computer mrie~.
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Arizona State University, Tempe. JAMES AZ P.85281 BiRK
Student-Designed Experiments in General Chemistry Using Laboratory Interfacing John R. Amend, Ronald P. Furstenau, and Kathleen Tucker Montana State University, Bozeman, MT 59717 Laboratory interfacing involves linking experiments with computers for experiment control, for data acquisition, and for data analysis. There have been several efforts to integrate computers into the general chemistry and science laboratorv throueh laboratorv interfacine. Some of these efforts have deen described in thk Journal fi-3) and elsewhere (48).In addition, commercial equipment has been available in this area. Most of these interface experiments have focused on usine transducers (specificallv thermiston and photocells) &measuring de&es for temperature and light. Project SERAPHIM has developed many individual experiments that use these transducers ( I ) . Powers (9-11) has presented an exceptionally good series of articles on interfacing resistance probes. The majority of these interfacing efforts have used the BASIC programming language to accom~lishs~ecifictasks in acouirine and re sen tine data. F& the past three years, our reiearcGgroup a t - ~ o n t a n a State University (MSU) has also been involved in a project to integrate computers into our general chemistry laboratories. In the heginning, our motivation was economic. T o update 60 laboratory stations for our teaching lahoratories-purchasine - 60 qualitv . . DH - meters, colorimeters, Geiger count& voltmeters, precision thermometers, and other items-was well beyond our budget. Since there were separate computer funds available t o us, along withadonation of computers from Zenith Data Systems, our group designed a single, unified laboratory interface system to make use of these computers and to take the place of these expensive instruments. We desiened the svstem to be easv for teachers and students to prog;am. This paper will briefly discuss our lab interface svstem and will describe how our students have used i t to design their own experiments. The MSU Laboratory Interface In a chemistry lab or any science lab, we should be giving our students the opportunity to participate in problem solving, to apply the scientific method. Students in the lab should have the chance to (a) look for unexplained behavior in nature; (b) design experiments which yield information concerning this behavior; (c) collect this information (data), and (d) organize this information to look for cause and effect relationships. T o save time, instructors often streamline the time-consuming aspects of experiments. Students perform experiments that instmetors design, collect only the data necessary t o prove the concept, and analyze the data necessary to validate the principle. Essentially, we start students a t step (c) of the above four-step process. A good lab interface sys-
tem (hardware and software) can help us start students a t step (a) by providing measurement options, speeds, and displays not available with conventional laboratory equipment. Personal comnuters with a lab interface can reduce the cost and increase the accuracy of laboratory measurements. C o m ~ u t e rcan s expand the time scale of student exoerimentation by taking hata a t a rate of hundreds of times per second, or for several days a t a rate of afew samples per hour. Computers become a powerful mathematical tool when used to analyze and graph experimental data quickly again and again. The rapid data acquisition and analysis ability of computers gives students rapid success/failure feedback and an opportunity to try another approach in their experiment. These advantages of using computers in the lab led our research group to develop the MSU lab interface. Several criteria were involved in the design of the MSU (1) T o he economic. i t interface and its s u ~ o o r software. t should make all of thk electronic me&rements required in secondary and lower division college science laboratories. (2) I t should make these measurements with research precision. (3) I t must be easilv so that students and . ~romammed, . teacher can concentrate on science rather than on computer proarammina. (4) It must be able to participate in simulated k ~ & r i m e n t s ; ~ i v i nstudents ~ ctmtrd of the system, and to provide time-based information for real-time simulation experiments. (5) I t must be expandable a t low cost to provide for additional functions not yet envisioned. A detailed descri~tionof the MSU lab interface. alone with a ~ h ~~~. o t o an. pears in a prior article submitted to this Journal (12).The vernatilitv and ease of use of the MSL' lab interface svstem prompted our research group to design an introductory chemistry lab course that taught students how to design laboratory experiments and which culminated in a studentdesigned project.
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Frlendly Software: A Key Ingredient Versatile, user-friendly software is the key to the successful use of computers in the chemistry laboratory. Computers must not detract from the laboratorv learnine ex~erience. . .they must enhance it! Using computers in alab&atory experiment should make the experiment easier, faster, clearer, more accurate, more fun, or even possible as opposed to non-computer-interfaced experiments. Data acquisition and analysis software should he transparent to the student, who should be concentratina on the science. Develo~mental software should permit a teacher or student to coneentrate on experiment design rather than on computer programming. We could not expect our students to be trained in any ~
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dents spent about 1h during each of the first five lah periods learning some of the basics of using and programming the MSU l i b interface. Menu-driven, user-friendly programming greatly facilitates the wide application of lahoratory interfacing for students. However, the student must still have a certain amount of "computer logic" or "programming logic" to design an experiment with our interface system. T o design an experiment using the MSU laboratory interface, the user must develop four program components: (1) Make the measurement (2) Repeat the measurement (loop) (3) Exit the measurement loop (4) Add instructions to make the experiment user-friendly
Figure 1. Programming the MSU lab interface is done through a succession of menus. This photo shows the appearance of these menus to the user.
particular (e.g., BASIC) programming language before takine our introductory chemistry course. Nor did we want to t&e the time in thelaboratoryto teach them aprogramming lanmage. These requirements led our research group to develop an English-language experiment design programming package that is totally menu-driven. In retrospect, we helieve that separating the user from having to use a programming language such as BASIC to develop interface experiments is one of the strongest points of our system. The menu-driven package removes most of the frustration associated with programming (e.g., debugging). Students save a tremendous amount of time, which can be used for chemical exnerimentation rather than for computer programming. Menu-driven programming allows the user to select possible actions (ex., displaying a signal from a detector on the screen) from 'list, & t h a t t h e user does not have to learn a programming language. An example of what these menus looklike isshown inFigure 1.Since onlyvalid statements are presented, students cannot make syntax errors. Only the ordering of statements is important. Using the menu-driven programming, students can write programs to display measured quantities on the screen, to graph the information in real time, or to save the data to a spreadsheet file for later analysis and graphing. In short, the software package developed with the MSU lab interface allows the user to decide exactly what data he or she wants and the manner in which to display it. Developing Experlrnent Deslgn Skllls
Over the past two years in our heginning lab courses, students using the lab interface software used "canned" programs that we had written. However, students a t the introductory level had not yet participated in designing experiments. T o see whether our interface system could he readilv learned and annlied toward student-designed experimknts, we developid an "experimental" test course durine the winter 1989 quarter. Twenty students from the normal introductory ch&nistry lab (Chem 126) were randomly selected to participate in this test course. As is typical for our Chem 125 students, only three were planning to major in science or enpineering. One-fifth had never had a chemistry class of any Grid, andover one-third had no computer experience. The course consisted of eight 3-h lab periods. During the last three periods, students chose a chemical problem and were required t o design an experiment using the MSU lab interface to collect and to analyze the data. The first five periods were spent doing "conventional" laboratories, such as thermochemistw. snectroscopy, and qualitative analysis. students used "ca&ed interfa&progr&s in these experiments to acquire data when appropriate. In addition, stu594
Journal of Chemical Education
These components are essentially programming steps, items the students must include in their experiment program to ensure its success. Developing a standard procedure for designingexperiments using the interface is anessential aid for students. Programming logic may not be logical to a student with little or no computer hackmound! We led the students in our test section through several simple examples of how to get the interface to accomplish a task using the four steps shown above. One such example was for the measurement of temperature using a thermistor. The first lines they were instructed to select from the menus appeared as follows: 1 PRINT INPUT FROM Temp ON LINE 12
2 STOP
This simple command sequence accomplishes program component #l. The computer takes asignal from the thermistor input to the MSU interface box (Temp) and displays the temperature value on line 12 of the monitor screen. Line 1 makes the measurement of temperature for the student. However, the two-line program above will cause the temperature to be measured once, then stop. After seeing the above program run, the students began to wonder what must be done in order to have the temperature value constantly updated, so the thermistor truly acts as a thermometer. T o illustrate how to cause the temperature .--. - -- -- measurement to be repeated (programming component ff 21. we then had the students select a line from their menu &t'would cause the program to loop to the measurement command: 1 PRINT INPUT FROM Temp ON LINE 12 2 GOT0 1 3 STOP
The simple GOT0 statement of line 2 does a good job of updating temperature, but the students found out that they cannot stop the program! They learned that they are in an "infinite loop" and that they must have some way of telling the computer they are finished making temperature measurements. T o exit the loop (programming component #3), the students inserted a conditional statement, which appears as line 2 below: 1 PRINT INPUT FROM Temp ON 1.1W 12 2 IF INPIJT FROM SwX = Off GOT0 4 3 GOT0 1 4 STOP
The conditional statement in line 2 tells the computer that if a user-controlled external toggle switch (SwX) on the interface box is in the "off' position, the program should stop. Otherwise, the computer should keep making temperature measurements. The above four-line program illustrates to the students how easy i t is to write a functional experiment for the interface. Yet, i t also shows them the importance of line placement in the program and some basic logic. T o make the
program user-friendly (programming component #4), we encouraee students t o use print statements that appear on the screen to tell the user what the program does ar;d how to use i t ~rooerlv.We then build on these simple experiments hy showing the students how to display a red-time graph of their data, or to send the data t o a spreadsheet file for further analysis and graphing. Such tasks only add a few lines to the program. Since the programming of the interface is menu-driven, the students must spend-only a minimal amount of time learning how to tell the interface what to do. Most - - .of ~- their ~ time can he spent exoerimentine. Thus, to develop experi&ent design skills using the MSU lab interface. we do the followine: " (1) . . teach a small amount ofcornputer'basics. (2) familiarize the students with the structure and seuuencine of the interface software. (3)euide students throug6 short,easy-to-write experiments, and (4) let students use more complex "canned" programs to do and let them the structure of these programs. ~
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Maklna - the JurnD: Student-Desbned - Experiments
The true utility of alaboratory interface system should be -iudeed - bv- how easilv and successfullv it can be applied by the user-in our case, our students. Students in the hem 125 test section chose an experiment project that they were to carry out during the lastthree weeks bf the quarter. For their projects, they were required to obtain and to analyze their ~ - data ~ usine ~the ~MSU lah interface svstem. These projects included ;variety of acidbase titrations on household chemicals and medicines usine a pH electrode. In addition. there were other projects i&ol;ing colorimetry, electro: chemistry, and turbidity measurements. The students were given a short description of their experiment. The description included some background information, the type of data they needed to obtain, a small amount of experimental ~rocedureinformation, and some reporting.requirements. In . some cases, students needed to use dutside references. Given this information, the students (working with a lab partner) then needed to decide how to configure the interface to get their data. Within 3 h of the 9 h available for the projects, every pair of students had properly configured the interface and had a functional program to acquire their data; some were ready within an hour. The remaining 6 h were then available to do experimental work. Because of the speed and ease of use of the lah interface system, students were ahle to repeat their measurements manv times and to trv different procedures-that is, experiment! All groups were required t o hand in tables and of their data with their report, along with a listing of the 2 shows a Beer's program that acquired their data. law plot of absorbance versus concentration for studentmade standards of C U ~ solutions. + The students obtained. analyzed, and graphed the data using the MSU lab interfacd svstem. The students used a homemade colorirneter similar those described in other references (10,13). Students then used their graphs to find unknown concentrations of Cu2+ supplied by the instructor. As seen in Figure 2, the spreadsheet portion of the software allowed the students to convert their light transmission data into an absorbance and to produce a linear regression graph with respect to concentration. Some students produced p H titration curves, voltage vs. ~~~~~~
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Figure 2. Student plot llluetratlng Beer's law for copper(l1)solutions. Note that me axes scales are in scientific notation. me software allows the student to analyze and plot data quickly. time curves, current vs. time curves, and other graphs. The final reports on the projects showed that the students had a very good grasp of how to design an experiment to acquire the data required t o solve the experimental problem. In other words, they were ahle to get the interface to do what they wanted i t to do. Conclusions
We have successfully taught introductory chemistry students t o acquire experimental data with computers in a minimal amount of time. In a post-course survey, students indicated that they liked having computers in the lab. They could see the usefulness of the lab interface system to make measurements and to analyze data. More important, students felt that the final project challenged them and that they learned a great deal from it. In addition, many of the students indicated that they subsequently felt more comfortable around computers in general. We have found that our lab interface sy&m can be used successfully by a wide variety of students. We believe having the students design an interface experiment, rather thanjust using "canned" experiments, greatly enhances the students' laboratory experience. We successfully expanded student-designed interfacing to all 1200 of our introductory chemistry lab students in the fall of 1989. Librature Cited 1. Moore. J. W.:Miies,P.:Raamussen,M.;Hartman.K.;Barker.P.II Chem.Edue. 1986, E" "*a "9" "","*-"*,.
2. Krauae. D. C . J . Chrm. Edue. 1988.65.876.
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7. P ~M. H.J. ~ ~ ~Math. ~ s~:. Teach. : 1988. VII (1&2), 68-71. 8. Laman. J. W.: DeJone. M . L.: Nalaon. J. H. "Teacher Tutorial for American A-iais, n ( . I ~ h y w ~. . i h r .h t t ~ r ~ o m p a ~c .r , r s . ~ ~ o p o1.anoraorv n ~ n t r r r a c ~ nEXy pcrlmmn1s.ngih~Apple i I \Il:r.~ompultrCsn,eP.rl".A.\FI'. 1983. Pnuer?, M H I ( ' m n ~ . ~ ~ ? ~ . ~ f oTt'w,. r ~ lW7, 1'1 > , ' , A -10 I'uarr. \I H .I I' m p d r r l dfrm l r v n I I h 7 . 1'1 I 1 . 5 h C 1 I 1 Pnacrs.\I H J C . r o ~ r c r a . ! f o ? n51, ?)'a n 19bZ I 7 1 .Sd 61
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ChmL Educ. 13. Adams. T.; Hartman, K.; Journeay, D.: Miisa. P.;Mwre. J. W. "Lsborstory Module W2:Diroctiansfor Buildingthe Blaektronic I";Pmjeet SERAPHIM: Eastern Michigan University. Ypsilanli. MI, 1985.
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