Energy released - how?

During a chemical reaction, an intermediate molecule can have an energy greater that that of the reactants. How does this energy get released as - e.g. a photon, etc.

Reply 1

EierVonSatan

21

It reacts to form a lower energy product - possibly releasing the excess energy as heat/light/entropy...

Reply 2

DeanK2

OP

I really can't see any of the above happening without releasing a photon though. Is there a specific mechanism as to how this excess energy is given up (not what we ultimately observe it to be - heat, light, etc)?

It just seems that the only way to do any of the above is by releasing a photon (but I can't find an explanation). :frown:

Reply 3

EierVonSatan

21

I think you are massively overthinking the concepts involved here, a full quantum treatment of chemistry will not lead you to the answers :nah:

DeanK2

I really can't see any of the above happening without releasing a photon though. Is there a specific mechanism as to how this excess energy is given up (not what we ultimately observe it to be - heat, light, etc)?

It just seems that the only way to do any of the above is by releasing a photon (but I can't find an explanation). :frown:

You first must differentiate between chemical potential energy and other forms of energy.

Try to see it this way.

Chemical energy is the potential energy a substance has by dint of its relative position in the universe. It has the potential to move to a lower chemical energy state if it rearranges its bonds during a suitable chemical reaction.

For example, hydrogen only has its chemical potential energy level value (which its not possible to calculate absolutely) because oxygen also exists in the universe, which can react with it to form water which has stronger bonds. (this is just an example, NOT a general principle or yardstick)

How is this energy lost?

Energy is never lost (law of conservation of energy) it is simply transformed from one form into another.

Before the reaction of hydrogen and oxygen the particles are moving (translation, rotation and vibration) with an average velocity that is the proportional to the square root of their energy (average). E = mv²

AFTER reaction the particles are now moving with more energy because the energy has been changed from chemical potentail to motion (i.e. heat).

Your problem involving the intermediate is simply a version of this in two stages...

stage 1 - the particles rearrange changing thermal (motional energy) into chemical energy to give an intermediate with greater chemical energy.

stage 2 - this chemical energy is changed into kinetic energy by the next phase of the mechanism and heat is released (i.e. everything moves faster)

If this is of no use to you, then I apologise for boring the proverbial pants off you :biggrin:

Energy released - how?

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