edited by: DAVIO A. PHILLIPS Wabash Coiiege Crawfordsville. IN 47933 PRUDENCE PHILLIPS Crawford~villeHigh School Crawfordsville,IN 47933
Electrochemistry
Goals in Teaching Electrochemistry
Ronald I. Perkins Greenwich High School Greenwich,CT 06830 Electrochemistry is one of the most importarit topics in my chemistry course. I t easily relates to attent.ion-getting activities and visually exciting demonstrations; it explains manv" uhenomena observed in the real world: an d electro. chemistry can serve to unify an introductory course because i t is related to almost every other topic in chemistry.
J. T. Maloy Seton Hall University South Orange, NJ 07079 I have started more than one lecture in electrochemistry by asking the class to arrange the known kinds of chemical reactions in order of increasing complexity. After a few minutes of weighing the intricacies of double displacement against of those of backside attack, I provide them with my own list:
Electrochemlstry Excltes I t is no accident that many early chemists such as Davy, Berzelius, and Faraday chose to investigate electrochemical phenomena. Many students relive some of the old masters' feelings of excitement when they watch bubbles of gas form in a two to one ratio around two inert electrodes immersed in a solution of acid; or by observing orange copper deposit on a graphite electrode immersed in a blue copper sulfate solution and then disappear when the battery connections are reversed. One does not need t o understand much chemistry to appreciate the beauty of vanadium or manganese solutions undergoing oxidation numher changes. Few will ever forget the electrochemical demonstrations-the grandest in the chemist's arsenal-of the exploding hydrogen and oxy~. gen balloon or the thermite reaction. One soon concludes that most of our favorite chemical changes are examples of oxidation-reduction reactions. Electrochemistw. Exolalns . Interest in the study of chemistry can he stimulated by color changes and explosions that are often remembered for along time. The power of chemistry, however, comes with its beautiful theories and models that help us first explain and then predict real world phenomena. I can think of no more useful topic to help us understand the world in which we live than thembject of electrochemistry. The study of reduction potentials answers questions such as why only a few metals, such as gold, silver, and copper, exist free in nature. The study of electrochemical cells explains the purpose of a salt bridge, and how to change the concentration of a solution in an electrochemical cell to increase the measured volta~e.Some are surprised that two dissimilar metals stuck into a grapefruit ran serve as a batterv. Althuuah rnanv f ~ n dthese endeavors intellectuallv satisfying, others are stimulated by mure practical examples. All itudenu seem to be interested in rheinistrs as applied to more practical "real-world" problems. The topic ofelectrochemistry is especially good a t answering practical questions. Why does one avoid connecting two dissimilar metals, whether in a work of a r t that will he exposed to the weather, or in household plumbing? Why do cities have building codes to define how a water pipe should be connected to the city system? Which is better, to use iron nails in a copper
1) electron transfer 2) proton transfer, and 3) other. Once the jeering subsides, I inform the class that electrochemistry should he important to them because i t deals with the simplest kind of chemical change: electron transfer across an interface. The simplicity of the kind of chemical chnnee " that is considered in electrochemistrv allows us to develop a high level of sophistication in our understanding of the nhvsical changes that accomuanv it. This is noteworthy b;ca;se physical changes accknpany every detected chemical reaction. Thus, while heing in itself important, the study of electrochemistrv also provides us with a unique o~portunitvto investigate the-interplay between chemical-and physical ohenomena a t a fundamental level. I contend that this interplay determines every facet of our temporal existence. This conviction ~rovidesthe basis for my primary goal when I lecture on electrochemistry. I look a t electrochemistry in the same way the Music Man viewed the game of billiards: electrochemistry allows one to develop a "keen eye" and "horse sense" about the necessary interplay between chemistry and physics. With this general goal in mind, let us consider some specific examples. Theory of Matter Electrochemistry is essential to the way that both chemists and physicists think about matter. Through bulk coulometry (chemistry) one may establish the relationship between the mass of an electrodeposited element and the charre necessarv to deoosit it. Because the charge of an eleciron is now known (thanks to Millikan's physics experiment), it is possible to count the numher of electrons passed in this deposition and, if the redox reaction is known, to use this numher t o count the numher of atoms contained within (Continued on page 1019, Col. 2 )
I In planning a chemistty course, some of the most important decisions a teacher must make involve me selection of material to be covered and the time to be devoted to each topic. For each column in tiis series, a high school and a college teacher have been invited to discuss why they feel a particular topic is important and how it
contributes to ma students' understanding of chemislry. (Continued onpoge I019Col. I)
1018
Journal of Chemical Education
