Chemical Education Today
Editorial: Balancing the Forest and the Trees How often do we stop and take stock of what we are doing? And how often do we really think seriously and creatively about it? My guess is, not that often. If you are like me, you are running awfully hard just to stay in place, and reflective thinking is a real luxury. I am declaring a Preparing this issue made me stop and think a bit about a moratorium on very fundamental aspect of manuscripts about chemistry: stoichiometry and equation balancing. This how to balance month’s JCE Classroom Activequations. ity sheet (page 1328A) involves the stoichiometry of the reaction of vinegar and baking soda. It illustrates simply and graphically the idea that one of the reactants can limit the amount of reaction that can occur. And we are devoting 15 pages to balancing equations—enough to prompt the editor’s note on page 1359. Because essentially everything that can be said has been said, I am declaring a moratorium on manuscripts about how to balance equations. Several of the equation-balancing papers provide algorithms by which a computer can balance any equation—at least algebraically. As ten Hoor points out on page 1367, the fact that coefficients can be found that conserve atoms in a chemical equation does not mean that the equation makes chemical sense. And in a letter on page 1257, Sobkowiak recommends that students ought first to predict what products are expected from a given set of reactants and then to balance the equation. I was prompted by these publications to ask two questions. Why am I teaching what I am teaching? Have I found an appropriate balance between the forest and the trees? Gillespie has thought about these questions and has argued that we are out of kilter (1). Others disagree (2, 3), but I do not. If a computer can balance any equation, even a nonsensical one, then why should a student need to do so? Even if a student needs to know how to balance equations, is it necessary for beginners to deal with ones as complicated as the examples in most equation-balIf a computer can ancing papers? Shouldn’t equabalance any tions consist of reasonable chemequation…why istry—products that are compatible with each other and reacshould a student tants from which students might need to do so? have a chance of predicting products? Perhaps we ought to think more about these issues and less about applying the last spit and polish to an algorithm for finding coefficients. We’re no longer using balances like the one shown here, mainly because their replacements are much more effective. How about applying the same criterion to how we teach? If I ask myself how many equations I have balanced in my life, other than those done in freshman chemistry, the number is minuscule. Most of those were trivial to balance.
Nowadays I turn the difficult ones over to Dick Ramette’s REACT program (4) and let Dick’s expertise do the job for me. Besides, in most cases it is more important to determine what the products are, or to predict what the products will be, than to balance the equation. The chemistry is more interesting than figuring out coefficients for the equation—and usually more important as well. Presumably that’s why organic chemists almost never write balanced equations. They concentrate on important reactants and products, with everything else over or under an arrow, and also recognize that the ideal represented by a balanced equation never really happens. There are usually side reactions and 100% yield is not expected. For a beginner, balancing an equation is an exercise that emphasizes the conservation of atoms in a chemical reaction. It will be effective for a beginning student in direct proportion to the student’s ability to see that conservation for herself or himself. Putting any algorithm in the way is likely to make the exercise less, rather than more, effective. Making the equation complicated will have the same effect—inducing the student to concentrate on an algorithm rather than the principle. If we want students to view the beauty of the forest, why should we make them look at the rarest of trees?
To get the point of stoichiometry across, give me a nice experiment or demonstration… To get the point of stoichiometry across, give me a nice experiment or demonstration instead of an algorithm any day. The one on this month’s activity sheet, for example, helps a student to discover that it takes between four and seven teaspoons of vinegar to react completely with a teaspoon of baking soda. That’s real and concrete, and from it we could proceed to find the ratio more accurately. Then we could go on to the chemical equation, to balancing it, and to the stoichiometry. And our students would be more likely to understand and appreciate what all the equation-balancing fuss is about.
Literature Cited 1. 2. 3. 4.
Gillespie, R. J. Education in Chemistry 1997, 34(1), 10. Plesch, P. H. Education in Chemistry 1997, 34(4), 94. Vincent, A. Education in Chemistry 1997, 34(4), 94. Ramette, R. W. REACT; JCE Software, 1995, 8B(1).
Vol. 74 No. 11 November 1997 • Journal of Chemical Education
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