In the Classroom
Providing Direction and Motivation for Students To Review Topics from Previous Chemistry Classes David F. Rieck Department of Chemistry, Richard A. Henson School of Science and Technology, Salisbury State University, Salisbury, MD 21801
When teaching courses subsequent to general chemistry, I am often discouraged by many students’ lack of retention of concepts introduced in previous courses. The basic principles of stoichiometry, thermodynamics, equilibrium, etc. are essential building blocks for an understanding of topics presented in higher-level chemistry classes. It is understandable that students will forget some material, especially things that they not did master in the first place. Therefore, a well-organized review of fundamental chemical principles is warranted in intermediateand upper-level classes. Clearly it would be inappropriate to spend a large amount of class time reviewing such concepts. However, telling students that they are responsible for all material presented to them in all previous chemistry courses simply frustrates and discourages them, rather than motivating them to review. In my sophomore-level descriptive inorganic chemistry class I have initiated a mechanism intended to provide a more directed review process. It includes a motivation factor. Each exam includes one extra-credit problem that is given to the students in advance (I distribute the question about a week before the exam by posting it on a computer conference we use for the class). The problem is related to a current course topic, but the principal goal is periodic brief review. Students are permitted, even encouraged, to work on the problems in study groups. Since they will need to reproduce the work on the exam, however, each student will need at least some understanding of the material by test time. In addition to reviewing and integrating topics, the questions should be fun for the students. Consider the example problem in the box (given to the students at about the time we were discussing the isotopes of hydrogen). The concepts an instructor chooses to include in a problem will naturally depend on the course material being studied at the time. In organic chemistry for example, one might choose a problem that reviews kinetics and rate laws before discussing reaction mechanisms; to review stoichiometry and chemical formulas, one might use a problem that includes the combustion analysis of a hydrocarbon. By directing students to recall a few selected topics (if they decide to do so for the reward of a few extra exam points) the review process becomes less intimidating and less frustrating. I have made no formal attempt to determine whether
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this method of “forced review” improves students’ understanding of chemistry or improves their performance in the course. Responses on student evaluations, however, have been positive, with students indicating that they appreciate the opportunity and are grateful for the direction it provides (as opposed to trying to review “everything”). This approach should work well in virtually all chemistry courses. Problems of the sort described here could also be useful as homework assignments or group quizzes. This type of problem, however, can be difficult to conceive and time consuming to write. For these reasons, a column featuring such problems will be published in JCE Online, the part of the Journal published via the WWW. Readers interested in contributing to this column are encouraged to submit problems to the author for possible online publication. Problem Naturally occurring hydrogen contains about 1 × 10᎑15% tritium atoms. This tritium is radioactive, undergoing beta decay with a half-life of approximately 12.4 years. Imagine a 1.0-L bottle of water that initially contains hydrogen consisting of 1.0 × 10᎑15% tritium atoms. Assuming no new tritium is produced in the bottle (a pretty safe assumption), how many beta particles will have been emitted after 3.0 years of storage? Assume a density of water equal to 1.0 g/mL. Solution This problem requires that the student review the mole concept to determine the number of tritium atoms present initially. Then she or he must review some aspects of first-order kinetics to obtain the rate constant, in order to use the integrated rate law to calculate the number of tritium atoms present after three years. The difference shows that about 1 × 108 tritium atoms decay during the three years. In addition to calculating this number of beta particles, it is my hope that the student will conclude the review by considering the significance of the answer (i.e., Avogadro’s number is really big—when dealing with moles, a number such as 1 × 108 is relatively small!).
Journal of Chemical Education • Vol. 75 No. 7 July 1998 • JChemEd.chem.wisc.edu
