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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