Spring Reflections

Spring Break is a good point to reflect on the semester thus far, and what changes I would like to make in the second half.

My second semester General Chemistry honors class is going very well (in my opinion)! On average the students did great on the first exam. While I would like to attribute it to my teaching prowess, more likely this group is simply a strong class. There is plenty of class participation and question-asking from the students without my prompting. After four solid weeks for thermodynamics, we started on a unit covering liquids, vapor pressure and solutions. There’s still a strong thermodynamic slant to the explanatory arguments, but I’ve also managed to weave in more origin-of-life research into the present unit.

Students started out reading the original 1953 Miller experiment paper, calculating substance quantities of in the reaction mixture, and considering the oxidation states of various reactants and products. I’ve used this exercise before, although I modify it slightly every year to streamline the questions. This time around I added a follow-up homework set that incorporated Henry’s Law to estimate substance solubilities in a reducing versus a neutral atmosphere and why Strecker intermediates might be favorable in the reaction. I tried to prompt the students to make use of other things they have learned without explicitly saying so. After the calculation questions, my two last two (more open-ended) questions were:

·      If instead of the reducing atmosphere, the main sources of carbon and nitrogen are CO₂ and N₂, suggest why might it be difficult to form glycine?

·       In a Urey-Miller atmosphere, the suggested reaction mechanism involves the formation of CH₂O and HCN from the reactants prior to forming glycine. Suggest reasons why this might make sense.

Some of the student responses were quite thoughtful, weaving in oxidation state considerations, bond energies, thermodynamic arguments, molecular polarity, and solubility issues.

In this unit, I spend a few minutes at the beginning of each class walking them through the follow-up experiments and discoveries with Urey-Miller-type syntheses. We talked about how different “atmospheres” synthesize different amino acids, the problem of racemic mixtures, and relevant compounds found in the Murchison meteorite. In the midst of discussing colligative properties with the students, I was able to bring up the 27-year old serendipitous NH₄CN “deep freeze” experiment, which the students found fascinating (judging from the rapt attention I was getting). When the students return from Spring Break, we will be discussing a paper on primitive cell membranes. (I assigned Spring Break reading along with discussion questions!)

My non-majors class started well, but it feels bogged down somewhat in the last couple of weeks. I think I might have been too ambitious in how much material I was trying to “cover” in the first half of the semester. While the students did marginally better on the first exam than the previous year, there were still some significant basic conceptual gaps in understanding. I think I need to do a few more formative assessment exercises. We did a couple in class the week before the exam, essentially having students critique some of the answers they submitted in earlier quizzes. (I pick 4-5 representative answers that may range from having minor flaws to major ones. The students discuss them in small groups, and then I call on students to present and we have a larger class discussion.) Yesterday, I prepared another set for my Monday class next week.

I also need to get started on the Potions project portion of the class. I told the students not to worry about it in the first half of the semester and to focus on learning chemistry basics. But now that we are moving into the second half, I need to start providing some direction. I have made no progress in my potions “textbook”, so my goal this week is to write an introductory section. Maybe I should commit to having part of it in my next blog post later this week. Hopefully that motivates me to get it done! I also need to settle on writing up one example of Potion Design that the students can use as a guide so they know what to expect. Unless I get any other good ideas, I will probably settle on the magical cyanide antidote I had previously considered.

Other than that, I’m taking advantage of the peace and quiet to catch up on research projects, write student recommendation letters and read some origin-of-life papers. All three activities are a pleasure, but they are more productive when one isn’t constantly interrupted, as befits their reflective nature. My research students will also spend some of the time catching up on their projects, but I’m sure they are very glad to also just take a break! I’ve told them I’m around if they have questions, but I’m not going to hound anyone. It is Spring Break after all, and one should take time to be reflective.