READ: Phases of Matter

The state of matter of a substance is a physical property. A given kind of matter has the same chemical makeup and the same chemical properties regardless of its state. As a result, when matter changes state, it doesn’t become a different kind of substance. For example, water is still water whether it exists as ice, liquid water, or water vapor.

Liquids have a fixed volume, but not a fixed shape. The particles of liquids are in close contact with each other but not as tightly packed as the particles in solids. The particles can slip past one another and take the shape of their container. However, they cannot pull apart and spread out to take the volume of their container, as particles of a gas can. 

Solids

Solids have a fixed shaped and volume. Solids have particles that are much more tightly packed together. The particles are held rigidly in place by all the other particles around them so they can’t slip past one another or move apart. However even though the particles can't move, they still vibrate in place.

Gases

Gases do not have a fixed volume, or a fixed shape. The particles of a gas can pull apart from each other and spread out. As a result, a gas does not have a fixed shape or a fixed volume. In fact, a gas always spreads out to take up whatever space is available to it. If a gas is enclosed in a container, it spreads out until it has the same volume as the container.

Plasma

Plasma is a state of matter that resembles a gas but has certain properties that gases do not have. Like a gas, plasma consists of particles of matter than can pull apart and spread out, so it lacks a fixed volume and a fixed shape. Unlike a gas, plasma can conduct electricity and respond to a magnetic field. That’s because plasma consists of electrically charged particles called ions, instead of uncharged particles such as atoms or molecules. 

Where Is Plasma Found?

The sun and other stars consist of plasma. Plasma is also found naturally in lightning and in the northern and southern lights. If you’ve never seen these shimmering colorful lights in the winter night sky, the Figure below shows what they can look like. Human-made plasmas are found in fluorescent lights, plasma TV screens, and plasma spheres like the one pictured below:

CK-12 Foundation, Physical Science. http://creativecommons.org/licenses/by-nc-sa/3.0/