advocate has been proposed by many reformers: a studentcentered approach with less lecturing and more discussion, more open-ended essay questions and fewer multiple choice examinations, attention to "why" as well as "what." Such pedagogical changes are difficult, especially with large classes. Indeed, they may prove to be the greatest impediment to change. In CiC, we have attempted to address this problem with an unusually complete Instructor's Resource Guide. In addition to standard features. such as solutions to exercises and problems, it contains number of novel components that draw heavily on the extensive class-testing experience. Included are syllabi of actual field-test courses, examinations, term paper topics. suggested demonstrations, references and reso"rces (both chemical and pedagogical), and excerpts from day-by-day journals maintained by field-test instructors. There are also brief pragmatic essays on how to use the decisionmaking activities with large and small classes, developing critical thinking, incorporating risk-benefit analysis, the associated role of the laboratow. and the use of the libraw. Finally, the loose-leaf format oithe guide provides a means of u ~ d a t i n eit annuallv. feature in -.a Darticularlv"important . a text based on current issues. While we hope that this guide will be helpful to the teacher, it is not a substitute for some direct experience with CiC. To that end, members of the writing team have already given a number of presentations, symposia, and workshons a t ACS national meetings and Biennial Couferences on'chemical Education, and $SF Chautauqua short courses. These have raneed in leneth from three hours to three days. More such acrivities areplanned, and they may become more common as other experimental books are introduced. Issues of content and pedagogy come together in a question that has been raised a t every presentation made on Chemistry in Context.: 'If this approach is successful with nonmajors, can it be adapted to courses for chemistry maiors and other science maiors?" Obviouslv. the hook was not "written for these studen&. The reliance ;n mathematics in CiC is less than is common in the general chemistry sewice course, and there is less drill on fundamentals. Nevertheless, an awareness of the applications and implications of chemistry is, if anything, more important for the chemist than for the nonscientist. Therefore, CiC might serve as a model for a revised general chemistry course. In the absence of a text that internates this approach at least three institutions are experiment~ngwith-a pedagogical hybrid. During the 1992-19YS academic year, Arden Zipp used the semnd ~ ~trial ~ - - edition ~~ ~ ol'CiC - and- a traditional ~ ~ text. Chsmrs. try:Principles and Reactions by Masterton and Hurley (41, with two sections of his science-major service course at SUNY College at Cortland. He typically made the initial assienments from the latter book and assiened su~norting rea&ngs from Chemistry in Context. His students Heemei satisfied with the two texts. but manv sueeested that the initial assignments should be made frim ~ Y C . In a similar experiment, which is part of a broader curriculum revision, Wil Stratton and his colleagues at Earlham College are using CiC plus a custom printing of selected chapters from General Chemistry by Kask and Rawn (5)in their science majors course. Stanley Bernstein is using tha same books in his course a t Antioch College. Chemistry in Context provides the organizing theme or story line, and supplemental assignments in Kask and Rawn provide the depth and rigor needed for science majors. Although using more than one book for a single " course is the standard ~racticein many disciplines, it is uncommon in chemistry and may Drove unwieldv. Nevertheless. educational ex~eriments k c h as these &ay lead to usiniselected chapter; from CiC with more traditional courses or, ultimately, to new texts
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for the mainstream chemistry course. If the result is neater orieinalitv and diversitv in chemistw texts and zhemistry courses, Chemistry in"~onteztwill have had an influence well beyond its original intent. Literature Cited 1. Chemistry in Context: Applying Chemistry la SacloLy, A Pmjed of the American Chemical Sodety:William C. Bmwn: Dubuque, lows, 1994. 2. chsmcom:chsmist~inth~community,~~mjenofthe~metiesnchemicsl~ociety; Kendell-Hunt: Dubuque, Iowa, 1988 (1st d l , 1993 (2nd d l . 3. MeKibben, W TheEndafNolun:Random House: New York, 1989. 4. Mesterton, W L.;Hurley, C. N. Chemisfr).: Pn'nciples & Rezetions; Seundera: Philadelphia. 1988. 5. Kaek,U;Rawn,J.D. &neml Chemistry; Wm. C. B m m : Dubuque, Iowa,
1993.
Polymers and Material Science: A Course for Nonscience Majors Janet S. Anderson Union College Schenectady, NY 12308
Many colleges and universities are revising their curricula to include more rigorous science courses for nonscience majors. The requirement at Union College is two courses, one of which must have at least 10 hours of laboratow experience during the term. The simplest approach to"this reauirement would be to have students take the standard in&oductory course in the discipline, which is both rigorous and has a lab. However. this mav not be the best anproach, because such courses are designed to provide's suwev of the discidine and to prepare students for further study; and so tend to cover a iot bf material quickly. The standard introductory course also has more than the required 10 hours of lab, usually 30 hours, in addition to 40 hours of class time. In an effort to provide a more appmpriate science experience for nonscience majors, a course was designed to introduce them to polymer chemistry and prop&ties. The course assumes no barkground in chemistry, and the required 10 lab hours are included in the regularly scheduled class time. Why Polymer Chemistry? Most students take an introductory chemistry course to satisfy a requirement for their major or for professional school admission. Why would a nonscience major want to take a polymer chemistry course? Many students are interested in environmental issues and participate eagerly in campus recycling projects. One of the rationales for teaching polymer chemistry to a general audience is to give students better backgrounds in the complexities of some recycline issues. and to enable them to a ~ ~ r e c i a what te polymers have that might makLthem more desirable than traditional materials in such areas as nackaeing, construction, and medical applications. The chemistry of polymerization is relatively simple for most common plastics, and the physical properties of polymers are accessible by both instrumental and non-instrumental methods. Students can take home what they svnthesize, analyze plastics that they find on campus, and become informed scientifically about issues in the economics and politics of recycling. B Y teaching an area new to most undergraduates, students with weaker backgrounds in chemistw are not at a sienificant disadvantage to those with good ehemistry cours~sin high school. Fin;lly, we alreadv offer a ~olvmerc h e m i s t ~course for c h e m i s t ~majors k d havd t& instrumentakon, laboratory space, and faculty expertise available, so that we can expose more students to this important area of chemistry by offering a polymer course for nonscience majors.
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The Course Format The course meets for two hours, twice a week, during Union's 10-week term. At least 10 hours of that time is spent in laboratory. The rest of the time is either lecture, discussion (including small group work), or student presentations. Because there is no clear boundary between class time and lab time, the class has the flexibility to talk about what happened in lab and to analyze laboratory data in lecture. Currently, the course is limited to 12 students, but that could increase to 24 if the class were split into two lab sections and some students were scheduled to take lab a t another hour. We have tried two texts so far: HansGeorg Elias' Mega Molecules (Springer-Verlag, 1987) and Raymond B. Seymour and Charles E. Carraher's Giant Molecules (Wiley, 1990), but neither text closely follows the content of the course. The course grade is determined by two hour exams (20% each), a laboratory notebook (30%) and a final paper and oral presentation (30%). Six problems sets are assigned during the term to help students prepare for the exam questions, but the problem sets are not collected or graded. The Course Outline I. Introduction to Polymers and Some Necessary Chemistry (three classes)
After a brief introduction, students spend an hour cycling through six hands-on experiments that give an overview of polymer chemistry: synthesizing poly(methy1methacrylate) (11, performing t h e nylon rope trick (11, melting sulfur (I), freezing rubber tubing in liquid nitrogen, making slime (21, and examining polyurethane foam from a can (Great Stuff'). In class, students are shown how Lewis theory and valence shell electron pair repulsion theory can predict the structure of simple organic molecules containing only C, H, 0,N, and C1 atoms. These three-dimensional structures are then illustrated with molecular ball-and-stick models. Each student builds a model of ethane that is polymerized by linking all the models together. This molecule of polyethylene introduces the concept of conformational flexibility and the random coil model of a polymer, which is . . shown graphically in a one-hour experiment where a twodimensional computer simulation of a random-walk polymer2 i s done to show the effects of restricting bond angle, O,on polymer dimensions. Each pair of students i s assigned a different number of bonds i n the polymer and a different value for the bond angle, 0, and then has the computer construct 10 random-walk polymers with those constraints. The students averape the end-to-end distances of their 10 polymers, and th; class data is pooled to demonstrate the effect that bond number and bond anple have on the end-to-end distance, and thus overall volume of the polymer. 11. Thermal Properties of Polymers (three classes)
The phvsical properties of common plastics are discussed i n terms oftheir molecular structukes and degree of crystallinity. The glass transition temperature and melting point are introduced a s physical properties that can be related to polymer structure. Polymers that form stronp fibers and boiymers that are elastic are shown to result from intermolecular interactions. The students then do a two-hour differential scanning calorimeter (DSC) experiment to measure the glass transition temperature, melting temperature, and heat of fusion of two samples of polyethylene having different densities a n d two samples of poly(ethylene terephthalate). They correlate their thermal data with visual observations of polymer melting (3).
111. Condensation Polymerization (three to four classes)
The svntheses of polyester and nylon are described aRer explain& some furkional group chemistry of carboxylic acids, alcohols, and amines. The number-average and weightaverage molecular weights that are obtained from different physical measurements of the same polymer sample are shown to be related to the moments of a distribution of different lengths of polymer chain. Acomputer spreadsheet is used to calcdate the nimber-average and weight-average molecular weights for a hypothetical distribution of polymer chains. Students do a two-hour lab in which glyptal resin ( 1 )and nylon 6 (4) are synthesized. Samples of each polymer can then be analvzed in the DSC to determine the class transition temperature and melting temperature in o&er to compare these properties for the semi-crystalline nylon and the amorphous glyptal resin. The observed differences in melting behavior between these two . ~olvmers can be explained in terms of cross-linking. IV. Chain Polymerization (three classes)
The mechanism of chain polymerization is described and examples of initiators, monomers, and polymers are shown. Students do a two-hour lab in which polystyrene is synthesized and reverse-phase thin-layer chromatography is used to look a t the distribution of molecular weights (5). If a gel permeation chromatograph is available, students can inject their polymers onto a GPC column to get a more complete description of the molecular weight distribution. The two major categories of polymerization, chain and condensation, are simulated on the computer2 to show how molecular weieht denends on the time of reaction. and how the number ofYinitiGor molecules affects the final molecular weight in chain polymerization. V. Infrared Analysis of Polymerization (two classes)
The basic principles of polymer identification by infrared analysis are explained. Students do a two-hour lab i n which they use FTIR to find the identity of polymer film samples that they bring into class (6).Additives and fillers to polymers are discussed when they appear in the IR spectra as peaks which the students cannot identify. Vl. Biopolymers (one class)
The three-dimensional structures of proteins and DNA are described as examples of complex condensation biopolymers. A computer program (7) i s used to visualize these molecules and to ~ o i nout t the kinds of intramolecular interactions that stabilize their structures. Vll. Polymer Recycling (two classes)
Although garbage is only about 8%plastic by mass, the percent by volume is much larper. Several issues in polsh e r recyciing such a s separation of different kinds of plastics and the cost of raw materials compared to the cost of recycled materials are introduced. A &-hour laboratory in which common plastics are separated by density (8) is done to illustrate a method that might be used in the recycling industry VIII. Student Presentations (two classes)
Each student presents a 20-minute talk on some aspect of polymer chemistry or recycling that is of personal interest. Topics done by recent students include the economics of recvclinz. " -. biodeaadable plastics. recvcline i n the cosmetics industry, and polymeric building materials.
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Conclusions Students have responded very favorably to this course both times it h:ts heen on'cred and have learned the chemIstry that was necessary in order to understand the issues in pdymcr rccycling They enjoyed the synthetic lalmraton e a and h:ld nu prol)lt:n~srunning the instruments to m a I n e their oolvmers. When 1;lhoratnrv is in" " exoerience . eluded in a science course for nonscience majors, students learn about safety issues in lab, how to keep a laboratory notebook, how to analyze data using a computer spreadsheet, and how to make deductions about chemical structure from IR and thermal data. Although we were able to use some instruments designed specifically for polymer chemistry, most of the experiments described here could he done with instruments available in a typical chemistry department. Current material in newspapers and magazines about novel polymers and about recycling can be included in the course to add to its relevance and student interest.
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Acknowledgment The author would like to thank the National Science Foundation for a n Instrument and Laboratory Improvement grant for support of polymer instrumentation and for their support of a Polymer Summer Course given a t Rensselaer Polytechnic Institute to train chemistry professors to teach polymer chemistry that I attended. Literature Cited 1. Seaife. C. W.J: Beachley, 0. T.. JF. Chemistry i n the Lahom(ory: Saunders College Publishing: New York, 1987,p 409.
4. Mathias. L. J.: Vaidya. R. A ; Canterbew J. B. J. Chrm. Educ 1984.61.805-806. 5 . h s t m n g , D.W.: M a x . J. N.: Kyle, D.: Alak. A. J. Chzm Educ 1985.62.705-706.
6. Ekpenyong, K I.: Okonkwo. R. 0.J. Chom. Educ. 1983.60,42940. 7. Myers, G,Blanco, C. 0 ; Hallick, A. B.; Jahnke, J. MocMolecule;University dmzona. 1990. 8. Kolb. K. E.;Kolb, D. K. J. Cham. Educ. 1991. 68,348.
