What is the transfer of heat through matter by direct particle-to-particle contact called?

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

Answer: (D)

Conduction is the transfer of heat through matter by direct particle-to-particle contact. In solids, neighboring particles collide and pass kinetic energy from a hotter region to a cooler one; metals also have free electrons that move quickly and ferry energy along the material. A classic example is a metal spoon warming up along its length when left in hot soup. This mechanism requires a material to transmit energy; it doesn’t occur in a vacuum. By contrast, convection relies on the bulk movement of fluids, and radiation transfers heat through electromagnetic waves without needing matter. Diffusion relates to the spreading of particles due to concentration differences and isn’t the primary way heat moves between neighboring particles.