G. E. Gordon, W. H. Zoller, and J. C. Ingangi'
University of Maryland College Part, 20742
Chemistry of Man's Environment A
course for nonscience majors
Since about 1969, much attention has been given to the design of chemistry courses for nonscience majors (see Ref. ( I ) for a bibliography citing 20 course descriptions). This long neglected audience had usually been offered a low level version of general chemistry. During the early 1970'9, increasing hostility from students and the general public made it clear that we had failed fully to communicate the nature, benefits, and limitations of scientific activity to nonscientists. Counes for nonscience majors are perhaps one of the best avenues by which to increase those communications. Thus, it is imperative that we improve those courses and tailor them better to the interests and needs of the audience than we have in the past. Below we describe a course that has been quite successfully given for nonscience majors (both full time students and adults in evening classes) since 1970 a t the University of Maryland. Objectives and Philosophy
In desienine the course we had two maior objectives: (1) .. to make I't interesting and (2) to prepare students to make decisions on scientific and technoloeical issues that confront all citizens of highly complex societies such as ours. In view of increased student interest in environmental quality, we decided to emphasize chemical aspects of man's environment. Courses along this general theme have been developed elsewhere, but often they have emphasized only the "negative" aspects of environmental chemistry, i.e., the clean-up of air and water pollution and the disposal of wastes. We take the broader view that environmental chemistry deals with the chemistry involved in providing a hTlgher quality of life and includes both the preservation of environmental quality and the development of resources needed for ma$s comfort and well-being, i.e., food, energy, and materials. The strong counline amone these broader asnects of the environment wa'indycated the controversiaf "Limits to G r o w t h calculations hv Meadows. et al. 12): and the conflictinn demands of knergy and environiental quality provide a clear demonstration. We feel strongly that one should not discuss just the applications of chemistry. Rather, one should provide a logical, scientific framework in which to treat them. On the other hand, one cannot expect students with little apparent a wiori interest in science to maintain high interest while bne develops the entire scientific background needed for "relevant" discussions. We have met these conflicting demands by building the course around a basic scientific framework in which we illustrate each principle with "real world" applications (see Table 1). With applications spread fairly uniformly throughout the term, students maintain a hieh level of interest. Furthermore. when each principle is coupled with dramatic applications, students understand and remember the principles more easilv. On material covered by both courses, we k n d that students of this course do just as well on examinations as students in general chemistry courses we have taught. 'Present Address: Assistant Chairman, Division of Agriculture and Life Sciences, University of Maryland, College Park, 20742. 668
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Order of Topics
The outline of topics is listed in Table I in two columns, the first listing basic principles and the second, the associated applications. The order of chemical principles is fairly conventional except for our early and rather extensive coverage of the nucleus. We have placed it early for several reasons, especially to provide a better basis for understandine atomic masses and eram atoms. These im" portant concepts are often approached via the historical route involvine the laws of constant and multide nrooortions, which u&ally produce enormous confusi&. B~ Eontrast, when students first learn about neutrons, protons, and the nuclear origin of most of the mass, the ideas on atomic masses and gram atoms follow quite naturally. We place considerable emphasis on nuclear concepts because of the intense debate on nuclear versus nonnuclear sources of future energy. The burning of fossil fuels is a process that most people can visualize, hut the production of energy from nuclei is almost totally outside of the experience of nonscientists. The very little that people do know about the subject is colored strongly by association with nuclear weapons. There are serious hazards connected with nuclear energy, but no rational debate of the issues can occur without an understanding of the related science. While much of our d&elopment of scientific principles is done to provide background for applications, we do not limit ourselves to just the required-concepts. 'we believe that a feeling for the excitement and intellectual curiosity of science can he best conveyed by discussion of some theoretical ideas beyond the reach of everyday experience, e.g., quantum theory and probability, relativity, "black holes," etc. The course includes material from many sciences other than chemistry, especially physics, astronomy, geology, biology, and meteorology. This is necessary for discussion of many of the environmental problems, nearly each of which has aspects in sciences related to chemistry. Since this course is often the only college level physical science course that the students take, it is appropriate that they have exposure to material from other sciences. From the list of topics in Table 1, it may appear that the applied portion of the course is rather disjointed. However, as outlined in Table 2, several unifying themes run through the discussions. The major theme is energy, including its fundamental role in determining stability, as well as the practical problems involving the great needs for energy and the environmental degradation accompanying its production and use. Although we do not discuss the second law of thermodynamics and entropy per se, the trade-offs between energy and order in relation to refining of ores and recycling are treated. Of course, it is necessary and desirahle to include some ecological theory to show how toxic substances affect biological species, how we can most efficiently feed the world population, etc. Another point that we emphasize is the difficulty of establishing one-to-one correlations of effects with environmental causes. For example, it is known that death rates from cardiovascular causes are highest in cities having high atmospheric concentrations of cadmium (8). By itself
Table 1. Sequence of Lectures Basic principles
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Examples of applications General discussion of the problems of man and the environment
Mathematia* metric system Substances, elements, compounde Atomie and nuclear mnstitvtim Atomic m a w , gram a t o m , and moles Energy and mass
~ u e l e a .stability snd radioactivity Nuclear fission Nuclear &on com*tim of Earth, Bun, and d a r system Nuclear -&ions in stars Synthesis of elements
Covalent bonding Molecular structure and bonding Hydrogen bonding-unusual properties of water
Electrolysis of w a k Acids and b e t h e carbonate system
T h e "energy crisiss'-world
needs,
sources, environments1 degradation caused by energy pmduction Environmental e e e t s of hydmeleet r i c olanta ~hermd pollution F"tenergy sou-: geothermal and solar Effe'eetr of radiation on biological systems Nuclear weapons: fallout Nuclear reactors; prineiplea and ble hazards Fusion R ~ M M of the future
Table 2. Maior Themes Covered in the Course
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Energy b d a m e n t a l role: stabilitg of atoms, molecules, and nuclei, AE driving force for transformations Energy and dimate warming of Earth by nunlight, evaporation of water. driving f o r e for wind end ocean currents; trapping of Earth's ir radiation bvatmosuhuic CO,. i.e.. ''meenhouse effect" Man's use of energy: Needs: heat, rehning of minerals, transportation, prodvetirm of fwd, d-Lination of water, reduction of heavy manual labor Environmental degradation by p-nt aavrees and -: strip mining, acid mine drains@, oil slicks. SO*and p n i d s a f m m pawer plants, smog from motor vehides, thermal pollution, radioactivity, pmbkme Of hydmeleetric plants (e.g., Aswan Dam) Sour- of energy: limits of p-nt sou(3); potential and teehnnlogical barriers for new sour-: wlar, gmth-I, nuclear Energy in the bicapheere: photosynthesis: ine5eieney of transfer of energy and nutrients determine pyramidal shape of f w d chains ( 4 ) Entmpy and Semnd Law Concepts Ine5cieney of eonverjion of heat to mechanical energy: waste of energy, producer thermal pouution Refining of ores: deerease entmpy a t theerpense of energy; with abundant energy could mine low-grade ores (even granite) to obtain vital metals: r s y d i n g conserves enem aa *wU as resources (5-7) Emlogy Food chains (or webs): pyramidal dupe often oeuees build-up of mncentmtion of toxic svhstances at higher tmphihic levels; loss of ef6eienoy in' Ynf world focd supply by eonsumption a t b i ~ htrophie levels (e.g.. beefatea* " e m plants) Movement of no"-biodegrsdable substances in the enviroviroent: parsiatent pesticides, polychlorinsted biphenyls (PCB's), older synthetic deteqents, methyl mercvry Mutations and evolution: development of resbtance to M d d ; effeda
water in the environment-modera-
tirm of dimate: relative humiditv. .. msteorology, i"d precipitation Inadvertant and intentions1 weather modihtion T h e SST and ozene in thestratasphem Fuel cells; the "hydrogen economy"
The "gleenhonh effect" of CO, Buffering effect d the oceaas for CO,
Chemical behavior of ae-al gmuw Alkali metals and alkaline earths
composition of sea water; waieF M ness Halo-multiple oxidation ~ t a t e s Fluoridation; household bleaches and other oxidiring agents Sulfur and oxygen Urban air poUuti~rbanairpo~utionaulfvrorides od~rbanairpo~utionaulfvrorides od~rbanairpo~utionaulfvrorides od f~fr oxidesand patiieulstes Nutrient cycles; world food problems. Nitrogen and phosphorus especially proteins Eutrophication of water bodies; phosphates in household detergent. Metal resa"reee--"tbe limits to Metabphysical and chemiesl prowrties growtw Recycling: recovery of -bride from urban trash Esaantial elements Toxic elements in the environment, especially Hg. Cd, Pb organic ehemi~-hydroearbons Petroleum; automobile p o l l u t a n t s Los Angeles smog; control of em* siom Alternate mobile souO i l slicks Corn-ds with functionel g r o u p Chlorinated hydrocarbon pesticides Movement of man-made svbstanees through eeo-systems--eonCe"ttttion in certain species Persistence of plasties in the environNatvral and synthetic polymers
--"* ...-.."
Biochemistry cells hoteins, carbohydrates, lipids Dieof vitamin deficiencies and Enzymes, vitamins exceases Nueleic acids and the-genetic mde Hormone-female reproductive Genetic d k s e a i c k l a e e U anemia Birth control-hemid contracepwele tives Strudand of drugs s d g up: Some weial, legdpolitieel, economic, and teehoologid euggestions for improvioe: the qudit" of our environment
this observation does not prove that atmospheric cadmium causes the increased death rate, since one could probably find many other variables that correlate with the death rate. However, there are studies of rats on cadmium-rich diets that show a direct connection between cadmium intake and hypertension (9). Students are often surprised to learn that,. despite our poor knowledge of the effects of very low doses of nuclear radiations, we know even less about the effects of common substances such as the caffeine in coffee.
Rwurees-outuf-Place ~ e v e beneficial l ~ ~ uees of pohtants: heat from thermal pollution, resourand energy from trash, energy and nutrients from sewage and animal wastes
Students sometimes wonder why chemists are involved in the environment, since the final concern is with the effects unon hioloeical snecies. However. chemistrv has a central involvement in nearly every environmental prohlem-the formation of sulfuric acid mist from the sulfur in fuels, the generation of acid in waters draining from mines, the interference of toxic metals with the action of enzymes in the body, to name hut a few examples. We were not even aware of certain environmental problems until chemists developed new, sensitive methods for detection of environmental pollutants. Regulations on the release of ~ 0 l l u t a n t scan he written into law onlv if there are standard analytical methods available that can be s~ecifiedfor measurement of the ~ o l l u t a n concentrations. t chemistry also has important roles in the discovery of methods for the prevention and control of environmental degradation.
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Laboratory
The lecture group is divided into sections of 24 students for a 3-hr laboratory per week. Most experiments are designed to require about 2 hr each to allow 1 hr for demonstrations and recitation. The design of experiments in environmental chemistry is very difficult because any segment of the environment is much more complicated t h a n a clean beaker containing a pure solution. However, we have assembled the set of 22 exoeriments listed in Table 3. from which we select 10 or ll'for use in a semester. We "ary the selection somewhat from one term to the next to k e e the ~ course "fresher." Some experiments are of a rather conventional sort, designed to develop skills (e.g., the density experiment, the reactions of copper). Others are a lot of fun for the students at the same time that they illustrate chemical principles or techniques (e.g., Nylon synthesis). The balance divide about equally between studies of household products (antacids, bleach, food additives in meat, vinegar, carbonated beverages) and measurements of environmental parameters (e.g., oxygen content of water, chemical oxygen demand, chloride in water, phosphate in water Volume 51. Number 10. October 1974
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Table 3. Collection of Experiments for Nonscience Majors Course Brief Desni~ti.3"
E-imente
Measvre densities of both liquids and solids. Obki"volumes of solids by direct me-rement and Archimedes method in a graduated cvlinder. c u metal tu c n - Demonstrate various Series of chemical m c - c&v.* SO,, C"0, and back to fomu an element tions (10) cu mete1 by Z" reduecan take and, if d* sirable, convert it tion. back to atarting material. Builds additional laborstor" skills, e.g., filtering. Recycling of aluminum convert serw A1 fmm a Demonstrntcs how beverage "in to slum. chemistry can be which is used in synused t o convert waste material into s thesis o f a dye erpt. useful product Synthesis of inorpannie Synthesize cis and trans S h o w that properties, in this ease color, d* isomem of ICl(en)rcomplexes end on structural CI?ICI. .mngeme"t, for the ssme chemical for","Is. Measurement of radio- Use a proportional mu". Demonstmtea statistiter t o messure ranges cal fluctuations, penactivity of 8- and "-rays etrating power of through various thicknuclear radiations. neof material. Titrirndric Experiments S t a n d d i z e stock sol". Develops volumetric Acetic acid content of tion of NaOH and tiskills and shorn how vinegar s consumer d v c t trate vinegar. can be tested: T h e earbrmate system: Titratesoda water a t var- Demonatrates solubilious temperatures to ity of gasesasafuncSo1"bilit~of C01 in tion of temperature determine H K O J wster
Brief Deseriptio"
Colorimtric Experimente Field collection of m t e r phosphate mneentrasamples. Analyze them tions inwater and de-
..
Learn eolorimetrie method and method for measuring P O F cone., s critical
ing ascorbic acid and (NHdzMoO. HSO, t o form blue complex with P O F . Extract N O 1 6 t h boil- Learn teehniqvs for ing water, add Grimessuring con-. realle"t. and measure eolorimetrically.
+
Nitritemneentrationin hot dogs
Cu in moonshine
P b in the environment
Fovm earbemate mmLhx. extract into CHCla, and measure mlorimetticdly. Measure Pb concentrations in sir, water, ceramics. mil. or mint.
surement. Olganic ond Bioekrniatry Experiments Reset aslieyli~acid with Synthesis of aspirin acetic anhydride t o form aapirin. Synthesis of a dye
con".
Synthesize dye on cloth by soaking in NaOH solution of 6-naphthol and then in HCI solution of p-nitro-andine. D y e a n u n t m t e d cloth and another treated with alum from Al-can.
Learn extraction method. measure ment of b h " k values. variety of environmental sampling methods. indudin. air filte4
Learn some typies1 organic p'ocedures; calmlate "idd of reaction. Additi0r.d experience with synthetic oresnie terhnique. Learn use foi recycled A1 pmdud.
The carbonate system:
Demonstrates bufferTitration of NaHCOs ing action, tests se6 t h N s O H . Add eretion of commercial HCl tocommercial antpreparations versus acid preparations and baking soda. back-titrate with NsOH. ha",wster ssmp1ing content of Field collection of water Dissolved 0% technique and redor samples and measure. water titrations with ment of diesolved On by starch indicator. ImWinkle= method: ox. of portance of dissolved MnP t o MnO?, red. with I-, titration of O2 conc. as waterquality indicator (re. I Zwith S?OaP-. late to following ex@): Chemical oxygen deField couection of water. Determine amount of mand of wster O? required for mmAdd exof Mn0.plete oxidation. Corand digeat to complete relate with results of oxidation and backabove erpt. titrate with I-. Chloridein t h e e n v b - Field collection of water Learn importance of c1- as indicator of ment and air filter samples. sea water and "laDetermine c1- by tirine aemmls. Demtration with AgNOz onstrates how using cr0.x- as indieadiffering solubilities tor of AgCl and AgsC1Od ,a ", be used as indiBuffers and antacid3
Synthesis of polymers
'
Chromatography
..
Enzymes
cator.
c10- mneentration in mmmercial bleach
Add exof I- t o N a OCl bleaehesand backtitrat. with S . 0 1 2 with stsreh indicator.
Testing of a eonsvmer product. Cheek NaOCI obtained P" dollar.
bleach. Heat freshly distilled This organic synthesis, espeeislly that of methylmethacrylate in nresenee of benzovi Nylon, is fun. peroxide t o form p l y methylmethacrylate. Combine solution of sdipyl chloride in Shelly-B with no1ution of hexanediamine in water. Form nylon a t interface and pull out in form of a rope. Demonstrates some Separate l-oetsdecene m a r a t i o n methods from einnamaldehrde that are "dextenby thin-layer chromasively in organic tography. Sewrate and biochemistry.
Growth of algae
..
the surface of pieces of chalk. Measure the rate of hydrolysis of starch in the presence of pancreatin as a function of temperature. Algae are g m m in a series of tubes containing various nutrient solutions, some deficient in c h i n essential
for metal ions.
and household detergents, lead in the air, paint, and ceramics). The laboratory has been highly successful. Most students enter the course with little chemical experience. By the end of the course, most have developed a number of skills. But more important for their future needs, they develop an understanding of the difficulties involved in the study of the environment-why it is, for example, that standards set by the Environmental Protection Agency change as more is learned through improved methods of monitoring. One of the hest aspects of the lahoratory is that students have fun doing the experiments, rather than 670
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Demonstrateri the d r pendence of ehemical rates on temperature. At hieh temo. enzvme is hestroiid. Demonstrates n d for "balanced diet" of nutrients; related t o control of eutrophication.
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viewing lahoratory as something to he endured. They particularly enjoy the experiments in which they bring in their own samples of water, detergent, etc., for analysis. Texts and Supplementary Material
Although several texts for courses of this type have appeared recently, none follows our plan of organization. Thus, we have written lecture notes that are distributed through the local bookstores. In this way we can revise the notes as some issues are resolved and new ones amear. .. There are some good supplementary readers available. One of the best is Hamilton's "Chemistry in the Environ-
ment" (II), a collection of articles selected from Scientific American. The articles contain excellent background material for the understanding of current problems, especially on nutrient cycles, the movement of lead and mercury in the environment, and sources of energy. Two other useful hooks are reports of conferences held during the summers of 1970 and 1971: the "Study of Critical Environmental Problems," (SCEP Report) and the "Study of Man's Impact on Climate," (SMIC Report) (12, 13). The former covers a wide variety of problems and the latter deals mainly with global atmospheric problems. In this rapidly changing field, it is essential that the instructor keep up to date by consulting current periodicals. We find that the best of these sources are Science, Science News, Scientific American, Environment, Science and Public Affairs (the Bulletin of the Atomic Scientists), Technology Reuiew (MIT's alumni magazine), The New Yorker, and Chemical and Engineering News. Outside Reading In view of the large size of our classes (generally more than loo), we have not had the staff necessary to handle outside reading. However, with smaller sized classes, outside reading could be a useful extension of in-class activities. There are many suitable books for outside reading: "The Closing Circle" (14) and "Science and Society" (15) by Barry Commoner, Rachel Carson's classic, "Silent Spring" (16). James Watson's "The Double Helix" (17). "Lawrence and. Oppenheimer" by Davis (la), and Inglis' "Nuclear Energy: Its Physics and Its Social Challenge" (I9), the last being probably the best work available on the problems of nuclear energy. Student Response The student response, as indicated by their attitudes and as measured by anonymous polls conducted by the Department. bas been excellent. The class roll is generally fillkd to capacity (currently 120). The excellent response throughout the course has been a pleasant surprise. We bad expected to encounter some
initial hostility among the students. Only a few would have taken the course were it not for the science requirement of the University. However, none of them was required to take this particular course, as similar courses are offered by other science departments. Apparently, this degree of freedom is important in reducing any animosity the students may have. Acknowledgment We would like to thank Professor Joseph T. Vanderslice, Chairman of the Chemistry Department, for giving encouragement and complete freedom in developing this course. Much of the success of our course resulted from the efforts of our excellent staff, including Ernest Gladney, Sydney Jackson, Dr. C. C. Lewis, Tom Zaucha, John Ondov and Joseph Reednick, who helped design the experiments. We thank Miss Elaine Kilborne for her help with demonstrations and preparation of slides. Literature Cited 11) F s h n h o l z , S.. J. CHEM.EDUC.. 50,5Wl18731.
(2) Meadow. D. H.. Meadows. D. L.,Fangem. J., and Behmns. W. W.. "The Limits ta Growth." Potomae Assoeiafcs, New York, 1972. (3) "The Potentid for Enersy Conservation," Staff Study of the Offiec of Emergency Repsrednosa. U.S. Government Printing Office. Washinkon, O.C.,1972, App n d u E. (4) RuascilLHunter. W. 0 . "Aquatic Pmductivity." The Maemillan Co.. New Yorh, ,m,n
(5) (61 (11 (81 I91 (10,
Berry. R.S.. Sci. andfiblicAflair,%27. No.5. 22(18711;28. No. 5,811972). Hannon, 9. M.. Enuimnmenr, 14. No.2, 11 11972). "MiningtheDump8:Tho Economies," Tech. R e v , 73. No.9.51 119111. Csrroll, R E . , J A r n e Med. Sor., 198,267 (19661. MeCaull, J.. Enu;mnmmt, 13. No. 7.2 (19711. . L.. ..chemistry in the ~aboretory;. ~ i i y nand ~ s e o n . ~ e p g D. . C. and ~ r o w n C. I n c , Boston. 1966. (111 Hamilton, C. L.. "Chemistry in the Environment." W. H. Freeman Ca.. Ssn Francisco. 1'373. (12) "Man's Impact on the Giobsl Environment ISCEPI." MIT Pleu. Csmhridpa, Msss., 1970. (13) %advertent ClimateModifieation ISMIC)," MITPmu. Cambridge. Msss., lWl. (14) Cammoner. B.. "TheCiosingCirele."Knapf, New York. 1971. 115) Commoner. B.. "Science and Survival." VihinePle.8. N w York. 1966.
l9M. : Physics and its Soeial Challenge," Addimn(19) Inglis. D. R.. '"Nuclear E n c ~ Its Wesley Pub. Co..Inc.. Reading. M e . , 1973.
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