Teach historically. Students need to learn the logic, concept-formation, fallacy identification, induction (i.e., generalization), conceptual integration (i.e., making connections, or “theory building”), and thinking skills that only teaching historically (or in a related way) affords.
In “Teaching Heat: the Rise and Fall of the Caloric Theory,” Dr. Michael Fowler (UVa), writes:
In my experience, there is much to be gained from teaching physics with some historical perspective. Unfortunately, the trend in physics textbooks these days is in the opposite direction. Thirty years ago, most standard texts included some discussion of how and when basic concepts in physics developed. Recent editions of these same books, much heavier and more colorful, have dropped that material in favor of endless detailed instruction on how to solve textbook problems. This may be, in part, a necessary response to less well prepared students, and possibly teachers, but the new texts, despite four color artwork on shiny paper, are rather dreary. My solution is simply to use the text as a source of problems and for back up reading, to use a fair amount of historical material (and demonstrations) in class, and to post my class notes on the web. Homework assignments include calculations based on historical experiments (for example: Estimate the mechanical equivalent of heat using Rumford’s cannon-boring data and Watt’s estimate of one horsepower.) Most of the students enjoy this approach.
I strongly believe that it is not a waste of time to discuss some earlier theories that turned out to be wrong. In fact, these earlier theories are often close to the students’ current thinking, so challenging them as to why those ideas were finally abandoned can stir the critical faculties and lead to better understanding. A case in point is the caloric theory of heat. Of course, the students are vaguely aware that it’s not right, but their intuitive ideas of heat, based on everyday experience, have probably led them to construct an operational model not too different from the caloric one, so we go ahead and discuss heat from this naive point of view, and mention the first recorded systematic experiments on heat and heat flow. For example, Ben Franklin measured heat flow down rods of different materials by seeing how long it took to melt wax, and thereby compared the thermal conductivities of different materials, a matter of real practical importance in designing stoves, for example. Franklin believed some weightless (or almost weightless) caloric fluid was flowing down those rods. Recall he’d thought the same thing about electricity—there was some electric fluid flowing when an object was being charged electrically—and there he was absolutely correct. Like the electric fluid, Franklin believed the caloric fluid would flow from one object to another, but overall there was always the same amount of fluid: it was conserved. That is the basic Caloric Theory.