Extensive Property
Definition and meaning of Extensive Property in chemistry.
An extensive property is a physical property of a system whose magnitude depends on, and is proportional to, the amount of matter present, such as mass or the number of moles.
In more detail
Because extensive properties scale with quantity, they are additive: if a system is divided into parts, the total value equals the sum of the values of the parts. This makes them useful for bookkeeping in thermodynamics, where quantities like total internal energy or entropy must be tracked as a sample grows or shrinks. Extensive properties contrast with intensive properties, which do not depend on sample size and stay constant when a system is divided. Dividing one extensive property by another (or by mass or moles) produces an intensive property, such as density or molar volume.
Key facts
| Field | Physical Chemistry |
|---|---|
| Key behavior | Additive over subsystems (values sum when parts combine) |
| Common examples | Mass, volume, total internal energy, enthalpy, entropy, heat capacity |
| Opposite of | Intensive property (e.g., density, temperature, pressure) |
If you have 1 mole of water (18 g, 18 mL) and combine it with a second identical mole, the combined sample has mass 36 g and volume 36 mL, both extensive properties, having doubled, while the density (about 1 g/mL) and temperature stay the same.
Frequently asked questions
What is the difference between extensive and intensive properties?
Extensive properties depend on the amount of substance present (mass, volume, total energy) and change when the sample size changes. Intensive properties (density, temperature, pressure, molar concentration) do not depend on amount and stay the same no matter how much material you have.
How can an extensive property become intensive?
Dividing one extensive property by another, or by the amount of substance, yields an intensive property. For example, mass divided by volume gives density, and heat capacity divided by moles gives molar heat capacity.