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Questions for Discussion

1. Common use of energy

Biology, chemistry, and physics all make extensive use of the concept of “energy”.  But this is a difficult concept and is broadly misunderstood by many students.  Some of the language we commonly use such as “getting energy by breaking chemical bonds” to stand for “getting energy by changing a bond from a weak bond to a strong bond” can be very confusing to students.  We could in principle help with this in physics, but essentially no introductory physics course – including those reformed to include biological applications – includes a significant discussion of chemical energy.  In a recent interview with a student in Physics I, a student who has already taken many chemistry and biology classes, we recorded the following statement:

“What I found in [bio and chem] classes is that even though we might talk about energy, it's more of an accepted fact in the class, like exothermic release energy, endothermic conserve-- or like, takes in energy, whatnot, but we never really talked about how it really, like the energy got there in the first place, how it breaks the bond, exactly what the energy is doing.  That [inaudible] usually what happens in like physics is my understanding is we really think about the transfer of energy and where things are going, and then in our bio classes it's always accepted as well.  We've never really, in any of the classes we've never really linked those all together into where the energy's coming from, how it's actually breaking bonds in the molecule, how it's actually like forming bonds in molecules as well. It's more of accepted facts in those kind of classes.  And in physics we talk about where the energy is coming from and whatnot, but we don't like tie it in to like the biology of the side, or the chemical side.”

2. Common thermodynamics

The use of thermodynamics in biology is an essential component of understanding biological mechanism.  It is taught in chemistry, biology, and physics.  But typically the three classes use totally different approaches, make different (unarticulated) assumptions, and in the end do not look like each other.  As one simple example, a biology colleague recently told me that “You teach pressure wrong.  I asked my students what pressure was and they said, ‘Force per unit area’.  What they need to say is ‘pressure is concentration’.”  I responded by grabbing his wrist and taking his pulse, saying, “You guys need the other kind of pressure too.”  But he is largely right.  In physics we tend to ignore mixtures of gases and the concept of partial pressure (and I describe a serious error in an intro physics text because of that tendency in a recent paper).  How do we create a common thermodynamics that the students can make sense of?

3. Common use of entropy

One of the most challenging concepts in thermodynamics is entropy. It tends to be treated in physics either as heat/temperature -- confusing because the heat is a small quantity but not an integrable one (there is no "heat energy" that "heat" is a small piece of) -- or in a highly mathematical way -- in terms of microstates and macrostates. Neither of these is satisfying nor leads to a good conceptual starting point that allows students to make sense of all the different uses of entropy (and free energy) that they will encounter. There are a variety of attempts at a conceptual treatment of entropy, but few that make the connection to actual quantification. Is there a good "common thermodynamics" treatment of entropy that will allow students to make conceptual sense of it, to make sense of calculations with entropy, and to bridge the use of the concept in physics, chemistry, and biology?

4. Modeling with math

Introductory physics classes traditionally use a lot more mathematical modeling than introductory biology classes. Often, the best and most reliable scientific results come when good qualitative reasoning and understanding is combined with good quantitative reasoning and understanding. Often, students do not perceive the math they learn in their math classes as an integral part (pun intended) of their development of scientific thinking.  Where is it most appropriate for biology students to develop these complementary and mutually supportive skills? In math class? bio class? physics class? a coordination of the three?