A sample of matter can be classified by the physical properties that determine its state. Specifically, the properties of volume and shape are sufficient to classify the sample.
| States of Matter | ||
|---|---|---|
| Solid | Fixed volume | Fixed shape |
| Liquid | Fixed volume | Variable shape |
| Gas | Variable volume | Variable shape |
As temperature increases (assuming there is no chemical decomposition):
These processes can be reveresed. As temperature decreases:
Depending on the pressure, a solid may go directly to gas as the temperature increases, through a process called sublimation.
The reverse process (a gas going traight to solid) is called deposition.
A useful property of matter is the density. Density is given by the ratio of the mass of a sample divided by its volume. And because density is an intensive property (independent of sample size), it is a useful property to tabulate for reference.
| Property | Type |
|---|---|
| Mass | Extensive |
| Volume | Extensive |
| Density | Intensive |
Notice how the ratio of two extensive properties causes the size of the sample size to cancel.
The units commonly used to express density depend on the state of the sample in question.
| State | Denisty Units |
|---|---|
| Solid | g/cm3 |
| Liquid | g/mL |
| Gas | g/L |