Nature Chemistry | The Sceptical Chymist

Educating Excimer: Room to fail

Posted on behalf of Aaron Finke

Chemistry lab courses should focus more on method and problem-solving rather than specific techniques, with room for students to “fail” so they can learn from their mistakes. The best approach is to use open-ended experiments that require students to formulate conclusions other than “it worked” or “it didn’t work.” However, these experiments usually require a significant time commitment on the instructors’ part, and so these kinds of experiments are usually only found in labs for chemistry majors with small student enrollments.

My undergrad’s senior capstone project for chemistry majors is a particularly good example of this kind of open-ended science project. In our instrumental analysis lab, teams of three or four were given an item the coordinators purchased from the store — a calculator, a bottle of glue, etc. We were then given questions to answer, such as the identity of the polymer in the packaging, trace metal analysis of the can, the propellant, and so on, which required us to use the instruments and techniques we learned in the semester. Since nobody knew the “correct” answer, sufficient statistical analysis was required to pass muster.

This project was one of the highlights of my undergraduate curriculum, but it required considerable time and effort on the TA’s part- and we had 5 TAs for about 30 students. How can large universities undertake such a project in a lab class with 500 students and 10 TAs?

Melanie Cooper, a professor at Clemson University, has spearheaded a program there to develop a high-enrollment laboratory course that is open-ended and focuses on method and reasoning rather than techniques. In a 2006 J. Chem. Ed. paper (vol. 83, p. 1356), she describes an example project for an organic lab. Each student was given an unknown, and after characterization of the unknown, the student would have to find a procedure for nitration of that unknown using the chemical literature, and justify that procedure before attempting it. Students monitored the reaction by TLC, and noticed that some unknowns reacted faster than others, and some even decomposed if the temperature was not controlled. Students could then collaborate and determine what factors led to such a disparity in reactivity, drawing from concepts learned in lecture and from each other.

This is the kind of project that requires students to think about what they are doing, rather than simply read off a recipe they are given. Furthermore, in such an open-ended project course, there is room for experiments to fail — a luxury that “cookbook” labs, scrambling to finish as many experiments as possible in a semester, do not always have.

Science is a humbling process — most scientists expect some portion of experiments they perform to fail. However, in today’s “cookbook” labs, failure to perform the experiment adequately leads to a lower grade in the course, leading many students to believe that all practical science is based in absolution — when an experiment fails, it is your fault, no matter what. (Then some of these undergrads join research labs, and have to learn the hard way that cutting-edge science doesn’t work like that!) Open-ended lab experiments give students the opportunity to perform “real” science in a more controlled environment.

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