At its condensation point, a gas turns back into a liquid. A solid retains a fixed shape. The strength of the solid depends on the strength of the bonds that hold the molecules together. Liquids, obviously, do not retain a fixed shape, but they do have a definite volume. Gases, on the other hand, have no fixed shape or volume.
Rocks do so when superheated in the center of the Earth.
A fourth state of matter, called plasma, exists when a gas becomes ionized. Plasma exists inside stars and in interstellar gases. An recently scientists have theorized about a fifth state of matter, called a Bose-Einstein condensate. Scientists describe it as the opposite of a plasma. This fifth state occurs at super low temperatures, near where atoms are not moving at all.