Programmable Calculators: Uses in Freshman Chemistry Laboratories Recent reductions in the cost of programmable electronic calculators make their acquisition by a chemistry department no mare extravagant than the wide-spread acquisition of poeket-sized units by students. In addition to their utility for upper-level courses such as physical and analytical chemistry, the programmable feature can he of considerable assistance in freshman instruction. We wish t o suggest two uses, one pedagogical and the other administrative, which have been well received in the Chemistry Department a t Illinois State University. 1 ) In a number of quantitatively oriented experiments, repeat determinations are required t o agree t o some tolerance as a means of reinforcing technique (e.g., acid-base and redox titrations). For such eases, we have programmed calculators which are located near the laboratow so that during the course of an exoeriment students mav enter their raw data after a serie< of runs and the calculator return* an indication of the tolerance in theic work. Our programs yipld relative devinrions from the student's mean divided hy the desired tolerance of the experiment fur each trial. Vnlues thnt fall between -1 and 1 then rndicate satisfactory work.To ill~~strats.~uppaae part of an experiment involved standnrdizntion of a hase by titrating samples of a primary standard. After, say, three titrations, students would enter into a programmed calculator the volume of hase and corresponding amount of standard acid for each run. Output from the calculator would be three numbers; if all of these were within the range from -1 t o +1, the student might assume that the standardization was satisfactory and proceed t o the neat part of the experiment. A larger range of values would suggest that further trials were necessary. The magnitude and sign of each number allows comparison of individual runs. Previously, even though instructed to cheek their work for agreement, practical experience indicated that students frequently left the laboratory without having data of adequate precision. The calculator in this manner acts somewhat as a tutor, enabling a student t o more quickly identify a problem in technique (rather than arithmetic), and correct it or call its attention t o an instruetor. We emphasize that such a use of a calculator need not do the student's thinking. Actual values of the determination are not available from the calculator, computation of average deviation by the student is a required part of most laboratory reports, and the necessity and methods for checking work are still emphasized. Hopefully, use of the calculators in this fashion facilitates the student's attention to the manipulative aspects of the laboratory, leaving the calculations t o a time when they may he cheeked without the pressure of having t o finish the experiment. While we have not attemoted a auantitative assessment of the contribution of this orncedure t o student oerformanee. rcw1m cdlected from daises as dcscrihed helow encourage us to believe thnt it has a positive effect. Furthermore, increased student awareners and conildanr~in uring calculators fur study purposes are added henefitr ahich alone might justify the programming. 2) The reliability of unknowns and grading on quantitative experiments can be improved through analysis of student data. With a calculator possessing some programming flexibility, this is an easy task, even far relatively large classes. On the day of an experiment, laboratory students are asked t o report (on short mimeographed or ditto forms) their raw experimental data. Programs have been written t o analyze this data for statistics relevant to the quantities students must report (e.g., percent composition of a n unknown, etc.) and the results give a numerical assessment of the experiment. We suggest using raw data, both as a means of avoiding student computational errors or possible "fudging" and t o expedite grading "turn-around." An upper-level work-study student can easily operate such programs and return results for a class of about 300 students in 2-3 hr. In addition to improving the reliability of grading by yielding quantitative estimates of the magnitude of random and determinate errors on actual student data, we have used these programs to evaluate performance of different types of apparatus (balances, etc.), techniques and samples. This has proved to be of substantial value in the improvement of our laboratory program. The calculator inventory in the ISU Chemistry Department consists of two Wsng model 450 calculators and an (older) Olivetti Programma 101, which appear to he adequate as "tutors" far three concurrent lah sections of about 25 stndenta. and a larzer ~~~, "~ Wane 520-B with taoe casette and orinter. which has been used a t the freshman level orimarilv far data svnluat~onand grading All of there calculnrors hare a means of entering stored programs ,punched cards, magnetic cards or magnetic tape, uhirh is a very desirnhle feature. The authors would be happy tu supply further infcmnat~on,al. gorithms, or actual program listings upon request ~
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Illinois S t a t e University Normal, Illinois 61761
G. J. C l a r k E. W. Kuemmerle L. R. Lieto
Volume 52. Number 7. July 1975 / 423
