a& tkc N e w England Association of
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William D. Hobey
Division of Chemistry Worcester Polytechnic Institute Worcester, Massachusstts
Undergraduate Curriculum
The paper here presented has been adapted from a lecture presented at the 333rd Meeting of the New England Association of Chemistry Teachers at the Massachusetk Institute of Technology, Decemher 4, 1965. On May 7,1965, the Department of Chemicd Engineering and Chemistry of the Worcester Polytechnic Institute sponsored a Conference on Physical Chemistry in the Undergraduate Currienlnm. This re~ortmieht best he subtitled "One Man's View of the Conference." I t is a synthesis of the organizing committee's preconference deliberations, the actual conference discussions, and some postconference reactions in an attempt to present a onified and meaningful summary of the more important ideas expressed. Slightly over one hundred college teachers attended. Invited particpants were Wilmer J. Stratton, Earlham; John Ross and James C. Baird Jr., Brown; Gordon M. Barrow, Case; Robert I. Walt,er, Haverford; Walter J. Moore, Indiana; Robert C. Reid, M.I.T.; and David F. Eggers Jr., Washington; The organizing committee consisted of Pmfessors Wilbur B. Bridgman, Robert C. Plumb, Imre Zwiebel and the present author. ~~~
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Physical Chemistry in the
The L1informationexplosionu in science of the past four decades where the amount of scientific information has been doubling every eight or ten years has generated considerable pressure on the chemistry curricula of our colleges and even of our high schools. Although all branches of chemistry have grown in this period, the growth of physical chemistry has been particularly outstanding. This growth, in part, can he traced back to the development of statistical mechanics by men like Boltzmann and Gibhs in the last half of the nineteenth century. But the real spark came about 1925 with the development of quantum mechanics, which not only gave a much improved understanding of the atomistic structure underlying all of chemistry, but also allowed statistical mechanics to be applied to many more problems of chemical interest. From this spark came an explosion of solved problems of atomic and molecular structure and of the relation of microscopic structure to macroscopic properties, providing new insights into all of chemistry. These two disciplines of quantum mechanics and statistical mechanics serve not only to provide us with new details of nature, but also serve to unify much of the experimental discoveries of chemists, and thus it is hard to resist including more and more of these disciplines in the undergraduate curriculum. The more traditional areas of physical chemistry
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have not been without growth. The development in recent years of fields such as chemical kinetics, surface phenomena, and irreversible thermodynamics has induced pressures to add more material to our usual treatments of electrochemistry, thermodynamics, etc. Teachers of chemistry have realized the importance of these products of research, and in their zeal to better train the undergraduate or perhaps (it was suggested at the conference), more egotistically, to show off their erudition by cramming more and more difficult material into the minds of undergraduates, have introduced more and more physical chemistry-particularly quantum and statistical mechanics-into the undergraduate curriculum. There is, of course, a limited amount of time available so that an increase in modern subject matter tends to squeeze out other material. One of the most affected areas has been analytical chemistry (1, 2). One pertinent change at some colleges is the incorporation of all or much of quantitative analysis into freshman or physical chemistry couraes (1, i).
Not all the changes in analytical courses have been squeezing-out operations. There is also a trend to put some of the more traditional physical chemistry into the analysis course. This is particularly true of chemical equilibrium, so that the object of a "quant" experiment is no longer to determine, for example, how much silver is in a sample of alloy, hut to determine the solubility product of silver chloride. On the other hand, the University of Illinois has placed much of electrochemistry in its analytical course which also includes some instrumental analysis (4, apparently at the expense of some traditional solution chemistry and solution equilibria. There seems to be a growing tendency to view the quantitative analysis course in more general terms as a chemical measurements course where the techniques of quantitative analysis are taught through their applications to measurements of significance, such as determining equilibrium constants, cell potentials, and physical properties. One motive here is the attempt to make the learning of techniques more interesting to the student by making the end result of the measurement meaningful in itself. Other factors are an economy in the use of time and a desire Volume 43, Number 1 1 , November 1966 / 607
to tie together the various branches of chemistry. The trend toward the decrease of analysis courses in the undergraduate curriculum has been somewhat offset by the increase in the amount of time devoted to instrumental analysis. Many colleges now have a junioror senior-level course in the subject (1). The 1965 revised minimum standards of the ACS Committee on Professional Training also suggest an analytical course with physical ch&istry prerequisite, interpreted to he an instrumental analysis course. Freshman Chemistry
Freshman chemistry has undergone more drastic changes than the introduction of qualitative and perhaps quantitative analysis. Chemistry faculties are realizing more and more that the traditional college freshman course which attempts to survey many aspects of chemistry appears to the freshman as a "disorganized, bewildering array of facts, compounds and reactions," and has little permanent value to the student. Consequently, ways have been sought to use more effectively the freshman introduction to chemistry. One well-known attempt was the old Brown University "Chemistry of the Covalent Bond" course (6, 6) that approached chemistry through the geometry of structure and involved considerable organic chemistry. However, the trend today, including Brown (7), is toward increasing amounts of physical chemistry in the freshman year. Twenty-five percent of the schools responding to a recent survey (1) have a substantial amount of physical chemistry in the first semester of the freshman year. Where courses have been eliminated from the curriculum, they have in general been replaced by physical chemistry courses, so that where ten years ago one found two semesters of required physical chemistry given in the junior or senior year, one now finds as many as five semesters of physical chemistry, starting as early as the first semester of the freshman year. Attacks on the Problem
Professor Gordon hf. Barrow in his discussion of recent changes made at Case stated the philosophy of curriculum design that also seems to he implicit in the other experiments discussed. Physical chemistry pmvides organized routes into all of chemistry. It provides means of organizing the vast amount of descriptive material and empirical correlations now in the literature and ways of giving them meaningful interpretations. There are three principal routes here: (1) thermodynamics, (2) structure and bonding, and (3) chemical kinetics.' Of these three routes, the thermodynamics one is the most developed, the structure and honding approach is well on its way although much research remains to be done, while the route emphasizing chemical kinetics is still largely underdeveloped. An example of this approach, indicated by Professor . Rnrrow nnd other .pt.nlws, is A logival proerc-iiori from tllr principlrs of chernicd honding arid molwt~lnrst nitture to discussions of the existence and composition of specific inorganic and organic compounds and classes ~
A similar view, but also including synthesis, is attributed to
J. D. Roberts by R. B. WAITNET,J. CHEM.EDUC.,4 3 , 116 (1966).
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of compounds, and of trends in the properties and reactivities of these compounds. The principles are developed first and then utilized in the presentation of descriptive material either immediately in the same course or in a following course, usually the next semester. This approach is not without its problems. As Professor Barrow pointed out, these three routes into chemistry must he developed before descriptive material is introduced and should therefore he early in the curriculum. The conclusion that the development can be as early as the freshman year has been based on the observation that the students entering from high school are considerably better prepared than they were five or ten years ago. This reasoning, in fact, has been the motivation for the recent changes at Brown where the faculty preferred, in the changes made fifteen years ago, to have physical chemistry rather than organic chemistry in the first year, but felt at that time that the entering students were not prepared to handle the subject (5). One wonders, though, whether they are yet adequately prepared for some of the material presented. For example, in the brand of quantum mechanics frequently given in the early college years, one sees presented the "usual" equation for wave motion which is then converted to the Schrodinger equation. The solution for the particle in a box problem is then present,ed and the students told to plug it hack in the equation to demonstrate that it works. The trouble with this method is that the wave equation (and perhaps even wave motion in general2) may he "usual" for an intermediate undergraduate physics student, hut certainly is not "usual" for the college freshman. A second problem is the question in the student's mind of the relevance of the theory he is studying to actual situations. If the theory is presented before the descriptive material the teacher can only refer ahead to what will come, while if the theory is presented after the descripthe material the teacher can refer back to specific cases and so reinforce the material. The whole before-and-after question is an important one and one on which opinion is divided. Accepting this route philosophy of curriculum design, at least as a working hypothesis, how do we implement it? There are two quite different approaches to this implementation. These may he termed the topical approach and the vehicular approach. The Topical Approach
The most developed curriculum organized according to the topical approach is the one at Earlham College (8). Here the courses are organized around the major concepts of chemistry, each course taking one, two, or three major topics and treating them from a number of appropriate viewpoints: descriptive, thermodynamic, structural, and kinetic. Typical course titles at Earlham are "Particles of Chemistry," "States of
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A large percentage of college frshmen have had a. long introduction to wave motion in the Physical Science Study Committee secondary school physics course. This introduction is largely qualitative and does not directly provide the partial differential equations of wave motion. Simple quantum systems like a particle in s. box csn indeed be understood quantitatively without use of the differential equations by an extension of the PSSC approach, but this method is not often followed.
IMatter," "Covalent Bond" (these three being the freshman sequence, Earlham operating on a 3-3 system), "Ions," "Chemical Energy," "Resonance and Aromaticity," "IGnetics and Mechanisms," "Structure and Periodicity," and "Thermodynamics," The nature of the topical scheme is seen, for example, in the "Resonance and Aromaticity" course which involves qualitative moderu valency theory, classical resonance representation, descriptive material on physical properties and chemical reactions, with descriptive and theoretical material on reaction mechanisms, all oriented toward aromatic compounds. On the whole, the Earlham curriculum attempts an orderly progression through the conceptual framework of chemistry. I t is a concise program with a minimum number of courses. There is, for example, no analytical course, but analytical work forms a part of every course. The physical chemistry, which is spread out over the four years, is largely the traditional type, there being little mathematical treatment of quantum mechanics or statistical mechanics. This lack of modern theory is counter to the usual trend nowadays and might be considered a deficiency by some educators. The Earlham faculty does not feel, however, that this is a serious deficiency. We will return to this point later. The Vehicular Approach
The antithesis of the topical approach a t Earlham is the vehicular approach represented, say, by the new Brown curriculum (7). This program, which has been operating two years, starts the freshman year with a semester of physical chemistry, followed by a semester of organic chemistry. Physical chemistry is taken both semesters of the sophomore year, and one or two physical chemistry courses are available (hut not required) in the junior year. This sequence permits a more advanced treatment of organic chemistry in the second and third semesters, using concepts of structure, kinetics, and thermodynamics. The three required physical chemistry courses are high-level courses with the usual format of physical chemistry. The first semester course, for instance, treats chemical equilibrium from both the empirical and theoretical views, rates of reactions largely from the empirical approach, and structure through the usual introduction to quantum mechanics proceeding up to molecular orbital theory. The laboratory for this course is closely correlated with the lectures and has experiments in optical rotation, magnetic susceptibility, etc. I n contrast to the Earlham program, the Brown curriculum maximizes the amount of physical chemistry in the curriculum and the rigor with which it is treated. Phenomenology Versus Theory
Before we attempt a preliminary evaluation of these two approaches we must discuss a narrower, hut related, problem-that of the relative roles of phenomenology and theory in the curriculum. If we view natural science epistemologically, we recognize three principal levels of abstraction. The first level is that of direct experiment, where we record results such as the formation of a precipitate or the heat of a reaction and where we may tabulate the results hut go no further. The second level, thelevel of phenomen-
ological relations is where we attempt to correlate the experimental results, where we establish empirical relations between observables, but do not ask the question "Why?" This is the level of thermodynamics and classical valency representations, including resonance. The third principal level is that of theoretical models, the level of quantum chemistry and statistical mechanics. I n many modern presentations of physical chemistry the phenomenological and the theoretical are presented in one package. For example, thermodynamics and statistical mechanics are taught intermixed, the statistical mechanics being used to illuminate the thermodynamics. Students of thermodynamics frequently have difficultygrasping the meaning of the second law, while the statistical method provides a readily grasped conceptual picture of entropy and its workings. However, as Professor Barrow pointed out, opinion seems to be divided evenly on this package deal. Two objections to teaching phenomenology and theory in one unit have been argued. Intermingling thermodynamics and statistical mechanics destroys the beauty and conceptual unity of each; the threads of logic in each are broken by the seesaw motion from one to the other. Psychologically, it is known (9) that when two approaches to a subject are presented in close proximity they tend to interfere with one another in the student's mind, resulting in lower achievements in each approach. I t is pedagogically more efficient to present one approach in its entirety first and then later present the second approach. The Earlham method suffers from this difficulty,if it is a difficulty. Here, method and theory, thermodynamics and statistical mechanics, are blended together with a possible decrease in pedagogical efficiency. I n addition, although the Earlham students get a feeling for the overall structure of science, as their faculty keenly wish them to do, they may not get a feeling for the logic and structure of theory. The difficulty with Brown's early introduction of rigorous physical chemistry is that the derivations of many relations used are not presented, or if they are, not understood. The laboratory (7) seems to have a good deal of black-box character in experiments, such as those using optical activity and magnetic susceptibility. Such a situation where many factors are not understood by the student appears unrealistic to him; he has difficulty accepting the results, and if he does accept them he may soon forget them since he has nothing to which they can be tied, either theoretically or descriptively. Questions for Considemlion
Returning to the overall place of physical chemistry in the curriculum, some see a trend closely related to the latter point that is rather disturbing. I n the expansion of physical chemistry we notice that more and more theory is being pushed lower and lower in the curriculum, going sometimes even into the high school chemistry courses. The two new approaches to high school chemistry-the CHENI Study and the CBA methodsare primarily responsible for this. Both of these approaches are built around laboratory experimentation and the relations that can be directly induced from the experiments. What is of concern here is that the theory Volume 43, Number 1 1 , November 1966
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introduced may become quite remote from the experiments the student actually does or that the emphasis may even shift from experimentation to theory. As one example of how this could occur, consider the CHEM Study text (10). This text is entitled, "chemistry, an Experimental Science," hut the first eleven chapters contain considerahle theoretical material, and it is only in chapter fourteen that the reasoning leading to the theory is indicated with any detail. Most other chapters of the book also contain appreciable quantities of theory. There is a possibility that the course will become centered around this text and the presentation of theory ab initio (with, perhaps, the laboratory heing primarily used to demonstrate some deductions from the theory) rather than around the laboratory with the text being used to develop the principles discovered in the lah~ratory.~ The disconcerting aspect of this push of theory into the earlier levels of education is that it pushes out the descriptive material it is supposed to he explaining. The earlier theory is introduced, the fewer real cases the student has to tie and apply it to, and the less meaningful the theory hecomes.4 We may he fast approaching the stage where a student knows all about the bonding in the naphthalene molecule hut would never recognize naphthalene in the odor of mothballs. We do not want to degenerat,e to the level of medieval science where scholars would argue for hours on how many teeth a horse had without ever thinking of looking in a horse's mouth to actually find out. The place of theory is even a question in the undergraduate college curriculum. The teaching of quantum mechanics and statistical mechanics at the undergraduate level was challenged (to varying degrees) by several conference participants. Some of the reasons for the challenge were mentioned above. Thermodynamics has itself expanded and could occupy a considerable portion of the undergraduate physical chemistry courses, particularly since the graduate schools seem to he de-emphasizing thermodynamics. I n addition, there are other arguments based on the difficulty of the material. I n order truly to understand quantum mechanics one needs an understanding, both experimental and theoretical, of wave phenomena in general and an appreciable background in mathematics. Perhaps undergraduate time would he spent better developing these items (which have a more general utility than their application to quantum mechanics). Some scientists hold that a good understanding of the first law of thermodynamics is a necessary prerequisite to statistical mechanics. A lack of such understanding has led to rather common mistakes in the literature. Professor Walter J. Moore pointed out that one can teach a11 of physical chemistry from the statisticalviewI hesten to add that this example is one selected from severapossibilities and is not intended to he a. criticism of the CHEM Study approach per se. Pode (11) has presented a comparative discussion (with references) of CBA and CHEMS which also touches on some problems related to those discussed here. ' I believe that this same difficulty is present in introductory college physics eourses. These courses are usually taught from a theoretical (deductive) stance. The difficulty that a majority of nonphysics majors have with introductory physics prohahly originates not in an inherent difficulty of the material, but in a lack of feeling for where the laws of physics originate in each particular case.
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point, hut that it takes at least a year at the graduate level to accomplish it. This again suggests that we should do a thorough job of teaching phenomenological thermodynamics at the undergraduate level and a thorough job of theoretical statistical mechanics at the graduate level and thus avoid unnecessary duplication. A Proposal
I would thus suggest, for purposes of consideration and argument, that education in chemistry be organized according to the three levels of abstraction I mentioned earlier. The high school chemistry course should he primarily aimed at giving the student an experiential grasp of nature. Actually, those colleges that give physical chemistry in the first semester of the freshman year are already counting on this. They hope, at least, that the student already has some descriptive material to which the theory can he related. I do not wish, by this suggestion, to rule out all phenomenological relations or theory in the high school course, nor do I wish to return to the rather boring former "traditional" course. We must develop a high school course in which theory is minimized and descriptive material presented in a truly interesting way. The undergradnate college course should be devoted largely to phenomenology. We should also develop here physical models of atoms and their behavior, including the nature of solids, liquids, and gases, without going much beyond the hard-sphere type of model. If quantum ideas are to be introduced, they should be induced directly from experiment, such as from an analysis of atomic line spectra or the Franck-Hertz experiment. As far as thermodynamics is concerned, we should perhaps give more consideration to topics like imperfect gases and irreversible thermodynamics. After all, the world does not go around infinitesimally slowly. An area that should receive greater concern is that of transport processes. The chemical engineer has great concern for transport processes, hut the chemistry curriculum only occasionally touches on them in things like Hittorf transference numbers, polarography, viscosity, and diffusion. We are so used to thinking of an electrochemical cell in its equilibrium state, bucking a potentiometer, that we forget that the voltage of the cell when it is heing used to do actual work may he quite different than the equilibrium voltage. And today, a chemist is just as likely to work on a fuel cell as is a chemical engineer. Graduate school, in my proposal, would be a place for doing theory and advanced experimental work. The whole of chemistry could he done over here, hut at the more abstract quantum mechanical and statistical mechanical level, which the students are now prepared truly to appreciate as the unifying theme of all that has gone before. A conference participant asked, only slightly facetiously, what would he left for the graduate schools if the undergraduate colleges attempted to teach most of the theory? One question that immediately arises is what would the graduate schools think of this proposal? Are they willing to accept students who have had little, if any, theoretical background? The answer is yes, at the present time graduate schools accept people with a
variety of backgrounds, but concern was voiced that the range 'of acceptability m a y narrow. In contrast, the analogous situation in physics is not nearly as favorable to physics graduates. The experience of the graduates of Earlham College is particularly pertinent here, since they have little mathematical theory in their program. Professor Wilrner J. Stratton claims that their graduates appear to do well; they go to good graduate schools, get good fellowships, and do well on placement examinations. Indeed, even though Earlham has no analytical course as such, its graduates do well on analytical placement examinations. Acknowledgments
The organizing committee wishes to thank all participants in the Worcester Polytechnic Institute conference, many of whom contributed to discussions leading t,o the ideas expressed in this report.
HUME,D. N., editor, "Experimental Curricula in Chemistry," Advisory Council on College Chemistry, Wabash 1bid.p. 15. COLES.J. S.. CLAPP.L. B.. AND ~ P P L E . R. P.. J. CHEM. . E D U C . ; ~10 ~ ,(1949): clapi, L.B., J. C&M. ~ n & 35,170 (1 95Ri. ~----,(7) Ross, J., J. CHEM.EDUC.,43, 112 (1966). (8) HUME,D. N., editor, "Experimental Curricula, in Chemistry," Advisory Council on College Chemistry, Wabash L. E., AND BENFEY,0. T., College, 1964, p. 29; STRONG, J. CHEM.EDUC.,35, 164 (1958); BAKKER,G. R., BENFEY, 0. T., STRATTON, W. J., AND STRONG, L. E., J . CAEM.EDUC. 41,133 (1964). W. H., Proc. Inst. Eke(9) ENTWISLE,D. R., AND HUGGINS, trical and Electraics Engrs., 51, 986 (1963) and references
therein. (10) PIMENTEL,G. C., editor, "Chemistry, An Experimental
Science," W. H. Freeman and Co., Ssn Francisco, 1963. J. S. F., J. CHEM.EDUC.,43, 98 (1966).
(11) Pode,
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