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CHEMICAL CONCEPTS AND THE COLLEGE CHEMISTRY CURRICULUM1 LAURENCE E. STRONG and 0. THEODOR BENFEY Earlham College, Richmond, Indiana
"I believe the leaders in chemical education can learn some i m ~ o r t a nthines t from the eneineers. We hear m m v voices these
fession of chemistry. "During the 20 years in which we have hadsuch arapidchange in education for the engineering and many other professions, there has been no substantial chanee in chemical education a t either the undergraduate or graduaG level, except possibly a trend toward greater speeialization." J. C. WA~NEEC. Preaidentisl Address to the American ChemioalSaoiety. September, 1956 ( 1 )
"The Paradox is now fully established that the utmost abstractions are the true weapons with which to control our thought of concrete fact." A. N. W H ~ T E H(9) E~
* * * Presented as a part of the Symposium a n New Ideas in the Four-Year Chemistry Currioulum before the Division of Chemical Education a t the 132nd Meetine of the American Chemical Society, New York, September, 1957
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chemistry curriculum finds itself in an impasse. There has been a mounting revulsion against the teaching of myriads of isolated facts and this has shown itself in the steady transformation of the first year course into a survey course of chemical principles. As time has gone on, more and more fundamental principles have edged their way into the freshman course, displacing most descriptive inorganic chemistry, much qualitative analysis, and almost all quantitative measurements. There is no room for more principles, nor can they be unified and simplifiedwithout the aid of thermodynamics or quantum theory. For these, however, the freshman is not prepared. Furthermore, the displacement of the learning of descriptive material and of skills into later years has meant the virtual impossibility of finding room in sophomore and junior courses for a detailed and mature discussion of chemical concepts. Only those who have survived a year of abstraction and two years of training in skills and the assimilation of factual data are granted the privilege of gaining in their senior year a balanced vision of the methods and aims of ehemistry.
JOURNAL O F CHEMICAL EDUCATION
The methods of chemistry are united in this, that they are examples of a fertile interaction of theory and experiment. And the aims of chemistry are all related to the understanding of the transformations of matter; it is this fact of transformation that marks off chemistry from the other sciences. The chemist traces the transformations of substances to the breaking and making of bonds in the individual molecules. The nature and properties of bonds are central questions underlying the science of chemistry. It is clear to the authors that there is rife among 'hemistry teachers a great amount of dissatisfaction with the present chemical curriculum. On the other hand, there has been, to our knowledge, very little experimentation with major aspects of the teaching plan. The Brown University Curriculum (5) is a notable exception achieving remarkable success by dropping general chemistry and making essentially a simple rearrangement of the present courses, with organic chemistry as the freshman course. By and large, inorganic chemistry has become the black sheep, displaced from its first year home and not accepted gladly into any subsequent course. Even within the American Chemical Society the Division of Inorganic Chemistry is officially "on probation." Nyholm (4) has pointed out that
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. .the earlier divisions of chemistry are disappearing and the subject is once more becoming an integrated whole. The modern inorgmie chemist has scant regard for the distinctions between inorganic, organic, and physical chemistry. Organic chemistry, though the first to achieve a t,horoughgoing conceptual framework for its subject matter, is commonly taught third perhaps because historically it began a little slowly, in part because it had to shed the complexities introduced by the belief in vital force. The teaching of organic chemistry still follows the early definition of Liebig that organic chemistry is the chemistry of compound radicals. We still take up organic compounds one functional group a t a time with very little thought as to the logical relation between the groups. They are taught as essentially separate and distinct entities. Analytical chemistry has more and more assumed to itself the teaching of exact technique, and students breathe a sigh of relief when they are released into the less strenuously precise organic chemistry laboratory. The freshman laboratory also has suffered from' this trend, the freshman seldom experiencing the joy of having made two parallel determinations that agree even within one per cent. Present-day chemistry teaching does not deal adequately with chemistry as it exists today. But more importantly it cannot do justice to thedynamic nature of science. A study of the amount of chemical literature covered by Chemical Abstracts (from 1906 to the present) and by Beilstein's "Handbuch der Organischen Chemie" (prior to 1909) indicates that the amount of chemical information has approximately doubled each thirteen years. If this is so, it is as important for the student to be able to locate information as it is for him to know a large number of facts. It is doubtful if from now on any body of factual material can be justly labeled essential or basie. The descriptive material taught in the future will. serve essentially as examples of the nature of chemVOLUME 35, NO. 4, APRIL, 1958
ical data. The teacher will hence have considerable freedom of choice as to the descriptive material he may use in his lectures. Given this "cancerous" growth of knowledge, and the rapidly developing theories and laws, how can we structure a chemical curriculum adequate to our time? One fact stands out in the history of science: concepts last lager than classiJEeations. The atom and the concept of affinity are still as important to our thinking about nature as they were t o the early Greeks because each generation has been able to reclothe these concepts suitable to its own need and knowledge (5). On the other hand, the Greek classificationof matter as also of living species has long been superseded. The chemistry curriculum has always been based on a classification; the study of organic compounds has been segregated from inorganic chemistry, and these empirical subjects have been carefully hedged off from the "theoretical" studies concerning their nature, physical chemistry. The resulting courses have very little logical connection with each other. Yet, it is generally agreed that much of the most fruitful contemporary research cuts across these compartments. THE EARLHAM PLAN It is our intention then to divide the subject matter of chemistry into sections intended to deal successively with the various major concepts through which chemical phenomena are understood and interrelated. I n this way each of the earlier courses will be limited to a small set of ideas hut a t the same time it can range over a considerable variety of descriptive chemistry. Central to the whole fabric of conceptual chemistry are two ideas: the chemical element and the chemical bond (6, 7). The perfecting of these inventions during the past fifty years has made possible the correlation of a wide variety of physical and chemical properties of substances and our course organization will necessarily be oriented toward these ideas. From chemical elements the path leads to atoms and atomic structure while chemical bonds are subdivided into the various bond types based on the behavior of electrons within atoms. These ideas give an understanding of the basis for affinities among the various chemical elements in the compounds which they form. Reactivities are modified by the effects of concentration and the concept of dynamic chemical equilibrium will be introduced. The energy involved in chemical reaction is an important part of chemical change and needs t o be discussed in its own right as well as in its provision of a way to a logical basis for describing equilibrium among substances. Further modifi~atio~of the ideas about the bonds between atoms involves the introduction of aromaticity and resonance. Beyond these applications of ideas to the statics of chemistry, i.e., the consideration of the initial and final states of chemical systems, there are the transformation processes themselves. Here, with the addition of the time dimension, we are concerned with the making and breaking of bonds. Clearly the concept of reaction mechanism, and its foundation in reaction intermediates and in kinetics, needs to be in the undergraduate curriculum. For this a number of related ideas and experiments will have to he introduced to the student. One of the problems is, of course, the amount of detail which can he used effectively.
CURRICULUM OUTLINE
Our plan then is to begin in the first semester of the college chemistry program with a consideration of the concept of the chemical element. Historical material will he given including some early attempts by Aristotle and others to treat properties as elements and the phlogiston hypothesis. Atomic structure will then be treated on the basis of weight composition in compounds, the electrical properties of gaseous discharge, radioactivity and other nuclear phencmena. Electronic arrangements within atoms will be discussed in terms of orbitals. The possibilities for various kinds of interatomic bonds will he listed and some of the correlation between bond type and physical properties will be discussed. A considerable amount of descriptive material will be included taken from the experimental properties of the chemical elements. The next two semesters d l deal with the covalent bond and with ions respectively. Longuet-Higgins (8) has recently pointed out the continuing validity of considering most chemicals on the basis of these concepts. Lowdin (9)has reemphasized the intrinsic difference between ionic and covalent bond formation. The covalent bond is possible only because of the indistinguishability of electrons. Without this fact, the bond hetween two hydrogen atoms would be quite unstable. Accordingly, in the second semester a more detailed consideration will be given to the features of those compounds which consist of atoms held together by covalent bonds. This will lead to a consideration of molecules with the gas laws introduced to give a physical basis for the molecular concept. Descriptive material for this part of the course will be conlined to the chemistry of the elements near the center of the first period in the periodic table. Major hut not exclusive attention will be given to what is ordinarily regarded as the chemistry of aliphatic carbon compounds. Some attention will be given during the first two semesters not only to the history of science but also to discussion of the nature of scientific methods as they are applied to chemical phenomena and a t least some allusions to the philosophical implications of the concepts that have proved fruitful in science. We believe these first two semesters can give a preliminary view of chemistry as a scientific enterprise in a way that should justify calling it a liberal arts course as well. At the same time much of the course content would differ strikingly from that taught in the usual high school, and we therefore hope to skirt the tendency for boredom on the part of students who come with good high school preparation. Furthermore the early introduction of organic chemistry will he of great value to biology majors and possibly to students planning careers in psychology and engineering. On this foundation of chemical elements, atomic structure, and the covalent bond we will then proceed in the third semester to construct the implications of ionic bonds and the properties of ions both simple and complex. A large part of this will hinge upon the properties of ions in solution, and so the properties of solutions and of ionic equilibria will he presented in some detail. I t is anticipated that by this point the students will be ready for a considerable amount of quantitative treatment of concentrations and equilibrium constants. Still further treatment of ions and their reactions
leads t o the consideration of oxidation-reduction reactions with particular reference t o electrode reactions. These topics will be taken up in the fourth semester and some of the logic of the energetics of chemical reactions considered. Through the treatment of electrode potentials we hope to develop a preliminary idea of the nature of "Free Energy" and its implications for a systematic study of chemical equilibrium. It would seem unlikely that with our students it would be feasible to give them any very complete treatment of the logic of thermodynamics as early as the fourth semester of their college work. An important aspect of the chemistry of systems in which atoms are bonded by the sharing of electrons is organized around the topics of aromaticity and resonance. During the fifth semester of our program these topics will he dealt with in a systematic way. Thus the work of the second and the fifth semesters will contain much of the material which is ordinarily presented in a more conventional course of organic chemistry. We intend, however, to include atoms other than carbon in our discussions and t o show that these ideas are powerful insights into the operations of chemical systems whether called organic or inorganic. These five semesters should give a reasonable introduction to the science of chemistry; an introduction that ought to he satisfactory for the premedical student, the serious student of biology, and for those mho expect to apply chemistry to other fields. Further work of a more advanced nature chemically is to be built on these foundation courses. This we propose to do in a way that will for the most part continue to cut across conventional subject-matter divisions. Among the topics which will be considered are those of stereochemistry, reaction mechanisms, and the related topic of reaction kinetics. The work on chemical energy, begun in the fourth semester, will be brought into a more systematic study of thermodynamics. Chemists are confronted with the fact that the chemical literature is expanding a t an ever-increasing rate. Fortunately this literature is organized in a remarkably effective way. I n fact among all the intellectual and practical disciplines probably the most extensive and usable indexing and abstracting system is that applied to the literature of chemistry. I t is our intention to place a good deal of responsibility upon the student to makeuse of the facilities of the library for acquiring the particular facts that he may need in his college work. Although our library is small in comparison with the hulk of the scientific literature, it is possible to make a wide variety of materials available to readers by various photographic procedures so that we should he able to secure almost any material the students may wish to refer to. We plan to make considerable use of microfilm, microcard, and interlibrary loan arrangements. LABORATORY WORK
If classroom work is centered on the concepts of chemistry, it would seem reasonable to consider techniques the focus for laboratory work. I n addition, we believe that students a t the elementary level are more likely to be intrigued by laboratory work in which one of the results is the preparation of a recognizable product, in our case some chemical. If the product which they prepare can also give some esthetic satisfaction, i t is even more stimulating. Therefore, during the first JOURNAL OF CHEMICAL EDUCATION
semester of our new curriculum we plan to make considerable use of preparative experiments involving the chemical elements with the aim of acquainting the student with the various techniques for handling chemicals in the lahoratory. These will include the techniques of crystallization, distillation, fractional freezing, sublimation, and others. Crystallization appears particularly useful since the growing of crystals can serve not only as a purification procedure but it can result in a beautifully formed product which will appeal in its own right as a satisfying object. We will also expect to make use of some of the simpler tests for identification and impurities including the use of the spectroscope. Preparative work will also be a major part of the second semester laboratory. Here we hope to begin the use of quantitative analytical work by introducing some experiments in volumetric analysis. The omission of quantitative analysis from the list of courses given earlier is intentional and is based on the belief that it is far better to make analytical work a part of each course and emphasize thereby the importance of quantitative and qualitative analysis and the value of precision measurements for all parts of chemical work. This should not mean lower standards of proficiency to be expected of each student but rather more reasonable motivation for the student to undergo the discipline of precision laboratory work CONCLUSIONS
We envisage, and have initiated in the fall of 1957, a chemistry curriculum which is divided into separate units determined by the particular concepts that are to be considered. These concepts will be illustrated by appropriate phenomena drawn from any of the traditional branches of chemistry. I n this way it is possible to give a quality of intellectual integrity t o the study of chemistry that is difficult to achieve with the present
VOLUME 35, NO. 4, APRIL, 1958
artificial subdivisions which form the course work of the college curriculum. Certainly, however, it would be presumptuous to declare a t this point that the proposed curriculum represents a completely workable scheme. It will, for us, take several years to complete the change presented here and during that time we assume that experience will lead to modifications and, we hope, to improvements. We do not offer this proposal, therefore, as a plan to he simply copied by others but as a starting point for exploration. The stature that chemistry has achieved is due to the ability of its practitioners to combine ideas with practical experiments. We believe that the same approach to our teaching activities can bear great fruits too. What we need is more research in chemical education. The results of well-conceived teaching experiments cannot help hut lead us rapidly to more effective chemistry instruction. LITERATURE CITED WARNER, J. C., Chem. Eny. News, 34,4786 (1956). WHITEHEAD,A. K., "Science and the Modern World," New AmericanLibrrtry, New York, 1948, p. 34. COLES,J. S., 1,. B. CLAPP,A X D R. P. EPPLE,J. CHEM. Euuc., 26,lO (1919). Concerning the present status of inorganic chemistry in the R. S., "The Renaissance of Incurriculum, ef. NYHOLM, organic Chemistry," H. K. Lewis, London, 1956. For a brieier version, ef. J. CHEM.EDUC.,34, 166(195i). Regarding the transformations suffered by the atomic conERYST,"Determincept since Greek times, cf. CASSIRER, ism and Indeterminism in Modern Physics" (17. bv 0. T. BENFEY), Yale University Press, 1956, pp. 144-52. H i i c m h W., "Stmcturd Chemistry of Inorganic Compounds," Elsevier, 1950, Vol. I, pp. 5, 15, 44. G., "Lehrbueh der Anorganiachen SCKWAAZENBACH, Chemie," Leipeig, 1941, quoted in ( 6 ) . LONQUET-HIC.GINS. H. C... (3m~1.Revs. (London). 11. 121 (1957). P., J . Phys. Chem., 61,55 (195i). LOWDIN,
