A Pre-Lab Assignment for a More Efficient and Effective Laboratory

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Categories: GSI Online LibraryTeaching Effectiveness Award Essays

by Jessica Smith, Chemistry

Teaching Effectiveness Award Essay, 2011

A persistent challenge of teaching a laboratory section is that students consistently don’t finish by the end of the class period. This problem initially seemed to me more logistical than pedagogical. When I examined my experience teaching lab, I realized that the students worked slowly because they never learned how to engage with a lab. While a few students are truly unprepared, the majority have read the lab manual and the relevant sections of their textbook. These prepared students are slow because they meticulously follow the directions rather than thinking critically about the purpose of each step. For instance, students often spend twenty minutes precisely measuring a solvent or reagent that is in excess and therefore doesn’t need to be exact for a reaction to work. Students of science become scientists as they begin to comprehend how different steps contribute to an experiment rather than blindly following directions.

I’d always been lenient about letting students stay after the end of the lab period in the several chemistry courses I taught before Chemistry 4B last spring. I wanted to instill independence in lab, so I resisted giving student answers that they could determine themselves. Since I let the students muddle while other instructors told their students exactly what to do, I felt guilty if they hadn’t finished and let them stay late. With this dilemma in mind last spring semester, I set out to have my Chemistry 4B students confidently finish their labs by the time the bell rang.

I needed a plan which would allow the students to become independent thinkers while keeping all of us on schedule. I decided to change the pre-lab assignment, which is usually a hypothesis and a summary of the procedure. Instead, I asked the students to write exactly what they planned to do for the first twenty minutes of the lab and why each step was necessary. This assignment was designed to coax the students to engage with the experiment beyond following the lab manual and had the added benefit of keeping them fairly calm in the beginning of the period. To emphasize the importance of this assignment, I graded it in detail every week, turning it back to the students promptly. This tight feedback loop allowed the students to improve over the course of the semester.

I implemented this assignment after the first class, and I immediately noticed a difference in the tenor of the classroom. Because the students understood the purpose of the steps better, they could move ahead in the procedure if a piece of equipment was occupied or do two steps at once without checking with me first. In this slightly calmer environment, I was also able to push the students to connect the lab to concepts in the course. Simple questions like “What do you plan to do next?” or “Do you need to do those steps in that order?” terrified some of my previous students, but my Chem 4B students and I had meaningful discussions about how, for example, an experiment using bleach and colored dyes related to both chemical kinetics and molecular orbital theory. They had thought about the lab before the class period, so they walked in asking about high-level concepts rather than asking me about details like whether their solution looked pink enough or how long they should stir their reaction.

This simple change in the pre-lab assignment significantly changed the way the students were able to articulate and perform the steps of the lab, and my class was also always done on time. In the last few weeks of the semester, the students in Chem4B carry out independent special projects with no instruction manual. My section was able to transition into this part of the course gracefully because the students understood that being prepared for lab requires more than writing down steps from a lab manual. This kind of understanding always requires a deep knowledge of fundamental concepts, so these students’ grades on lab reports and exams were strong. I’ve taught some of my Chem 4B students in an upper division course, and I believe that the reason they outperform their peers is that they have taken responsibility for making connections themselves starting with their first-year coursework.