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What kind of energy is released during combustion

  1. Aug 10, 2014 #1
    I always like to be specific when talking about "energy released". It is too vague for me, there is what to specify there. Take the example of the ATP molecule. When you break the bond, it will be the phosphate groups repelling each other, so it will be their kinetic energy that results in repulsion and hence, motion.
    What about oxidation? Am I right it would be electromagnetic radiation due to electrons falling into lower energy states?
     
  2. jcsd
  3. Aug 11, 2014 #2
    Your understanding is incorrect. The energy released in chemical reactions is chemical energy. Chemical energy is the potential energy of chemical bonds.
     
  4. Aug 11, 2014 #3

    Borek

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    Staff: Mentor

    Nope. Are you trying to say that the projectile shot from the gun has a chemical energy?

    Energy released can take many forms. Kinetic (thermal), electromagnetic (light and other wavelengths), electric (charge separation in batteries).
     
  5. Aug 11, 2014 #4
    Well, that's exactly what I'm asking here. In what form is the chemical energy released? Does it cause a sudden conformational change in a molecule (that's movement again), or are the newly formed molecules suddenly repelled because of their electron structure (movement again), or are the rearranging electrons radiating electromagnetic radiation as they fall back to lower energy states?

    (I don't want to be off topic by the way, but I think ultimately almost all forms of energy released is kinetic, even if on quantum levels.)
     
  6. Aug 11, 2014 #5
    Oh sorry, I misunderstood the question.

    In general oxidation reactions produce heat. If the reaction is fast enough to be called combustion, the temperature of the combustion products (and the surrounding gases) increases sufficiently to emit electromagenetic radiation which we see and feel as a flame.

    I don't think that contemplation of what is happening at the quantum level is helpful to a general understanding of chemistry, but if you want to go down this route start with the basics of a good undergraduate physical chemistry text and work on from there.
     
  7. Aug 11, 2014 #6
    Okay.
    So when the oxidation does not produce visible flames, is the heat produced by molecular movement (the newly formed molecules gain momentum), or is it infrared radiation because of the new energy levels of the electrons? So which one is the cause and which one is the effect? It looks like both of them appear here.
     
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