What is a defining characteristic of gases?

A defining characteristic of gases is that they do not have a fixed volume or shape. Instead, gases take the shape of their container and can expand to fill the available space. This property is due to the high kinetic energy of gas particles, which allows them to move freely and rapidly in all directions. As a result, gases can occupy varying volumes depending on the size and shape of the container they are in, making them highly versatile compared to solids and liquids. This behavior is integral to understanding the physical properties of gases in various scientific contexts.