Is Fire a Plasma? Answers & Discussion

[Synetos]

So is it? I had a long discussion about it in school and the internet gave very mixed answers. Because we are wondering if fire is ionised and this magnetic?

 

[LostConjugate]

Fire is just the process of hydrocarbons breaking down into water and carbon oxides. It is hot air and vapor.
Plasma is atoms becoming new atoms. Usually protons and neutrons being combined to make a heavier more complex atom. It is much hotter.

 

[Synetos]

But is it ionised?

 

[LostConjugate]

I don't know. It is in such a chaotic state. Are you trying to find if the substance as a whole has a charge?

 

[cepheid]

Fire is just the process of hydrocarbons breaking down into water and carbon oxides. It is hot air and vapor.
Plasma is atoms becoming new atoms. Usually protons and neutrons being combined to make a heavier more complex atom. It is much hotter.

A plasma is just a gas hot enough to be completely ionized. What you are describing is nuclear fusion. Granted, at the temperatures required for fusion, it would probably be taking place in a plasma. But that does not mean that they are synonymous.

 

[LostConjugate]

A plasma is just a gas hot enough to be completely ionized. What you are describing is nuclear fusion. Granted, at the temperatures required for fusion, it would probably be taking place in a plasma. But that does not mean that they are synonymous.

I stand corrected. I suppose that's why plasma tvs don't get as hot as a sun.

 

[Synetos]

But it is partly ionised, otherwise this would not be possible:

 

[schip666!]

Some flames (I'd hazard but not commit to all, due to the randomness involved) contain ions which can be affected by magnetic fields. You can dope the flame to have more ions and make a Flame Speaker: http://en.wikipedia.org/wiki/Plasma_speaker

 

[Synetos]

Yea, I've heard of those, they are awesome. :P
I should make a post asking how exactly they make the air vibrate in the right way.

 

[pergradus]

The gas given off in combustion is usually CO2 and some water vapor. Take a look at the ionization energies of these gases and see if its reasonable to assume that they can be ionized at the temperature fire normally burns at.

 

[Synetos]

So it is plasma? xD

 

[pergradus]

I don't think so. Remember that fire is also associated with soot and smoke - and in fact if you've ever seen a "dirty flame" it glows brightly while a "clean flame" is almost invisible.

I would suspect the glowing is mostly due to the little bits of soot and solid particles in the flame. I think I know a way you can test this though:

Take a 9V battery, connect it to a small lightbulb but somewhere in the circuit introduce a gap across the wire. First make sure your circuit is working by placing the gap in some salt water and seeing if your light turns on. If it's working, try now holding the gap inside of a flame.

A better way would be to try to do it using a multimeter, but you probably don't have one of those handy.

 

[Synetos]

We have some at uni, I might be allowed to try it, if they won't nag about me putting those connectors in fire :P

 

[Drakkith]

A link from an old post here at PF about the same thing.

http://www-spof.gsfc.nasa.gov/Education/FAQs7.html#q97

Short answer is no, fire is not a plasma.

 

[falcon32]

In combustion, we would be happy if we got only molecules like CO2 and H2O, but sadly no combustion process is 100% perfect. Therefore, ions do exist in a flame, but not nearly enough to be detectable (the above NASA link simply said that a standard multimeter would not detect a current, implying very few ions). So a proper answer would be, fire is a very, very weak plasma. Almost not.