What is plasma, the fourth state of matter?
Quick answer
Plasma is often called the fourth state of matter, after solids, liquids and gases. It forms when a gas gets so much energy, usually from extreme heat or electricity, that electrons are stripped from atoms. The result is a glowing mix of ions and free electrons. Stars, lightning and neon signs are made of plasma.
The states of matter
| State | Particles | Shape and volume |
|---|---|---|
| Solid | Packed tightly, vibrating | Fixed shape and volume |
| Liquid | Close but able to slide past each other | Fixed volume, takes container’s shape |
| Gas | Far apart, moving fast | Fills any container |
| Plasma | Ionized: charged ions and free electrons | Like a gas, but responds strongly to electric and magnetic fields |
Adding energy usually moves matter from solid to liquid to gas, and finally to plasma.
The most common state in the universe
Although plasma is rare in everyday life on Earth, it makes up most of the visible matter in the universe, because stars are giant balls of plasma. The Sun’s core reaches about 15 million °C; see how hot the Sun is.
Plasma all around
| Natural plasma | Human-made plasma |
|---|---|
| The Sun and stars | Neon and fluorescent lights |
| Lightning | Plasma cutters for metal |
| Auroras; see what causes the northern lights | Older plasma TVs |
| The solar wind | Fusion reactors |
| The ionosphere | Plasma balls (novelty lamps) |
Where the name comes from
American chemist Irving Langmuir named it “plasma” in 1928, perhaps because the glowing gas reminded him of blood plasma carrying particles.
Plasma and the future of energy
Scientists are trying to recreate the Sun’s energy on Earth through nuclear fusion. Machines called tokamaks hold plasma hotter than the Sun’s core inside doughnut-shaped magnetic fields; see what a doughnut shape is called in math. The international ITER project in France is one of the largest of these efforts.
Even more states
Scientists have created more exotic states in labs, such as the Bose–Einstein condensate, formed near absolute zero, where atoms behave like a single “super atom.”
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