provocative opinion David W. Brooks Center for Science. Mathematics, and Computer Education, 118 Henzlik. University of Nebraska-Lincoln, Lincoln. NE 68588
Mine was the generation of students that used both twonan balances and ton-loaders "so that we would learn the brincip~es~. And, of course, you really couldn't understand a visible s ~ e c t r u mfrom a ratio recording instrument unless you had'taken a point-by-point spectr;m with a Beckman -7.
UU.
Mine was the generation of young teachers that forbade the use of hand-held calculators lest "students not understand the calculations they are performing", or some such nonsense. (Actually, the students with calculators so far outdistanced those without them that there was no "fair play" during exams until all could afford a calculator!) Mine was the eeneration of teachers that eliminated the manufacture of t i e glass wash bottle a t the first-day-of-lab activitythat activity being the one which inevitably led to cuts, gashes, burns, and a subsequent great respect for conducting laboratory practices in a safe manner. The sophistication of calculations that we now expect of students on exams is an order of magnitude greater in the age of the hand-held calculator than i t was in the age of the
slide rule. But its impact on the curriculum was a mere nick; a huge gash is on the way. All of the things we need to know in order to do chemical stoichiometry are becoming readily available by machine. In May 1985, this writer made his first attempt at Using a spreadsheet program for doing stoichiometry. One sets three columns of permanent data: element names, atomic symbols, and atomic masses. Then, for each reactant and product substance of a particular problem instance, one sets two columns: the total number of atoms per "molar" unit, and the product of this number and the atomic mass. For each substance, at the end of this column, one sums these products: the sum is the molar mass of that substance. The product of the molar mass and the coefficient of a balanced chemical equation gives a reaction equivalent mass. The mass of any reactant or product, divided by this quantity, gives a number of equivalents. One selects the smallest of these equivalents among the reactants and assumes that this limiting reactant to be converted into product and that all else is left behind as an excess. The most
Volume 64
Number 1 January 1987
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difficult limiting-reagent prohlems are solved in seconds by the spreadsheet. One readily computes the excess reactants, converted, etc. Although 60 a m o k t s of products, hours were spent learning about the spreadsheet program (Symphony, by Lotus), this particular limiting-reagent program took less that 30 minutes to write and test. All a student needs to know is how to enter a formula for each substance and how to enter a coefficient for that substance in a balanced chemical eouation. Of course, there wss still the balanced equation. In June 1986, this writer obtained a copy of an equations solving program (TK!Solver, by Universal Technical Systems, Inc.) A lonatime fan of the method of diophantine .equations, he tried balance the following equation: aHC103+ bSnS + cA&
+ d H ~ =0 eSndAsOA
+ fH2S04+ gHCl
For this equation: H balance: a+Zd=Zf+g CI balance: a =g 0 balance: 3a+d=16e+4f Sn balance: b = 3e S balance: b+3c=f As balance: 2c = 4e T h e s e a t o m balance equations were entered i n t o TK!Solver. The coefficient e was set equal to unity, and the program was set toguess a t a value for a. I t ground away for a few seconds; nearly immediately, i t spat'out a suitable answer for each coefficient. The coefficients were fractional, however. with some xx.3333333'~ on the screen. So e was rhangrd to 3, a gurss was made for a , and the processstartrd arnm. Nearly inmediately a suitable set of whole numher coefficients popped up. Okay, so today all a student needs to know about the mechanics of eq"ation balancing is how to write algebraic relationships for atom balances for each element. One may need to keep track of charge, too. Then the software will balance the equation-and the coefficients can be plugged in to the snreadsheet where nearlv.anv .stoichiometrv"~.r o b l e m can he solved. These skills are mechanical and alaorithmic. One still must know what one's doing to solve textbook problem. Take a look a t the piece by Franklin Hoggard in this Journal
a
issue. In my opinion, Hoggard has set forth one set of systematic rules whereby we use language clues/cues in stoichiometry prohlems to set up and solve those prohlems. Until now, noone has been able to write these rules down in a systematic, algorithmic fashion. There is not yet a commercial computer program that takes Hoggard's algorithm(s) and exploits it (them) to solve chemical prohlems. But that product will come along; perhaps some bright person reading this issue will already have begun work on this task-since programming an algorithm is something computer folks are very good at. All this leads to a simple question. Stoichiometry represents a huge chunk of what we teach-in highschool chemistry and in college general chemistry. Solving stoichiometry prohlems is about to become automated to the point where it will not he appropriate to teach more than conservation of mass and conservation of atoms. How should weorganize the curriculum of the next century to accommodate this development? Much of what we teach is mechanical. Not convinced? It took this writer about 1.5 hours to prepare a generic spreadsheet to have Symphony compute pH's for the titration of a weak acid with strong base using the traditional approximations and to graph the result. Others have reported doing a better job by having TK!Solver solve simultaneous equations for the titration. My intuition suggests that datahase programs can enhance vastly the effectiveness of my use of descriptive chemistry. At least one potential program for this is KC Discoverer, developed by SERAPHIM, and originally based upon a freeware datahase program. Quality generic programs, ones not written particularly with chemists in mind, are providing opportunities to do chemistry in a very different way than we now do it. The impact on teaching should he very great. Much of what we teach is drill and practice. After some very rudimentary point, it makes no sense to teach drill and practice material to high skill levels as we now do. The methods of "long." and "short-swings" are occasionally remembered a t cocktail parties. Will those methods soon he joined by recollections of seemingly impossihle-tobalance equations, truly tricky mole prohlems, and pointhy-point-calculated titration curves? If the time has not yet come torethink the entire introductory chemistry curriculum, that time can't he too far away.
Chemical Health and Safety Award An award has been established by the Division of Chemical Health and Safety of the ACS to recognize outstanding contributions to the science, technology, education, or communication of chemical health and safety. The award consists of $500, a certificateof recognition, and travel expensestothe National ACS Meeting where the honor is conferred. Whenever
possible this will be the fall meeting, and the awardee will he the speaker at the Divisional Banquet. Nominations are now being sought for the 1981award. Each nomination must be accompanied by a Letter, no more than five pages long, that details the nominee's accomplishments and identifies the work to he recognized; a biographical sketch of the nominee; and a list of publications by the nominee. Reprints or preprints of not more than five publications mav be included. Books or tams mav not be included. Abstracts or reviews may be used in dace of publications. Should the words C~~mm~rtpr consider'that n o nominee m m t a the award, no ward wili be g w m tl& scar.. Four copies 01 all items used ior l9R7 nommatims shvuld hc sent hy hlarrh 15, 1Yb7, to the Awnrdi ~ummitlee Chamman. .lay A. Puung. 12916 Allertm Lane, S11,t.rSpr:ng. MI) 20901.
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Journal of Chemical Education
