What is the transfer of kinetic energy between substances referred to as?

The transfer of kinetic energy between substances is referred to as heat. This process occurs typically when there is a temperature difference between the substances involved. When one substance is at a higher temperature, its particles have more kinetic energy, and when they come into contact with a cooler substance, some of that energy is transferred to the cooler substance, resulting in a rise in its temperature. This energy transfer is driven by the second law of thermodynamics, which states that energy will naturally flow from areas of higher energy to lower energy until thermal equilibrium is reached.

This concept is fundamental in thermodynamics and physical chemistry, and understanding heat transfer is critical for explaining various physical phenomena, from everyday occurrences like cooking to complex industrial processes. It is also distinct from work, which involves the transfer of energy through force applied over a distance, and temperature, which is a measure of a substance's thermal energy. Energy flow might be a concept that describes the overall movement of energy, but it does not specifically refer to the transfer due to temperature differences, making heat the more precise term for this phenomenon.