Which process describes the heat transfer from one molecule to another within a substance?

The process that describes the heat transfer from one molecule to another within a substance is conduction. In conduction, heat is transferred through direct contact of molecules in a solid or liquid. When one molecule is heated, it vibrates and transfers its energy to adjacent molecules, causing them to also vibrate and increase in temperature. This transfer continues through the material until thermal equilibrium is reached.

Convection involves the movement of fluid, such as air or water, where warmer parts of the fluid rise while cooler parts sink, creating a circulating pattern that transfers heat. Radiation refers to the transfer of heat through electromagnetic waves, which can occur in a vacuum, such as the warmth received from the sun. Insulation, on the other hand, is a material or method used to reduce heat transfer, rather than describing a method of heat transfer itself. This understanding of heat transfer processes is critical in refrigeration and HVAC applications.