I've been fascinated by this discussion, both in terms of increasing my ability to make
logical sense of the concept of energy and in the suggestions of how to teach students
about energy.
One factor I see missing from the discussion is the "thinking" ability of students. For
many years I did a simple test of reasoning ability with my chemistry students (almost
entirely 11th and 12th grade high school students). One example of the test is to have
students watch as I fill a small beaker with water, I pour all of the water into a
larger beaker. I then again fill the first beaker with water and pour all of it into a
graduated cylinder. I ask the students to tell me which has more water in it, the large
beaker or the graduated cylinder AND WHY. Each time I did this test between 5 and 10%
of the students would respond that the graduated cylinder contained more water because
the level was higher. This tells me that 5 to 10% of the students can't think at the
most basic concrete level, much less at an abstract level.
The problem then becomes how to teach a very abstract concept like energy to students
who have difficulty with even concrete concepts. The idea that energy "flows" is
concrete enough for most of them to understand. I've been able to get about 30% of my
students to understand that energy isn't concrete and that energy changes are really
molecular interactions but what do we do with the other 70% (and only about half of our
students take chemistry)? Do we decide not to teach them about energy because they
don't have the necessary abstract thinking skills or do we continue to construct
concrete models that do a pretty good job of explaining macroscopic behavior even if the
models don't work at the atomic level?