Chemistry for Everyone edited by
View from My Classroom
David L. Byrum Flowing Wells High School Tuscon, AZ 85716
Putting A Human Face on Equilibrium Neil Glickstein Waring School, 35 Standley Street, Beverly, MA 01915;
[email protected] Lack of a human touch is what often keeps high school students from connecting with scientific principles in the way they might connect with literary or historical works. For most teenagers human relationships are intensely important, so lack of this sort of connection in what they are studying can be a determining factor in whether they put their full effort into understanding a concept. I have found that using biographies can be an effective means of engaging students in technical topics. Standard chemistry textbooks can inadvertently place a barrier between students and the understanding of complex concepts. Chemistry, an inherently abstract discipline, often provides little tangible evidence from everyday experience from which a beginner can verify, by direct observation, the phenomena being witnessed. Equilibrium chemistry is one such concept with which I have struggled to make a presentation that touches my students in a personal way. We discuss how reactions are dynamic and how stress is relieved (Le Châtelier principle). Simulations of equilibrium dynamics help students to see what is taking place in solutions that merely change color when a stress is applied (1–4). We write equilibrium expressions and predict concentrations by calculation but I am sure that the majority of the class treats the concept as an esoteric and abstract technical oddity that will have little if any value in their life after the test on the unit. My goal has been to find a way to help them to understand chemical equilibria in a fundamental and personal manner. Equilibrium: A Personal Experience No one among us would choose a textbook as reading material. Imagine the effect these books have on students who may only have a passing interest in the topic presented. To personalize the study of equilibria I needed a piece of writing that was at once engaging and focused on the topic. One of the workhorse equilibrium reactions traditionally studied is that describes the Haber–Bosch process:
N2(g) + 3H2(g)
2NH3(g) + energy
For economic, historic, and scientific reasons it is worth considering this reaction in a first-year course. Fortunately, a brief and very well-written biography of Fritz Haber is included in Roald Hoffman’s book, The Same and Not the Same (5). Reviewers have praised the quality and accuracy of this volume written by the 1991 Nobel laureate in chemistry who has spent a lifetime illuminating the principles of the science for the lay public (6). By considering the irony of balance or equilibrium in Haber’s personal life my classes have success-
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fully approached an important chemical principle from a compelling biographical foundation. Other brief, high quality biographies also exist that provide a variety of perspectives on Haber and his historical context (7–9). Fritz Haber Haber was born to a Jewish family in Silesia. Though he was surrounded by a Jewish community as a youngster he chose to convert to Christianity as a young adult; a path typical for Jews with aspirations of moving into the elite ranks of leadership in turn-of-the-century Europe. He was a hard worker and intensely patriotic. When World War I began he turned his energy to developing chemicals that could help the war effort. Besides the ammonia synthesis that allowed Germany to overcome the effects of the British naval blockade of nitrates from South America, he was responsible for the idea of using a gas cloud of noxious chemicals to overcome soldiers in an opposing trench. He suggested that chlorine be used in the first large scale “chemical weapons” attack at Ypres in April, 1915. His wife Clara, also a chemist, for humanitarian reasons pleaded with him to give up his research into chemical warfare agents. He refused, seeing them as his contribution to the war effort. Clara eventually committed suicide, the reason not being completely clear, but one can begin to imagine. Haber was awarded the Nobel Prize for 1918 for his work on the fixation of nitrogen from air. He died in 1934, his spirit broken by being rejected by the Germany he served so well. Haber could rightfully be named the father of toxic chemical weaponry that, ironically, had more than a small part in the murder of millions of his own people in the Nazi gas chambers of World War II. Those chambers employed the efficient and toxic products of the German chemical weapons industry that he helped to found. In our present time when a focus of international effort is on the possession and potential use of chemical weapons of mass destruction, it seems important that Haber’s contributions to the technology and its applications be remembered and discussed. Returning to the famous ammonia synthesis; it can be shown that hydrogen and nitrogen can be persuaded to react under the proper conditions of pressure, temperature, and the presence of a catalyst. The product, ammonia, is the raw material for many possible industrial processes. Once it has been created in commercial quantities, does one choose to use the substance to produce fertilizer to feed people or to make explosives for weaponry? Even the nondestructive fertilizer choice has had long term unanticipated results. Synthesized nitrogen fertilizers have affected the global nitrogen
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cycle causing a variety of serious environmental problems especially in aquatic systems (10). Addressing this topic provides a natural place to discuss environmental balance, risks and benefits, and the ecological stoichiometry of unrestricted additions of usable elements to a cyclical system. So, the equilibrium equation of the ammonia synthesis we manipulate in class might be used in the metaphorical sense to describe the balances or trade-offs Haber made in life. He gave up his religion and heritage and may well have alienated his wife in the cause of patriotism. Once the Nazis came to power they considered him Jewish though he had converted to Christianity. Ultimately he lost his power, prestige, and position as a result of the political views of the new government. His efforts and sacrifice for his government were rewarded by disenfranchisement. In addition, the fledgling industry that he created to further the interests of the fatherland resulted in compounds used to kill millions of his own people. Equilibrium Explored through Life Experiences As we explored the complexities of chemical equilibria in the laboratory, my students and I tried to keep in mind the analogies that this chemistry has to the way one lives a life. Once a synthetic process is discovered should one employ the product to grow crops or to make war? Are there long-term problems inherent to what seems initially to be a constructive and helpful discovery? One can prepare toxicants to help your country but they might return to kill or threaten your own people. You can sacrifice what is fundamentally important, only to have the winds of change shift your fortunes in unpredictable ways. Living and making choices is a dynamic process. Decisions, or changing concentrations if you will, at one point can result in responses from the system that can only be predicted if one knows the rules by which the system plays. In laboratory test tubes the rules by which the reactions play can be known and therefore the reactions can be anticipated and manipulated. Unfortunately, in our human experience, most often the rules of the game become evident only in hindsight. Haber, the man whose equilibrium
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synthesis is so commonly studied, provided us with a life in which balance takes some interesting and ironic turns. Conclusion This human introduction to the study of chemical equilibria, enriched by its colorful historic nature, has in no way diminished the quality or quantity of the traditional chemistry studied. But instead, incorporating this approach engaged many of the students for whom chemistry had been just one more technical requirement in a long list of required courses. A human face, a human story to identify with, has become worth a great deal to many of the students who pass through my classroom but who will never become chemists. Literature Cited 1. Howland, R. J. Chem. Educ. 1999, 76, 208. 2. Edmonson, J. L.; Lewis, D. L. J. Chem. Educ. 1999, 76, 502. 3. Pavia, J. C. M.; Gil, V. M. S.; Correia, A. F. J. Chem. Educ. 2002, 79, 640. 4. Pavia, J. C. M.; Gil, V. M. S.; Correia, A. F. J. Chem. Educ. 2003, 80, 111. 5. Hoffman, R.The Same And Not The Same; Columbia University Press: New York, 1995; p 167. 6. Review by Book News, Inc. is found under the title of the book at http://www.amazon.com/exec/obidos/tg/detail/-/ 0231101392/ref=olp_product_details/103-91957298747034?%5Fencoding=UTF8&v=glance (accessed Oct 2004). 7. Fritz Haber Biography. http://nobelprize.org/chemistry/laureates/ 1918/haber-bio.html (accessed Oct 2004). 8. http://www.woodrow.org/teachers/chemistry/institutes/1992/ Haber.html (accessed Jan 2005). 9. NPR: Fritz Haber and the Nitrogen Cycle. http://www.npr.org/ programs/morning/features/2002/jul/fritzhaber/ (accessed Oct 2004). 10. Nutrient Overload: Unbalancing the Global Nitrogen Cycle; World Resources Institute 1998–1999 Report; http:// pubs.wri.org/pubs_content_text.cfm?ContentID=1412 (accessed Oct 2004).
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