Physical Changes

Single Phase Changes

Let’s focus on phase changes that involve materials changing from one state of matter to another. These phase changes can be brought about by heating or cooling. The terms used to identify the various changes are shown on this diagram. If you are already familiar with this terminology feel free to move on to the next topic.

Phase changes can be brought about by heating or cooling. For example if water (a liquid) is heated enough, it evaporates and becomes water vapor or steam (a gas). This kind of phase change--liquid to gas--is called evaporation or vaporization.

Water vapor can in turn be cooled to form liquid water. This kind of phase change--from gas to liquid--is referred to as condensation.

If you were to continue to cool down the water and change it from a liquid to a solid, you would have another kind of phase change that is called freezing or crystallization.

If you were to then take a solid and warm it up to change it into a liquid, that change is called melting. (It is also sometimes called fusion.)

Another change that can occur for some solids is to change directly into a gas instead of changing into a liquid, and that is called sublimation.

The reverse of this process can also occur. Some gases can be cooled down and changed directly into a solid. That process is also called crystallization, a second meaning for that word.

Multiple Phase Changes

In addition to these single phase changes, you can have a string of changes, one after another. There are three of these multiple phase changes that are very important and you should know them by name.

Dissolution and Crystallization

Recap