Extensive variable

Definition

An extensive variable is a property of a thermodynamic system that changes with the size or extent of the system, such as mass, volume, or total energy. Extensive variables are additive for subsystems.

5 Must Know Facts For Your Next Test

1. Extensive variables depend on the amount of substance present in the system.
2. Examples include volume, mass, and total internal energy.
3. When two systems are combined, their extensive variables add up.
4. Extensive variables can be converted to intensive variables by dividing by an appropriate extensive quantity (e.g., density = mass/volume).
5. In thermodynamic equations, extensive variables often appear alongside intensive variables.

Review Questions

• What happens to an extensive variable when the size of a system is doubled?
• Give three examples of extensive variables relevant to thermodynamics.
• How can an extensive variable be converted into an intensive variable?

Related terms

Intensive Variable: A property that does not change with the size or extent of the system, such as temperature or pressure.

Thermodynamic System:

A defined quantity of matter or a region in space chosen for study where energy exchanges with its surroundings are analyzed.

Internal Energy:

The total energy contained within a thermodynamic system due to both kinetic and potential energies of its particles.