Final answer:
Free moving molecules refer to the behavior of molecules in liquids and gases, where they can change positions due to less restrictive intermolecular forces compared to solids.
Step-by-step explanation:
Free moving molecules are characteristic of liquids and gases. In the solid state, molecules or atoms are in close contact and held in place by intermolecular forces, and while they may vibrate, they do not move freely. In contrast, molecules in the liquid state are also in close contact but can slide over one another, which allows them to change their positions relative to each other. Finally, in the gas phase, molecules move about freely and are separated by large distances, allowing them to change positions with great freedom.
Plasma is another state of matter where molecules can change positions, but it is not typically encountered in everyday conditions. It consists of ionized gas with free-moving ions and electrons, and it becomes relevant at very high temperatures, such as those found in stars or lightning strikes.