variety of atoms (e.g. carbon dioxide). A gas mixture would contain a variety of pure gases much like the air. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. The gaseous state of matter is found between the liquid and plasma states,[1] the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases[2] which are gaining increasing attention.[3] High-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these exotic states of matter see list of states of matter.

Contents [hide] 1 Elemental gases 2 Etymology 3 Physical characteristics 4 Macroscopic 4.1 Pressure 4.2 Temperature 4.3 Specific volume 4.4 Density 5 Microscopic 5.1 Kinetic theory 5.2 Brownian motion 5.3 Intermolecular forces 6 Simplified models 6.1 Ideal and perfect gas models 6.2 Real gas 7 Historical synthesis 7.1 Boyle's law 7.2 Charles's Law 7.3 Gay-Lussac's Law 7.4 Avogadro's law 7.5 Dalton's law 8 Special topics 8.1 Compressibility 8.2 Reynolds number 8.3 Viscosity 8.4 Turbulence 8.5 Boundary layer 8.6 Maximum entropy principle 8.7 Thermodynamic equilibrium 9 See also 10 Notes 11 References 12 Further reading

Elemental gases[edit] The only chemical elements which are stable multi atom homonuclear molecules at standard temperature and pressure (STP), are hydrogen (H2), nitrogen (N2) and oxygen (O2); plus