by Mercedes Taylor, Chemistry
Teaching Effectiveness Award Essay, 2016
The student pulled her test tube out of the ice bucket for the tenth time, then slumped in despair at the sight of the clear liquid. She shoved the sample back into the ice and put her head in her hands. Nestled in the ice next to her own, her classmates’ test tubes were full of fluffy white crystals, the result of a four-hour lab on recrystallization. The student had done something different from her peers at some point during the afternoon, and now not a speck of product was visible in her test tube.
The recrystallization lab is like most experiments in Chemistry 3AL: there is a single desired outcome, intended to teach the student a chemical concept or laboratory technique, and there are myriad ways for the experiment to go off-course. Although the students aren’t graded on the outcome of their experiments, there are many negative consequences to getting the “wrong” result. Students may internalize an incorrect trend or principle. Even if the instructor explains clearly to the students what went wrong and what was meant to happen, this is a much less compelling way of learning a concept than witnessing it in their flask. And their frustration with perceived failure often leads to a dismissive, negative attitude towards that particular concept, which can prevent them from making the mental effort necessary to learn and retain it.
In such situations, I found that the following strategies prevented students from reacting emotionally to “bad” results and helped them learn the intended concept. First, I used my tone and body language to convey positivity and curiosity. “Really? Cool! Nobody else’s reaction turned that color!” By engaging warmly with them, I lessened their frustration and incited their curiosity about the result. But in reassuring a distraught student, it’s important not to say “Don’t worry, you won’t be graded on the outcome of your experiment.” To many students, “it’s not graded” means “it doesn’t matter,” and you need to keep them invested in the lab. The GSI must alleviate stress about the result without causing the student to check out.
Secondly, I questioned them from a scientific standpoint about what happened and why, and led them firmly towards an explanation that reinforced the concept at hand. For example, recrystallization depends on a compound’s solubility in a particular solvent; a successful recrystallization teaches students how to manipulate slight differences in solubility. Rather than letting a failed recrystallization confuse this topic for them, I would reason with students about how volume, temperature, or solvent might have prevented their recrystallization, invoking the same principles of solubility that would have explained a positive result.
Finally, it’s important to recognize that failed experiments are an opportunity to teach the philosophy of science. The goal of Chemistry 3A lab (and all of science) is to make observations about the physical world and develop explanations for those observations. Scientists encounter unexpected results, contradictory results, and uninterpretable results on a daily basis. As a PhD student in chemistry, it was easy for me to tell my students how often my own research experiments fail and how important it is to view failure as a part of the process. I made sure to reinforce this attitude when grading. Next to their gloomy descriptions of unexpected data, I wrote “Good observations!” “Interesting result,” and “Why? …Oh, good point” if they ventured an explanation.
In grading my students’ lab write-ups, I was able to assess the extent to which they understood the possible reasons for their undesired result. With no GSI intervention, a surprisingly high number of students write things like “Didn’t work. I don’t know why” or “No crystals ?” or “For some reason my partner’s reaction worked but mine didn’t.” After a short conversation showing curiosity about the lab outcome, a student was much more likely to write, “My recrystallization failed but I think it’s because I used too much solvent,” or even better, “My test tube didn’t yield any crystals because I used a lot of solvent.” This latter sentence describes the outcome without passing judgment on it. The best possible scenario is for the student to omit words like “failed,” “wrong,” or “didn’t work,” and instead to simply describe the result and offer an explanation.