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I was wondering why a lightning bolt is coined as "plasma", or a "spark" from an electrical wire/device is as well, yet flares, molten lava, and burning buildings are not(flares are pyrotechnic, exothermic, and very much like flames).

I hear arguments saying that plasma is ionized gas, but how can a flare not be ionized at such high temperature(and why isn't ionized, very hot flames considered plasma)?

This guy, the top answerer, says that fire is not plasma because it's not ionized:

Is fire plasma?

Also, some lava exceeds 3,000 Fahreheit. How is that not plasma, and what draws the fine line between plasma and fire itself(not as a state of matter, but as a relation with gas)?

Fire is gas, but some say it's plasma if you can see it (check the link the poster added below in the first comment), so when does it become a full-on plasma if it's not normally one?

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Here's an answer about fire & plasma on a different site. The author claims fire is a plasma, and has some neat photos. askamathematician.com/2013/05/q-is-fire-a-plasma-what-is-plasma –  BMS Nov 5 '13 at 19:31
This guy, and many other people disagree - that is why I am asking: physics.stackexchange.com/q/23469 –  Entertainment Nov 5 '13 at 19:33

2 Answers 2

The key concept to defining plasma is the Debye distance/length/radius. If the particles are so close the Debye distance plays little or no role in particle interaction, than it is not a plasma. This Debye distance depends on the charge of the particles, so if their is no charge...

Though temperatures like 3,000 Fahrenheit would force a separation between particles of a gas to distances on the order of the Debye, for a solid, like lava, this is not the case. Fire is a very small presence of plasma under the pressure of 100 kPa, so it does not exist much for long, if at all.

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Plasma is when the electrons are "freed" from their host atoms for a short time, due to high temperatures. Fire is plasma, it responds to electric fields. Lightning is also plasma. When a column of electrons flows from sky to ground, the air that it passes through lights up with energy. What we see as lightning is actually the air where the electrons are at, getting excited and giving off light. Not the electrons itself. Lava refers to molten rock. Molten. Liquid. Not ionised gas. It's a plasma when it's ionised gas, nobody cares about temperature. If a gas can be ionised (IF) at -100 degrees Celsius, it's still called plasma.

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