What is defined as the direct transfer of heat between molecules of objects in contact?

The correct answer is conduction. Conduction is the process by which heat is directly transferred from one molecule to another through direct contact. When two objects at different temperatures come into contact, the molecules of the hotter object vibrate more vigorously and transfer some of their kinetic energy to the slower-moving molecules of the cooler object. This transfer of energy continues until thermal equilibrium is reached, meaning that both objects reach the same temperature.

In contrast, radiation involves heat transfer through electromagnetic waves, which doesn’t require direct contact or a medium. Convection refers to the transfer of heat through the movement of fluids, where warmer areas of a liquid or gas rise while cooler areas sink, creating a convection current. Evaporation is a process in which liquid molecules gain enough energy to transition into a gas phase, which does not involve direct molecular contact but rather the escape of molecules from the surface of a liquid.

Understanding conduction is essential, as it plays a significant role in various phenomena, including heating systems, cooking methods, and understanding thermal conductivity in materials.