The Forum Refocusing the General Chemistry Curriculum
General Chemistry Course Content J. N. Spencer Franklin & Marshall College, Lancaster, PA 17604
General chemistry has been the subject of countless symposia, meetings, and conferences over the past 30 years. There is little left to be said about this course which has not been ~reviouslvsaid. The oitfalls have been noted. various phil&ophies iebated, dLlivery and assessment 'have been treated in detail. Nothing much has come from all this attention. Never before, however, has there been such a consensus movement toward a reconsideration of the general chemistry curriculum. There have been calls for reform of this course from the ACS Committee on ProfesAAAS (31,NSF (41,and an sional Training (1),Sigma Xi (2), ACS Task Force (5)among others. Arecent editorial in Science (6),drawing on coverage of a n ACS meeting, came down hard on the present state of teaching in general chemistrv. entitled "The Need to Imorove the ~ - - ~ ~ The - ~ editorial - ~ Image of"chemistry" pointed out that lectures were boring and contained little relevant material, the extent and quality of laboratory experience was judged lacking, the chemistry-related issues prominent in the media are rarely discussed. The editorial concluded with "The poor public image that chemistry now has will not disappear quickly. However, some of its deleterious effects can he blunted if the ~rofessionheeds the criticisms of some of its members andmakes a thoughtful but revolutionary revitalization of its curricula." After the launch of S ~ u t n i kin 1957, the scientific community of the ~ ~ ~ r e a cini part e d by attempting to reform the science curriculum. I t was assumed that if students could see science a s scientists see it, students would be a s fascinated a s the scientists. Thus courses were developed a s a set of research disciplines. The main principles of chemistry were taught a s isolated snhjects (7). ~
The Current State of General Chemistry
The world has changed but general chemistry has not, except to add more topics. Compare my college chemistry text, the 1957 edition of Sienko and Plane, to almost any text written in the last 10 vears. There is more structure and bonding, more thermo&namics, and less descriptive inorganic in modem texts. The lenzth of Sienko and Plane was-about 600 pages while a rough estimate of modem texts eives about 1000 Dazes. Chemistw has certainly advan& since 1957 but i d&bt that our knowledge of equilibrium suitable for a general course has changed that much over these years. I suspect that no matter what the changes in the field of chemistry, the chemistry of students has nbt changed sufficiently to-master twice the material. Students may be better prepared now, but I do not see the connection between a higher state of preparedness and the quantity of material to be learned. I doubt that instructors Presented at the 201st American Chemical Society meeting in Atlanta, GA, April 1991,as part of the FlPSE Symposium.
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cover all this material-I certainly hope not. I believe there is a selection Drocess according to what the instructor thinks is relevant to a general c o k e . T h s means that there is no commonly. tauaht - set of principles. Each aelecta according to some previously learned ckterion, or more commonly, we teach what we were taught. What do we teach? Arecent report by Hessy Taft of the Educational Testing Service gave the results of a curriculum survey of general chemistry courses a t colleges and universities that typically receive large numbers ofAP students (8).The survey sought to determine the relative emphasis on the major topics included in the general chemistry curriculum. Alist of 115 aspects of chemistry was generated to obtain information on inclusion or exclusion of specific subtopics within each major category; 114 institutions responded. Distribution of coveraee amone " the tonics follows a nattern, with no topic receiving a preponderance of detailed attention. Within each maior tonic there is considerable variation with regard to theexteAt of coverage a t different institutions. One conclusion of the AP study was that:
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The mllcge general chernrsuy course 1s crowded unh respect to the number of tapics it covers. This 1s true despltr the aft-cltedrntiurirns that the curnculurn of rntroductov college chemistry attempts to cover more tapics than students can be reasonably expected to learn. There are those who think our current general chemistrv course should be a senior year capstone course. On the basis of the Taft survey perhaps it should be the senior year curriculum. At a n i r a t e , general chemistry is a course of a different color. The course a s presently taught does cover everything. I t is, but should not be, a quick survey of everything the student will encounter i n later courses. What we have is what the 1990 Sigma Xi report (2) on entry-level undergraduate courses calls 'the tyranny of knowledge--a tyranny derived from the compulsion to cram so much accumulated knowledge into each course." The Missing Framework What should, and, equally important, what should not be taught? There are no guiding principles for general chemistry. We need to ask what we should do in the classroom and laboratory and why we should do it. Why are we teaching this? What do we hope to accomplish with the students? What are the desired outcomes? Why not behavioral objectives for the instructor? We lack a framework. Textbooks are t w thick because we have no common core, no agreed-upon set of principles, no teaching strategy. I t seems clear that general chemistry has to change. Imagine, for example, how a beginning history course would be structured if the chemistry model were followed. First,
there would be lots of facts. that is. dates a ~ ~ r o ~ r i a t e l v Table 1. Topics That Require Careful Consideration isolated from each other in time and'space sothat'no conbefore Being Taught in General Chemistry (or, What Is nectedness could be ascertained; there would be many Unteachable at the General Level) events that may or may not be shown to have something to do with each other, and every aspect of history that the Calorimetry student might encounter in later courses would have to be AGO touched won. Evervone would have a favorite e~isodein Phase Diagrams history that turned himher on to history and therefore IGP would be assumed to be equally as enlightening to others; Atomic Spectra for some it would be the Peloponnesiau War, for others Quantum Mechanics agrarian land reform in the pampas. A sort of ready referColligative Properties ence would be produced. This is what we have now in general chemistry-a compendium, an encyclopedia. We parSchrodinger Equation cel similar concepts to different chapters or different parts Clausius-Clapeyron Equation of the course. We have available a general reference text LeChatelier's Principle from which we select, encyclopedialike, topics to be discussed in the course. accumulated knowledge could be arranged under these I am concerned about what we teach and how we teach three laws and a concept into a core curriculum? We might it; that is, content and process. It is difficult for me to dibegin by asking ourselves some questions. vorce content and process. I believe content has in large Is it ~ossiblethat we trv to teach some thines that are part dictated process. We limit our discussion of the methunteacLable at the generailevel? Perhaps the &ase "presodology of chemistry in order to permit time to discuss all entlv unteachable" should be used. If there are t o ~ i c that s the material we seem to think is necessary. neei to be mastered we need to find new ways appropriate I am not referring to demonstrations, technology, and to the general level to teach them. There are some presvideos in the classroom and laboratory when I use the ently unteachable things that could be taught if we are word "how", but rather I refer to the method whereby we willinn to soend more time on that subiect and less on anintroduce the thoughts and structure of chemistrv. We ~ t h e r . ~ ~ oofmthese e topics are listed in Table 1. have taught generaychemistry as though chemistiis an Consider, for example, standard free energy. The stateunconnected set of principles. We have not shown our stument, "if AG is negative the reaction is said to be spontanedents why we believe what we do. We should not teach genous and if AG is positive the reaction is nonspontaneous," eral chemistry as a body of knowledge, we should teach appears in numerous texts. Aside from a questionable chemistry as a method. Textbooks are not the problem but usage of the terms spontaneous and nonspontaneous--I texts could be Dart of the solution. Textbook authors simply have seen it written that the more negative is AG, the more meet the demands placed on them by publishers 'nd spontaneous is the reaction-the statements are generally teachers. Most everyone agrees that texts should be thinincorrect. Note further that AG itself has a very restricted ner but no one agrees on what could be left out. We believe usage. The conditions must be that T P are constant and that what interests us as chemists will also interest our thatnon-pressure-volume work is not permitted. students, that what is compelling in our research will also Whv do we introduce AG a t all? Presumablv so that AG = be clear and transforming to our students, and so in an -RT in K can be introduced. Can we teacc the concepts effort to please everyone we put everything in our texts. without AG? I think we can. and I think we should because Can we agree on some fundamentals? There is room for principles first learned are'most difficultto unlearn. If we doubt. A recent conference, for example, found general believe standard free enerev is essential. then we must agreement that the general chemistry course should have teach standard states, we &st introduce the relation, AG more descriptive chemistry but nobody could agree on = AG + RT In Q in some manner, but does this not go awav what descriptive chemistry was (9). from an introductory course and over into somethGg else? Are there a few basic conceptdprinciples which could be We believe we must simplify ideas so they can be learned used as a rubric under which general chemistry might be for the first time. These simplifications are remembered organized? Is there a "core" of chemistry that is being more easily than correct descriptions. taught? If there is a "core", is this the core curriculum that It has been pointed out that the correct phase diagram, works to the best advantage of the student? Can this core the 3-D one. is rarelv seen in favor of the more sim~listic or a differently designed core be liberally supplemented acbut incorrect 2-Ddiagram (10).Should we take the time to cording to the background of the students so that one or cover this topic adequately; can we cover phase diagrams several curricula may be proposed? adequately a t this level? An article in 1966 (11)detailed some of the difficulties Working toward a Core Curriculum involved in relating I&,to solubility. It was pointed out In an attempt to answer these questions the members of that in the commonK-. ex~ressionthere are three assumu' the Task Force on the general chemistry curriculum were tions in connection G i h t6e calculation of a solubility: asked to submit their-ideas on a "core" curriculum. Six (1) The electrolvte is camoletelv dissaeiated. prominent educatordauthors were contacted and asked to (2) The ion products maybe u& rather than activities. describe in general terms their reaction to a core curricu(3) There are no competing side reactions. lum. In addition, the Taft report and analysis of the content of several eeneral chemistrv textbooks were utilized The rigors of an exact treatment were given to show the to determine if indeed there exist basic concepts or princirelation hetween K., and solubility for CaS04. First, it 1s oles that might serve as euidelines for a eeneral chemistrv necessary to find the activity coefficients,this reauires suceurriculum.hot surprisXgly, there are o h y a few basic te"cessive iteration, then ion-pair formation must be taken nets of chemistrythat encompass most of general chemisinto account, and finally side reactions such as try These are the laws of conservation of atoms and energy, the entropy law, and bonding. Given the quantity of SO? + H ~ O + = HSOL + H20 material-115 different aspects could be covered according must be mnsidered. These authors go on to state that: to the Taft report--is there any way that the sheer mass of ~~~
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It is hy no means suggested that high-school students or even college freshmen should be subjected to the rigors of the exact treatment outlined here...we feel that teachers and authors on these levels should seriously consider whether the solubility-product principle is in fact closely enough related to solubility to justify its presentation in that context...the currently custamary approach is one that the student must eventually eradicate from his mind if he is to acquire a correct understanding. We are unable at this level to develoo the various relations for colligative properties. For freezing point depression or boiling point elevation the equation AT= Km is evoked. The constant is mysterious, molality appears suddenlv for no satisfactorilv explained reason. We ask students to "fillin" the appropriate numbers and calculate AT or molecular mass. We are guilty here of wanting to do a calculation. Rather than teaching the concept, we calculate. I believe that one reason we do what we do is because of ease of testing. Conceptual understanding is more difficult to test than numerical plug-ins. Content-oriented exams reward memorization; exams should reward understanding and concepts (2). -of process . LeChatelier's principle is quite complex for presentation at the general level. We must specify if pressure, volume, or temperature is constant. The pressure-volume relationships may be such that in some cases we can't really predict the direction of the reaction. The way we ask students to use temoerature variation to ~ r e d i c direction t of reaction leads io an apparent contradiction in the application of the LeChatelier principle (12). Suppose AH is positive and AS negative. LeChatelier's principle comctly predicts that a rise in temperature will shift the equilibrium to the right. But a rise in temperature makes AG more positive, which should shift eauilibrium to the left. Students often remind us that we are always teaching the next course. There are some questions that should be allowed to occur to the students before we answer them. Table 2. TopicsThat Might Be Better Reserved for Later Courses (or, We Should Not Answer Questions Until We Ask Them)
MO Theory CFTILFT Hardisoft Acids-Bases Statistical Thermodynamics Metal Carbonyls and the EAN Rule Nomenclature for Compounds with a Bridging Ligand
Table 3. Topics ThatAre Not Necessary for General Chemistry (or, Why Do They Need To Know That?)
Balancing Redox Equations The SaponificationValue of a Glyceride Extended Buffer Calculations Metal Clusters Valence Bond Theory of Complexes Geometrical Isomerism of Coordination Compounds lodination Number Delocalization and Shapes of MOs Band Theory of Metals 184
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Table 2 lists some topies which might be better taught in a later course. The fmal question I want to raise could be the guiding philosophy behind everything we teach "Why do they need to know that?" In this context a careful consideration of what we are attempting to have the student take away from the course must be made. Do we teach some material because it is easy to test? How is the student supposed to be changed after encountering this material? Some suggestions are made in Table 3 for topics that perhaps students do not need to know after a course in general chemistry. Before presenting any topic at the general level, these questions and others should be asked: Has this material been simplified to the point where it has lost all integrity? Are we answering questions before we ask them? Why do they need to know that? Philosophical arguments about what is essential or desirable in general chemistry are not new, but little progress has been made in addressing new directions in this curriculum. There are always those who say we who want to change are trying to make the course easier. This is not what I advocate. Chemistry is a demanding s u b j e c t i t will remain so. We must set high goals, but those goals must be attainable. and havine been attained must have been worth the effok. ~ e m o v i material 6 that is basically incom~rehensiblehmteachable mav. ". in fact. make the material hthe course more attainable because by doing so we may focus more time and attention on certain topics. But, the course should not be made less demanding. I thinkit is inconceivable that we as chemists can't agree upon a few basic concerns that could constitute a course. One very important aspect for me, and it could be the sole aspect of certain courses, is that the student understand that science is not a collection of facts; that science is a method. Dick Teresi in a recent book review has written (13): Murray Gell-Mann, a Nobel laureate in Physics, once commented that his high school physics class was "the dullest course I'd ever taken because the course treated heat.. lieht. .. . mechanics, dound, electnrlty w d rnagnetlsrn as if they had norhing ro do with one another"..Science 1s not a random assortment ufarcaw facts. There 1s a struLture, a hrerarrhv that gives meaning to the mountain of theories and data. ...The sciences all rely on the scientific method-theory, experimentation, replication of experiment. A well taught course can train a mind to think in a vigorous, scientific manner. ....So educated, a mind can see through the spurious arguments of the nonsensical ideas... . A Personal View Here is what I believe. We need an agreed-upon core of chemistry which can be liberally supplemented according to the background of the student. Aunifymg theme should be established that would show that chemistry is not a "random assortment of arcane facts." We need to show how chemists approach a problem. Students should do experiments in the laboratory. Content is not as relevant as process. I believe that there is too much content and not enough process. We try to teach too much, some of which is undesirable, some of which is unteachable without simplifications that are difficult to remove later on. We should teach the method whereby chemists come to believe what they do. Students should understand the method of science: theory, experimentation, replication. The process involved in developing the mind is more important than content. Because chemistry is hierarchical and requires vertical development, the course should provide some preparation for hieher courses. The idea. however. that there is a certain akount of material that must be covered is not as important as covering less better. We have been constrained
in part by what we think our advanced courses and other disciplines expect of us. I do not believe we should slavishly follow a certain content. It is better that students understand what a saturated solution is than to be able to do K,, calculations. No student should leave general chemistry without knowing why chemists believe in atoms. Students should get a n understanding of the macroscopic picture of nature and the structure of matter, properties of elements, their compounds, and their reactions. Students should have a sense of the overall structure of chemistrv: that is., thev" should have a sense of the micmscopic st&ture and properties of matter that allow chemists to exolain. oredict. and control macrosco~icorooerties of matter. I t is not my function in this report to deal specifically with the laboratory part of the course. This aspect of general chemistry is being treated by a group working with the Task Force on the general chemistry curriculum. Another Task Force group is working on a subject area approach to help define those subjects which could be taught a t the general level and yet another group is studying a corelmodular curriculum. There is no one approach that is likely to meet all requirements, but a core curriculum supplemented by modular material may meet many objections. The core aporoach a s s u m e s t h a t t h e r e i s a basic s e t of ~ o n ~ e ~ t s / ~ r i n ct hi a~tl every es student who takes the course should know. Once this core is defined. the core is supplemented. A thin book, containing-if such things e x i s t g u i d i n g principles, basic knowledge, a thematic approach to general chemistry, would be prepared. Modular material, depending on the background of the student, would augment the text. The philosophy of this approach is that students do not need to be introdnced to every area of chemistry a t a snperfkial level. Afirm foundation would be established with the core material, supplemented by a n in-depth study of specific topics chosen by the instructor. An important philosophical component of the corelmodular approach is to provide students with evidence to show how we have come to know what we know. The teaching of the core should be on the basis of evidence t h a t implies a strong relationship to phenomena and experimental results a s well as historical perspective.
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Suggested Core Curriculum A representative core cumculum is given in the box a t t h e right. Each section begins with one of t h e conceotsl~rinciolesand is introduced bv a model. Ideallv there should be a continuous micmscopic-macroscopic interplay. In the first section of the core curriculum on conservation of atoms, the principle is introduced by a model and historical context. Aconsistent theme is followed throughout this section, a theme that provides a logical introduction to the next section on bondine. Further, the law of conservation of atoms may be usedto introduce equilibrium, thereby raisin^-a question which can be treated more fully in the . following energetics sections. The modular oart of the core aooroach can be illustrated by consideringthe core materi& on bonding. Here the basic knowledge necessaw for bondina .. is assumed to be I.ewis dot structures. Some instructors may wish to carry the hondinrr conceot further and oroceed to VSI.:PR theow for which modile would follow the core section. some mav wish to extend the treatment of bondine bevond VSEPR to hybrid orbitals and some may wish tgconknue to MO theorv. For each, a module, could be incor~orated into the text:l'echnolo& now the prcpara;ion of a thin text which could be suo~l1:mentcdin differcnt wavs au that several texts could be based on the same core material.
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Subject Material for a Core Curriculum
I. Atoms are Conserved. The Structure and Composition of Matter A. The Atomic Model 1 Dalton's atom c theory 2. Modern atom c tneory, s~baromc pan.cles. electronic structure 3. Elements: names and symbols 4. Atomic weights 5. Nuclear phenomena: radioactivity, disintegration rate, fission, fusion 6. Mole concept,Avogadro's number 6. Periodicity Model 1. Classificationof the Elements 2. Periodic properties, periodic table 3. Formulas, equations, and stoichiometry II. Bonding ,Compounds, The Structure of Compounds A. Modelsfor lonic Compounds 1. Types of ions 2. Nomenclature 3. lonic lattices B. Models for Covalent Compounds 1. Bonding 2. Lewis structures 3. Nomenclature 4. Geometry II. Energy is Conserved Kinetic Energy A. Kinetic Molecular Theory 1. Gases Potential Energy 6. Kinetic Theory of Liquids 1. Liquids 2. Solutions Thermal Energy C. The First Law I . Making and breaking of bonds 2. Equilibrium 3. Rates of reactions 4. Theory of reaction rates IV. The Entropy of the Universe is Increasing The Direction of Natural Processes, Reactivity A. The Second Law 1. Entropy and the first law 2. Extent of reaction 3. Thermochemical determinants of extent B. Types of Reactions
I have not mentioned specifics. I have presented a n outline in broad form. I believe we can teach these principledconcepts in a way that is meaningful and relevant to our students. Students want to know about acid rain, the ozone layer, drugs, pollution, and recycling. Where better to teach oxidation-reduction than in the treatment of corrosion? Acid rain has its obvious place in the treatment of acids and bases. Structure and reactivity can be related to everything we teach. We have lavished great attention on "delivery'-that is, demonstrations, tapes, disks, supplementary workbooks, Volume 69 Number 3 March 1992
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ete.-but little on how we teach how chemistry works. We can continue to teach this course as we are now teaching it-a course based more on history and custom than on n e e d - x we can seek new ways to bring meaning and life to this most important science. Literature Cited
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3 . The Libem1 M of ScipnOengnoengndo for Action: American hamiation for the Advancement of snenee: Washington, DC, 1990. 4. "Repart on the NSF Undergraduate Cumculum Development Workshop o n M a k ds":National Science Foundation:Waahington, DC, April 1990. 5. Tomomw'. The Report ofthe Task Force for the Stvdyof Chemistly Education in the United State8:Ameliean Chemical Society: Waahington, DC, 1984. 6 . Abetson. P H.S&nee 1990,249,225. 7 . Lagowski, J. J. J.Cham. Educ. 1988.65, 1. 8 . TaR.H. L. J. Cham. Edue. 1990.67,241. 9. Bodner GM; H m n , J. D. J. Chem Educ 1980.57.349. 10. Parker,R. C.; Knstal, D. S. J ChpmEduc. 1914,51,658. 11. Meites,L.;Pode,J. S.F.;Thamas,H.C.J Chpm.Educ.1986,12,667. 12. MacDonald, J. J. J Cham Educ Ism, 67,745. 13. Teresi, D. TheNew Ywk TimaaBwk Reukw, Feb. 3,1991.
