GUINEA PIGS IN THE CLASSROOM HORACE G. DEMING University of Hawaii, Honolulu, T. H.
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FIRST of the experiments here related was undertaken when the experimenter was only 19. The guinea pigs were a group of freshmen of the class next following his own. They were given a concentrated dose of chemical instruction, so ingeniously divested of every difficulty that it was termed "Science for the Simple Minded." Twenty such meetings (at ten cents per person per meeting) resulted in the whole group passing their regular course in chemistry. That was cheap instruction, even for those days; it enabled the experimenter, for the first time in his life, to blossom out in a panama hat and a pair of tan shoes and to afford a half interest in a canoe. The experiment did something more than prove that chemistry could be made easy. It showed what items in chemical instruction were most necessary to an understanding of the rest. The experimenter, with the prejudices of his 19 years, would have told you that the sole difference between a good teacher and a poor one is that the former makes students work and the latter lets them loaf. So each of these meetings was followed by plenty of work to be done at home in preparation for the next meeting. Experiments that followed, with other sets of guinea pigs, were for a long time chiefly concerned with tightening the screws on students without causing too much pain to their instructor. Let others concern themselves with pedagogic theories or even goals and objectives; we were out to teach chemistry, That themethods used werenot unpopular may be judged by the lifelongfrieudships that developed with some of the mem%ers of those classes. Students can be made to enjoy effort, if they see that effort pays out. In the years that followed many other groups of guinea pigs were the subject of instructional experiments. Lecture and quiz classas grew in size. To date, about twenty thousand students have passed through them. I n addition, several hundred thousand others were involved indirectly and unconsciously in using texts based on experience with earlier groups of guinea pigs. Looking back toward those early days, when the American Chemical Society had only about 5000 members, as compared with more than 50,000 a t the present, one is impressed with the extraordinary progress of the, science of chemistry and the equally striking changes in experimental equipment and the content of textbooks and courses. Yet methods of instruction seem but little improved. In the laboratory they have often become worse.
Still today we must contend with teachers who have no gift for teaching. Beginners are still often taught by assistants who are hardly better prepared than the best of students they teach. We still have courses that are concerned with details of information rather than with training in the art of chemical thinking. We still put up with laboratory instruction that is trivial, confused, neglectful of technique, improperly supervised, unrelated to other parts of the course, and a refuge for sloth, carelessness, and dishonesty. Classroom expedients developed with those early groups of guinea pigs are as valuable as ever today and deserve to be widely practiced. We pried students out of their easy classroom chairs and stood them in long rows a t the blackboards, solving problems or answering questions dealt from a deck of cards. The instructor, a t a glance, could determine which of 20 students had come to class prepared. For recitations on paper we seated all the worst students next the classroom aisles, where one could stroll up and down and determine by a glance, from a distance of ten feet, whether anyone had misplaced a decimal point. We recommend that method still, to all not handicapped by bifocals. We were not long in becoming aware of an important law: Every student has credit onthe registrar's books for several preparatory courses that he cannot actually use. So, in every course in elementary chemistry, in spite of previous credits in English, algebra, and physics, some time had t o be set aside for such details as the proper manner to set up a dehition, the use bf logarithms and powers of ten, the distinction between force and pressure, the arithmetic of the simple gas laws. So we began to perceive the need for being sensitive to defects in students' backgrounds and willing to remedy them. GOALS AND STANDARDS
As years went by, we would sdmetimes meet former students who would suddenly challenge one t o name them. A glance at the challenger's face might then identify his ancestry and so permit a guess a t a name. Thus what was merely an interest in anthropology gained reputation as a memory for names. These men admitted being distinguished members of the bar or distinguished filling-station attendants. Few admitted remembering any chemistry. So we began t o give more thought to goals, objectives, destinations. What good had been done the thousands of forgotten men who had won a passing grade in elementary chemistry then had faded from academic remembrance, except for chance glimpses a t football games? I n pessimistic moments one reached the dismal con-
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clusion that our most important service had been in dissuading students with no talents for chemistry from entering careers based on that science. Positive benefits for persons who never had intended to use chemistry were harder to discern. Had we taught them much about the scientific method during those few months? We doubt it. But positive benefits there were, though indirect ones. To perceive these was to direct effort toward attaining them with succeeding classes. What goals should be set for the great host of students for whom chemistry is only a part of a general education? Had we no larger duty than just to teach them chemistry? Perhaps our duty might be to contribute in a n y way we could to their intellectual deuelopment. We thought that sound chemical instruction could afford side glances a t spelling, the precise definition of technical words, short cuts in calculation, neat laboratory records, the preparation of charts and graphs, effective methods of study. We found ways to apply pressure, even to largegroups of students, t o make sure that some attention was paid to these "secondary goals" of a course in beginning chemistry. One ruled, for example, that misspelled words rated as so many blanks in written recitations; and that infractions of standards of care and neatness, if persisted in, would be noted and would limit a student's final grade. The childish interest in grades may be made a weapon in the service of scholarship, pending awakening t o -what scholarship means. Beyond these secondary goals, there was one primary goal, which seemed the same for students of the most diverse probable futures: T o teach the f u n h m e n t a l s needed to read and understand chemistry in textbooks and periodicals. Students were never asked to recall the formulas of other than major compounds; nor details of analysis, except as they might illustrate principles; nor industrial uses, except as they could be related to properties. There was danger that an interest in mere facts might reveal many which the instructor himself did not know. Instead, we gleaned fa$, by the hundred, from textbooks that were mere compendia of facts, and asked students to survey them in a search for principles. Here is an expedient in instruction that deserves to be widely practiced. In pursuing our main purpose of teaching students how to read chemistry we moved toward such secondary goals as increased precision in the use of language, increased common sense about numbers, experience in using tables and in recording data, experience in summarizing information in tabular form. We still often have students search half a dozen textbooks for the clearest definitions of important technical words and the clearest statements of important laws. Student opinion, after such a comparison, might reasonably determine a choice of texts. At present, the year's work is begun with drills intended to develop essential skills: accurate use of about a hundred technical words, writing of formulas of about a hundred common substances, the use of ionic and conventional equations, the use of logarithms and powers
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of ten, relative weights from balanced equations, and relative volumes of reacting gases. Following a halfsemester or full semester of such drills, during which the poorest students are eliminated, it is assumed that those who remain have acquired the most necessary preliminary skills. Emphmis, from this moment, is on the development of ability to thinlc which is tested by "openbook" examinations. CHEMISTRY IN A LIBERAL EDUCATION
The value of chemistry as a part of a liberal education is surely by virtue of its contacts with other intersts. So momentary dips into human history or literature were ventured, when asbestos occasioned a quotation from Marco Polo; or when the physical properties of steel recalled the contest between King Richard and the Soldan in Scott's "Talisman"; or when the deoxidation of metals as a prelude to casting was illustrated by the precautions taken by Benvenuto Cellini in puring the bronze statue of Perseus and the Medusa; or when sulfur as a component of black gunpowder was related to some incidents in the history of Sicily. Such illustrations doubtless helped t o make chemistry a little less like dust in the mouths of those whose chief interests were elsewhere. Nevertheless, we felt disillusioned and frustrated when we introduced a course in beginning chemistry by an account of the chemical voyages of the Phoenicians. The whole thing fell Eat because none of the class had ever heard of Phoenicia, Albion, Ultima Thule, or the Pillars of Hercules. With premedic or engineering students one may often 6nd apt illustrations of chemical principles by stepping across the artificial boundaries that separate the different sciences. I n speaking of crystals and crystallization we make contact with geology by exhibiting geodes. The broader view of oxidation and the release of energy in oxidation may be illustrated by the sources of energy of different classes of bacteria. The energy stored in a tank of compressed air may be recognized as potential energy. Conservation of energy can be seen in the flow of liquids in pipes-a simple idea which is often ohscured by being dressed up in mathematical symbols and labeled Bernouilli's theorem. I n speaking of transformations of energy one may quote Faraday and ask whether he was right in tracing all of the earth's energy to a.solar origin. Here in Hawaii we may show movies of an eruption of Mauna Loa and speculate about the sources of energy in vulcanism and the consequences of the low heat conductivity of gas-filled lava and volcanic ash. The point of all this is that the most interesting illustrations of chemical principles have not yet been embalmed in chemical textbooks. Publishers have always hailed each new text as a literary spineless cactus or puckerless persimmon. Yet each new one runs in the same old channel. One wonders why a new book is not more often produced by inquiring, "What minimum skills must a beginner acquire t o he able to read existing books or periodicals with understanding?" Our
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versatile science should speak with a thousand voices. The best approach to it is not through the usual parade of the elements. Why waste what is presumed to be literary skill on the same old story?
It seems important for the instructor not t o be so burdened with papers that he has no time for students. The most obvious escape is to resort to true-and-false or multiple-choice tests, which may he graded by an assistant. We have often used these for a preliminary sorting of an entering freshman class; or to determine which of several groups had learned the most during the freshman year; or in experiments to discover which of our students had the ability to recognize, understand and remember the essential features of an assignment, within a brief study period. However, such tests do nothing toward training in the art of connected exposition. They fail t o reveal methods of thought that may stumble upon correct answers, yet are meandering and confused. They ignore the fact that there are elements of falsity in almost any statement which at first thought seems to be true. They usually give no opportunity for the student t o learn from his mistakes. So over many years, we have sought for a plan for written recitations that would have high instructional value, yield abundant evidence about student progress, and spare the instructor. The best of the many schemes we have tried is still in use: Each student brings to the first quiz of the semester a recitation pad (Hopaco 206) and a sheet of carbon paper, cut to size. At the end of a 15-minute written recitation the original sheets are collected by the instructor. Students retain the carbon copies, and immediately grade and revise their own papers, during a discussion in which the instructor indicates what answer should have have been made for each question. ,4t this time, questions asked by the students may bring out other possible interpretations or points of view. The iffstructor may thus improve his list of questions for the benefit of later groups of students. The revised carbon copies should be retained by the students, for subsequent reviews. Each student rates his oauer on a bonus voint scale. ranging from -2 to +4, &iih the followingpercentage equivalents, which students copy a t the first quiz, on the back of the recitation pads : Percentages: 0-52 53-60 61-68 69-76 77-84 85-92 93-100 Scores: -2 -1 0 1 2 3 4 At the end of the period, pads and carbon sheets are collected. Students who claim positive scores record their scores in ink on sheets in manila folders (20 names to a sheet) on the instructor's desk. During the early part of the semester (while establishing standards), and when difficult topics are first introduced, only about a third of the students claim positive scores. At other times 65 to 80 per cent do so.
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Of the papers handed in, those for which no positive score is claimed are scored zero and discarded. Negative scores are incurred only by students who are absent from class or who are so inattentive during the discussion that they claim positive scores for nearly worthless papers. For some of the papers for which a positive score is claimed, the instructor accepts the student's own estimate. The remaining papers are graded and the scores recorded on the manila sheets, in a separate column from the students' estimates, for easy comparison. Rule a vertical line in the instructor's column through squares representing ungraded papers. Student's selfrated scores should nearly always agree with the instructor's rating. If they do not, more time should be given to the discussion on which their rating is based. I t has instructional value and should not be hurried. In the end, the total score is based in each student's own estimate of his work; but those who have often rated their papers too high have their total scores proportionately reduced a t the end of the semester. An averaged total score, s, is converted into a percentage by = 65 8s. Students who usually score +3 are invited to attend conferences with the director of the course to have their work more critically examined, and to benefit from special assignments or other interesting variations from routine instruction. There is an important follow-up for poor students. Each paper scored zero must be rewritten a t home, together with the alternate set of questions (odd vs. even seats). This must be handed in with the new paper a t the following recitation, or the,new paper is refused. Students who pergist in scoring zero are asked to hand in extra textbook questions until their work improves. These written recitations are only a part of the course, and early zero scores are interpreted as a pass with a low made if the student eives evidence. in survev examinations before the end of the semeste;, %hathe has learned some chemistry, after all. If he can attain the goals that are set for him, one should not be too deeply concerned that he started slowly. An instructor thus freed from wasting his time on trifles and triflers can devote more thought to goals, purposes, and standards. For students, there is untold benefit in following each quiz by an immediate discussion of what should have been written. To criticize one's own work and correct one's own errors is certainly much more valuable than t o glance at a grade bestowed by someone else, and give no thought t o correcting the faults that a low grade discloses.
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LABORATORY INSTRUCTION
I n most colleges, laboratory instruction in elementary chemistry is utterly unimaginative. Poor supervision,untrained assistants, and overcrowdingcontribute to sloppy manipulation, lack of student interest, unceasing noise, disorder, and confusion. Some courses include no quantitative work whatever. Others take pride in quantitative experiments which are performed
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with inadequate equipment or which absorb so much time in the techniques of what is really physics that there is little time left to learn any chemistry. The chief fault lies in the laboratory manuals. Most of them are overloaded with tests and details that are trivial and unrelated. Moisten a piece of filter paper with dilute sulfuric acid and lay it on the steam radiator! Leave a sample of calcium chloride lying around until the next laboratory period! Evaporate a solution of sulfur in carbon disulfide and sketch one of the crystals you obtain. (Try that yourself!) Such piffle sheets, printed or mimeographed, teach nothing that is not already known to smart quiz-kids a t the age of ten. College instruction belongs a t higher levels. It needs better defined goals in laboratory instruction. A five-minute visit to any typical freshman laboratory will reveal that the most immediate need of beginners is instruction in technique. Even simple things are all done wrong! Freshmen will try to dissolve coarse crystals without ever thinking to grind them; they will use cloudy reagents, then falsely report the formation of a precipitate; they will attempt to compare the color of a liquid held to the light in a test tube with the color of another in a bottle on a dark shelf; they will take a gram of material when a microgram would serve; they use dirty glassware; they spill reagents in the balance cases and on the tables, shelves, and floor. So the 6rst assignments in our present (unpublished) laboratory course all hammer on technique. While lectures run through the usual preliminary textbook chapters on oxygen, the gas laws, water, and what not, students in the laboratory are learning to manipulate. In approximately the order here given they learn about: silence and neatness in the laboratory, cleaning glassware, the metric system, weighing, recording dath, measuring, grinding, transferring liquids and solids, estimating quantities, significant figures, dissolving, filtering, plotting curves, evaporation, distillation, determining density, bending glass, bodng corks, assembling equipment, the use of stands andclamps, makingup normal solutions, titration, spot tests, qualitative separations, blank tests and confirmatory tests, contrifuging, special types of manipulation (such as the reaction of a gas with a liquid or solid; fusion; bead and blow-pipe tests). These are the sort of things that anyone must learn to do right who expects to be worth thirty cents a week in the chemical laboratory. Though the emphasis is on correct technique this is taught by a succession of little laboratory problemsdozens of them. The course is called FIND OUT. I s sodium carbonate or soap as good for cleaning glassware as Calgon or certain commercial cleansers? Find out. Is one solid denser than another? Find out. Which of two tests for copper is the more delicate? Find out. Is sodium carbonate appreciably decomposed by heat? Find out. The earliest problems are solved by techniques that are obvious and simple. Later ones require apparatus to be designed and assembled. Students are encouraged to look for minor problems that turn up in
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solving the major ones, and to think their way through them. That is teaching the scientific method by example. The instructor himself will often be puzzled by the minor mysteries that appear in such experiments. Why does one student get well-formed ferric alum crystals, but his neighbor an uncrystalIizable sirup? Why is stockroom hypochlorite sometimes pink? Why does a sulfite solution sometimes keep for weeks and a t other times completely oxidize within a few days? Why does silver react with hydriodic acid? The better the technique and the more closely directions are followed the fewer minor mysteries appear; or, it may be that the more sophisticated the observer the fewer mysteries he will notice. It is a quieter and more thoughtful group of guinea pigs who enter the second semester. The problems they are asked to solve become more and more elaborate. Will silver sponge reduce ferric iron? Make some and find out. (That problem begins with a search in a reference book to find out how silver sponge is made.) Is the reaction between sulfur dioxide and sodium carbonate reversible? Find out. What are the proper conditons for the gelation of water glass by an acid? Find out. By the time such problems are reached, directions for manipulation may be very sketchy, since students have already acquired a considerable number of standard manipulative skills. In problems such as the last one just mentioned, students learn that one of the characteristics of the scientific method is that it systematically explores the effect of different variables by varying one of them a t a time while holdihg the others constant. Certain IoEkers are assigned to individual experiments instead of to individual students. When a student begins a problem that requires equipment not found in the usual student lpcker, he gets a key to a special locker, signs a card beneath the names of those who have previously used this equipment, and is on his way without needing to visit the stockroom. Each student works through the little problems of the course a t his own speed, and alternate routes are provided. So independent work is assured, if there is just a little supervision to discourage collaboration. Students mubt be trained to keep orderly and neat laboratory records, recorded in ink as they are obtained, on final report sheets, and not recopied into laboratory notes from scraps of paper. Noxredit is given for the mere doing of an experiment. The student must submit acceptable notes; and he must show, in future work, that he is really practicing the techniques the experiment was intended to teach. BLIND SPOTS
The chief problems of chemistry, viewed as a science, would seem to be able to predict, when specified substances are brought together: 1. Under what conditions a reaction will take place.
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2. What products will be produced and in what proportions by weight or volume. 3. How nearly complete the reaction will he. 4. How the products may he identified and separated. 5. What energy changes are involved in the reaction. Beyond all these, and more important than any of them is the problem of explaining why things happen as they do. That is the purpose of chemical theories. Such are the fundamentals of chemical thinking. Surprisingly, it is right here that elementary chemical instruction has its most deadly blind spot. Ask any group of freshmen how sodium thiosulfate is made. They won't know even though they all prepared it yesterday in the laboratory. Someone may give you a balanced chemical equation. He memorized that from the text; but he still doesn't know a thing about it. Whether the reactants were brought together as solids or in solution and at what temperature, he has not the ghost of an idea. Only yesterday afternoon, he sat for an hour on a laboratory stool in a sort of trance, watching a sodium sulfite solution boil dry, while the sulfur it was supposed to be dissolving clung to the upper wall of the beaker, out of reach of the solution. This peculiar psychic state is well known everywhere. Here in Hawaii we call it the labtrance. It is hypnosis. Climb on a laboratory stool and fix your eye on a boilig solution or on a liquid dripping from a funnel. Better yet, hold the funnel in your hand. Presently you are in a state that inhibits thought. The remedy is to insist that every moment in the laboratory be devoted to thinking, not merely to manipulation, and certainly not to watching something boil or drip. Explain that laboratory directions are supposed to be correct so far as they go, hut are never complete directions, and in a good laboratory course grow constantlv less detailed. Each exveriment involves some difficulty that the student is supposed to notice, then remedy by some little invention of his own. Ohserving that the powdered sulfur was not c&ng in contact with the boiling sulfite solution, some ingenious fellow may tie his sulfur in a little cloth ba.g, with some sand to weight it. Someone more sophisticated, hence less ingenious, might have lowered a small inverted funnel into the boiling solution, thus pumping the solution over powdered sulfur, contained in a larger funnel or perforated crucible. To apply effective pressure to five hundred freshmen one must train and discipline the laboratory assistants to sense the evils we are trying to cure. With their aid we may finally get students to think in the laboratory and to try to remember what they do and see. Then the fatal labtrance and the consequent blind spot in the very center of chemical instruction will be much less common. I n the end, ask a class to anticipate in advance of experiment whether lead dioxide will react with sulfur dioxide, under what conditions, and what the products will he. You will get some ingenious suggestions on
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how to carry out the reaction. Many students mill anticipate that the reaction is a case of direct union of a metallic oxide with a nonmetallic oxide to form a salt. Others may think of it as the reaction of an oxidant with a reductant to form products which themselves combine. One student wrote PbOa S 0 2 - + S 0 O3 P B. He was evidently an alchemist. To encourage chemical thinking as distinct from the mere memorizing of textbook information, we demand that students tell something about the conditions under which each reaction occurs, what equipment would be used on a small scale in the laboratory, what products are produced, what properties of the reactants are illustrated by the reaction. The textbook equation.counts for nothing unless the other information goes with it. Weight and volume relations, as deduced from balanced chemical equations, are introduced relatively late, and systematized with the aid of a diagram which emphasizes reasoning in terms of moles and equivalents (THISJOURNAL, 23,259 (1946)). The use of dimensions as a guide to calculations ought constantly to be emphasGed. Assistants need to be trained to keep a part of each chss st,mdina a t the blackboard. to outline from ...... memory the textbook treatment ? f topicshaving important subdivisions, or to outline the logical steps in solving a problem or in proving a proposition. (For example, how one may prove that a molecule of oxygen contains two atoms). Students are unbelievably poor a t this sort of thing. Half of a class may correctly deduce that the answer to a problem is 11.2 liters; but only a few of its members will be able to set down, in logical order, clear and complete etatements of the steps that led to that fesult. Here is another blind spot which needs earnest attention.
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CONCLUSION
As new chemical discoveries are made or as old principles receive new applications textbooks tend to increase in size. That is unfortunate. It is better to treat a few topics in such a manner that students learn to think, rather than range over many topics in a superficial way. We might do better if we could demand of entering freshmen the necessary preliminary skills already mentioned. But an iron curtain seems to separate high school from college instruction, to prevent our needs from being well unklerstood by those who work on the other side of it. So the way to future progress seems to lie in more thought on the part of college instructors about goals and purposes. To teach the useful properties of substances, thence inferring their applications in industry; to suppress numberless textbook details, intended for reference or illustration, and concentrate on principles; to teach chemical thinking and discourage memorizing; to make the lahoratory yield proportionate benefit for all the time spent in it: these are the marks of intelligent in(Catinued a page 468)
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GUINEA PIGS I N THE CLASSROOM (Continuedfwnn page 449)
stmction. College teaching in elementary chemistry must take a long step upward, if it is to deserve the admiration that we give to chemical research. For the instructor himself there is unmeasured inspiration in feeling that each class is a group of guinea pigs, to be used in a search for better schemes of instmction. Teaching, then, can never be a bore. After many years of classroom experience a teacher of chemistry will still be thrilled by turning up more effective methods. His interest in students will enable him to render them services they will remember all their lives. He will even receive letters of thanks, years afterward,
for saving someone's character or career by administering timely discipline. He will aid the chemically uutalented in finding something else to be interested in. He will help the talented to gain, not merely incieased information but increased capacity for thinking, for organizing information, and for scientific exposition. Knowing his students better, he will not be so dependent on anthropology to identify them after many years have passed. If one of them should venture to challenge him a second time he can crack right back: "I told you your name five years ago, Mr. Cohen. Have you forgotten i t already?"
