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States of Matter

This figure shows the four common states of matter: solid, liquid, gas, and plasma.

Consider water as an example. Solid water is ice. Liquid water is, well, water. We call water in its gaseous form "water vapor". A plasma created from water would include electrons, protons (hydrogen atom nuclei), and oxygen atom nuclei (protons and neutrons).

There are special names for most transitions from one state to another. Freezing is turning from a liquid to a solid; melting is turning from a solid to a liquid. The transition from liquid to gas can happen by boiling or evaporation. Condensation is changing from a gas to a liquid. Sometimes (usually at low pressure) a solid can become a gas directly (without first melting to become a liquid); this transformation is called "sublimation". Removing electrons from atoms (usually in a gas) to produce a plasma is called "ionization".

Stars are made of plasma, so plasma is the most abundant form of matter in the universe.

There are several other very exotic and unusual forms of matter that we don't encounter in daily life. A Bose-Einstein condensate can only form at temperature near absolute zero, and was first created in a lab in 1995. Degenerate matter can come into being under incredibly high pressure inside white dwarf and neutron stars. There are other very strange, very rare forms of matter as well.