from the hot liquid into the spoon by touching it. Radiation, by contrast, transfers heat through electromagnetic waves and can occur without any touching. Convection involves the movement of a fluid; warmer parts rise and cooler parts sink, carrying heat with the flowing fluid. Reflection isn’t a heat transfer process at all—it’s the bouncing of light off a surface.

Conduction is heat transfer through direct contact between substances. When two objects touch, the particles in the hotter object vibrate more and transfer some of that kinetic energy to the cooler object through collisions and molecular interactions. This is why a metal spoon left in hot soup becomes warm—the heat moves from the hot liquid into the spoon by touching it.

Radiation, by contrast, transfers heat through electromagnetic waves and can occur without any touching. Convection involves the movement of a fluid; warmer parts rise and cooler parts sink, carrying heat with the flowing fluid. Reflection isn’t a heat transfer process at all—it’s the bouncing of light off a surface.