Traditionally, we’re taught that there are only three states, or phases of matter; solid, liquid and gas. The form that matter takes is a function in differences in the motions and forces and molecules that go into its makeup. In solids, the molecules are limited to vibration about a fixed position, giving it a definite volume and shape. When energy in the form of heat is added to a solid, the molecules begin to vibrate more rapidly until they move from their fixed positions. It is at this point that solid matter changes to liquid form. If more heat is added, some molecules can break away from the molecular bond that holds liquid together, and matter becomes gas.
In the classical science that most of us over 40 learned, this constitutes the complete description of the states of matter. Each of these phases has many subgroupings. For instance, solids can be crystalline or glassy. There are also forms of matter that are magnetically ordered. There are also changes in the state of matter when subjected to subzero temperatures approaching absolute zero.
Scientists have, based upon recent study, developed additional classifications of matter beyond the traditional three.
Ionized gas, or plasma, is a phase of matter that exists at temperatures of several thousand degrees Centigrade, such as the charged air produced by a lightning bolt, or the gasses in the sun. Plasma can be thought of as gas made up of extremely ionized particles, but its properties are sufficiently different from what we traditionally view as gas that it is considered by scientists to be a completely different state of matter. Even plasma is not a monolithic entity. In 2000, a state of matter known as quark-gluon plasma was discovered. While still classified as plasma, it too has properties that are sufficiently distinct to justify considering it at least a different sub-state.
There we have four states of matter, but the journey is not yet over. The collapse of atoms into a single quantum state, which scientists have named the Bose condensation or Bose-Einstein condensation, creates a state that is the opposite of plasma. This phase occurs when atoms are cooled to temperatures near absolute zero. The first instance of the Bose-Einstein condensate was produced at the University of Colorado at Boulder in 1995, but it was predicted in the 1920s.
It would appear, therefore, that what we learned in the 1950s has been supplanted by an analysis of scientific discoveries and theories that date as far back as the 1920s. There are clearly more than three states of matter, and it is probably safe to predict that in many of our lifetimes, as we penetrate farther into the universe, we will discover there are more than five. The universe is infinite (on a human scale), and infinitely diverse. It stands to reason, then, that the phases of what we call matter are likely just as diverse.