Hey guys. From my understanding, Temperature is a measure of the average kinetic energy of the molecules within a substance. Heat is the transfer of thermal energy between a system and its surroundings Internal Energy is the total energy (kinetic + potential) of the molecules of a substance. What is thermal energy? Is thermal energy the total KINETIC energy of the molecules within a substance or the total KINETIC energy and POTENTIAL energy of the molecules within a substance? If it is the latter, isn't it the same as internal energy? I have looked for this on the web but am getting mixed responses. Some say thermal energy is the same as heat whereas others say it is the same as internal energy. From my knowledge of the topic, I believe that Thermal Energy is the total kinetic energy of the molecules within a substance, but am not 100% sure.