Represents a process or reaction that releases energy from the system very often relief in the form of heat, but it may be in the form of light. Electricity, or sound.
Refers to a process or reaction that releases energy from the system. Usually in the form of heat release. It may take the form of an electric light or sound.
Refers to the process or the reaction energy release out of the system. The most often released in the form of heat, but it may be in the form of light, electricity, or sound.