Intensive properties::Intensive and extensive properties


Center::system    Volume::property    Energy::density    Which::redlich    Amount::specific    Example::molar

Intensive properties An intensive property is a physical quantity whose value does not depend on the amount of the substance for which it is measured. For example, the temperature of a system in thermal equilibrium is the same as the temperature of any part of it. If the system is divided the temperature of each subsystem is identical. The same applies to the density of a homogeneous system; if the system is divided in half, the mass and the volume change in the identical ratio and the density remains unchanged. Additionally, the boiling point of a substance is another example of an intensive property. For example, the boiling point for water is 100 °C at a pressure of one atmosphere, which remains true regardless of quantity.

According to the state postulate, a sufficiently simple thermodynamic system requires only two independent intensive variables to fully specify the system's entire state. Other intensive properties are derived from the two known values.

Some intensive properties, such as viscosity, are empirical macroscopic quantities and are not relevant to extremely small systems.

Combined intensive properties

There are four properties in any thermodynamic system, two are intensive and two are extensive.

If the set of parameters, <math>\{a_i\}</math>, are intensive properties and another set, <math>\{A_j\}</math>, are extensive properties, then the function <math>F(\{a_i\},\{A_j\})</math> is an intensive property if for all <math>\alpha</math>,

<math>F(\{a_i\},\{\alpha A_j\}) = F(\{a_i\},\{A_j\}).\,</math>

It follows, for example, that the ratio of two extensive properties is an intensive property - density (intensive) is equal to mass (extensive) divided by volume (extensive).


Examples of intensive properties include:

Intensive and extensive properties sections
Intro  Intensive properties  Extensive properties  Related extensive and intensive properties  Generality of classification  References  

Intensive properties
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