Facts and Their Roles in Chemistry Facts, which are defined as "truths known by actual experience or observation," occupy a unique position in chemistry. Facts must he carefully distinguished from theories, which are ..vohrrent group5 utgt~neralpropusitions used as prinviples of rxr)lanation ior classes ot'phenum~n:~" At the iilmc lime facts'and theories are also intimately interrelated. Facts are necessary to support theories, and hence, are essential in an intellectual sense. Facts are also the medium in which theories operate. The details of theories are structured by facts, and in a real sense facts and theories are synergistic. The trouble with facts is that we often don't really know which of them are imoortant-or are even likely to become important. This, of course, is a result of the evolitionary nature of chemistrv as a discidine. Some facts never achieve the status of long-te"m recognGion for their importance, although thev. mav. aaoear . . to be momentarily consequential. Consider, furt!xamplc, the critical rolc played bv theelectr~,nicsl~rctrn v f T i l ' ions in diffewnt ligand environmcn~sor by the NMH spectrum of the compound with the molecular formula Fe(C0)3C4H4, cyclohutene iron tricarhonyl. Because some facts are widely recognized as being critically important to increasing our understanding of chemistry, interest in ohtaining them quickly rises to a crescendo. Once facts of this kind have made their contribution, however, they often disappear into oblivion. Some facts are wrong, but useful nonetheless. Thus, Lewis chose the octet as the measure of a stable electronic arrangement because it was thought that "inert gases" did not form compounds. We now know that octets are no longer critically important, witness the existence of compounds such as SF6 and PFb. Furthermore, some of the "inert gases" do form stable compounds and/or polyatomic anions, and hence the inert gases are now called "rare gases". Chemistry also incorporates a large hody of "facts" that derive from relationships among facts obtained by actual experience or ohservation. The importance of some of these relationships is without question, e.g., molecular weight.
Others have not stood the test of time. For example, the parachor was thought to be an important quantity in helping decide questions of molecular structure f i r a number of years in the 1920's. ivarachor = 347' ',(D- d ) ,where1 is thesurface tension of a iihstance, M it; molecular weight, D the density of the liauid state, and d the density of the saturated vapor, all rnens&ed at the inmr temper at&.^ Today the paravhor finds little use or application, and thc idea essentially has been relegated to an hi&ical cul-de-sac. In a continually evolving subject, some facts which are important have no obvious connection to currently important theories; these facts and/or their existence need to he remembered if they are to he of future use. Still other facts may have a practical usefulness. In a very broad sense facts have come to he cherished. Since facts have such a special position in science, i t is not at all surprising that many current instructional techniques stress their acquisition. Indeed facts can have a mesmerizing effect on both teachers and students. But teaching or learning chemistry involves more-much more-than acquiring facts. Students need to learn to interact with the facts and concepts which underlie their subject. This can be accomplished in a variety of ways, each providing for the development of one or more analytical skills. Students should he encouraged to practice their chemistry using a variety of different methods. Hands-on ex~eriencesare critical. Students need to write and learn to receive criticism as well as be given opportunities to rewrite and refine their abilities to exaress themselves clearlv and succinctly. They need to practice their chemistry, try to defend their ideas, test out potential solutions, and discover why aparticular approach didn't work. Facts are the medium in which modern chemistw ooerates. The aresent educational process works well to helpstidents acquire facts; hut we need to eive more attention to heloine students acauire the skills to manipulate these facts and toarticulate theideas and operations involved in their manipulations.
JJL
Volume 61
Number 1
January 1984
1
