It is commonly taught that there are three basic states of matter: solid, liquid, and gas. Elements and molecules behave differently in these states based on how excited they are. In solids, the molecules vibrate, but are mainly held in the same structure. In liquids, as temperature increases, the molecules move more freely, but still stay together. When a molecule becomes very excited, the molecules break free of each other and go in all directions: the gas state.
This simple explanation, however, doesn’t account for many new discoveries. These three simple states of matter are enough to explain every interaction with matter that the average person should have on a normal day, but they are not the only phases of matter that physicists have observed.
Plasma, or superheated ionized gas, is another phase of matter. It exists at very high temperatures of several thousand degrees Celsius, and consists of free moving particles like ions and electrons. While plasma has many of the same properties as a gas in this regard, it is considered a new phase of matter because of several differences.
For instance, plasmas can generate magnetic currents and conduct electricity, two properties that are not observed in the behavior of a gas. Many free electrons at this temperature allow for this rapid movement of charge. The charged air particles produced by a lightning strike are plasma, as well as the interior of our sun and other stars. Plasmas respond strongly to electromagnetic forces.
Other states of matter have been theorized, but not proven. Quark gluon plasma is a proposed phase of matter that occurs when quarks break free of the bonds that group them together. In this state, temperatures are very, very high, as the particles are moving very fast, and the quarks float freely in a soup of gluons, the particles that ‘carry’ the forces between them. Experiments with quark-gluon plasma are carried out in hadron colliders, which accelerate particles to near the speed of light and smash them together to observe what happens after the collision.
Another state of matter that has been theorized is dark matter. What is dark matter? Well, this kind of matter cannot be directly observed, as it does not emit or absorb electromagnetic radiation, including visible light. However, scientists have hypothesized that the universe is made up mostly of dark matter, based on gravitational effects that cannot be accounted for by visible stars.
