What is the term for heat transfer that occurs between closely packed molecules?

The term that describes heat transfer occurring between closely packed molecules is conduction. This process involves the transfer of thermal energy through direct contact between molecules in a solid material. When one molecule is heated, it vibrates more rapidly and transfers energy to its neighboring molecules through collisions. This results in the gradual heat movement through the substance without any overall movement of the material itself.

In contrast, convection involves the movement of fluid (liquid or gas) that carries heat with it, while radiation refers to heat transfer through electromagnetic waves, which does not require a medium. Diffusion, on the other hand, describes the movement of particles from an area of high concentration to an area of low concentration and is not specifically related to heat transfer. Thus, conduction is the appropriate term for heat transfer through tightly packed molecules.