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[Phys-L] Re: what is "physics"



However, two atoms are very useful in getting students to think about
potential energy. We need to apply the results of PER to the problem that
students have the misconception that chemical bonds store energy. I have
even been told that some texts even explicitly propagate this misconception.
Students need to think through the idea that bonds are like rubber bands
that store energy when stretched, and give it back when they pull the atoms
together. Of course one could introduce the idea that they store negative
energy, but that is the kiss of death for intro. students who can not handle
the idea of conserving positive quantities.

The other part of this is that chemists speak about breaking bonds. That
particular image makes students think of rubber bands which release energy
when they break "after being stretched". In truth bonds never break, they
just stretch out to infinity and after a certain amount of stretch they
essentially cease to absorb energy. One certainly can argue about whether
bonds exist when they are well stretched, but the potential for them exists.
The term "forming" a bond also brings to mind the idea that you have made
something which of course has to contain energy, when in truth it has
negative energy.

While it is very tempting to bring in the idea of negative energy, this
should not be done until students can handle positive energy. They first
need to be able to reason with the help of bar charts how energy can be
transferred from one place to another. Once this has been firmly
established the idea of having a hole in the ground can be a place where the
E_g is negative can make sense. Only at that point can the idea of a bond
being a hole make any sense.

Unfortunately this concept can not make sense when students are introduced
to chemistry before physics. At that point they generally can not handle
negative quantities. While this may be an argument for physics first, many
states already have physics first in the form of IPC (Integrated physics and
chemistry). Physics first would then just be an extended conventional
physics course which would still not help much. But if IPC teachers were to
use good pedagogy such as that developed at AZ state, or even IPS by Uri
Haber-Schaim then perhaps students would come into chemistry with a more
productive view of bonds.

So in the end I would firmly say that two atoms can be physics, but
interactions between multiple atoms is often chemistry. Notice that solid
state physics is a big exception here. So perhaps the dividing line is not
as easy to establish. Perhaps a better division would be along the lines of
molecules, but then one must consider the physics of snowflake formation.
The only firm division might occur when one considers the formation of new
molecules from other molecules. Incidentally heat transfer is considered to
be both a physics and chemistry topic and the influence of various modes of
vibration and rotation of molecules is also part of the topic. In the end a
topic can be considered to belong to a discipline only when it is completely
ignored by other disciplines. This would reduce the number to a precious
few.

John M. Clement
Houston, TX



John,
As a former chemist masquerading as a Physics teacher, I concur
with your colleagues. A single atom is physics, more than one is
chemistry. <!>

Seriously, I never understood the division of science that could
lead to the establishment of the Journal of Chemical Physics and the
Journal of Physical Chemistry at the same time.


THO

Thomas O'Neill
Physics
Shenandoah Valley Governor's School

-----Original Message-----
From: John Denker [mailto:jsd@AV8N.COM]
Sent: Friday, September 30, 2005 1:26 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: what is "physics"

SSHS KPHOX wrote:
.... when we do thnk of a project it is Engineering we lean to
rather than simply Physics. Do we set these up to emphasize Physics?

Just pondering ....

My opinion:

1) Small answer: Usually, any given project can be tweaked so as
to emphasize physics.

FWIW when I go bike-riding with my 10-year-old nephew, it turns
into a physics lesson. PE converts to KE and back when we
come to a dip. Going up a mountain in low gear exemplifies
mechanical advantage, explainable in terms of conservation of
energy (small force with many strokes, versus larger force with
fewer strokes).

2) Big answer: I tend to take an expansive view of what "physics"
is. Not everyone does; I have met physicists who thought that
anything with more than one atom in it wasn't physics; in particular
solid-state physics wasn't physics. I thought these guys were nuts.

In contrast, there are guys like Carver Mead. He was professor
of electrical engineering, and IEEE named him "Engineer of the
Century" or something like that. But he was trained as a physicist.
I always thought of him as a physicist (which didn't make him
any less of an engineer). Perhaps more to the point, Feynman
thought Carver was a physicist.

On the other edge of the same sword, Feynman wasn't above taking
a job as "Chief Engineer of the Metalloplast Corporation" or
offering a prize (1000 dollars, back when that was a lot of
money) to the first person who could make an electric motor
smaller than 1/64th of an inch on a side, and another prize
for the first microlithography. He also had a longstanding
interest in computation, especially parallel computation and
biocomputation.

Read the lists of Nobel Laureates in chemistry, medicine, and
even economics, and see how many were trained as physicists.

Think about how much of what we call mathematics was invented by
physicists.

I'm not saying every physicist has to be an expert in every
possible application and tangent ... I'm just saying that if
you see an opportunity to make a connection, make it!

By way of contrast, in some places the chemistry department
takes a narrow view of chemistry. The P-Chem (physical
chemistry) instructors take such a narrow view of entropy
that they contradict the notion of entropy that is used in
the electrical engineering department (error correction),
the math and computer science department (cryptology),
the physics department, and even the English department
(librarianship). It's a scandal. Also because of those
narrow views, biochemistry became part of the biology
department, and the chemistry guys wonder why they are
on the outside looking in.

Bottom line: Taking a narrow view of one's field is a recipe
for sclerosis and death. Some fields deserve to die this way,
but physics does not.
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