sodium reacting with water, I want them to be able t o write something like this: A soft, silvery, metallic-looking solid dropped into a nonconduct-
ing, colorless, phenolthalein-spiked liquid balls up into a spherical shaoe. . . skitters about on the surface of the water as if .iet-oro. pelled, and produces a colorless, odorless, less-dense-than-air, highly flammable gas and a pink, electrically conducting solution, and disappears. And I want them to understand that such a statement corresponds to this chemical expression: 2Na(c)+ 2Hz0(1) = Hz(g) + 2Na+(aq)+ 20H-(aq) + heat And, finally I want my students to see, eventually, that the chemical expression above corresponds to such statements as those below.
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Production of hydrogen from action of an active Group I metal on water. Formation of sodium hydroxide from sodium and water. Destruction of waste sodium with water. Drying of hydrocarbons with sodium wire. Displacement ofhydrogen from water by sodium. Reduction of water by sodium. Oxidation of sodium by water. Protonation of sodium's valence electrons by water molecules yielding doubly protonated electron-pairs(H-H, i.e. Hz). Deprotonation of water molecules by sodium's valence electrons, yielding deprotonated water molecules (OH-). Electron transfer from metallic sodium to oxygenated hydrogen, yielding Na+, Hz, and OH-
Such literacy is not quickly acquired. I t requires learning new words for new sensory experiences. It's like learning a first Howhid we learn our first language? Not from books and lectures. We learn a first lanmagc by heing around people who use the language seriously, for rial-life purposes. Andit helps if they point and tell ~ o - h estudents l~ become chemically literate, we need t o show students what chemists can show, sav to students what chemists can say, write for students what ihemists can write, and describe for students what chemists imagine. Providing students with those experiences is the alphaand omegaof my beginning course in chemistry, beginning the first day. I ask mvself. . . What can I show? Oulv then do I consider, What can I say? The opposite procedure, which I followed for many years, of deciding f i t on a syllabus and then wondering what demonstrations (if any) I might do, puts the cart before the horse. It's jobbing backwards. It's jumping to conclusions before the facts are in. As Lavoisier advises in the preface of his "Elements of Chemistrv." .. "lIln . . commencing the study of a physical science, we ought t o form no idea but what i s a necessary consequence, and immedite effect, of an experiment or observation." Lavoisier's Rule of Restraint is not easy t o adhere to. But it makes for a good game. The game's called Science. Anything less, in Robert Frost's words, "is like playing tennis with the net down." My course is designed around simple, short, safe, striking, and inexpensive lecture experiments. Chiefly we exhibit pure substances. heat nure substances.. droo ..nure substances into pure substances, and record in our notebooks what we've done, what we've seen. what chemists sav. -.what chemists write. and what chemists imagine. On Day 1 we might heft and drop wood and lead bricks; strike a match; drop dry ice into water; spray water into burning paraffin; heat iodine, sugar, or ammonium dichromate; immerse burning magnesium in steam and carbon dioxide; allow nitric acid to act on copper. I t doesn't matter where one starts. We can reach the center from any point on the compass. The previous speaker has left us iodine in a flask on a hot 804
Journal of Chemical Education
plate. That is a pretty color-one of the prettiest in chemistry. Let's add some water. (Let's hope we don't crack the flask). Ah! There's the color of iodine in water. Brown. It's brown, also, in alcohol and acetone and ether and amines. But it's violet-the vapor's beautiful violet-in hydrocarbons and chlorinated hvdrocarbons. I t doesn't interact with those solvents. You don't need a spectrometer t o see that. But the iodine molecules do interact with oxygen- and nitronen-containing solvents-indeed with any b& solvent. ~beaolvents' lone pairs attack the back sides of Iodine-Iodine bonds. It's the first step of an S N displacement ~ on iodine. With hydroxide ion the interaction goes all the way to a reaction. The case for chlorine is familiar: OH- CI-C1= HOCl + C1-. But now a paradox: Add one of the "violet solvents," for example heptane, to the aqueous solution, and shake. (Oil and water don't mix.) Surprise! The iodine molecules leave the water molecules with which thev were interactine and end UD in the inert hydrocarbon layer. That's counter-intuitive. Or is it? It's not that iodine molecules don't "want" to interact with water molecules. They do. But water molecules, given a chance, would prefer to interact with water molecules, via hydrogen bonding. The iodine molecules, like hydrocarbon molecules, are saueezed into the hvdrocarbon nhase bv hvdroeen-bond formation in the aqueous phase. 1n bioche&ry, &at effect is called "hydrophobic bonding." But we can get the iodine back into the aqueous phase hy adding potassium iodide. I t is soluble in water but insoluble in hydrocarbons. (Like dissolves in like, and water is salt-like. Its molecules are dipolar.) Formed is the triiodide ion. With alcohol as a solvent, we'd have a tincture of iodine. You see what happens. As individual experiments are woven into a whole, the; gain power to represent the whole, and transitions to the whole become possible from any experiment. Gradually students acquire new mental images and a new language for describing and thinking about the world around them. They become more observant, more expressive, more thoughtful, more knowledgeable, and more imaginative individuals. Becoming chemically literate, they acquire a general education. There's a good education for good living in chemistry. That's what I try to suggest the first day-and every day-in a first course in chemistry.
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My First Day of Class-is a Typical Class Day David W. Brooks University d Nebraska, Lincoln. NE 68588
The first dav of class has alwaw worried m+it is the only class day during which I am likeiy to have "butterflies in my stomach." If the dav means so much to me, there is a nagging -.. feeling that i t mustmean alot to my students. Analysis shows that my worry is usually greater than is theirs. In past years, I have tried all sorts of things to involve students during the first day of class. At one time, I greeted each student a t the classroom door with a handshake, an event that was never noted on over 1,000free-recall student evaluations at the end of the semester. Later, I had students stand up and introduce themselves to the whole class, or break into small groups and introduce themselves to one another in the group. Flashy demonstrations, jokes socomy as to he memorable, and other snecial events seemed more noted hv me than bv them. When you ask students about the& classes duiing the first week, they will tell you how they feel. However, most of them can tell you how they feel before the first class session meets, especially if it is a chemistry class. That opinion is formed-at the latest-in the dormitories on the days before classes start. Nothine sets the tone for the first dav of a college chemistrv class b e k r than to have a high school chemistgteacher say,
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perhaps years later, "Professor Xxxxxx teaches a tough course, but is very good and gives students fair treatment." I suspect that this chain of expectation permeates down through all school systems. In recent yea% I have taught my chemistry classes using media to present lecture material, and from a detailed set of notes available a t the outset of the semester. Everything is scheduled; it is possible to predict to the hour if not the minute when a particular topic will be covered, when a classroom experiment will he performed, and so forth. This system has worked very well for me, and for most (hut not all) of my fellow teachers. In general, and especially under these circumstances, the first day cannot really he anything but the first day of a planned curriculum of chemistry study. We do demonstrations and experiments. We use synchronized lap-dissolve slide-tape programs. We have a computer-generated newsletter. There are detailed classnotes. And we have all of these things every day of the semester. What really matters to the students is your reputation, and this is based on how you treat them all of the time, not just on the first day. If you expect student participation, it must be encouraged the first day and every other day of class. The students can never fear that you will ridicule them, even when there may he some justification. Students prefer to be treated as if they can and will learn the subject matter at hand. When treated this way, most of them do learn. There are organizational details to accomplish on the first day, many of which are essential. I postponed discussion of the grading system until the second day. This gives my students ample time to read the grading handout, figure out what i t means to them, and ask pertinent questions in the allotted time. Since I began this practice, the quantity of grading-
related questions has diminished and the quality has improved. Because this article was written after the Storrs presentations, there has been an opportunity to reflect upon the remarks made by other speakers. What struck me about the talks was that-basically-all speakers said the same things about their treatment of students in class. Some did treat the first day as a special day, as I once did. The speakers seemed more flexible than I with respect to curriculum; the large, structured class I teach deprives me of the freedom to respond to a particular student input as I once did. In our program, every day is the same-lots of chemistry presented systematically, presented with appropriate visualization, and presented in amounts that previous student groups have been able to learn well. Some semesters, 85%of the students pass the class; other semesters, particularly in trailer classes, less than 65%pass the class. Anyone with experience or a thorough knowledge of human information processing theory can alter the success rate, rspwinlly in the direction of lower in^ it. (An intellecrualls honest 1Wq student success rates has always eluded me ib large classes, however.) Another theme not stated explicitly by any speaker hut implied by all was: we should try to confront our students with observations about matter that are either a t the edee " of or beyond their experience, or ones they usually over- or underinterpret. This is how we can tease out and expose student thinking processes and how we have to improve those processes. I suspect that as much if not more student participation is expected in the highly planned, structured class setting than in those that are less structured. The olannine involved outside of class is often the key to the amount i f and the success of student participation in any program.
Volume 62 Number 7 July 1985
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