Loops of plasma arc above the sun’s surface in this NASA image.  They can be 30 times Earth’s diameter.

In physics and chemistry, a plasma is an ionized gas. It is considered to be the fourth state of matter, apart from normal gases, because of its unique properties. “Ionized” means that a plasma has electrons that are not bound to an atom or molecule. This makes them highly conductive to electricity, and makes them respond strongly to electromagnetic fields. Fire and lightning are plasmas; so is the core of the sun, as well as 99 percent of the matter in the universe.

There is a great deal of information on the web about plasmas. The Coalition for Plasma Science is a group of institutions, organizations, and companies joining forces to increase awareness and understanding of plasma science and its many applications and benefits for society. Its website was designed by and for teachers to round up the best online resources on the subject.

Plasmas are a core concept in astrophysics, and they also provide the foundation for important industrial applications such as the processing of semiconductors, the sterilization of some medical products, lamps, lasers, diamond coated films, high power microwave sources, and pulsed power switches. They also provide the foundation for important potential applications such as the generation of electrical energy from fusion, pollution control, and the removal of hazardous chemicals. The Coalition’s site links to several good overviews of the subject.