Which term refers to the transfer of heat through direct contact within a substance?

The term that refers to the transfer of heat through direct contact within a substance is conduction. This process occurs when molecules in a solid material or a fluid come into contact with one another and transfer their kinetic energy, which results in the transfer of heat. Conduction is most evident in materials such as metals, where closely packed atoms can efficiently transfer energy.

In contrast, convection involves the movement of fluids, where warmer, less dense regions rise while cooler, denser areas sink, creating a circulation that facilitates heat transfer throughout the fluid. Radiation, on the other hand, is the transfer of energy through electromagnetic waves, which does not require any medium. Lastly, insulation refers to materials or methods used to reduce heat transfer, rather than a means of heat transfer itself.

Understanding conduction is essential in fields like air conditioning and refrigeration as it plays a crucial role in heat exchange processes and system efficiency.