Promoting Understanding from Experiments by Visualizing Results in an Introductory Organic Chemistry Lab

Categories: GSI Online LibraryTeaching Effectiveness Award Essays

by Jakob Dahl, Chemistry

Teaching Effectiveness Award Essay, 2020

When I taught Introductory Organic Chemistry lab (Chem 12 A) as a first-year graduate student, it quickly became clear that it was a very challenging class, both for the students and for me as a GSI. There was a rapid pace of assignments from both the lab and the lecture portion. Students managed to learn well, but a couple of concepts seemed surprisingly stubborn. One concept that stood out to me was understanding thin-layer chromatography (TLC), an analytical technique measuring how far a molecule travels up a solid support that is used in many laboratory experiments. Students developed misconceptions based on a simplistic application of previous chemistry knowledge and would continue to hold on to those ideas long after they had performed experiments in which the outcomes contradicted their previous beliefs. It became clear to me that while the students had performed the experiments and written about the results, they had not compared the results to their previous beliefs and thus had not been able to truly learn from them. Guiding them through the process in later labs was difficult, as they had further cemented their conceptual understanding and had difficulty remembering the details of previous experiments. This struck me as a missed learning opportunity at the time.

I returned to this course in my third year as head GSI and took on the task of reworking lab reports into lab worksheets. During this process, I took the opportunity to think about what could be done to help students learn directly from their results. Based on the adage, “A picture is worth a thousand words,” I designed a set of graphs that the students would fill in themselves. As a pre-lab for their first lab in which they used TLC as a technique, they would draw two lines showing how far they thought two different molecules would travel under solvent mixtures with different properties. In a second graph, they would plot the outcome they actually measured, and then were prompted to discuss the differences between the two graphs. In this way, they could directly compare the outcome they expected with the outcome they measured.

As this was part of a general reworking of the written assignments in the lab, the course instructor Prof. Barranger had asked the GSIs to provide some example of student work every week to allow us to evaluate the types of answers students provided. From the examples we saw, it appeared that students were easily able to perform the visual tasks and were able to either confirm or correct their conceptual understanding directly in the lab. Prof. Barranger later stated that, “The graphical worksheets helped the students to realize their confusion, grapple with their conceptual understanding of the material, and formulate questions to ask their GSIs for assistance.” I repeated this technique for several later laboratory assignments to offer additional help to more visual learners, and to continue deeper engagement with the processes used in the lab. To judge whether students preferred the new type of assignments, I added a course evaluation question: on a scale of 1-7, with 7 being much preferred and 1 being not preferred, more than half of the students chose 7, with an average of 6.01. Analyzing grades for lab and related assignments in the two years before and two years after the change showed no significant trends. However, the strong student preference for the new type of assignment and the readiness of students’ answers convinced me that adding visual questions and problems was a worthwhile effort. I intend to continue doing so in future teaching experiences and would highly recommend it to anyone else writing lab assignments.