Which form of heat transfer occurs through direct contact between substances?

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

Answer: (C)

Direct contact transfers heat by conduction. When a hot object touches a cooler one, its fast-moving particles collide with the cooler object's particles, sharing kinetic energy. This energy transfer continues until both substances reach a similar temperature. Conduction is especially effective in solids, where particles are tightly connected and can pass energy quickly, such as metals. By contrast, convection relies on the movement of a fluid to carry heat, and radiation moves energy through electromagnetic waves without needing contact. Insulation slows heat transfer overall but is not itself a mode of heat transfer. So, the process occurring through direct contact is conduction.