Laboratory Simulations by Computer-Driven Laser .
David W. Brooks. Edwards J. Lvons.. and Thomas J. Tinton University of Nebraska-Lincoln, Lincoln, NE 68588 Several years ago, the editor of THIS JOURNAL asked DWB to speculate upon the future of general chemistry.' At that time, the possibility of combining computer technology and videodisc technology was suggested. I t came as quite a surprise t o end u p pioneering in the application of this technology t o chemistry education. Laser videodiscs, in principle, allow one to capture up to 30 min per side of continuous motion video, or just over 50,000 individually addressable still frames per side of a single piece of medium which, though destructible, is highly wear resistant. There is no good way to single-frame accurately using a videotape medium; under the start-stop conditions, the tape stretches and eventually breaks. Placing videotapes in heavy service situations such as resource rooms leads to tape breakage with attendant replacement costs. Also, the players tend to jam up as a result. Discs allow rapid access time between frames; modern disc players allow one to search through each of the addressed frames in a couple of seconds. The end-to-end transit time through a videotape is much longer. Students tend to lose interest while the videotape under CAI control is being searched to the area of interest. Arlene Russell and coworkers2 were the first t o report on the use of laser discs in teaching chemistry. Her use involved nroeram codes nlaced on the disc or otherwise entered into the ~" player which allowed for selertion of frames by student users. (This is called Levrl I1 in the terminuloay of videodisc designers.) Under computer control, two things are possible. First, the computer program can control branching just as in other forms of computer-assisted instruction. More importantly, the coml uter can generate overlays that greatly enhance the use of the medium. (The videodisc terminology for these applications is Level 111.) We chose titration and qualitative analysis as experiments for simulation. Why titration? Since "everyone" has a titrating CAI lesson, titrations have become a benchmark. Why qualitative analysis? There already exist some excellent programs in this area, so one could try to assess the degree to which added reality of the video image enhanced the instruction. In thr tirratiun diw, we attempted a generic approach. Weighings, use of various indicators, pH meters, end points, and other routine titration phenomena were simulated. When using the pH meter, fur example, the pH readings were com~ u t e dVerv . few disc iramrs were devoted tu the meter. Instead, a bl&k mask was filmed over the digital readout of the meter, and a numerical reading was superimposed on this mask by the computer. We had to pioneer several simulations. For example. what happens if sou leave a solution in a flask stirring f i r 3'0 min? B; definition, any continuous, real-time footage would use up a disc. In order to simulate this aspect of a titration (the continuous stirring of a flask) when the student enters this portion of the disc, the computer instructs the discplayer to reverse itself a t the end of a brief sequence of frames. Astute observers can pick out a point where the stirrer reverses itself; novices never notice this effect, and
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' Brooks, D. W., J. CHEM.EOUC., 55,90 (1978).
Russell, A. A., Staskun, M.. and Mitchell, B., J. CHEM. EDUC.. . 62.. 420 (1985). Bell, J. A.. "The mSolution hoblern." available from SERPAHIM. Apple Disks I and II, Eastern Michigan University, Ypsilanti, 48197.
514
Journal of Chemical Education
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Disc olavet , . at lefl TRSSO Model Ill in center. and monitor at riqht. The charaderr blR the other parts
displayed on the monitor were generated by the computer, of the image came from the videodisc.
never auestion how a flask can a .m.e a r t o be stirred continuously for weeks from the same disc! Simulating the buret sto~cockw w achieved IJV a paddle runtroller. To simulate adding solution from th; buiet, one turns the controller. A graphic is overlaid on the screen to simulate the position of the buret valve: i t is a sort of "Newman projection" of the buret valve. Just as in a live titration, this program rewires attention todetail. "Experimental results"'suffer ifair is not removed from the buret rip. if samples are not weighed. if the indicator is forgotten, and;; f o r t h . ~ h eresults suffer inmuch the same way as they would in laboratory, although hints ("You must add indicator") are provided the first time through. The simulation, although verv realistic, is easier t o accomplish than is the actual laboratory work. The analysis lesson has three parts: a lowlevel intmduction asking students to relahel three hottles of differentlv cdored ~~~-~ ~--solutions; a traditional qualitative analysis sequence involving four metal ions: and a version of the six-bottle simulation most recently presented by Jerry BeIL3Let us consider the six solution simulation. There are onlv 36 wavs in which one can add, dropwise. equnl amounts ot'six solutions taken two at a time.The six liauidiare watcr and aaueoussolutionsof sil\.er nitrate, sodium>hloride, sodium bromide, sodium carbonate, and nitric acid. That is, to 10 drops of water we can add 10 drops of water, 10 drops of aqueous silver nitrate and so forth. All 36 possible combinations are on the disc. How many unknowns can a student he given? That number is 61, or 720. Rather than write a discframe (in practice, three disc frames) for each unknown, all of this material is "computed." The computer randomly assigns an unknown keeps track of which solution "belongs" in which tube, shows the student what would h a p w n when 10 d r o ~ from s tube 1 are added t o 10 d r o p fromube 2 (or vire versa), and grades student repnses. The keypresses are fwile, and allow students to correct their entries, etc. This program is fun; we observe teaching assistants playing with it in the resource room. The technology we used to achieve the overlay (shown in the figure) was a TRS-80 Model 111computer and a Pioneer Model I11 videodisc player, neither of which are currently
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commercially available. (The"world supply" of disc players was bouaht up by manufacturers of the arcade game, "Dragon's ~ a i i . " )~ h e k x a chardware t configuration to be used for further work is as yet undefined because of the technical problem of achieving a video overlay, but, as of this writing, the authors are able to achieve overlays from both Apple IIe and IBM-PC computers using appropriate boards. In our titration disc, communication from the player to the computer was reouired. The student chooses to s t o the ~ titration a t some point, Hnd the rumpliter requests the number oi that frame from the ola\.er and uses this todecide how close thestudent has come'to the "accepted" end point of the titration. Not all laser videodisc players are able to communicate hack to the
computer, a point that interested progranimerr should notc. Even though wc are unahle to define an exact hardware svstem, Our early results make this report necessary to encourage further experimentation. Indeed, using the laser discs we have manufactured, other programmers far more clever than we can imbed them into CAI of their own design and thus extend still further the titration benchmark. Clearly the marriage of two of the most powerful media used in chemistry education a hvduring the last decade-video and CAI-has orodoced ~~~~hrid capturing the l~enrfeaturci uf each. Additional details on videodisc r,rodurtion will be nrovided by the senior author upon request.
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Volume 62
Number 6 June 1985
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