edited by
JAMESP. BIRK Arizona State University
computer series, 17 1 Retrospective Tutoring David W.Brooks University of Nebraska Lincoln, NE 68588
The shift from carbon-based cognition to silicon-based cognition is well underway. New computer software tools t h a t subsume tasks previously performed by scientists emerge regularly. Software that takes input in the form of IUPAC names for organic substances and returns structures is available and was shown a t the 1994 San Diego National Meeting of the American Chemical Society (1). Software to assist those engaged i n the designing of synthetic pathways is emerging (Z),and molecular structure software to assist in the selection of appropriate target molecules is used widely. Chemistry education, however, seems to be in a paradigm that involves using today's computer tools to teach yesterday's curriculum. Machines are being used to teach students skills that, when the student is pitted against the machine a t performing the task, the machine almost always is more successful. Skills Change When Machines Are Used Some skills are lost hut others are gained when new technologies are introduced. Current wisdom has it that estimating, a skill well in hand for those who learned chemistry in the era of the slide rule, is diminishing. Please stop reading for a moment to locate your hand held calculator. Now, please enter four in the calculator, press the square root key, and the instant appearance of two will enhance your faith in the power of your calculating device. Clear the result. Now, please enter 4 (negative 4) and repeat the same process. You now likely confront the reality that some important knowledge is a t risk of becoming lost. Your calculator probahly balked at the second task. An H P 11C. for example. flashes the word "Error." One's faith in the first answer is a h i t misplaced. Aperfectly correct andvalid answer, -2, usually is lost in the device's response to the first sequence of button presses.' The point is that skills related not iust to o b t a i e square roots b;t also related to understanding them is a more fundamental may be waning. (If the reader did not mentally amend the first readout by saying to herhimself there's also -2, then skill loss probably is real.) Lament this loss of skill however much you might, the attendant gain in skill surpasses that loss in importance. Machines do make us more productive (3). Stoichiometer, A Silicon-Based Chemists' Tool Stoichiometer is a tool that does for stoichiometry much of what the square root key does for taking square roots (4-6). I t findsbalanced chemical equations, figures mass relationships, predicts gas volumes from masses, figures yields and theoretical yields, generates recipes for prepar-
'It was pointed out during a recent exchange on the ChemEd listsew that at least one modein hand held calculator provides answers (0,-2)) when the square root operations are of {(2.0),(-2.0) and (0.2). oerformed. This observation suooorts mv ooint. For at least some iechnicallyinclined humans, s o k lost ar&ers have been found!
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ing solutions, and even tries to use empirical data to determine chemical formulas. These tasks form a core within most general chemistry cumcula a t the secondary and college levels. The skills provided by Stoichiometer have been availahle from spreadsheets for many years, and solving these kinds of problems has been well described a t meetings and in the literature (7-10). There a r e a t least two strategies for teaching spreadsheet use. One involves having each student create individual cell formulas; the other involves giving the student "templates3'withthe necessary formulas in place. In 1987 I had the opportunity to teach the use of spreadsheets to solve stoichiometry problems, and chose the first strategy (i.e., the students generated their own cell formulas.) This actually took more instructional time than teaching stoichiometry traditionally. Many concepts and details related to the spreadsheet had to be mastered. In 1987 I used a spreadsheet to prepare my income taxes. Since 1987, several programs have caused my views to change drastically. I have begun using task-specific software for o e tax returns. Chemistrv drawing . r e.~ a r i n income tools for drawing organic structures make drawing them fun. Molecular structure programs make predictions possible that were unheard of 30 years ago. The biggest impact came from Mathematica. Who would ever have thought that mathematics could become the subject of mental d a y rather than mental work! These tools are wonderful; they reduce drudgery significantly. Today I also use Stoichiometer, a tool t h a t can make stoichiometry mostly a "black box." In the case of each of these examples of software, I know what the software is trying to a ~ c o & ~ l i sIn h . most of the cases, I am totally unaware of how the tasks actually are accomplished (althoueh I could venture some guesses &rthy of a ~"bstantialwager.)
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Understandingversus Button Pressing The dilemma that experienced chemistry teachers face is simple to describe: we understand what the chemistry sofb ware is doing for us. How will we teachers ever eet our students to use rottware on the m e hana and understand what thrv nrr doinr! on rhr other? In iicht oS the tuol, awilable today, a large Traction of the labor invested during my formal education consumed intellectual e n e m that could have been used to go beyond where I stoppedrfor example, to have taken courses in advanced biochemistry or graph theory or modem physics. My intuition tells me that chemistryinstruction related to "siliwnized topics" should end up requiring a quantity of time somewhere between where the student usually starts (little or no understanding based upon no time invested in learnine) and where the more experienced among us have come to & (considerable understaking based up& much time invested). Intermediate positions of higher effciency in balancing understanding and time that were not available for us now are available for our students.
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Wrap-Around Curricula: The Conventional Alternative for Teachers How should instruction he accomalished? One approach is the development of a curriculumthat wraps around existing software. There are many instances of this approach (ll).Erperiments in computatEonal Organic c h e s t T yby
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W. J. Hehre e t al. (12) is a remarkable example. This text includes 53 chapters with titles like "Bredt's Rule," "W Spectra of Conjugated Carhonyl Compounds," and " S N ~ Reactions in the Gas Phase and in Water." In creating a wrap-around curriculum, the teacher develops exercises that demand student use of software tools in such a fashion that specific principles are explicated, particular tasks performed, etc. In many ways, this approach i s not terribly different from developing a spectroscopy exercise in which a particular substance or family of substances is synthesized and then studied spectrally.
Arequest for tutoring leads to the following: The standard units for these problems in Stoichiometer are volume in milliliters, pressure in millimeters mercury and temperature in the Kelvin scale. Sforchromefefa s s m e s tnal tne Inlens ve propert es (tempera!-re an0 pressure are set oy aooralory cond tons and thal tne vo Lrne of gas s ca CL ale0 In this problem, the volume (tt3)of 0.0839 g of dihydrogen {Hz]at a wet pressure of 755 mm Hg and a temperature of 27 C is to be determined.
Retrospective Tutoring I n late 1993, I developed the retrospective tutoring technique i n which software tools themselves offer context-sensitive tutoring on any recently performed task. This tutoring provides a description of exactly how a n answer to the problem t h a t you posed was developed. I t processes the user's substances and numbers. I n addition, i t provides topical tutoring (of a page-turning character). Retrospective tutoring differs i n a fundamental way from other forms of tutoring. I t does provide the teacher a n alternative for instructi&. At t h e same time, i t provides the user a record of the steps used i n arriving a t a n answer. I t i s mv orediction that. a s more and more tools come into being, 'and users face greater demands for tool use. the strateev -" of havine a built-in refresher will Drove important. I t will he more important a s the distance from the user's area(s) of trainine increases. IBv comhints and helps and parison, my tax program clues, and does scads of things for me automaticallv and transparently, but it does not provide retrospecti;e tutoring!] o n e quickly learns that no computer tool, not even the tax return tool, works miracles. The user must have a good idea of what he or she i s about a t the outset! Areas in which software tools might be well suited to retrospective tutoring include statistics a n d taxonomy. Stoichiometry fits this pattern very well.
The temperatdre 1s n Ce SI-sscale, and In s s convene0 to the Ke vln sca e oy aod ng 273 15 lo 27 log ve 300.1 5 K
The gas is presumably saturated with water vapor. At 27 "C. water has a vaoor oressure of 26.7 mm Ha. The corrected pressure fo; thd d~hydrogengas is 75
