What Happened to Descriptive Chemistry? Teaching is a subtly dangerous affair, especially for rapidly evolvingscience s i b j e c c like chemistry. ~ u c c i s s(or railure) is often delicately balanced on a knife edge that can cut into the fabric of a subject and sever critical components from each other. This may have been the fate of descriptive chemistry. Those involved with the process of teaching chemistry-teachers, textbook authors, publishers-must recognize the difference between organizational schemes that are eoistemoloeicallv useful t o oracticine orofessional chemists and those ;hat can he used advanti&usly by students in the early. stacesollearning about the subiert. Although both extremes are valid as orgakational devices, they ar;probablv not eauallv useful if interchanped. An organizational stiategy that describes what we know about ch&istry (i.e., the usual litany starting with atomic structure followed by molecular structure, etc.) may be ideal for practicing chemists to organize their interest in the subject. However, it probably does not provide the beginner, in general, with an understanding of how we know what we know. Thus, organizational efficiency does not necessarily equate to optimal learning strategy. Beeinnine students of chemistrv need to be assured that the subject derives from a rational interaction between ohservations and hwotheses which in turn ultimatelv lead to tbeories. The cy& of thought associated with the scientific method has been a powerful force in the development of chemistry. Nevertheless, today, few beginning students are exposed to the role of observation in this cycle let alone appreciate its importance. Rather, they are presented with an organized array of principles. Accordingly i t is not surprising that these students often get the impression that chemistry is driven primarily by theoretical considerations. Indeed. the tenuous relationshin between laboratorv work and coirse lectures often reinforces these impressio&. Laboratorv" exoeriences. which should be the source of details . regarding "descriptive chemistry," often not only are poorly coordinated with the lecture. but also have little thoueht given to pedagogy. The perceived need to incorporate mire
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and more subject matter into the curriculum has driven the system of education-textbook writers, publishers, teachers-to squeeze out descriptive chemistry. We now decry the results, i.e., a curriculum that bas become essentially an expositionof pure principles. As we have seen, principles can certainly be organized effectively and then, in turn, be converted into an efficient curriculum. This approach permits a large number of subjects to be "covered" in a minimum of time. Modern chemistry instruction, in passing beyond the simple observation and classification of ideas (which are still valid), has become essentially only a discussion of principles. Our current organizational structure very effectively describes what we know, but how well does it address the other important issue, viz., how do we know it? Indeed, if all chemistry is reduced to principles, leaving the impression that all is known, what is the incentive to study chemistry? Moreover, why do we need teachers to help students learn principles if the subject is so thoroughly organized as to suggest to the untrained mind that there are no "loose ends"? Students need to understand that facts come before theories, and that tbeories are products of the human mind developed to "explain" facts. A theory that explains unknown facts is decidedly less useful than is a fact that cannot be explained by a theory. In the latter instance we still have the fact, which may have a practical usefulness that stands apart from the deficiency of theory. Indeed, i t is just such facts that drive theories to higher levels of refinement. At this point, one might be able to mount an argument that the pendulum shall swing away from principles back toward descriptive chemistry. This would be equally as wrong for the student and the subject as was the swing away from descriptive chemistry toward principles. Clearly, the time has come to reintegrate descriptive chemistry back into the fabric of this subject which is now nearly all principles oriented. Nothing really happened to descriptive chemistry. I t disappeared, a victim of the principles it was organized to butJJL tress.
Volume 62
Number 11 November 1985
915
