9.3: Thermal Energy Transfer and Equilibrium

Describe the transfer of energy between two systems in thermal contact due to temperature differences of those two systems.

Two systems are in thermal contact if the systems may transfer energy by thermal processes..

• Heating is the transfer of energy into a system by thermal processes.

• Cooling is the transfer of energy out of a system by thermal processes.

The thermal processes by which energy may be transferred between systems at different temperatures are conduction, convection, and radiation.

Energy is transferred through thermal processes spontaneously from a higher-temperature system to a lower temperature system.

Thermal equilibrium results when no net energy is transferred by thermal processes between two systems in thermal contact with each other.

• Energy is most likely to be transferred from higher energy molecules to lower energy particles.

• After many collisions of molecules within different systems, the most probable state is that in which both systems have the same temperature.