mnething new from the pwt
Edited by: JOSEPH S. SCHMUCKLER Chairman of Science Education Temple University 345 Riner Hall Philadelphia. PA 19122
Topics:
Oxidation Reduction Electrochemistry "Redox Revisited," Karl L. Lockwoad, J. CHEM. EDUC., 38 (19fil). .161,326-229 . The admonition by Inckwood in this 1961 art& is still appropriate Ibr the 1980's. "Teaching oxidation-reduction may develop a great deal of unnecessarv confusion in minds of students if clear distincLions are not made between the concepts of stoiehiornetry and r n ~ c h a n i s mas , well as hetween valence and oxidation state. Reeagnixing that thereare several approaches 1.0 the teaching of balancing complex redox equations, the teacher is urged tu keep in mind that whichever methud is chosen, it is essentially an algebraic process, " . . . and that one method is as good as another." To emphasize his point, Lockwood suggests that " . . . perhaps several methods ought to he taught to the st.udent to encourage him to think his own way thmugh several, thus to see that the process is purely a mechanical ~~~
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"Writing Oxidation-Reduction Equations," A review of textbook Methods. Richard G. Yalman, J. CHEM. EDUC., 36 151, . . 215-218 (1959). Starting with Linus Pauling's statement, "Xe sure t h a t YOU hnou. ,what the wortants n w and what the products arc," Yalman analyzes most of the textbooks in use uo to the time of his writing. Yalman examined th* texts for the following topics: 1) General Advice to the Student 4) Definition of a Chemical Change
:I) Definition and Assignment of Oxidation States 4 ) Definition of Oxidation 5) Methods of W~itingEquatiuns 6) Hydrogen and Oxygen Balance For the teacher who would like to have a quick review of onidatim-reduc1,ion concepts, this article serves such a purpose. "Algebra For Balancing Redax Reactions," Harold W. Ferguson, C h ~ m i s t r y 40 , [Z], 18-20 (1967). Ferguson's article deserihes one approach and serves here as an enampk for the teacher to use. Ferguson ends his paper with problems to be done and gives their detailed solutions. , .. This demonstration and variations of it have appeared many times in the journals. 1,aburatory investigations have been written for beginning chemistry students involving the stoichiometry of the reaction (CHEM Study Experiments 7 and 8, W. H. Freeman and Co. San Francisco, 1960). This article gives complete details for producing a Silver Christmas Tree for next Decemher. Refer also to this feature column that appeared in the October 1980 issue of this journal k,r other references related to the Silver Christmas Tree.
"Oxidation S t a t e Determinations for S o m e Reduction Products of VanadiumsW), A Multi-colored Titration," F. C. Hentz, Jr., Q. G. Long, d. CHEM. EDUC.,55 [I], 55-56 (1978). Of all of the articles found an this most interesting colorful oxidaIton-reduction reaclion, Hent7. and Long give the most complete di-
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Journal of Chemical Education
rections on how to do it. They refer to the CHEM Study film, "Vanadium-A Transition Element," (Rrasted. R.C.. Modern Learning Aids.) Their procedure allows ". . . the student to a b e r v e the four oxidaticm states of vanadium obtainable in aqueous solution.. . ." It can be done both as a demonstration or a laboratory experiment investigated hy students themselves. As an interesting follow up to the experiment, the teacher should read and use "Vanadium in the Living World." N. M. Senozan, .I. CHNM.EIIIIC.,51 181, 503-505 (1974). Sennzan, in addition to citing the presence of hcmowmadin as a respiratory pigment in the corpuscles of certain living animals, gives examples 01' other transition elements needed as respiratory pigments of other living animals. "When Your C a r R u s t s Out," W a r d Knockemus, J. CHEM. Enr~c.,49 .Ill, . 29 (1972). Corrosion of metals is hy far one of the most insidious economic prohlems we face today. The author uses this prublem for illustrat.ing the principle of electrochemistry. He shows, in theory, the tendency for dilferent areas of metal tu be anodic or cathodic employing the Nernst equation. "The Midas Touch," Floyd Sturtevant, T h e Science Teacher, October 1974, pp. 42-45. Here is an aetivitv that has ereat anoeal in that it can oroduce ion, and Avogadm's number using Faraday's Law. In other words, in addition to teaching the principles of chemistry involved, it has take-home value. The pmcedure involves the electrode~mitionof copper andlor nickel on plant leaves. Sturtevant gives ample directions for the ~rocedure.Other "natural nwduets" such as dried insects can be plated also. Indeed this appears tl, he a highly motivating activity for courses in beginning chemistry.
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"Another Mnemonic for Oxidation-Reduction," Virginia Levin, Thp Science T e a c h e r , April (19741, p . 47. I ) L E O t h e lion says G E R Loss of Electrons is Oxidation Gain of Electrons is Reduction 2) R-C cOlA Reduction at t h e Cathode Oxidation a t t h e A n o d e In t h e s a m e issue, same page, Julius Dereo outlines two procedures t h a t have practical application a n d involve oxidatian-reduction. I ) Percentage of H e 0 2 in drugstore hydrogen peroxide. 2) Analysis of'Vitamin C (Ascorbic Acid) in citrus juice. T h e procedure involves t h e oxidation of vitamin C by iodine to a n e n d point using starch indicator t o absorb t h e unreacted iodine. Tn s f e i r l i r C inc m t s snnolmons ot ar' 0.5 ; a v s ot inc .c .aha. and otner F L , ~ ~ CI PF ~ , Lno ~ ~ O,,~O s T ~ ~ . -
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when the topic is taught in a typical high school curriculum. . Joseph S. Schmuckler is currently the chairman of the Department of Education and a Professor of Chemistry at Temple University. ~e was formerly a chemistry teacher at Havertord Township Senior High School in Pennsylvania where hetaught for 15 years.
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