provocative opinion Let's Separate Theories from Calculations Mark 6. Freilich Memphis State University, Memphis, TN 38152 "It's time we rethought the way freshman chemistry is taupht." How many times have we seen essays and articles based on that premise! And here I am, another voice in what is now a rather crowded former wilderness. At this time, however, my concern is not with the approaches we take to actually teaching subject matter. I leave such concerns to the learning theorists and the empiricists who, together and individually, develop techniques that work. (See, for example, the recent "Provocative Opinion" ( I ) in which David Brooks has raised the specter of the machine (need I say "computer"?) that solves stoichiometry prohlems (with a little help from its human friends) and warns about the changes that will have to take place in the way calculational prohl'em solving is til0ghr.j ~ a i h e r1, wish to discuss a situation that wa5 highlighted by the recent Symposium on Algorithms and i'robiem Solvinr ( 2 1ouhlished in rhis .Journal. particularly the issue raised by Miles Pickering and Susan Nurrenhern (3).As the svmnosium makes clear. we ask our students to accomplish two bhjectives during their study of eeneral chemistrv: (1) . . thev " must learn how to solve calculational prob1ems"for numerical results, and (2) they must assimilate and manipulate facts and theories (they must learn concepts) in order to explain chemical behavior. In order to demonstrate satisfactorily that they have accomplished the goals we set for them, students must pass tests that require them to solve prohlems and to demonstrate mastery over (not memorization of) facts and theories. Miles Pickering ( 4 ) , building upon the work of A. H. Johnstone (5, 6). has described the limited ahilitv of manv students to handle multifaceted prohlems andior lab experiments in which the directions are, as he says, buried in "noise" (the background information that we think is so important to "flesbineout" an ex~eriment). Inother words, we cannot ask our students to d o t o o much or to do too many different things at one time. Julien Gendell has said (7) that " . . . working prohlems in an introductory chemistry class . . . is a most valuable way for students to increase their understanding of scientific
- .
442
Journal of Chemical Education
concepts." While I agree with this statement, I am concerned that most students cannot make (or refuse to make) the connection between a calculational prohlem and the coucepts upon which the problem is based. Given this inability or refusal to link calculational prohlem solving and chemical theory in the minds of our students, I would like to suggest that the order in which we traditionally introduce topics (at least the order as it has evolved during the last several years) actually hinders the chance many students have to succeed in general chemistry and to create the linkages we seek. Moreover, it is possible to rearrange the order of topics to give our students a greater opportunity to learn the material. As a side benefit of this rearrangement, we may he better able to serve the needs of other disciplines that require general chemistry for their majors in addition to giving us better prepared chemistry and potential chemistry majors. I propose that we separate the computational aspects of general chemistry from the theoretical ones and teach them in different semesters (or quarters). (Please do not interpret this as a suggestion that we eliminate problem solving from a large portion of introductory chemistry. Quite the contrary. We will now have to place much more emphasis on solving "thought" problems, and some tests will he oriented toward more "explain" and "predict what will happen" questions than is the case today.) This "new" approach has its advantages and, unfortunately, its disadvantages, though I argue that the former far outweigh the latter. The major pedagogical advantage would come from emphasis and repetition, resulting not from doing the same things over and over again, hut from doing thesame kinds of things. Calculations of various types would continually reinforce one another and the underlying unity of many aspects of chemistry via the atomic theory would become much more apparent. On a more mundane level, this division of subject matter would mean that the grades we assign would describe the abilities of our students more precisely. A grade earned in the computational course would speak to the demonstrated ability of the student to perform the basic computations
required in general chemistry; it would not imply anything about the student's understanding of the underlying chemical behavior. Similarly, a grade earned in the theory course would address the student's demonstrated ability to understand and exnlain chemical behavior without directlv addressing the ability to perform calculations. (Let us keep in mind. thoueh. that internretine erades is an art that is best left artistes who are free to assume whatever they wish.) Another advantage becomes apparent when we remember that, for most of our students, general chemistry is a service course. Though it makes little sense to me, there are majors that require only one semester of chemistry and thereby accept the first course in the two-semester sequence. Chemistry I and 11, as I have described them above, would, perhaps, allow such majors to select the one that contains the more appropriate material. This is not to imply that the careful separation of material, in whatever way it is done, obviates the need for taking Chemistry I and I1 sequentially. I t will always be necessary for us to make some assumptions about our students' prior knowledge whenever we introduce new topics or reconsider old topics, and, moreoften than not, we must assume that there is some prior knowledge. However, it would certainly be easier for students to schedule their classes and take their one chemistry course whenever they needed or wanted i t if the two semesters were mainly independent of one another. The membrane between Chemistry I and Chemistry I1 would be semipermeable; each would allow in some concepts to sumort .. calculations or some calculations to sunoort .. concepts. Thus, if Chemistry I were the computational course, and I believe that it should be, then, much as is done today, we would inject the concepts of atoms and molecules intoour discussion of stoichiometry. However, the detailed discussions of atomic and molecular structure (including bonding theories and molecular geometry) would be saved for Chemistry 11. ~hermochemistryand chemical thermodynamics would fit naturally into Chemistry I, as would the study of rate laws, chemical equilibrium, solutions, and pH. Thus, in Chemistry I, the student would repeatedly work with the mole and the balanced chemical equation, far more frequently than he or she does today during the initial semester. No longer would there be the lona break that tv~icallv .. occurs between the basic coverage ot'chemical stoichiometry and the description of gaseous hehavior. (Commonlv, this is the time whed severalweeks pass in detailed discussion of atomic and molecular structure and nary a mole is mentioned.) If memory serves me correctly, this almost sounds like a return to the '50's, doesn't it? But, of course, i t isn't, because we are not seeking a return to the days when an atom was a nucleus and rings (or shells) of two, eight, eighteen, etc., electrons.
It is not difficult to raise obiections to mv. suekestions. The ,... most ob\,ious one decries the teat hing of the mechanics uf chemistrv without vrovidinr tht theoretical iustification for those mechanics. These hard-won explanations, extracted after decades of studv, are the crowning alorv of our science. They also make it eaHier for professioni~Hand talented amateurs to bring reason to the solution of problems rather than , first-year stu&nts are not profesrote. ~ n f o r t " n a t e l ~our sionals, and the vast majority of them are not even talented amateurs (nor will they eser he such). A calculational approachand its underlying theory do interact and gi\,e mutual suppurt, but one must be learned htfore it can reinforce the other. That requires more time for digestion and assimilatiun than most of our students ha\,e or are willinr to devote. A mure serious objectiun is the delay that w18;ld he given to the study of some important areas of chemistrv. Given all the ropics I have tried to squeeze into Chemistry I, thrrt is little roum left (no room I r f t ? ~for discussions of the elements and chemical periodicity, classes of chemical reactions, and the similarities and difference9 among solids, liquids, and gases. I would grratlg regret making it possible for a student t o complete an entire first semester of chemistry without beine exnosed to a rather detailed discussion of the periodic tabG. his would be particularly true for the student whose maior reauired onlv one semester of chemistrv. Problems of this nature already exist, however, and we would not be ireatinn anvthing new. The situation would be far worse if we triedto preveit it by introducing too many topics too briefly in inappropriate places, as some textbooks do today. It's an imperfect world, and we must work within its limitations. As much as we may want to consider the needs of the student who takes only part of the sequence, we cannot design a two-semester (or three-quarter) course of study for the student who will take only part of it. As dearly as we may want to tie un each tonic in a neat little nackaee, with no loose ends, fo; all of ouigeneral chemistry &ude;ts, we have tried such an annroach for several vears. We have found that it has its weaknesses, some of whiih are apparently fatal for many of those students we want so much to help. Concentrating separately on the calculational and the theoretical aspects of general chemistry may not be the only way to make us more successful in the classroom, but it certainly deserves serious consideration.
-
Literature Clted
Volume 65
Number 5
May 1968
443
