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Re: [Phys-L] defining energy



This seems to be a decent telling of the tale ==>
http://sciencequestionswithchris.wordpress.com/2013/06/27/when-does-the-breaking-of-chemical-bonds-release-energy/

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsci@verizon.net
http://mysite.verizon.net/res12merh/

-----Original Message----- From: jbellina
Sent: Wednesday, October 30, 2013 2:25 PM
To: Phys-L@Phys-L.org ; Bruce_Sherwood@ncsu.edu
Subject: Re: [Phys-L] defining energy

This is a very important issue, and has its origins I suspect in elementary and middle school science where students learn about energy being stored in materials and transformed, so a battery is an energy source and makes the bulb light. (This also leads to a lack of understanding about complete circuits, but that is another sad tale.) It shows up again often in college biology where students are told that energy is stored in bonds and becomes available when the bonds are broken. They ignore completely that the energy is released when more stable bonds are formed with surrounding hydrogen. I call it the egg yoke theory of energy production, crack the egg and yolk comes out, crack the molecule and the energy comes out. It is how they think about it, so I am not surprised it is occurring is high school teachers as well.

It's no yolk!

joe

On Oct 30, 2013, at 12:55 PM, Bruce Sherwood wrote:

Following up on John Clement's comments about gasoline and oxygen, I found
when teaching a distance education version of Matter & Interactions for
in-service high school physics teachers that many of them were surprised to
discover that they had been carrying around a view of binding energy that
was basically backwards, with the wrong sign. The view was something like
"there is energy stored in the bonds in the gasoline molecules which we can
use" instead of "in combustion the molecules transition to a lower energy
state and become more bound". To put it another way, they seemed to have
thought that "more" in the bonds (more binding) meant more "bond" energy
was available, instead of more bonding being associated with lower energy,
not higher.

I'll admit I can't express the issue very clearly, but the teachers
themselves were convinced that useful energy resulting from transitions to
lower energy levels (greater binding) was a new idea for them.

Bruce
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Joseph J. Bellina, Jr. Ph.D.
Emeritus Professor of Physics
Co-Director
Northern Indiana Science, Mathematics, and Engineering Collaborative
574-276-8294
inquirybellina@comcast.net




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