Pop quiz: States of matter

[unixronin]

OK, folks, let's test your scientific knowledge.

[Poll #1278483]

Most grade school science classes still teach that there are three states of matter — solid, liquid, and gas.  But there are several others.

• If you heat and compress any substance beyond its thermodynamic critical point, the result is a supercritical fluid that behaves in many respects like a liquid and like a gas simultaneously.  If you drink decaf coffee, it's likely it was decaffeinated using supercritical carbon dioxide.
• If you pump sufficient energy into any substance possessing atomic structure, its electrons become dissociated from the atomic nuclei, forming a plasma, a highly energetic cloud of free electrons and nuclei.  Plasmas behave like gases in most respects, but have several useful additional properties.  Fluorescent lights (including CFLs) and neon tubes employ plasmas, as do the various experimental fusion reactors that rely on magnetic confinement.
• Compress any normal atomic matter enough, and its atomic structure collapses.  This gets us into a whole class of states of matter known collectively as degenerate matter.  The most common form of degenerate matter is probably the electron-degerate matter believed to compose white dwarf stars, while the best known is what used to be called neutronium, now more correctly termed neutron-degenerate matter.  Weirder, possibly speculative members of the family include strange matter, quark matter (aka QCD matter), and possibly preon matter.
• As several people have reminded me, if you cool a substance sufficiently, slowing its atomic motion until the atoms are essentially at rest, their position becomes uncertain due to Heisenberg's uncertainty principle, and the wave functions of the atoms spread out accordingly. If you can cool therm enough that their wave functions overlap, you get a Bose-Einstein condensate — a cloud of atoms all in exactly the same quantum state, acting as though they were one giant atom.  (However, the atoms you start with have to be bosons.)

So if you answered "Six or more", you're correct.  Probably.  As far as we know.  For now.  And remember, this isn't an exhaustive list.

Comments

[argonel.livejournal.com]

I'm reasonably familiar with the standard 4 and as a metallurgisy I'm also familier with those parts of phase diagrams where the distinctions are basically dotted lines. As such I'm not sure that supercritical fluids should count as another state of matter. I should read up on them sometime and see what the more detailed arguments boil down to. Degenerate matter is another one of those cases that are fuzzy enough that I'm not sure it should count as a state of matter or as an exception. Based on the physics and and second or third hand observations we can be pretty confident that they exist, but without an atomic structure should they really count as matter? After some thought I'll provisianally classify them as matter since they have both mass and volume, but they definately don't fit into nice neat little niches.

[cipherpunk.livejournal.com]

Gravitational singularities are degenerate matter consisting of mass but no volume. I'm not sure if this is an argument for or against degenerate matter being counted as a distinct phase, but I figured the data point of "not all degenerate matter has volume" should be thrown out.