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Asked by Bookworm_Fangirl to Scott on 8 Mar 2016.
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Scott Lawrie answered on 8 Mar 2016:
Hello Bookworm, I’m glad I’ve piqued your interest 🙂
Fire is an interesting example. It’s ALMOST a plasma, but not quite. It’s not ‘ionised’ enough. Ionising is the process where electrons get stripped off atoms, leaving positive and negative charges – the things that make up a plasma. A plasma also needs to be a bit denser than fire. Fire is just free to float up into the air – to be a plasma it would need to be confined in some way with electric or magnetic fields.
So as I say, fire isn’t quite a plasma: it’s just a hot gas undergoing chemical reactions with the air.
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Comments
552rdme39 commented on :
so what causes its distinctive shape.
Scott commented on :
Gravity. Hot, burnt gas is less dense than the cold fuel so it rises up due to buoyancy (like a hot-air balloon). This sucks new, cold oxygen into the bottom, near the candle wick. The cold stuff gathers at the bottom making the flame bulge out there. The hot stuff quickly rises up into the air so doesn’t hang around long, meaning the flame is narrower at the top.
In space, gravity effects are removed so a flame is almost a perfect sphere! You should look for pictures of fire in space – it’s pretty cool 😀
552rdme39 commented on :
okay thanks
MagicOfReality commented on :
(This is Bookworm_Fangirl)
Thank you very much for your answer!