When a substance turns changes from a solid or liquid into a gas, the process is called vaporization . The material is said to vaporize or evaporate. We can classify most materials as solids, liquids or gases. Each molecule interacts closely with those around it and has very little freedom to change position. Those that have no long-range order are called amorphous .
Liquids have somewhat weaker interactions between the atoms or molecules.
The molecules can move fairly freely past one another, and the material will tend to take the shape of its container. Gases have little or no interactions between the atoms or molecules. The distance between adjacent molecules is many times larger than in liquids and solids. Gases generally diffuse , spacing themselves throughout the container. We can express these states of matter pictorially.