What is a characteristic of gases compared to other states of matter?

Gases are unique among the three primary states of matter—solids, liquids, and gases—due to their lack of both a definite shape and a definite volume. This characteristic stems from the behavior of gas molecules, which are in constant random motion and are much farther apart compared to the molecules in solids and liquids.

This spacing allows gas to expand and fill any container it occupies, adjusting its shape to match that of the container. Furthermore, since the molecules are not bound by strong intermolecular forces, gases will compress and expand significantly when subjected to changes in pressure or temperature. This feature of having no fixed volume also means that if a gas is contained within a specific volume, it will push against the walls of that container rather than holding a specific form.

In contrast, other states of matter have distinct properties. For example, solids have a definite shape and volume due to closely packed molecules that do not move freely, and liquids have a definite volume but take the shape of their container due to more loosely packed molecules than solids but still with some interaction. Thus, the defining characteristic of gases as having neither a definite shape nor volume is critical to understand their behavior and interactions in various situations.