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Whats fire made of? What element atoms are it.?

  1. Apr 21, 2012 #1
    why does peak of fire of a matchstick face upwards ie away from ground.why is it not effected by gravity,is there any reason other than pressure considerations.
     
  2. jcsd
  3. Apr 21, 2012 #2

    Borek

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    It is affected by gravity which is why it is pointing up. Buoyancy being the key word.
     
  4. Apr 21, 2012 #3
    The flame is a state of matter known as plasma.
     
  5. Apr 22, 2012 #4
    Someone correct me if I'm wrong, but the flame is not made up of any particularly special atoms or substance. It is simply a regular substance, such as air, that has been heated to the point that it releases light.
     
  6. Apr 22, 2012 #5

    Borek

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    You are right about "nothing special", but it is not "just air". Think combustion products.
     
  7. Apr 22, 2012 #6

    HallsofIvy

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    A large part of a flame is carbon dioxide (or if the fire is "starved of oxygen" carbon monoxide). And it is affected by gravity but hot gasses are less dense than the colder air around them.
     
  8. Apr 22, 2012 #7
    It's made of the vapors of the burning object plus oxygen from the air.
     
  9. Apr 22, 2012 #8

    Borek

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    So there is no combustion products in the flame? If so, where does the energy heating the flame comes from?
     
  10. Apr 22, 2012 #9
    fire is light emitted by the excited atoms of the material when excited to the point of combustion

    Heat = light = magnetic radiation just on a diffrent frequency
     
  11. Apr 22, 2012 #10

    Borek

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    No. Fire is not just a light.
     
  12. Apr 22, 2012 #11
    what you "see" and "feel" as fire is simply radiation visible light and infrared

    Aside from smoke and other random particles but the "flame" is nothing more then light from atoms that have been excited to the point where they begin an exothermic reaction with the air around them

    Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.[1] Slower oxidative processes like rusting or digestion are not included by this definition.
    The flame is the visible portion of the fire and consists of glowing hot gases. If hot enough, the gases may become ionized to produce plasma.[2] Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity will be different.

    http://www.cbsnews.com/8301-504784_162-20106378-10391705.html
     
  13. Apr 22, 2012 #12
    can a flame be in such a way that it gives out only light of frequencies other than visible light..I meant flame exists but its hardly visible to human eye
     
  14. Apr 22, 2012 #13
    yes there are several materials that burn off into UV instead of visible light
     
  15. Apr 23, 2012 #14

    Borek

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    What about hot soot that is no longer reacting due to the lack of oxidant, but still emitting the IR/light just because of its high temperature? It doesn't fit this definition.

    Even assuming your original answer was technically correct, it addressed only what the flame is, while the question is about fire. You listed definitions of fire and flame, so you know these are two different things, but you still insist your partial answer is the correct one?
     
  16. Apr 23, 2012 #15
    like what?
     
  17. Apr 23, 2012 #16
    ssme2.jpg Note how hydrogen flame from the main engines is almost invisible, especially in comparison with solid propellant SRBs.
     
  18. Apr 23, 2012 #17

    HallsofIvy

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    Lsos didn't say "just air", he said "such as air" which allows other things.

    Antiphon said "vapors of the burning object" which Merriam-Webster defines as "diffused matter (as smoke or fog) suspended floating in the air and impairing its transparency"
     
  19. Apr 23, 2012 #18
    pure magnesium burns into some uv light along with visible light
    and i believe so does methanol

    Wild-land firefighters occasionally come across this phenomenon where its "on fire" but burning so cold that the flame is not visible to the naked eye
     
  20. Apr 23, 2012 #19
    If it is burning cold, then it should radiate even less in UV than normal fire. As for Mg, you said yourself its flame is visible, so these examples are invalid.
     
  21. Apr 23, 2012 #20

    K^2

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    Flame from most organic fuels, like wood, candle, gasoline, etc., is primarily glowing soot. Products of combustion are translucent gases, meaning they aren't going to emit much via black-body. Soot, having very high absorption coefficient is also very good at emitting radiation.

    I'm not sure about natural gas burners, to be honest. But if a gas burns clean, the flame is not going to be very visible. Case in point,
    Enthalpy of formation of H20 is -242kJ/mol. That's enough to heat water vapor to at most 7k K. (Realistically, significantly less.) This is still well within visible band. The reason you don't see the flame is because it also happens to be very close to the minimum in absorption spectrum for H2O, so the emission intensity is very low.
     
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