EDUCATION
Models — Versatile Teaching Aids Whether it's the structure of metal alloys or inorganic complexes, models explain it better steric effect in steric hindrance can be shown. However, because of the char^ N ^ M A S figuration in •JM&QHGjxaf space, difficult foracteristics of materials of construction the student to vis- and compromises that must be made ualize, is made in design, models still cannot be conextremely clear if structed to represent some organic comthree - dimensional pounds of known structure. Even with models are used as a teaching aid. these limitations, the model presents Confusion in interpreting pictorial rep- a much clearer picture of steric factors resentations in a flat plane of relation- than can be obtained in any other way. Atomic and molecular orbitals can ships in space is eliminated if the student can see and handle models of the be clearly represented by a unique system of models developed by Frank actual structure. But enthusiasm over the value of L. Lambert of Occidental College. models as a teaching aid should be Constructed of Styrofoam, these models tempered by the realization that there are unusually large, the scale used being are some pitfalls connected with the one inch to an Angstrom. Styrofoam use of these devices. The student must was chosen as the material of conrealize that models are far from perfect struction because it can be fabricated and that the model is a representation fairly easily, in contrast to the difficulof a structure, not the actual structure ties encountered in working with hard wood, the usual material. In addition, itself. Here are some of the many ways that Styrofoam can readily be dyed and models are being used as demonstrated colored. In Lambert's system, colors are used at the symposium on the use and abuse of models in teaching held by the Di- to distinguish the orbitals. For example, s orbitals are vivid scarlet while vision of Chemical Education. To J. A. Campbell of Oberlin College, p and pi are purple. Some of the effective models need not b e expensive. models can be taken apart to show Using solid wooden spheres about the cross-sections with the probability patsize of croquet balls, Campbell con- terns for the location of the electrons structs pyramidal models that can be plainly delineated. From his experience so far in using used to illustrate principles of metal structure and properties. By stacking these models in teaching general and the balls inside a movable wooden base, organic chemistry, Lambert says that external stress can be applied so that the models convey ideas of atomic and dynamic behavior leading to fatigue molecular orbitals better than the best text illustrations. cracking can be shown. • Inorganic Too. Nearly every type If smaller spheres such as ping pong balls and marbles are added to the of isomerism known in organic chemoriginal spheres, Campbell can use the istry has its counterpart in inorganic model to illustrate such properties of chemistry. Most of the examples are solid chemical compounds as solubility found among coordination compounds. and reactivity. Big advantage of To John C. Bailar, Jr., of the University Campbell's models is that they are of Illinois, models are almost indissimple, cheap, and can be constructed pensable in teaching the stereochemistry of these complexes. from readily available materials. T o show the structural relationships • A Must for Organic. Understanding problems in the field of steric inter- that give rise to the isomeric forms, ferences is made much easier by the Bailar has constructed a series of "stick" use of models, says Alsoph H. Corwin models. These models can b e easily of Johns Hopkins University. Yet it and cheaply built using dowel pins and is in this field that imperfections in small, colored wooden balls. Those models are most apparent. In earlier home-made models can be used to illusdays, models fell into disrepute when trate the stereochemistry of both tetrathe tetrahedral models then in vogue hedral and octahedral complexes. Commercial models used in teaching could not explain the formation of cerorganic chemistry can easily be moditain compounds. Models in use today have overcome fied to show the stereochemistry of inthese defects. With them such things organic compounds. In some cases, as strain in rings larger than six, color Bailar prefers to use these commercial and strain, and the magnitude of the models. For example, in demonstrating *•—-* «!«£?*•'-»
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By applying external stress to model, J. A. Campbell, Oberlin College, shows dynamic behavior of molecules
With t h e s e Styrofoam models, Frank L. Lambert, Occidental College, explains molecular and atomic orbitals
Alsoph H. Corwin, Johns Hopkins, demonstrates a dynamic model illustrating infrared frequencies of benzene
EDUCATION the mechanism of chelation, the commercial models show more clearly the actual sequestration of the metallic ion. The type of model chosen depends on the purpose for which it is to b e
used. In Bailar's opinion, stick models are adequate for most class demonstrations, but for advanced courses and research studies, the commercial models, built to scale, are preferred.
Is Qua! Disqualified? Educators hold divergent views on importance of qualitative analysis in modern curricula
Quali The trend in college curricula today is to eliminate qualitative analysis as a separate course and combine it with t h e course in general inorganic chemistry. In fact, in 1950 qualitative analysis was included in the second semester of t h e course in general chemistry in 50% of the colleges in this country, compared to 3 5 % in 1940. Yet, to many teachers, qualitative analysis must continue to b e taught as a separate course because the basic chemical principles learned in an intensive study of qualitative analysis are of tremendous importance in professional development. It is i n this course, they say, that the fledgling chemist learns the principles of ionic equilibrium and the chemistry of metals. Here are some of the views on teaching qualitative analysis expressed by participants in a symposium on qualitative analysis held by the Division of Chemical Education. • Modern Trends. Development of modern instrumental analytical techniques, such as spectrographic analysis, has outmoded the wet analysis procedures of classical qualitative analysis. Therefore, according to Esmarch S. Gilreath of Washington and Lee University, less emphasis should be placed on laboratory work in present day courses. Instead, major emphasis should be placed on the broad theoretical aspects of qualitative analysis. The most important of these are t h e laws and theories pertaining to the various forms of equilibria that may exist in aqueous solution, such as ionization, solubility, complex formation, and oxidation-reduction. However, in taking the theoretical approach to teaching qualitative analysis, great care must be exercised, to avoid making the course a rehash of
general chemistry or having it degenerate into a diluted presentation of physical chemistry. At Indiana University, according to Frederic C. Schmidt, integration of qualitative analysis into the second, semester of first year chemistry has been very successful. This system, in use for the past five years, i s not designed to teach analytical chemistry, but, Schmidt says, qualitative analysis is used as a scheme to teach the chemistry of metals. With the instrumentation now available, laboratory training in the classical qualitative separation schemes is not necessary. One of the advantages of integrating qualitative analysis with the chemistry of the metals and their compounds is that the ideas of solubility product, ionization constants, and complex ions are put where they belong and are in better perspective for comprehension by the student. Another advantage of integrating the two subjects is that a separate course is eliminated from the already overcrowded chemistry curriculum. • Keep Qual Alive. Decrying the modern trend of downgrading the qualitative course to streamline the crowded undergraduate chemistry curriculum, Henry Freiser of the University of Pittsburgh made a strong plea to return qualitative analysis to its proper place in the curriculum. Brilliant developments in instrumental methods of analysis seem to have overshadowed the role of separations processes i n analysis. Yet, Freiser points out, knowledge of separations is extremely important. For example, the chemist's chief contribution to atomic energy has been the development of separation processes. The principal function of qualitative analysis in Freiser's opinion is not t o teach detection, but to give the student a thorough grounding i n the principles of analytical chemistry It is i n this course that the student will learn what he must know about the chemistry of metaiS, ionic Gqui-iioriurxx, und tiie basis of analytical separations.
To Frederick C. Strong III of Stevens Institute of Technology, the qualitative analysis course should teach analysis. From a study of methods used in some commercial laboratories, Strong concludes ihat the classical fractional precipitation scheme for cations is outmoded. For this purpose the laboratories make spectrographic determinations or use spot tests. However, anion procedures usually taught in colleges are used extensively. For a modern course in qualitative analysis Strong suggests that determination^of anions should be emphasized. Brief mention should be made of hydrogen sulfide separations, but no laboratory work should b e done in this field. Instead, the theory of arc, spark, and flame spectrography should be taught. Practical training in the use of the spectrograph should b e given. However, Strong warns, heavy emphasis should b e placed on the theoretical approach to avoid training technicians instead of analytical chemists.
Problems in Teaching Organic Analysis teach
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• ranged to produce analysts ready to g o to work in an industrial laboratory? Or should our goal b e to produce competent chemists thoroughly grounded in the basic principles of organic analysis? These are some of the questions discussed at a symposium "teaching organic analysis," held jointly with the Division of Analytical Chemistry by the Division of Chemical Education. To Nicholas D. Cheronis of Brooklyn College, the reason for teaching organic analysis is not to train industrial analysts but to give students thorough training in the fundamental principles of chemistry. Once the fundamentals have been acquired at the undergraduate level, the mechanical details can be learned on the job. To teach qualitative analysis, Cheronis combines the classical procedures such as crystallization and distillation with the most modern procedures such as those using adsorption and ion exchange. But in teaching quantitative analysis, h e uses what he calls the chemical approach. According to Cheronis, the traditional approach t o functional group analysis consists of a few elegant methods applicable to only a selected numOCT.
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