A specialization of tangible thing and an instance of state of matter. Each instance of gas is an object of a single chemical species in the gaseous state of matter. Objects in the gaseous state of matter are at a high enough temperature or low enough pressure for the type of matter involved that the molecules are not bonded even weakly to their neighbors, and readily break free. Gaseous objects are characterized at the macroscopic level by having diffuse boundaries (when outside of containers), no shape independent of a container, and by great expandability and compressibility. Examples of things that typically have this attribute are: the helium in a child's balloon; the oxygen in Earth's atmosphere; the water vapor in Earth's atmosphere.