Joseph Nordmann
Lor Angeles Valley College
The Introductory Chemistry Laboratory and the "Real" Sample
Van Nuys, California 91401
Dare we tell what chemists do?
If
for a moment one can divest himself from overconcern about instructional purity and dispassionately regard the fare fed beginners in chemistry, he will come upon some questions which should not be dismissed lightly. Consider that the laboratory often is little more than exercises in retesting well-tested laws, redetermining handbook constants, and analyzing artificial unknowns. Add to this homework and examinations consisting of theoretical problems which aver that the outlines of science must remain forever shrouded to anyone without considerable mathematical skill. Then add lectures of conceptual physics and thermodynamics which seem to say that chemistry is a grim form of mental calisthenics derived from first principles by a few genius minds. How much distortion and confusion does this implant in the impressions beginners get? If they are asked a t the end of such experience to write essays on the significance of chemistry and the activities and contributions of the country's two hundred thousand chemists, how close can they come to the essence of what we are actually doing? Reality as a Unifying Idea
At Los Angeles Valley College we have been trying to circumvent the self-incrimination implicit in the teaching described above as we revise a one-semester nonscience majors' survey course we call Chemistry 11. Few of the students in this class have had high school chemistry. Most of them are taking programs which call for their registration the following semester in general chemistry, our Chemistry 1. Each week, Chemistry 11 meets three hours for lecture, two for quiz, and two for laboratory. In changing the laboratory program (lectures are still fairly classical) we have been guided by one desire: to let the students experience the things chemists do in research and industry. This apparently trivial unifying idea is surprisingly innovative and controversial when strictly applied. By recognizing that chemists do not work per se with principles but rather with problems and apparatus which principles underlie, we were able to junk the pure principles exercises that have been anathema for far too long and atypical of science-the kind whose ideas cannot be fairly tested by freshman apparatus, which have no interest, or meaning in the student's future, and Presented as part of the Seventh Annual Two-Year College Chemistry Conference. The Conference, a program of the Division of Chemical Education of the American Chemical Societv. was held at Miami-Dade Junior College just prior to the SO& ty's 153rd Meebing, April, 1967, at Miami Beach, Fls.
whose answers can be guessed by reading the book. To be fair in substituting for these, we reinforced our assumptions on how chemists are employed by visiting forty local research, industrial, governmental, and private laboratories before concluding those people functioning as analysts could model for us best; that is, their work could he translated to the classroom to teach the principles we agreed are important. It was but a short step then to adapt a series of experiments to our purpose and stipulate that only "real" samples be considered as a particularly economical connection between theory and practice and one fulfilling the full scope of the promise of liberal arts. The Laboratory Program
Our program comprises seventeen experiments (more than enough for a semester's work) in the following ten categories. 1. Physical Properts and Measu~ementsintroduce basic techniques of instrument r e d m g and limitation, data graphing, error evaluation, and the determination of several physical properties of matter: density, bailing point, melting point, viscosity, refractive index. 2. Librarg Oricntatia-a, homework assignment in the library giving practiee in finding scientific-technical references that will be needed for lab notebook writeups, research projects, and support reading. 3. Gravimetric Analyses-these range from desicoation of foods to determination of silica in cement; manipulative techniques are kept to a minimum. 4. Qualitative Anolyssesinclude classical ion tests, paper chromatography, chemical microscopy, and the electrographic technique; give experience in conducting reactions, writing equations, and reasoning inductively from nhservntions. ..-. ~
6. Gas Analysi~illustmtesgas behavior snd gas calculations. 8. Volumet~icAnolyse-how methodology and stoichiometry
in precipitation, acid-base, camplexrttion, and redox. 7. Colorimelry-illustrates this analytical method both visually and instrumentally. 8 . v H bu Indicators and Glass Elect~ode-uses acid-bsse concep&, the water equilibrium, and the pH meter. 9. Electx$ating and Ektrograuirnetq--demonstrates chemicalelectrical relationships. 10. Organic and Colloid Chemistry-investigates the preparation and analysis of emulsifiers and practical emulsions, and certain riactions that lead to polymers; polymer properties are evaluated and related to structure.
Organization of Experiments
Each experiment is written for lahoratory execution and quiz section review in the following pattern. Introduction-orients the student at aome length to the problem and its investigation; gives background material not duplioated in texts.
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Demonstration--give the .instructor opportunity to show the techniques needed in theexperiment as well as any other equip ment he has which is relsted to the problem being investigated. Ezperimenkd Diredh-iven in detail to minimiie errors and thus save time; students keep a research-type notebook; forms for data sheets are illustrated; at least two experimental options (see below) are included. Research Projects-abbreviated directions for better students; some library reading is required. Sample Calculations-solved problems similar to those involving the experiment's data. Study Supplemmts-summaries of techniques or reaction possibilities as needed by the experiment and which may not be t~veilablein the text; example: reactions at electrodes during elect,rolysis. Vocabulary-the experiment's new words, to remind the student he cannot discuss chemistry unless he can define its term. Pmblems-homework to illustrate other real examples and further utility of the experiment's principles.
Physical and Biochemical Options
Since men are generally oriented more toward physical chemistry and women more toward biochemistry, we give in each experiment directions for a physical-inorganic-engineering option and a biochemical option. Thus, in the colorimetry experiment, the "engineers" analyze brass for copper while the "biochemists" analyze tap water for fluoride. By having both determinations going simultaneously and asking each group to know about the other's work we catalyze discussion and double their normal exposure to applications. Computations throughout require only high school algebra, the mole concept, and the factor-unit method. Research Projects Extend Coveroge
In the several research projects which follow each experiment we extend the student's sight to let him know the chemistry and methods he has used are not rcstricted to the work just concluded. For example, after the directions on qualitative analysis comes a flow sheet that permits differentiation of twenty-nine natural and synthetic fibers by examination under the microscope. Following the iodine titration experiment is a method for the iodimetric analysis of thiols in hairwaving preparations. After gravimetry is a method for finding the percentages of pigment and resin in paints. After the polymer experiment are directions for hardness testing and the preservation of specimens in plastic. After the experiment on physical properties of liquids is a method for monitoring evaporation of an alcohol-water mixture by refractive index change. After compleximetry are suggestions for investigating the use of mixed and fluorescent indicators-and so on. Real Versus Synthetic Samples
It should be emphasized again that all the experiments involve real samples. We think the student cannot be belabored in lecture, say with an artistic acid-base presentation, and gain any sense of universality from it if in lab he finds the titration sample is theoretical t o e a vinegar the stockroom mixes up a t this time every year. To take another example from the list of research projects, if acid-base is the lesson for the day, why not furnish each lab bench with a different brand of beer and let them titrate with sodium hydroxide to the phenolphthalein end point and compare 692
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answers for lactic acid? For that lab period they are doing what chemists do because they are facing real problems (the beer must first be degassed and the color diluted) and analyzing a real sample. If that seems too theatrical, consider titrating the diprotic acid($ listed on packages of gelatin desserts. I n precipitation work why titrate stockroom salt mixtures with silver nitrate, when chloride in the student's own urine can be titrated directly? I n complexometric experiments why titrate calcium in prepared solutions when calcium in milk or the total hardness in tap water is so handy? In redox applications why oxidize synthetic ferrous mixtures with permanganate when oxidation of frnit juice ascorbic acid with triiodide is only slightly more work? Both analyses in each pair of these teach the same principles, but there the comparison ends. It always does. There is no comparison in interest incited or avenues opened for digression when truth and fiction contend. The real situations that are transposed from laboratories staffed by chemists who make their living working with these things have no equal, in our opinion, a t elementary levels of instruction. Significantly, it is this normal operational order of the scientific method opening with practicality and closing with disclosure of principles, which at first blush displeases theoreticians who think it is technology they wouldn't stoop to, that does the most for many a liberal arts major. This student, who found only repulsion in science so long as he believed it a branch of mathematics whose theorems held no communication for him, now concedes it might be an occupational field vitally related to many of his daily conveniences and one in which responsible humans practice for a reason. He begins wondering why he never regarded his environment from this angle before. And long after the inadequately illustrated principles we labored over lovingly at the blackboard have become lost in his memory and he has forgotten the equations and perhaps the instrnctor too, he may still be associating chemistry d h his physical world because we gave him the opportunity once to examine authentic pieces of it in the lab. Conclusions About Analysis as on Instructional Tool
I n our department we have come to regard chemical analysis as an ideal framework for elementary instmction. Updated from older general chemistry, its reactions still have simplicity, its machines have logic, and it proves chemistry works. We like seeing the learner's enthusiasm come on when in his own hands he finds the principles have more than academic meaning. We like its potential for evolution because it can be brought into any discussion and satisfactory explanation of its activity made without leaving the student behind. As analytical chemists we hope to see it lead freshman courses back to a more natural path from an artificial one which has been made too steep too soon. When the traditional "quant" course is eroded away we feel sure its elements will be found in other laboratories, especially the one discussed here. Certainly analysis has never had greater relevancy to research and industry than it has now. Analytical chemistry can be almost anything we want it to be. Under professional command it gets answers nobody else can get and demonstrates capa-
biiity that is proud to be useful. Under pedagogical command it shows teaching can be creative. It cuts across the whole of science and technology in a way that beginners can understand. It takes reactions from everywhere, builds the theories and instruments it needs, illustrates measurement, precision, and limita-
tion, and deals with every size and kind of sample. It can be fit, therefore, to the teaching of many principles and specialties by simply selecting the material to be analyzed and the method to be used, and we auticipate the pendulum swing of teaching attitudes mill allow us to prove just that.
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