Heat and thermal energy are related concepts in thermodynamics, but they have distinct meanings:
Heat: Heat is the transfer of thermal energy between two systems due to a temperature difference. It is a form of energy that flows from a region of higher temperature to a region of lower temperature. Heat transfer can occur through various mechanisms, such as conduction, convection, and radiation. For example, if you place a hot object in contact with a colder object, heat will transfer from the hot object to the cold object until they reach thermal equilibrium.
Thermal Energy: Thermal energy, on the other hand, refers to the total internal energy of a system due to the random motion of its particles. It is a form of kinetic energy associated with the microscopic movement of atoms and molecules within a substance. The thermal energy of a system is determined by its temperature, which is a measure of the average kinetic energy of the particles. The higher the temperature, the greater the thermal energy.
In summary, heat is the transfer of thermal energy from one system to another, while thermal energy represents the total internal energy of a system associated with the motion of its particles.