Phases of Matter

The four phases of matter are solid, liquid, gas, and plasma. A solid is matter in which the molecules are very close together and cannot move around, such as ice or wood. In a liquid, the molecules are close together but move around slowly such as with water. In the gas phase, the molecules are widely separated and move around freely at high speeds. Finally, a plasma is a gas composed of free-floating ions (atoms stripped of some electrons - positively charged) and free electrons (negatively charged). A plasma conducts electrical currents. Plasma was discovered by William Crookes in 1879 and has since been considered one of the general phases of matter.