In thermodynamics, a physical property is any property that is measurable, and whose value describes a state of a physical system. Thermodynamic properties are defined as characteristic features of a system, capable of specifying the system's state. Some constants, such as the
ideal gas constant, , do not describe the state of a system, and so are not properties. On the other hand, some constants, such as (the freezing point depression constant, or
cryoscopic constant), depend on the identity of a substance, and so may be considered to describe the state of a system, and therefore may be considered physical properties.
"Specific" properties are expressed on a per mass basis. If the units were changed from per mass to, for example, per mole, the property would remain as it was (i.e.,
intensive or extensive).
Regarding work and heat
Work and
heat
In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by such mechanisms as thermal conduction, electromagnetic radiation, and friction, which are microscopic in nature, involving sub-atomic, ato ...
are not thermodynamic properties, but rather ''
process quantities
In thermodynamics, a quantity that is well defined so as to describe the path of a process through the equilibrium state space of a thermodynamic system is termed a process function, or, alternatively, a process quantity, or a path function. As ...
:'' flows of energy across a system boundary. Systems do not ''contain'' work, but can ''perform'' work, and likewise, in formal thermodynamics, systems do not ''contain'' heat, but can ''transfer'' heat. Informally, however, a difference in the energy of a system that occurs solely because of a difference in its temperature is commonly called ''heat'', and the energy that flows across a boundary as a result of a temperature difference is "heat".
Altitude (or elevation) is usually not a thermodynamic property. Altitude can help specify the location of a system, but that does not describe the state of the system. An exception would be if the effect of gravity need to be considered in order to describe a state, in which case altitude could indeed be a thermodynamic property.
See also
*
Conjugate variables
Conjugate variables are pairs of variables mathematically defined in such a way that they become Fourier transform duals, or more generally are related through Pontryagin duality. The duality relations lead naturally to an uncertainty relation— ...
*
Dimensionless number
Dimensionless quantities, or quantities of dimension one, are quantities implicitly defined in a manner that prevents their aggregation into unit of measurement, units of measurement. ISBN 978-92-822-2272-0. Typically expressed as ratios that a ...
s
*
Intensive and extensive properties
Physical or chemical properties of materials and systems can often be categorized as being either intensive or extensive, according to how the property changes when the size (or extent) of the system changes.
The terms "intensive and extensiv ...
*
Thermodynamic databases for pure substances
*
Thermodynamic variable
References
{{DEFAULTSORT:List Of Thermodynamic Properties
Thermodynamic properties