There are four phases of matter: solid, liquid, gas, and… plasma.
I read a little bit of the Wiki article on plasma. I don’t understand all that chemistry jargon, so I gave up reading it.
Can someone please explain why plasma is not considered a gas?
Plasma is not considered a gas simply because (but not to simplify or shorten it’s meaning) it contains unique properties/ characteristics that govern or control it’s existence that set it apart from the form of gas and those properties/ characteristics which constitute it. For plasma to exist it needs to meet certain criteria or ‘matters of fact’ and that without getting into the semantics or scientific jargon is the be all and end all… I think!!!
To consider a plasma to be a gas can be compared to considering a liquid to be a solid.
Plasma and gas, like liquid and solid, are very different on the atomic level, and this difference is reflected in their observable properties in the larger world.
Actually, there’s more than four. Here’s a list. Granted, several of those are merely specific types, or special combinations, of existing phases, but others are wholey unique.
My personal favorite is the Bose-Einstein Condensate, which is when certain atoms are damn clsoe to absolute zero, and sort-of become one wave/particle.
The main property that makes a plasma different from a gas is the abundance of ions in plasma. These particles cause the plasma to be highly charged and thus to exhibit electromagnetic effects and a sort of ordered structure, neither of which are present in a typical gas.
That is as short an answer as I can give without resorting to jargon.
Hey, you guys are beating around the bush, here. 
I *can * take a little jargon.
Now a gas behaves according to PV=nRT, correct? (Or at least approximately.) Does a plasma also obey PV=nRT?
Differences between plasma and gas:
Plasma electrical conductivity is very high, gas is very low.
Velocity distribution of plasma can be non-Maxwellian, gas distribution is Maxwellian.
Types of particles: Gas has only one type, all acting the same way. Plasma has 3, electrons, ions, and neutrals, and they can act differently.
Particle interactions: Gas consists mainly of two particle interactions, with rare 3 particle interactions occurring. Plasma particles each act with many others simultaneously.
I don’t believe Plasma follows the Ideal Gas law, but I’m not 100% sure.
My admittedly limited understanding is that in a gas (as in a liquid or a solid) the individual atoms retain their basic integrity. In a plasma, the surrounding energy is high enough that it starts to affect the atoms themselves and cause them to break apart.
The Ideal Gas Law is based on the Kinetic Theory of Gases. It comes about by proposing an ideal gas that that has these properties:
The gas is composed of point particles that have no actual volume.
Gas particles do not interact with eachother.
Because no gas is actually like this, the Ideal Gas Law is only good as an approximation for determining the behavior of some gasses over a moderate range of temperatures.
Plasma is characterized by ionization, where one or more electrons have broken loose from the constituent atoms, giving them a net charge. Because they’re charged, they interact with eachother, and now you’ve gone and violated one of the fundamental assumptions needed to make the Ideal Gas Law work.
That seems like a good link, but there’s something about the closing sentence that doesn’t seem quite right to me:
The laws of physics have ceased to hold? Bwuh?
I mean, I get what it’s trying to mean; the laws of physics as we observe/understand them, in normal space may not be particularly pertinent, but surely singularities are subject to some laws or other, and if these laws are not laws of physics, then what are they?
Plasma and gasses are different phases because you have to go through a phase transition to go from one to the other. There are many, many phase transitions in physics; in a given substance, you might, for instance, go from a solid with one crystalline structure to a solid with a different crystalline structure. For that substance, those two different structures, though both solids, could be two different phases.
Nah, the laws of physics only have to hold everywhere in the Universe. It is quite possible that the singularity at the core of a black hole might not be part of the Universe, in which case its effects on the Universe are due to the fact that the Universe itself has a gap there. It’s also quite possible, of course, that there aren’t any true singularities at all, with some weird quantum gravitational phenomenon preventing their existance, in which case you would presumably have actual matter at the core of a black hole in some bizarre phase. I think most theorists are betting on this latter possibility, but it’s not certain.
Because you can’t make a TV out of gas, and you can out of plasma.
Now… can somebody give a brief explanation of what plasma TV is and how it works?