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Q & A: Is fire a plasma

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Most recent answer: 04/04/2018
Q:
https://van.physics.illinois.edu/qa/listing.php?id=19592
Is fire a plasma? This one says yes: http://www.askamathematician.com/2013/05/q-is-fire-a-plasma-what-is-plasma/ This one says no: https://van.physics.illinois.edu/qa/listing.php?id=19592 They can't both be right. Which one is less wrong? Cheers, Julia
- Anonymous
A:

Great question!

As you can see in the two answers you cite, in typical flames an easily detectable fraction of the molecules are ionized, but not the large majority of molecules that are ionized in typical things we call plasmas. If there were an abrupt phase transition between weakly ionized gases and strongly ionized gases, like between liquids and gases at lordinary pressure, then there would be a definite answer to the question "is the flame a plasma?" Since under ordinary pressures there is no such gas-plasma transition, it's pretty much just a matter of taste where you draw the line and say that some gas is ionized enough to call a plasma.

So the two sites agree on the actual facts of the matter, but tend toward different name choices. I kind of like the mathematicians' site better than ours, not because of the name choice but because they give some nice experimental facts about ionized gases.

Mike W.


(published on 04/04/2018)

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