Definitions
- It is something which may be transferred from one body to another, according to the second law of thermodynamics.
- It is a measurable quantity, and thus treated mathematically.
- It cannot be treated as a substance, because it may be transformed into something that is not a substance, e.g., mechanical work.
- Heat is one of the forms of energy.
Several modern definitions of heat are as follows:
- The energy transferred from a high-temperature system to a lower-temperature system is called heat.
- Any spontaneous flow of energy from one system to another caused by a difference in temperature between the systems is called heat.
In a thermodynamic sense, heat is never regarded as being stored within a system. Like work, it exists only as energy in transit from one system to another or between a system and its surroundings. When energy in the form of heat is added to a system, it is stored as kinetic and potential energy of the atoms and molecules in the system.
