An intensive variable is a state variable that does not change with different sizes of the system under consideration . A distinction is native intensive variables such as temperature and pressure , and material's intensive variables, like all molar and specific quantities of pure substances .
The dependency of a variable on the system under consideration can be traced, for example, using two identical systems that are separated by a partition. If one removes this separation and extends the consideration to the entire system, the difference between intensive and extensive quantities becomes clear: All quantities which now have the same value as before the removal of the partition are intensive quantities; on the other hand, all quantities which now have a different value are extensive quantities.
It is possible to convert extensive quantities into intensive quantities by relating them to a certain mass ( specific size ), to a certain volume (density of size) or to a certain amount of substance ( molar size ). The volume is an extensive quantity, but the molar volume is an intensive quantity.
The change in an intense quantity results in a change in the thermodynamic equilibrium .
|Characteristic||Sizes depend on the amount of fabric||Sizes do not depend on the amount of fabric|
|property||Changes with the size of the system under consideration. Extensive sizes are additive. If the amount of substance is multiplied, all extensive quantities multiply.||Is not affected by the size of the system. Intense sizes are not additive.|
|Examples||Amount of substance n , volume V , internal energy U , free energy F , free enthalpy G , mass m , electrical charge Q||Temperature T , density ρ , pressure p , concentration c = n / V , viscosity , refractive index , electrical voltage U , permittivity ε , dipole moment|
|Specialty||A state variable is also extensive if it is proportional to all other state variables known to be extensive. The proportionality only applies as long as all non-extensive state variables remain constant.||The ratio of extensive quantities is an intensive quantity.|
|context||The product of an extensive and an intensive quantity is an extensive quantity|
- intense sizes. In: Spectrum Lexicon of Physics.