An Assignment To Prepare Students for Physical Chemistry Experiments
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times slope of graph of l n p vs. 1fT
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Measured quantities
Students' preparation far physical chemistry experiments is a key to learning from them and to doing them correctly and expeditiously. Ipromote this preparation by requiring students to submit a preliminary analysis of the next experiment a few days prior to the laboratory. This analysis consists of a flow chart showinx how fmal results are obtained from directly measured quantmes. 'lhr figure provides 3 mudel analysla of the dcrcrminatiun ofthrrmodynarnlc DrODWllCS hs Knudsen elfu,wn. The chart i s hiehlv " " abbrev~stedsymbols to represent physical quantities, arrows showing which - R T l n p quantities are calculated from which others, and summaries of the ealculations. This brevity serves one purpose of the analysis-to provide an overview of relationships among the several quantities. Even if preliminary analyses were not required, students would have to do the equivalent work after the experiment in order to calculate their results. From a preliminary analysis, they reap the additional benefit of understanding the experiment while performing it. When an analysis reveals misunderstandings, I can correct these prior to the experiment. Iask students to write the analyses in their laboratory notebooks and to submit photocopies. This emphasizes that preparation is an integral part of experiments, and that the notebook is the appropriate location for preparation that will be referred to later, notably during calculation of results. Ialso direct students to begin each chart with final results at the top, and to work their way down to directly measured quantities. This emphasizes the best perspective from which to understand or design an T experiment, since desired results should motivate measurements that lead to those results. In contrast, instructions for calculations usually proceed from raw data to final results.
Terry S. CarRon Oberlin College Oberlin. OH 44074
50
Journal of Chemical
Education
