Student Response to Simultaneous Instruction in SI and Conventional Units Arthur E. Grosser McGill University, Montreal, Quebec, Canada. H3A 2K6 In the continuing debate over the introduction of S I units there are three major positions: (a) non-introduction,' (b) presentation of solely SI units2 and (c) presentation of a "hybrid" system of mixed conventional and S I t e r m s . W e have decided that a fourth point of view confers the most benefit to the students: the simultaneous. rieorous teachine and ~ n g f a i d No . matterwhat the final outcome of the scientific debate over SI units, students deserve to be prepared to read texts and journals written in countries or research labs which favor a particular unit system. Pedagogically, this means the use of conventional units as well as a rigorous system of SI units. Method of Presentation Units of both systems were introduced only when called for by the particular chemical topic and the equivalences were then set forth. When were presented in lecture they were always set forth with both sets of units: "The sum of the concentrations of all ions dissolved in hlood serum averages ~~" to 0.260 mole liter-' (0.260 m ~ b d m - ~You ) . are asked to preDare an NaCl solution that is isotonic with hlood serum. that is, a solution with the same total ionic concentration. What will the weight of NaCl be in 1 liter (1 dm3) of this solution?" However, the solution was given in only one set of units. (The assignments had solutions provided in hoth unitary systems-one detailed and the other abbreviated.) It was hoped that the students would develop a feeling for the relative magnitudes because of the obiquitous equivalences s ~ r i n k l e dthrouehout the course. " The students were required to he able to solve problems in either unit svstem. For instance.. a ouiz . on thermochemistrv might have bne question in which all the calculations weie done in kJmol-' while the next question would require a calculation in kcallmole. The benefits of such a presentation, if successful, are obvious: the students will be able to work in whatever unit system subsequent references are given or courses are taught. But there are some pitfalls which can he imagined: (1) the double system will confuse the students and prevent full mastery of either system, (2) learning two unit systems will he considered too much time spent on dull material and will result in students turning away from chemistry. ~
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Student Evaluation We are able to present some research which bears on these matters. During the last lecture of the semester the students were polled about "learning to do problems in both S I and conventional unit systems." Their responses (as percentages of the 152 respondents) are indicated in parentheses.
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Journal of Chemical Education
A. I regard it as -. (a) very useful
(b) somewhat useful not very useful (dl useless B. I found it -. (a) very easy to learn (b) relatively easy to learn (c) took some time to learn (d) hard to learn (e) impossible to learn (c)
Not only is this a positive response to the units system, hut also it has not heen purchased a t the expense of the students' interest in chemistry. Asked "To what extent has this course stimulated your interest in chemistry?," the percentage who responded "greatly increased" rose from 4% to 1290,for those who responded "increased," it rose from 21 to 39%in a comparison with the previous year. In detail: (SI t (conventional conventional) alone) (12%) ( 4%) (a) greatly increased (b) increased (39%) (21%) (c) about the same (34%) (36%) (20%) (d) decreased (11%) (e) greatly decreased ( 4%) (19%) While it is improper to draw too much from these results (since many factors in addition to the method of teachineunits had changed), it is clear that it is not necessary to bore students while teaching them hoth unit systems. Conclusions It is clear that the students were aware of the importance of ~ r e ~ a r i themselves ne for all eventualities. unit-wise. and weie, b y a i a r g e majority, not put off or confused by it. Moreover, the number of students whose interest was raised by the course is greater than those whose interest was lowered. While admitting that our results are preliminary, we find only positive response from the introduction, in a gradual but ubiquitous manner, of both conventional and SI unit systems a t the general chemistry level.
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Adamson, A. W., "SI Units? A Camel is a Camel," J. CHEM. EDUC., 55,634 (1978). Masterton, W. L. and Slowinski, E. J.,"Chemical Principles Using the International System of Units," 4th Ed., W. B. Saunders Co., Philadelphia, 1979. Wright, P. G., "An Apologia for Accepting at Least an Approximation to SI," J. CHEM. EDUC., 56, fi63 (1979) and most recent general chemistry textbooks, for example. Butler, Ian S. and Grosser, Arthur E., "Relevant Problems for Chemical Principles," 3rd Ed., W. A. Benjamin Ca., Menlo Park, CA. 1979.
