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A Moment of Science

The Fourth State Of Matter

Plasma, created in a lab by heating gas, constitutes the fourth state of matter.

a photo of the sun

A photo of the sun processed so that viewers can better visualize the way plasma is emitted from the Sun’s corona. (NASA Goddard Space Flight Center, Flickr)

Everybody is familiar with the three states of matter: solids, liquids, and gases.

Typically, heating one state turns it into another. For example, ice will melt and become a liquid—water. Water will boil and become a gas—water vapor.

Electron Soup

But if you heat gas, its atoms will break apart into negatively charged electrons and positively charged ions. This soup of electrons and ions is plasma—the fourth state of matter. It was discovered by William Crookes in 1879.

Plasma is seen in the glowing streamers in plasma lamps. Plasma glows because when an electron moves to a lower orbit around an ion or atom, energy is released as light. Fluorescent tubes and neon lamps rely on glowing plasma, too.

Sun Plasma

Though plasma rarely occurs naturally on Earth, in most other places plasma is everywhere. The sun and stars are made of it, and very thin plasma fills space. Plasma makes up 99 percent of matter in the visible universe. The fourth state of matter is its most common state.

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