What is the term for the transfer of heat from one molecule to another, or through one substance to another?

The term for the transfer of heat from one molecule to another, or through one substance to another, is conduction. Conduction occurs when heat is directly transferred through materials as molecules collide with one another, resulting in the energy being passed along. This process is most effective in solids, where molecules are closely packed together, allowing efficient energy transfer.

In contrast, convection involves the movement of heat through fluids (liquids or gases) where warmer areas of a liquid or gas rise to cooler areas. Radiation is the transfer of heat in the form of electromagnetic waves, such as infrared radiation, and can occur through a vacuum or empty space. Insulation refers to materials used to reduce the transfer of heat, rather than a mechanism of heat transfer itself. Therefore, conduction is specifically the correct answer regarding the direct transfer of heat between molecules and through substances.