Intensive, Extensive Properties

All the quantities we just discussed (i.e., temperature, volume, mass, etc.,) describe the properties of a substance. Many properties can be classified as extensive or intensive.

Extensive Properties:

dependent on the amount of substance. Examples: mass, volume, energy

Intensive Properties:

independent of the amount of substance. Examples: temperature, pressure, density

For example, if I took 1.0 liter of water at room temperature (25 °C) and added another 1.0 liter of water at the same temperature then I would have 2.0 liters of water at 25 °C. From this example we see that Volume and Mass are extensive properties (i.e., volume and mass doubled), while Temperature is an intensive property (i.e., temperature stayed the same). You would also expect the density to remain the same, so it is also an intensive property.

In the language of thermodynamics we say: when two identical systems are brought together extensive properties will double in value, and intensive properties will stay the same.

Can you explain why pressure is an intensive property?