What are the practical differences between a gas and a plasma?

[Pantastic]

There are also degenerate matter states in extremely dense stellar objects, like white dwarfs and neutron stars, where extreme pressure from gravity forces matter into states that behave very differently than anything on Earth.

[Chronos]

Yeah, those are examples of “density proportional to pressure raised to some power”.

[boffking]

@MichaelEmouse

What are the other arguable states of matter?

In my college chemistry class, we were taught that a solution was a state of matter.

[Leo_Bloom]

Fascinating thread; tell me, though, before I go hit the books on this “plasma tv” you youngun’s are talking about: you say each glowing unit (I want to say phosphor but no it’s not) is at some crazy high temperature?..what is it?

[Yumblie]

One could also consider Bose-Einstein condensate a state of matter. If you cool something down to a low enough temperature, it will act more like a wave than a collection of particles. You’re not likely to come across one out in nature though, as this happens a few nano-Kelvin above absolute 0. We’ve made them in the lab, though.

[Leo_Bloom]

@Chronos

There are an infinite number of possible fluid states. An ideal fluid is described by its pressure and its density. Any given kind of fluid will have something called an equation of state, which gives the relationship between pressure and density. For a lot of fluids (at least, under Earthly conditions), the equation of state is simply “density is a constant” (or something close enough that that’s a good approximation). We call those “liquids”. For a lot of other fluids, the pressure is proportional to the density and to the temperature. We call those fluids “gases”. But there are many other equations of state actually observed in nature. You can have density that’s directly proportional to pressure, you can have density that’s proportional to pressure raised to some power (and the value of that power can be almost anything), and so on.

Plus, if you’re going to say that some kinds of gases are different enough from other kinds of gases to call them a new state of matter (like we do with plasmas), then you can do the same sort of thing with liquids and solids. Water, for instance, has at least a dozen different solid phases, with different crystalline structure, densities, and other material properties, at various values of temperature and pressure.

Introducing: The new, weird, Oak Ridge squashed liquid phase!

ORNL researchers discover new state of water molecule | ORNL