mnething new From the p a ~ t Molecular S~~UC~UN?: "HOWDOWe Know What We Know?" A s t u d e n t came UD t o m v demonstration table after class o n e d a y a n d asked "HOW 20 you know what you t h i n k you know about molecular structure and behavior?" M v attemnt to answer was less t h a n satisfactory. T h i s month's article reviews a r e intended t o give t h e teacher some background resources to answer this question. "The Electromagnetic Spectrum," Albert F. Eiss, The Science Teacher. 34.61 (1967). . . . "An understandiug ofthe electromagnetir spectrum is. . . impartant in sci~nre.In addition w the phycical n n w p r s related t~ frpquency and wavelength.. .waves are particularly important in the field of communication. . . radio, television and optics. Almost all of our information about the sun and our universe.. .and the atom itself comes from an understanding of the electromagnetic spectrum." Eiss presents a rather complete diagram of the electromagnetic soectrum that is easilv reoroduced for students notebooks. In addition, his suggestions.for'graphing the spectrum can be useful in visualizing and understanding exponential notation.
Looking at the Visible Spectrum "A Readily Made Simulated Optical Spectrum for a n Overhead Projector," Colin J. Rix a n d Keith A. Phillips, J. CHEM. EDUC.54,579 (1977). "The projection of a large image of an optical spectrum is often useful for teaching simple concepts as an introduction to visible ahsorption spectroscopy!' In this paper the authors "present a means of producing a useful approximation to an optical spectrum." A series of 15 solutions are detailed alone with soecifies of cell construction. "Uaing these demonstrati~ns.11 ran be readily shown that the transmittrd colur of a solutiun isa result oftherel~ctiveabsorption of light from sertions ofthe vistblesp~rtrum." ~
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"A Mass Analogy for Milikan's Oil Drop Experiment," Rubert E.Glasser. Thu Science Teacher.. 37.82 . tlYiOl. . "To introduce Milikan's Oil Drop Experiment and the concept of quantization of charge. . .an analogy using 20-30 marbles (all of the same mass), a wide mouth container and a balance (readable to 0.1 g) are very useful." An excellent chart, showing the Milikon Experiment and theMass Anoloev -" is .oresented bv the author. I t is indeed a good analogyand good teaching exercise! The container withallof the marbles is placed on the balance and the class is asked to suggest how the mass of one marble might be determined.
Some Construction Projects 1) "A Simple Sp~ctroscupr,"Dnrid Fansler and Paul B. Hounshell. The Sozncr T+.acher,42,54 rl9?3,. Based on Fraunhofrr's de. 2)
3)
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sign, thissimple spectroscope hnsenouph rewlutiun tosplir the sodium doublet. "A SimplePolariscope," WilliamVan Doorne, J. CHEM.EDUC., 47,699 (1970). This device is "constructed from readily available, low cost materials." "An Inexpensive Refractometer," H. Courtney Benedict, Chemistry, 47,27 (1974). Theconstructicinand calibration of this instrument used to study the index of refraction is given in this well-detailed article. "Optical Rotation," J. G. M. Evans and H. R. Tietze, J. CHEM. EDUC.41, A 973 (1964). "A Device for Easy Demonstration of O p t i d ActiGty and Optical Rotatory Dispersion," John B. Kinney and JamesF. Skinner, J.
Edited by: JOSEPH S. SCHMUCKLER Chairman of Science Education Temple University 345 Riner Hall Philadelphia. PA 19122
CHKM.EDIIC.54,494 119771. Good ronstruction directionsaw riven. ax are expected ohr~rvations.The authurr claim superior demonstration of optical n,tat-". -,. This article is the first (of eieht) in a series that exolore the manv kinds of soectroscoov . . . used in;ci&ce. The first sev& articles eganline fundamental concepu common to all spectnwcopic meaauremcnts-the nntur? 01' light, the elrrtrumagncric spectrum, and the interaction of radintim nnd ntatter. " [ T ~ remaining P artilks uf the series] . ..study specific techniques and application including emission spectroscopy, infrared spectrophatometry, nuclear magnetic resonance and others . . . [visible and ultraviolet absorption spectroscopy]." ~
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T h e next three articles a r e instructional b o t h i n the theoretical content and i n technology a n d application. "Infrared Spectroscopy: A Chemist's Tool," George C. Pimentel, J. CHEM. EDUC.37,651 (1960). Teachers using the CHEM Study and its "offsprings" will recognize Dr. Pimentel as the editor of the original text published by Freeman and Company. "The purpose of this paper is to explain why this branch of spectroscopy has assumed such a role of prestige in chemistry." Pimentel enumerates six types of applications and examples of great interest to chemists. Volume 59
Number 12
December 1982
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"Atomic Ahsorption Spectroscopy," Robert D. Brown and Joseph P. Sapio, Chemistry, 47,9 (1974). "Atomic ahsorotion analvsis is a relativelv . simole. . ~inexoensive. .. -. sensiriw, and accurate method to determine trace nmounts of numerous chemical elements. I t has lrerwna a useful analyrirnl m~thud in clinical chemistry, geology. and pullu~ionanalysis . . ." "Scientific Instrumentation in Criminal Investigation," Alexander Joseph, The Science Teacher, 36.38 (1969). "Progressive police agencies constantly strive to use the most effective investigative approaches in their continuing battle with the criminal elements of the community." Instrumentation allom a so-
1028
Journal of Chemical Education
called nondestructive analytic technique that preserves evidence. In his article Professor Joseph describes the uses of various nondestructive techniques including emission spectroscopy, gas chromatography, infrared and ultraviolet spectroscopy, X-ray diffraction, mass spectrometry, and neutron activation aGlysis. This last article is excellent as culminatinc readine for this month's reviews. After reading especially thLlast fivearticles, I believe that the teacher of beginning chemistry classes could give a good understandable answer to the student's question, "How do we know what we know about molecular structure and behavior?"
