Which term describes heat transfer due to molecular interaction in direct contact?

The correct answer is conduction, which refers to the process of heat transfer that occurs when molecules interact directly with each other. In conduction, heat moves through a material as faster-moving molecules collide with slower-moving ones, transferring energy in the process. This typically occurs in solids, where molecules are closely packed together, allowing efficient energy transfer through molecular vibrations and collisions.

For instance, when a metal rod is heated at one end, the heat travels along the rod through conduction as the molecules at the hot end collide with neighboring cooler molecules, increasing their energy in the process. This direct contact between molecules facilitates the transfer of thermal energy.

Convection, on the other hand, involves the movement of fluid (liquid or gas) and the transfer of heat through that fluid's motion, which does not require direct contact between molecules in different regions. Radiation refers to the transfer of heat in the form of electromagnetic waves and does not require a medium, unlike conduction. Saturation generally pertains to the state of a substance (like water) at which no more of another substance can be absorbed, which is unrelated to heat transfer mechanisms.