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Topic: Making sense of "chemical potential energy"  (Read 3033 times)

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Offline sodium.dioxid

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Making sense of "chemical potential energy"
« on: May 09, 2012, 01:37:34 AM »
How do you even begin to describe "potential energy of the bond". It seems nonsensical.

Offline fledarmus

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Re: Making sense of "chemical potential energy"
« Reply #1 on: May 09, 2012, 08:34:42 AM »
How so?

Offline sodium.dioxid

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Re: Making sense of "chemical potential energy"
« Reply #2 on: May 09, 2012, 01:17:18 PM »
How so?

Well, my book says chemical potential energy is "energy resulting from attractions and repulsions among electrons and atomic nuclei in molecules." Is that supposed to mean something? Could he be any more ambiguous? It is literally like someone is talking to me in a different language. I don't even know what to ask.

Gravitational energy makes sense: you raise something (store energy) and let it go (allowing it to release its energy)

Electrostatic energy makes sense: you bring two negatively charged particles against their wish (storing energy) and let them go (the shoot in opposite directions releasing their energy).

The common theme here is that you are working against the natural state of two things and then allowing them to return to that state.

Offline fledarmus

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Re: Making sense of "chemical potential energy"
« Reply #3 on: May 09, 2012, 02:09:12 PM »
Excellent. In both the examples you gave, you have a higher energy state dropping to a lower energy state, and energy being applied to raise a lower energy state to a higher energy state. The further apart the two states are, the more energy is required or released when the system changes from one state to another. 

Chemical potential energy is similar. Molecules have energy tied up in their bonds and in other interactions, and changing those interactions will either give off energy or require an energy input. A mixture of hydrogen and oxygen molecules, for example, has a higher chemical potential than the same atoms in the form of water. Consequently, under the appropriate conditions, hydrogen and oxygen molecules (high energy state) will spontaneously react to form water (low energy state), giving off energy. Similarly, energy can be added to water in the form of electricity (under the right conditions) to produce hydrogen gas and oxygen gas.

Offline sodium.dioxid

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Re: Making sense of "chemical potential energy"
« Reply #4 on: May 14, 2012, 08:00:13 AM »
Excellent. In both the examples you gave, you have a higher energy state dropping to a lower energy state, and energy being applied to raise a lower energy state to a higher energy state. The further apart the two states are, the more energy is required or released when the system changes from one state to another.  

Chemical potential energy is similar. Molecules have energy tied up in their bonds and in other interactions, and changing those interactions will either give off energy or require an energy input. A mixture of hydrogen and oxygen molecules, for example, has a higher chemical potential than the same atoms in the form of water. Consequently, under the appropriate conditions, hydrogen and oxygen molecules (high energy state) will spontaneously react to form water (low energy state), giving off energy. Similarly, energy can be added to water in the form of electricity (under the right conditions) to produce hydrogen gas and oxygen gas.

I actually understand this now, and not in the way I was expecting to have understood it. I guess I was expecting something different. But nevertheless, here is what it is: the "potential" of a molecule is it's relative instability (this right here made all the difference in understanding it). A molecule with a higher potential is more unstable than one with lower potential (stability is determined by the nature of the bond(s) and the particular atoms involved). It is exactly what the reaction coordinate advertises. You break a relatively unstable bond by giving it an energy boost. Once the broken stuff rearranges to form something even more stable, it releases a certain amount of energy as determined by the difference in stability (or potential) of the starting material and the final product. It is in this sense that energy is released. And the energy released, I am told, is in the form of electromagnetic radiation (which gets into quantum mechanics). Furthermore, any kinetic energy remaining in the product helps to get other non-reacted material over the energy barrier (kinetic energy is redistributed through the system).
« Last Edit: May 14, 2012, 08:22:13 AM by sodium.dioxid »

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