teaching aids I
Evergreen State College Olympim, Wmhington 98501
Molecules and Life McGrow-Hill Films, 1221 Ave. of the Americas, New York, New Yark 10020.20 min, 16mm. sound, color film. This film brings to the screen some monumental work hy five Nobel laureates in a most enlightening and well-developed sequence of film. Dorothy Hodgkin (Nobel Prize, 1964) effectively communicates her research efforts in X-ray analysis in determining the 3-D structure of vitamin B m She cites the early work of Sir Lawrence Bragg (Nobel Prize, 1915) who developed the use of the X-ray analysis in crystallographic studies. Dr. Frederick Savger (Nobel Prize, 1958) follows with a n exciting narrative of his work. An animated sequence an the chemical methods used to determine the amino aeid sequence of a protein is effectively made clear. Savger's work in elucidating the amino aeid sequence of insulin is modestly explained when Savger says, "Strange, but it's never quite so difficult once you've done i t before." Another highlight of this film is the discussion by Max Perutz (Nobel Prize, 1962) and John Kendrew (Nobel Prize, 1962) of their separate research efforts on the structure of hemoglobin and myaglobin. Avoiding needless technical terminology, the film introduces students to some rather sophisticated concepts in X-ray analysis of 3-D structures, the chemical analysis of proteins, and some principles of paper chromatography. Efforts to provide evidence of the 3-D structure of proteins are discussed giving the viewer some insight as to the laborious, time-consuming task of building molecular models. The student is correctly led t o believe that such important research reveals something of the biological func-
relevant. Transition from researeh effort t o research effort is surprisingly smooth as the film reveals the work of the five Nobel prize winners. The film sequences with the Nobel laureates had a granular effect on the 16mm film which is not oarticularlv lea sine. but does
min of filming. Students and instructors will gain by having seen "Molecules and Life."
C. Benjamin Meleca The Ohio State University Theory of Crystal Growth McGrow-Hill Films, 1221 Ave. of the Americas, New York; New York 10020.20 minutes, 16mm, sound, color film. The film, Theory of Crystal Growth, is an excellent aid in augmenting the study of crystals and crystal growth a t the junior or senior level. It could be of interest to a general chemistry class, hut unless considerable preliminary information has been given the class, many of the illustrations and terms used will not be understood. The film shows first the idea of close packing by the use of spheres, and gives the concept of average binding energy per atom, along with the idea of cubic and octahedral holes. The concept of cubic and octahedral faces to certain kinds of crystals are then introduced. At this paint, illustrations are given using the growth of silver crystal as a n example. The illustrations using the deposition on a single crystal and the contrasting device show beautifully how the crystal growth proceeds. It is not clear from the film, however, whether the 642 /Journal of Chemical Education
Film Reviews gmwths are speeded-up or are actual rates from the solution. The idea oi screw dislocation is then introduced and illustrated again with solid spheres to give the student a sound concept of what this term means. The spiral growth is seen in actual crystal growth, again using the contrast device and microscope. The "Frank Theory" of crystal growth, introducing the concept of hidimensional nuclear site, is presented both in illustrations using spheres and actual crystal growth. All in all, it proves to he a n interesting and informative film for students interested in crystals and crystal growth, even though they may have considerable variation in background. However, the students should be familiar with certain terms before they can get the most out of the film. Such terms as cubic and octahedral holes, dodecahedra/, rhornbadoeeeohedral, close pocking, oueruoltnge, are used mostly without definition or illustration. The students will get much more from the film if these have been discussed beforehand, It is also desirable for the students to have a general idea of crystals, including the concept of single crystals, crystal systems, and some other types of crystal imperfections. Charles Caughlin Montann State University
Wondering about Things For Purchase: Modern Learning Aids, P.O. Box 302, Rochester, New York 14603. For Rental or Free Loan: (as a sponsored film, when available) Modern Talking Pictures, Znc. (any local office) or Modern Talking Pictures, Main Office, 1212 Avenue of the Americas, New York, New York 10036. 22 mi", 16mm, sound, color film. This perfectly delightful film makes you do just that-wonder about things-ven though I have the feeling that its intent is to defend science and scientists and research. It consists of 20 min of what I consider "cameo" shots, the longest of which may be 30 see but most are much much shorter. Several segments consist of many rapid-fire pictures of scientific historical significance that take you back many years and bring you t o the present very rapidly. The film is introduced very effectively by those most curious of all-children-and then proceeds through a series of questions asked of several people from all walks of life, from the research scientist to an economist, a n artist, housewives, the man on the street, and students. Following each question and the responses by the people is quite a bit of chemistry that is easily visualized and understood regardless of one's background (Fig. 1). I feel that the film could be shown to virtually any type of audience; a chemistry class, a history of science class, nonscienee majors, an ecology club, etc. based upon the feelings of my Environmental Chemistry class (nonmajor, terminal students) who viewed the film with me. To quote them "There is something in it for everyone." Cliffcrd C. Houk Ohio University
Collision Dynamics of Chemical Reactions Harper & Row, 10 East 53rd Street; New York, New York 10022.20 min, 16mm, sound, color film. The availability of CRT computer output devices has made it possible to display the calculated time behavior of a system in the form of animated sequences. We can now see the molecules in a hard sphere fluid as they collide with each other in ultra-slow motion, or we can trace the path of a molecule as it diffuses through a liquid. Collision trajectories can also be illustrated in the same way. The film, "Collision Dynamics of Chemical Resc-
material is summarized by the simultaneous reprise of earlier scenes on a split screen. The images are too small to be seen and are on the screen too briefly to be followed. This shortcoming is symptomatic of the film. The images and the narration would he suitable for a hwk, where they could be studied and reviewed a t the student's own pace. But they are seen too briefly and taa densely-packed for a film. The film is an example of goad and exciting science that has been amateurishly packaged and organized without sufficient thought about its audience. Selected clips from i t probably could be used to ereat advantage to illustrate soecific ooints in both introductory and advanced courses, but i r is unlikely rhnr i r w.l ha advnnrngeotns m ure i r in itsenrlrery.
Chuck Knobler Uniuersity of Cali[orn~o Mechanism of an Organic Reaction
Figure 1. Animated and slow moton sequence from "Wondering about Things" showing properties and Characteristics of polymer. tions" by Martin Karplus shows the results of classical calculations of trajectories for T Hz. Circles representing the atoms fly across the screen and collide; t o give a three-dimensional effect, their diameters decrease and increase as they move away and toward the viewer. This is a tantalizing film. It demonstrates how the eomputer/film combination can make complex molecular motions and interactions real to the student-much more clearly than words, drawings, or the hand-waving descriptions by the tescher-but i t has major copceptual and technicalsbortcomings. It is difficult to think of any specific group of students for which the film is suitable. The a o ~ r o a c his essentiallv, encvela. pedir. I t begins with a d~monsrratwn01 four haw 1"pt.s of rulll. sions elact~r.melastlc, reactive, and drsociative. The I' - H2 pcrtentlnl cnerm sunace i, then introducrd. but the discussion nf its features is so condensed that it is meaningless to the elementary student and superfluous for the advanced student. In another section, the terms impact parameter and scattering angle are defined, and the qualitative relation between the two quantities is mentioned, but there is no further development of these ideas. The effect of collision energy on reactive collisions is nicely demonstrated, but the.advanced student, for whom the distinction between abstraction, displacement and stripping is of interest, should he told something more about the energies involved than the qualitative terms low, intermediate and high energy. Other sequences show comparisons between trajectories far a simple barrier and one with a well. The transfer of energy between translation, vibration and rotation is beautifully shown in some of the trajectories, and this is pointed out in passing. The CRT display used to produce the film was apparently not of "broadcast" quality. The images are fuzzy and numbers used to identify the atoms are barely distinguishable. Even poorer is a contour plot of the potential energy surface. It is very dark, the scale is so small that the contour lines run together into a blur, and the coordinates are illegible. At several points in the film
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Douidson Films, 1757 Union Street, San Francisco, California 94143. 19 min, 16mm, sound, calm film. It is not clear t o me for what level this film is best suited. It would appear to be useful with high school students after a semester or so, hut it also could be viewed with beneficial results by students in a beginning organic course. As is usual with the CHEM study films a good deal of serious thought has gone into its production. The question raised by the film is: "What is the mechanism of hvdrolvsis of rnethvl benzoate?" To begin with the reactants (methi1 benzoate and water containingiodium hydroxide) are identified and it is shown that after they are mixed and stirred all of the methyl benzoate disappears (there are no longer two phases) (Fig. 2). Methanol and benzoic acid are identified as products of the reaction. As was pointed out by one viewer, this lesson (if you want to talk about the mechanism of a reaction be sure to identify the products) has not been learned by some research chemists. The equation for the reaction is shown using molecular models of methyl benzoate, water, henzoic acid, and methanol. The similarity in structure of most portions of the initial and final malecules leads to the question of the origin of the oxygen in the benzoic acid. Does i t come from the initial methyl benzoate or from the water? The method of answering this question involves synthesis of 1"-labeled methyl henzoate and analysis of both products by mass spectrometry. A good deal of time is spent explaining how the mass spectrometer works. A bright student is likely to ask why bother with the synthesis of labeled methyl benzoate. One could simply label the water and see where the 'W iis found. A high degree of sophistication is required to understand the advantage of the procedure in the film, and it is not essential to the results obtained therein. Finally, the proposal that a n S N mechanism ~ is involved is tested by hydrolyzing methyl-2.6-dimethylbenzoste.The prediction that the rate of reaction will decrease due to the steric effect of the methyl groups is confirmed. However, the experimenters fail t o test the possibility that the decreased rate is due to decreased solubility of the substituted ester in the aqueous phase. Details such as this and the method of labeling the ester could serve t o initiate further discussion in an organic course, although they prabahly would pass unnoticed in an elementary course.
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Figure 2. Scene from "Mechanrsm of an Organic Reaction" showing the hydroiysisot methyl benzoate. Volume50, Number 9 , September 1973 / 643
All in all the film comes off well. It is particularly good a t emphasizing the relatively small changes in structure which accompany many organic reactions and the methods by which one might distinguish between them. Ratings by shout fifteen viewers were: Excellent, 16%; Good, 70%; Fair, 7%; Poor, 7%. John Moore Eastern Michigan University
Modern Methods of Chemical Analysis Mass Spectrometry Educational Seruiees, John Wiley & Sons, Inc., 605 Third Avenue, New York, New York 10016. 33 min, 16mm, sound, color film. Mass spectroscopy, nuclear magnetic resonance, and chromatography are, of course, valuable tools that teachers will often refer to in a variety of courses. These films provide ready access to introductory explanations of the theory and application of the respective techniques. The presentations in every case are concise and well done. It may be that some will feel that too much has been sacrificed for the sake of brevity, but the films will certainly provide a point of departure for discussion by the instructor. "Mass Spectrometry," by Pecsak and Sudmeier, provides adequate answers for the questions posed in its hilling: Haw does a mass spectrometer work? How is a mass spectrum obtained? What kinds of information are obtained? What is the relationship between precise molecular weight and the chemical formula? What are some of the common ways in whieh molecules fragment? The descriptive analogies and animation do a fine job of explaining the m/e:radius of curvature relationship, end the general operation of a mass spectrometer. It shbuld be noted that various sampling techniques, including GC interface are neatly included. Several examples of molecular interpretation are presented with explanations offered for the origin of the various peaks. The use of both high and low resolution data is explained. The use of M 1 and M 2 information is summarized. I t would have been nice, however, to have introduced the P 1 and P + 2 designations far these peaks, in the light of their use in a number of current texts; and further it would have been warthwhile to describe how the parent peak is identified. The nitrogen rule for parent peaks is another unfortunate omission. Metastable peaks are mentioned, but only in passing, and their usefulness is not indicated. In summary, a very useful introduction to a technique that will undoubtedly be presented at some point in any chemistry euniculum.
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Nuclear Magnetic Resonance Educatioml Seruiees, John Wiley & Sons, Inc., 605 Third Avenue, New York, New York 10016. 28 min, 16mm, sound, color film. "Nuclear Magnetic Resonance," also by Peesok and Sudmeier, is again a quality production. It provides a nicely animated illustration to develoo the resonance uhenomenon albeit the exulanalions ow a bit rryptlc. ('hemica1 shifts rrsulting fmm inductive elfrcrs art- presented by d~amarneticankotropy is not. 'l'hc use 01 tms .s rlearl) stated but, unfonunntdy, the inductive eiferts just established are not used to explain why tms appears where it does nor why it is the reference of choice. Resonant frequency, frequency shift, and ppm shift are all mentioned, but will require clarification by the instructor. In a similar way spin-spin coupling, J values, and failure of like protons to spin-spin split will require follow-up explanations. Peak broadening lmm field inhomogeneity is stated but unfortunately not explained: and this point could have profitably used animation. Solvent requirements and selection are not covered. These are examples of numerous slights in this film, but they are undoubtedly predicated on limited film length. That which is presented is done well and will provide an excellent introduction upon whieh the instructor can build. One isinclined to suggest that a Part 11is in order for nmr. ~~~~~
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644 / Journal of Chemical Education
Chromatography, Parts I and l l Edueotianol Seruices, John Wiley & Sons, Inc., 605 Third Avenue, New York, New York 10016. Part I: 28 min, Part 11: 20 min, .16mm, sound, color. "Chromatography, Parts I and II," by Hamld MeNair, is a gwd resume of a variety of techniques. Partition, adsorption, permeation, and ion-exchange are used to categorize the various separation phenomena. Gas-solid, gas-liquid, liquid-liquid, and liquid-solid designations are used to illustrate the numerous manifestations that chromatography can take. Animation is used to advantage in describing mobile and stationary phases, and is particularly effective in illustrating the partition process. The part on gas chromatography would be much better if isothermal and temperature programming had been described along with their relative merits. As one views the animated readout, it is difficult to assess which process is heing used. The use of log-retention times for homologous series identifications is unfortunately not presented. The use of more than one column for identifications would also have heen welcome. The concept of theoretical plates is presented with no real rationale for its use. Column efficiency is described and related to column length (no mention of diameter. however); and bases for choice of liquid phases are given. Liquid chromatography via column and thin layer is described, hut again omissions are apparent, i.e., descending and ascending column techniques are illustrated with no reason given for choice. Gel permeation is described, but somehow the animation which I would have expected to be a natural is not impressive. Citing points that one would have liked to see included should not be construed as serious criticism of the value of these two films. Chromatography comes across as a valuable tool and a good deal of gmund i~ covered in a short presentation. They will he valuable aids to an instructor, but he prepared to elaborate and clarify. Graeme L. Baker Florida Technological Uniuersity ~
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The Chem Tech Chemical Technician Curriculum, Lawrence Hall of Science, Berkeley, California. 18 min, 16mm, sound, color. I must admit that I was a little apprehensive before I saw this film-the reason heing that I started my chemical career, and subsequently worked for several years as a Chem Tech. The film pleasantly surprised me. The approach was certainly a very credible one. The young people appeared sincere and were obviously "sold" on their careers a s chem techs! I thought that the film was particulary honest (this was important!) when it tackled the motivational aspects of why one became a chem tech in the first place. The girl technician was particularly impressive in this respeet-the right blend of interests, background, sincerity, etc. I was a little worried about statements made during the film about "the only math I needed . . .," was "slide rule math," or "machines and computers do the major part of calculations," or "I didn't need calculus." Obviously this is a laudable attempt not to try and scare people away from a career as a technician, hut 1 wonder-is math background one of the realistic problems that affects a young person's choice of a chem tech career? My major criticism of the film is that there was no obvious example of a chem tech working in the area of commercial quality control or actually working in an industrial environment (plant etc.!). Surely a major proportion of chemical technicians are employed in just this kind of situation. Not everyone is going to wind up operating an esoteric vacuum line or a high resolution nmr spectrometer! A glimpse of the role of the chem tech in the area of water waste treatment-a rapidly developing area, would perhaps have been warthwhile. Other than the above criticisms, I think the film was well photographed, the color was good and the people "sell" excellent! Apprehension turned to Nostalgia! Stephen Thompson Colorado State Uniuersity
