We might refer to this model of teaching and learning as the “telling” model. Teaching is about transmission of ideas. To learn you need to receive and memorize these ideas. Another way to say this is that students come into our classes as blank slates on which we write information. What are the learning outcomes? Students repeat ideas and often sound approximately correct when we ask them about what we taught them. But what have they really learned?
In her Ph.D. thesis (University of California, Berkeley, 1999), Melonie Teichert showed that the lecture model was not successful in helping students understand that energy is required to break bonds. She reports that despite the fact that this idea was stated explicitly several times during several lectures, many students believed the opposite. Indeed, Teichert found that fewer students were able to answer correctly that energy is required to break bonds on a posttest at the end of the semester compared to a pretest given at the beginning!
It is tempting to try to dismiss these data. Perhaps the students are not very good. Their backgrounds are poor. The explanations were not complete. I assure you that the students involved in Teichert’s study are talented, bright, and capable. The faculty instructor is a dedicated teacher who received high ratings from students and from faculty observers. No, it is not possible simply to make excuses about preparedness of the individuals involved. We need to think more deeply about what might be going on, and look beyond trivial assumptions we might make to dismiss these data.
It is interesting to consider why students might draw the opposite conclusion about bond energies from what we tried to teach them. Why might students think energy is released when bonds break? Consider their prior experiences and observations that they have made. Students have watched paper burn. As the paper breaks down, energy is released. The paper is gone, and to the observer, it appears as if nothing is left. Students speak about getting energy from the foods they eat. Again, as the food is broken down through digestion, energy is released. In my opinion, students are making reasonable conclusions on the basis of these experiences. When things break down, energy is released. Why should they believe that energy is required to break a bond just because we tell them? It simply doesn’t make sense given these prior observations and little counterevidence.
There is plenty of other evidence in the literature that students hold ideas that are contrary to those we think we have taught them. The videotapes “Private Universe” and “Minds of our Own” (The Annenberg/CPB Math and Science Collection) contain other cases. An example from these tapes regards photosynthesis. From where does the tree get its mass? A common response from students is soil and water. This answer is given even after detailed instruction about photosynthesis. Students write down the equation that carbon dioxide and water are involved but draw little meaning from it. Again, it is not possible simply to dismiss this example as anomalous. Students have good reasons for the ideas they hold. In this case, it is hard to believe that a gas (which does not crush us) can give rise to something as massive as a tree.
Now back to our entering graduate students. They believe in the “tried and true” transmission model of teaching and learning. After all, this method has apparently worked for them. They are the success stories. They have been told repeatedly that they are the best and the brightest (because only the best and the brightest succeed in science). But, indeed, they also hold many ideas that are counter to those they have been taught. They are still struggling to gain an integrated knowledge of chemistry beyond doing well on tests that often emphasize memorization. It is these students with these experiences whom we now place into the classroom to teach undergraduate students.