Plasma : The Fourth State of Matter

Plasma (from Ancient Greek πλάσμα, meaning "moldable substance" is one of the four fundamental states of matter, and was first described by chemist Irving Langmuir in the 1920s. Unlike the other three states, solid, liquid, and gas, plasma does not exist

freely on the Earth's surface under normal conditions. Plasma can only be artificially generated by heating or subjecting a neutral gas to a strong electromagnetic field to the point an ionised gaseous substance becomes increasingly electrically conductive, and long-range electromagnetic fields dominate the behavior of the matter.

Plasma and ionised gases have unique properties and display behaviors unlike those of the other states, and the transition between them is mostly a matter of nomenclature and subject to interpretation. Based on the surrounding environmental temperature and density, partially ionised or fully ionised forms of plasma may be produced. Neon signs or lightning storms are examples of partially ionised plasma, while the interior of the Sun is an example of fully ionised plasma,along with the solar corona and stars.

Positive charges in ions is achieved by stripping away electrons orbiting the atomic nuclei, where the total number of electrons removed is only related to either increasing temperature or the local density of other ionised matter. This also can be accompanied by the dissociation of molecular bonds, though this process is distinctly different from chemical processes of ion interactions in liquids or the behavior of shared ions in metals. The response of plasma to electromagnetic fields can be usefully employed in many modern technological devices, such as plasma televisions or plasma etching.

Plasma may be the most abundant form of ordinary matter in the universe, although this hypothesis is currently tentative based on the existence and unknown properties of dark matter. Plasma is mostly associated with stars, extending to the rarefied intracluster medium and possibly the intergalactic regions.