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:
- linearly dependent on the amount of substance. Examples: mass, volume, energy
- Intensive Properties:
- independent of the amount of substance. Examples: temperature, pressure, density
Useful tip: Take two identical samples with all properties identical and combine them into a single sample. Properties that double are extensive. Properties that remain the same are intensive.
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.
Can you think of a property that is neither extensive nor intensive?
Related to intensive properties we define:
- Uniform phase sample:
- In this sample each intensive property is constant throughout space.
- Homogeneous sample:
- In this sample each intensive property can vary continuously throughout space.
- Heterogeneous sample:
- In this sample each intensive property vary discontinuously throughout space.
