Pictures and Toys
Prepared by: Gale Rhodes, assisted by John M. Daly
It is said that Aristotle believed that life arose spontaneously from the non-living. For instance, he presumed that fireflies have their oriein in the morning dew: the soarkline droplets which lie upon the grass at sunrise disappear as the day passes and, at evening, fireflies rise sparkling from the grass. While we may find Aristotle's observations somewhat imprecise, it is hard to fault him as a theorist. His theory rationalized the facts as he saw them, it was simple, and it was beautiful. These remain the criteria by which we judge our theories, by which we choose our models. With regard to the objects and phenomena we as chemists wish to model, we are more fortunate than physicists, since most of our objects of study can he visualized and simulated with rather simple devices-with pictures and molecular models. While Kent Wilson mizht - refer to these as the Stone-Age implements in our attempts to explain chemistry to our students, for most of us they are the tools which will remain more accessible than the fruits of the computer, a t least for a time. For all of us, if we are thoughtful and creative, they can he vital. They can help in clarification of structural conceots, in teaching. students to work with structures on paper-and in helping concrete operational students grow into formal thinkers (like us, of course!). Aside from those papers which dealt with computer graphics (covered in another Summary Paper), a variety of presentations, primarily exhibits, focused upon the use of the pictures and toys of chemical education. The most imoressive of the non-comouter oictures were I in the ~ a ~ - h i s s o ~format Ge (3). presented by E ~Krakower While he focused primarily on the use of this method in prelah instruction, it is clear that lap-dissolve can provide vivid, inexoensive animation of hulk chemical urocesses like chromatography as well as microphenomena like molecular motions and collisions. Krakower's presentation featured ultraprofessional slides and photography. For those on a tight budget (everyone still listening?) Jane Copes' exhibit showed how to create useful pictures with tin cans and thumb tacks, without expensive photographic techniques-even without a darkroom (I).The user not only produces pictures hut learns the chemistry of ohotoerauhv in the orocess. u . Not only pictures but the answers to problems appear magically in Smith's latent image process (7). Both visible (questions, for instance) and invisible information (answers, perhaps) are run off on a regular spirit duplicator. After attempts to solve problems, the solutions appear, almost PLATO-fashion. under a soecial develooer Den. mimickine computer-assisted instruct& a t low cost. i~nfortunatel< quality control is a problem). In his beautiful presentation of the Chemistry Machine (discussed in another Summary Paper), Wilson stated that, as humans, our hands are very important to us. Molecular models speak to our hands, allowing us to build, to hold, to manipulate molecule-like objects and thereby help us and our students to understand molecular structure and behavior. It modela are used to help us visualv.e things not ea5il.v seen, rhw I i u p p it~is a hopeless task to describe adequately the models on riiiolav at the exhibit sessions. It must sul'fice to tell you a bit of d h a i can he done with them. My son and I have built cars, houses, cranes, and earth movers with Legos", a toy brick construction set. In all those 12 / Journal of ChemicalEducation
hours it never occurred to me to build molecular models with them. I t has occurred to B. D. Kyhett of the University of Regina, Saskatchewan, whose exhibit featured Lego-built models illustrating crystal packing, atactic and syndiotactic polymers and structures for which rotational isomers are possible (4). While sp2 and spQybrids are difficult to con-. struct, s p V and spQ2 hybrids work quite well. I was unprepared for the variety, accuracy and illustrating power of models made with nothing more than paper. Larson of Ferris State College, with deft hands and rapid patter that would befit a medicine show, whipped up tetrahedra; diamond unit cells; spiral models and R/S analyzers; Ce, hicyclic, fused-ring and cage structures; and polypeptide and steroid simulacra (5).And then he got rolling, with an exhibit as much art as science, and a good example of hoth. Many of his structures were based upon "cubelts," strips of paper folded repeatedly a t 60" (for tetrahedra and octahedra), 90" (for cubic units and stacked cubes) and 110' (for Cs and Cgrings). I plan to write him at Route 2, Box 234, Big Rapids, Michigan, and order "one of each," 30 (count 'em) items for $7.40. You may wish to do the same. I am not on commissiou, but I know a bargain when I see one.
All models are adequate to only a limited number of tasks, since, as Jacob Bronowski has said, they are architectural analogs, taken from the world of sight and touch, used to explain objects ultimately unknowable. Piper, who uses laboratory exercises with molecular models in his organic chemistry courses a t Simmons College, displayed these exercises and also pointed out the stren&hs and weaknesses of various types o f commonly available models (6). Ball-and-stick models locate nuclei clearly, hut fail to delineate van der Wads or contact radii; framework models show bond angles and orbital orientations, hut, nuclei and, again, van der Waalsradii are difficult to see; space filling models show the contours of the molecule, hut disguise nuclear position and bond angle; and all of them make bond distortion aooear too eaw while bond vibration looks impossible. Thus choose thlmodel which best does the iob we want to do. and we are constantlv reminded therehy that nature is eve; more subtle than we suuoose, or can suouose. .. Walking away fiom these exhibits I was struck, as I am so often, with the power of these simple pictures and toys. Mixtures of pigments, cellulose sheets, plastic blocks and metal uins build for us a foundation in realitv of thines never observable. They provide for us the beginnings of the under-
st:inding 01 the l'orres of nature; forces which mold under a .;tar-flvcked ik\. the dew\ dmolet. which direct the chnnee of state which is the dew drip's &wdaily disappearance, firces which set in motion the fireflv to sparkle and to evoke wonder. that catalyst of human understanding. Annotated Bibliography (1) Copes, Jane, Out i n t h e Open: A Non-Darkroom Photography Experience, Tompkins-Cortland Community College, Dryden, NY 10353. (2) Hoffman, D. K., Ruedenberg, K., and Verkade, J. G., A Novel Pictorial Approach to Teaching MO Bonding Concepts i n Polyatomic Molecules, Department of Chemistry, Iowa State University, Ames, IA 50011. (3) Krakower, E., Lap-Dissolve Slides: Multiple Use Formats f o r Pre-Laboratory Instruction and Appli-
(4) (5)
(6)
(7)
cations of Image Registration Techniques t o Chemistry Instruction, Rochester Institute of Technology, Rochester, NY 14623. Kybett, B. D., A Cheap Molecular Model Kit f o r Students, Department of Chemistry, University of Regina, Regina, Saskatchewan, Canada S4S OAl. Larson, G. Olof, Show I t with '~nbelts': A Demonstration-Workshop Presentation and Survey of Paper Models f o r Molecular Structure, Department o f . Chemistry, Ferris State College, Big Rapids, Michigan 49307. Piper, James U., Molecular Models Exercises i n Beginning Organic Courses, Department of Chemistry, Simmons College, Boston, MA 02115. Smith, Wesley D., Latent Image: Another Useful Gimmick, Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
Volume 54, Number 1. January 1977 / 13
