The States of Matter
Matter is ordinarily observed in three different states, or phases (see states of matter), although scientists distinguish three additional states. Matter in the solid state has both a definite volume and a definite shape; matter in the liquid state has a definite volume but no definite shape, assuming the shape of whatever container it is placed in; matter in the gaseous state has neither a definite volume nor a definite shape and expands to fill any container. The properties of a plasma, or extremely hot, ionized gas, are sufficiently different from those of a gas at ordinary temperatures for scientists to consider them to be the fourth state of matter. So too are the properties of the Bose-Einstein and fermionic condensates, which exist only at temperatures approximating absolute zero ( - 273.15°C), and they are considered the fifth and sixth states of matter respectively.
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