electrodes in the samvles to be analvzed. The votential is automatically logged i d the concentrkion is computed from the fitted equation and printed. In this system, as well as the multiple standard addition system, user attention is minimized during the typical 40-150 s equilibration period of the electrode with each new sample since the system will not log votentials until eauilihrium is reached. This frees the user to do other things during this interval. This same system is used in a sevarate exverimental design vroiect in which the students are asked'to evaluate the-reproducibility of the calibration curve for a given electrode. For this thev discover that they should use the "paired-data" design in Eontrast to the "two-group" design. The "two-group" design is more appropriate for the previously mentioned prohlem of comparing the multiple standard additions method with the direct calibration curve method. In general, we have found that when properly used, these on-line svstems sienificantlv" imnrove . the exveriences undergradu&e studeits can have in the chemis&y laboratory. Students' laboratory experiences are closer to the situations they will encounter in the real world, and students can be made to think about exuerimental desien. - . interoretation of data, and preparation of adequate reports much more than they would in a conventional laboratory course.
Let the Medium Fit the Message Jeff C. Davls, Jr. University of Sam Florida Tampa, FL 33620
Consciencious teachers have long. used a variety of supplemental tools to stimulate their students and to clarify the concepts they are teaching. Tahle 1 lists some of the media most used in the classroom to supplement the spoken word and chalkboard illustration. Many of these have proven particularlv useful for sunnlementarv instruction outside the classroom as well. I t s k u l d seemobvious that a particular technolorn is not necessarilv best suited for everv educational goal or jiiuatinn. Y1.t muit ( ~US f ha\.eexperiencedtheeuphoria imd excitrment of discovering a valuahle new tool only ioslip
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Table 1. Technique
Instructional Media Advamages
Disadvantages
Slides
Clarity, detail
Overhead Projection Slidelaudio Cassene
Clarity, detail as above plus sound as above plus , motion Motion, short Size, semiinteractive Clarity, motion. sound Interactive, data. computation as above plus visual
Film Film Loop MicroficheICassette Videocassene Computer ComputecVideo
Static, remote equipment Static True tutorial difficult Sequences fixed, equipmenl as above. no sound Static Sequences fixed Visual limitations Speed of visual access
Table 2. Exam Types
30
eventually into discouragement when students have not responded to having that tool thrust upon them a t every turn. In Table 1I have included some comments regarding the advantages and disadvantages of the various media listed. We are seeing today a wave of excitement generated by the availability of remarkably powerful personal microcomputers. This excitement extends throughout the business and educational world to say nothing of those engaged in technological applications and entertainment. There is no doubt that in the years ahead this excitement will wear thin and many of the rosy promises will not be realized. Nevertheless we can easily recognize educational applications for which the computer is ideal and provides the best tool to accomplish our goals. In other applications, a marriage of the computer with other media will he far more effective for instruction than either the computer or the audio-visual medium alone. One of the most striking educational applications for which the computer is ideally suited is the generation of objective examinations, scoring examinations and recording scores, analysis of the examination items, and manipulation and analysis of student scores and grades. While i t is clear that subjective essay and prohlem-solving tests must he designed and graded by the instructor, we also should recognize that the time has come when there is no reason for an instructor to put together all the items for an objective exam, grade them, and analyze student and class performance by hand. Tremendous savings in time obtained by having these jobs done by a computer are obvious. Perhaps less obvious is the additional information about exam items and ahout students that becomes availahle. Equally valuable are the new means for communication between instructor and student. Tahle 2 summarizes some of the aspects of managing objective examinations. Two decades of development make it clear that there is tremendous versatility in what kind of computers we can use, whether we develop printed examinations or use the computer terminal directly, whether exams are individualized for each student, whether responses are multiple-choice or not, and what kind of reports are generated for the instructor and for the student. While complete versatility requires imaginative and sophisticated programming skills, more and more tools are becoming available for the non-programming teacher. In many other applications the computer clearly is a useful tool. However, it often is not as effective by itself as when merged with other audio-visual techniques. We have come to appreciate the fact that tutorial lessons can he programmed with considerable flexibility for individual student differences of understanding. The limitations to accomplishing true tutorial instruction are less in the capability of the computer than in the ability of the author to design a truly effective instructional plan. With many topics, however, the most serious limitation is that the computer cannot portray real things as well as photographs, film, or videotape. On typical low-cost microcomputers, even the best high resolution display is only an approximate representation in which important aspects and details may he lost. Animation of motion is difficult and often unrealistic. The most obvious examples of this visual limitation are the portrayal of actual substances, reactions, and the manipula-
Objective Exams on Computers
Exam Formats
Exam Construction
Fill-in Response
Computer-Printed Fwms: Response forms batch scared by computer.
Select items randomly hom stored question-answer sets.
MuitipleGhaice Response
On-Screen Query: Typed-in response scored and stored by campuler.
Generate random or sequential numbers for data in items.
Journal of Chemical Education
Computer Advantages Time and Effort Savings Fast Response for Student Flexibility Instructor-Student Feedback Item Analysis
tion of laboratory apparatus. This limitation is easily overcome, however, by utilizing videocassette or videodisk material on the same monitor as an integral .. nart . of the comoutercontrolled tuhrinl program. This terhnique permits t he disnlav" of "live" action wh1:n nwded in the lesson, inrludinr repeat viewing of the appropriate scenes as determined by&dent responses to questions in the program. Table 3 suggests some of the kinds of tutorial programs in which interactive comnuter nrogramming combined with video illustrations can be mostkff&tive. ~ r o m the standpoint of soeed of access and volume of video material available, it is ciear that videodisk offers the greatest potential. There is no reason, however, why any instructor should hesitate to develop video material &itable for his or her needs and to utilize it in tutorial programming via videocassette until the costs for videodisk production become more realistic.
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Exploring Chemistry's Mathematical Models with Computer Simulations John W. Moore Eastern Michigan Un~verslty Ypsilanti. MI 48197
In manv cases what I call "instructional simulations" can provide a new pedagogic approach to teaching chemistry. Such simulations can place students in a role similar t o that of a I sign~firesearch chemist, rt:quiring the student ~ I furmulntr rant questims, design appropriate simulated experiments, and internret intellken& the data obtained from such ex.~ - - ~ ~ ~ ~ periments. At the same time the computer can provide a set of tools for dealine with exoerimental data (ex.. software for plotting or transforming data) that compresses time, bringing the satisfaction of successfullv ~ r o h i n enature's secrets much more quickly than is usual in real l i f l Curiosity and disciplined inauirv can be rewarded ranidlv. and students are afforded tce opportunity to play with o&models of how nature works, thereby discovering implications of the models that even experienced chemists may not he aware of. The student user of an instructional simulation is able t o interact with a mathematical model through the medium of a computer. The student chooses parameters and the computer responds by calculating results on the basis of model
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-
Table 3.
chemistlprogrammer and on the computer. The situation to he simulated must he well enough understood that model equations are available and provide a reasonahle approximation of reality. The situation chosen for simulation should be one where red-life experiments are too dangerous, too slow, too fast, too complex, or too expensive for the student to do. In some cases, such as display of electron densities from quantum calculations, there may not even be a real experiment that could produce the simulated output. The programmer must make studentlcomputer interactions flexible and convenient-the computer should not get in the way, but rather must be an essentially transparent medium that lets the student focus on chemistry and chemical models. Finally, the comnoter must calculate ranidlv . .enoueh " so that almost instantaneous results can he gotten from realistically complex models. Currently this last is often a stumbling block, hut faster, more powerful microprocessors are just down the road, and numeric coprocessors, such as the 8087 now available for IBM Personal Computers, can achieve considerable speed-up in cases where overall resoonse of a simulation is limited hv calculation speed. Several examoles will serve to illustrate the diverse wavs ill which sin~ulationsare already applied. Gordon Harrow (16) hnsdescrihed the oussihilitv that phvsiral rhemisrrvrould he made a "playgrou~d"withan appropriate collect
