I've been sitting over in my corner watching Jim Green spin his web so
delicately. As he finally remarked, there were quite a few e-mails
promoting both mass and energy as substances rather than abstractions. Like
Jim and Leigh, I also cling to the strict orthodox view of these attributes
of systems as inventions of the mind (Leigh puts it so well.)
However, John Clement's contribution, where he writes "Yes, but is this how
energy should be taught?' deserves, as always with John's contributions,
much thought. It is his view that a concrete rather than an abstract notion
of energy is needed to be presented to students so that they can bridge from
the unknown to the orthodox; he reminds us that only a small minority of HS
graduates are at a "formal" level, a level necessary to appreciate an
abstract notion. Further he draws our attention to the fact that the
Modelling people (and I acknowledge their success) model energy as
"something which can be transferred sort of like a fluid".
So we have Jim and Leigh and I and, I hope, many others saying that energy
is an abstraction and it is NOT a fluid and we have Jim and the Modellers
saying that HS (and perhaps College) students cannot understand abstractions
and we are therefore forced to produce curriculum material that represents
energy to them as a thing, a substance, a fluid. What is the answer? Do
we need an answer?
I'd like to step back a little and ask the following question. What is it
that we want HS students (and non-science majors) to know about energy? It
seems to me that we have two answers to that question. One is that perhaps
we want to discuss energy transformations: bodies falling off cliffs,
objects (not masses) bobbing up and down on springs, ice melting and some
liquid water being brought to its boiling point and changed into steam, and
so on and so forth. The other is that we want to equip them with background
understanding to follow discussions on the "energy crisis". I can elaborate
on the first answer and to what extent it demands any understanding of
energy, if anyone is interested, but I am more interested in looking at the
second answer because there is where, in the popular mind, energy is lying
about or, rather, flowing as a substance.
Energy, the abstraction invented by the early nineteenth century natural
philosophers and used by them and by engineers, has become the property of
the media, of entrepreneurs and of politicians. The energy they talk of and
understand (?) is indeed a substance. It's the stuff that is found in coal,
in gas and gasoline, in uranium, in the wind, in reservoirs high on the
hills, in sunlight, in moving water and in hydrogen. All of this is good
energy, especially if we own it (perhaps we can fight a war for it if we
don't). A trouble is that some of this "energy" is non-renewable - we
squeeze it out of the coal or the uranium and sell it and the customer uses
it and it's gone - a non-renewable resource. Other brands of "energy" are
renewable and that's a bit of a worry too because we mightn't own it at the
moment but if a corporation can own genetic codes then owning sunlight and
wind and tides won't be too much of a worry.
So, if we look at that (and ignore my cynicism) there is a problem for us as
educators to prepare students for a debate about a different sort of energy
than the orthodox physicist's abstraction. These important everyday uses of
the word energy really deal with processes which the scientist and the
engineer can, with a little bit of effort and a little more care, describe
in terms of transfers of energy within and between systems. So our
educational starting point should be concrete examples - take coal and burn
it and boil water and run steam turbines and etc, etc. I think we can do
that, for coal and for gas and for uranium and for wind and ...the first
time through without the use of the concept of energy! However, we will
want to compare costs and efficiencies (and, I hope, pollutants) so we will
need numbers and a scientific accounting, and that could be the place to
bring in the notion of energy, a property that we can tag on to all the
stages in the processes.