Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] Energy & Bonds



First, thanks for all of the help. I am beginning to improve my understanding. George, Jeff, and others have helpfully pointed out that binding energy is a misnomer. I am now thinking of binding energy as being similar to a work function value. I think that is a fair analogy. I am open to being corrected there.

I am still having issues with one (at least) concept. Endo-thermic graphs (like this one: http://bit.ly/184Ow3E (full url below)) show the products with more energy than the reactants. This makes me wonder a couple of things. First, what 'energy' is being plotted on the y-axis? Second, why is the product (which for an endothermic process has a higher 'energy' than the reactants) the more likely substance?

Keith and others have pointed out (constructively) my silly (my choice of words) skipping of sign values for potential energy. Thanks to all there.

Springs... I think part of my problem is that I mentally construct an image of springs holding atom-to-atom to form molecules. It works as a mental model for holding stuff together. However, it causes great problems when thinking about a reaction. It is easy and natural (for me at least) to think about energy stored in the springs holding atoms together. It is NOT easy nor natural (for me at least) to think that when the ions are roaming free and the fictional springs are not connected... there is actually more potential energy in the system of ions.
If I completely abandon the idea of springs, it is easier to understand a more accurate (i think) model of electrical potential energy for bonding.

I wonder about the E=mcc thought. At what grade-level are we doing a disservice to students talking about conservation of mass as opposed to conservation of mass-energy? Kids have seen that equation and have little idea of what it means. They do seem to appreciate learning what it means.

That is a bit of a brain-dump, but I think it summarizes things to this point.

I still need to figure out what the deal is with endothermic reactions. I am reading some old chem books, but they don't mention or allude to my questions so far.
http://www.emsb.qc.ca/laurenhill/science/exo_files/image007.jpg)

Thanks again to everyone for their help and insight.

Paul.