During my studies and general course reading, I have come across some conflicting messages regarding the nature of chemical potential energy. Can anyone help clarify this?
I like the basic concept of PE as being energy stored due to overcoming a given force... the classic example being the ball at the top of the hill - it got there by some means, that involved work done overcoming gravity.... fine no probs.
I also like the notion of gases having more PE due to the atoms by definition having to have more of it in order so that they can overcome the VDW forces that would otherwise force them into states of liquidity or solidity.
Now where the conflicts arise in terms of PE is where bonding is concerned. Many sources cite PE as being stored in chemical bonds but I have seen others and my uni lecturer has stated, that this is misleading.. PE is NOT stored in chemical bonds. My lecturer in fact went on to discuss how the phrase "bond breaking" is also misleading as it gives the wrong visual impression as to what is going on during reactions. He prefers the phrase "atom separation".
In my mind this is how I see it.... please if poss give me some feedback on it and as to which camp you believe is correct!!
*When you have covalently bonded atoms, for example, there is a high electron density between the 2 nuclei and it is the electrostatic attraction between this negative charge and the positive charge of the 2 adjacent nuclei that bonds them together.
*When energy is applied to this molecule, the electrons begin to absorb energy and in doing so can be promoted to higher energy levels. This promotion to higher energy levels occurring in both atoms has the gradual effect of forcing the 2 nuclei apart, thus increasing the internuclear distance and hence decreasing the coulombic force of attraction occurring between the opposing charges of the electrons and the nuclei.
*Eventually with enough energy the 2 atoms are pushed apart and the bond is "broken". The individual atoms due to the energy they have absorbed now have a higher level of PE within their electron cloud. How much energy is required depends on the electronegativity difference and/or the ratio of bonding/antibonding within the molecule.
*When the atoms proceed to form new bonds in order to become the final product, energy will be released, the quantity depending on the strength/stability of the new bond being formed. In an endothermic reaction, the products will have a higher level of PE than the original state and in an exothermic reaction, the products will have a lower level of PE than the original state.
*Since electrons in atoms have KE and PE, during bond formation, the decrease in PE is accompanied by an increase in KE. However, the magnitude of KE increase is only half that of the PE decrease - the remainder being released as light and/or sound energy.