J.
DUDLEY HERRON
Purdue Unwers~ty West Lafayene,Indiana 47907
Establishing a Need to Know J. Dudley H e r r o n P u r d u e University
It is not enough that students learn chemistry. They need t o know why they are learning the material taught. I have recently found t h a t beginning teachers don't know why students studv the . ~ r o.~ e r t i of e smatter.. gas laws. atomic structure, equilibrium, enthalpy and entropy, oxidation and reduction. kinetics. and a number of other t o ~ i c taught s - in a hepmning course. This paper is one teacher's attempt roestnhlish a "need tu know." I hop? that it will stimulate readers t o develop their own. Let me begin by giving two reasons t h a t I do not consider satisfactory; t h e first is, "Because it will be on the test," and the second is, "Because that's part of chemistry." T h e teacher who justifies what he is teaching by saying it will he on the test is giving a n excuse rather than a reason. H e is teaching a topic because it is in the t e x t a n d has some kind of blind faith that the author of the text knows t h a t i t is important. It may he, but only the most dediratrd or submissive students will acrept this a s a reasun to I m r n the mntcrial. If the onlv value u f t h e material is to Dass the teit, the studenr is perf&tly justified in forgetting ;bout it when the test is completed and likely will. T o justify what you are teaching because it is part of chemistry and this is a course in chemistry is a little better hut not satisfactory. I t is better because it says t o the student, "This is the sort of thing that chemists are interested in," and may help them decide whether they would like to live their life a s a chemist. Still, it begs the question, "Why are chemists interested in this sort of thing?" When asked why he wanted t o climb Mount Everest, Sir Edmund Hillary, the New Zealand mountain climber, supposedly remarked, "Because it is there."There is an element of truth in such a response, but it masks a more serious reason; the sense of satisfaction t h a t comes from knowing what no other man knows, from doing what no other man has done, from accomplishing a difficult task. Every scholar, every person of great accomplishmmt, e\.ery straipht-A student prohahly acts out of iimilnr motivation. It's heady stuff, this sophisticated game of one-up-manship, h u t it is not a game that everyone plays. For every Hillary willing to climb the peak "because it is there," there are millions who would rather watch the report on the six o'clock news! Then what justification can we give for studying chemistry? Chemistry is the study of matter-what i t is, why i t exists in its various forms, how it can be changed from one form t o another. how it cannot be chaneed from one form t o another. the conditions necessary for those changes to take place. he more we know about matter the better able we will he to shave the world for o w cnmfort and pleasure. New drugs, new fibers, new building materials, new forms of transportation, new means of communication, new sources of energy, new means 3f conserving what we have, cleaner air and water, less noise, nore music, more nnd better food, less work, more play, better lealth, longer life, painless death. All of these seem worthwhde m d we believe that the more we understand about matter, the more likely we are t o have them. I n our attempts t o learn more about matter, there are sev?ral questions t h a t are asked. One of the very first is I S 0 / Journal of Chemical Education
What is this matter that Ihove? To understand matter we need to know what it is and alarge part of chemistry is devoted to answering that question inanumher of contexts. Is that clear liquid water that I need to survive, alcohol that dulls my senses so that I don't care to survive, or sulfuric acid that will ensure that I don't survive? Is the paint on the victim'scoat thesame as the paint an the ear of the hitand-run suspect? Is there mercury or asbestos in the water Idrink? Is there enough protein in my food? Is there enough phosphorus in the soil to grow corn? It there too much pollution in the air that we breath? Identification is always a matching process. From Kojak's lineup to the analyst's test tubes, the detective always asks whether the characteristics of the culprit are identical to those of the suspect under investigation. The more characteristicsthat match, the more positive the identification. The chemist has learned to look for and trust a number of eharacteristics from simple measures such as density, melting and boiling points, solubility, pH, crystal structure, odor, surface tension, index of refraction. and on occasion. even taste. to more so~histicated mensure, such as the wavelengths of light a h k b d hy thesuhmncr. ns mi:mricm in a n rlrrtrir ticld, its hhnvlor in a strong magnrti fi~ld. thespcrd rhar thesuhsrancc muvwnlcmg apieceoipaper or through :, lulw p ~ k e d with ponder as i r is swept along hy allquid orgaseous solvent. hnw the iubs~nnrercratrs polarized light, and how it renets or fnik t u reart with a host of other chemicnls. If we are to identify matter, we must know about the properties of matter and we must know how to measure these properties. Identification of matter isn't alwavs . easv. and it isn't alwavs fun. though it mny be. Success in identitiration takes patience, practice, skill. nnd agreat drnld judgment. The criminnl suspect srldrm looks in the lineup as he looked at the scene of the crime. His mustache is gone and his smile; his behavior is altered by surroundings. So it is with matter and we must be aware of the influence that the environment has on behavior. Analytical chemists need the insights and daring of Sherlock Holmes and even more information. How much do I haue?We all know the daneers of havine too much of ngwd thing. l l l e rhernisr mtrst often ask how much of a rubstance 1s prerent in addition to what kind. Axmr might expert. knowledge of properties is necessary ds brfore, hut 'horr much" implies meacuremrnt and the chemist must employ rnnnyquantitnti\.e skills in order to gct the hed poss~hleanswer to t h ~quwt r ion. Frwn the very iirrt inrroduction of stwchicmrtry, the gas law. pH, titmtim. gravimetric analysis of chemical composi&n, various spectrophotametric measurements, enthalpy measurements,and a host of other procedures, we have tools for learning how much. How can I change it? Never satisfied with what we have, man searches for something new and different. Should chemists be any different? We not only want to know what we have and how much, but how to make a silk purse from a pig's ear or turn lead into gold. This was what the earliest chemists sought to do, and they are still at it in the labs of duPont, Eastman Kodak, 3-M, Eli Lilly, Dow, and Merck. Most of the early effortsto make new materials were trial and error, and despite the impressions left by the erudite theory that permeates introductory courses in chemistry,serendipity still plays a major role in discovery. But we would leave to chance only what we must and prefer to work from an understanding of the nature of things. Atomic structure, kinetic theory, bonding theory, and thermodynamics all furnish a foundation from which predictions of change can he made with more confidence. From the best theories of atomic structure we can predict the probable shapes of molecules and from the shapes predict many properties. Why, for example, does water defer its boiling until such a high temperature or expand when it changes to solid or dissolve so many substances or attach itself so firmly to so many other molecules? It is the polarity that results from its shape and bonding made possible by the attachment of tiny hydrogen to the eledrophilic element of oxygen. How are the enzymes that catalyze the thousands of chemical changes now taking place in your muscles, ~~
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stomach, and brain able to sort one molecule from another except by matching their shape with another and then interacting to change the shape and attachments of atoms? The more we predict from theory, the . less we need to learn hv chance. From thermdynamirs we mn predict what rrarrions con occur ( b u ~not neresiarih which ones will) and tonrrnrrnw efforts in the realm of rhe possible \Ve can determine the amount of energy that we can get from a chemical system and since we need energy to survive, that in itself is important. How do you think that the nutritionist knows that one cup ofalmondsgives 12 times the caloriesas aeup of string beans? How does the testing laboratory determinethe heat that can he obtained from various samples of coal or oil or natural gas or various types of wood? Is it not the same enthaply of combustion that we study in beginning chemistry? Do you imagine that the hundreds of batteries on the market resulted from chance combinations or from a narrower search based on knowledge of free energy? As we struggle to prevent our limited metal resources from being scattered throughout the environment to the point that sound economics prevents their recovery, is it not a knowledge of the electrochemistry of corrosion that we turn to for salvation? Thermodynamics is not a mountain to he climbed just heeause it is there! Atomic theories are not created just to behold their heauty! They help us see how to change the world to our liking. How much eon I get and how fast? If I can get 12% yield for the ~~
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same cost that you get lo%,I will stay in the market while you look for another job. If I know what affects the speed of a chemical change I can speed up reactions that I like and slow down those that I don't, The implications are vast, from body metabolism to corrosion tc growing crops ta eliminating wastes to killing bacteria to curing cancel toliving for 500 years.The more I know about equilibriumand reaction kinetics, the closer I come to such answers.
Most of what we study in chemistry can easily he related t o just these four questions, but not all. Some of what we learn is simply for the purpose of communication or because it opens u p possibilities for learning still more. Chemical formulas, eouations and much of the mathematics t h a t we learn are simply aids fm mmmunication and thinking: some or what we reach mav have no value at all. I h a w never figured out, for example, wgy anyone needs the words anode 61 cathode or anion or cation when we have other words t o take their place. Nor would I argue t h a t every person needs t o know any one of the things t h a t I have mentioned in this paper. B u t I d a believe that the things t h a t we teach in chemistry are worth knowing by some . . . and the worth does not come from a grade on a test or the satisfaction of havinglearned "because it is there."
Volume 55, Number 3, March 1978 I 191
