* It exists in a gaseous state at room temperature and standard atmospheric pressure. This means oxygen molecules are far apart and move freely, taking the shape of their container.

* It lacks a fixed volume and shape. Unlike solids and liquids, oxygen readily expands to fill any space it occupies.

* It is highly compressible. This is because the molecules are far apart and can be squeezed closer together.

* It exhibits low density. Oxygen molecules are relatively light and therefore spread out, resulting in a lower density compared to liquids and solids.

In summary, oxygen meets the defining characteristics of a gas.