I t is interesting to observe, in the light of the above remarks, that physical properties correspond to an "inanimate ~enetics."The ohvsical properties of inanimate obiects are the analog of the intrinsic genetic features of livingobjects. They are both reproducible, invariant, and completely characterize that species. Although signifying nothing, it is curious that the inanimate and animate worlds are bridged, in a sense, by this physical propertylface-feature isomorphism. Several conclusions are in order. It seems t o be possible to represent physical properties effectively by face features. T o be useful for purposes of chemical education, a "good", standardized set of face features must be established; once standardized, the variablelface-feature isomorphism is easily learned. A "good" parameter set is one that seems to give a pleasing overall appearance while associating the most distinctive face features with the most obvious and important physical properties. Face-feature assignments allow "ne, literally, toser the differences in physical properties of chemical species. This is, curiously, a perspective which nature has denied u j with our restriction to observing dolely a hulk appearance. Acknowledgment Theauthor gratefully acknowledges the useof the Universitv of Michigan comoutinr facilities. the MFHI'I' Network. anb the ~ i l h i ~ adtate n kniversiti computing facilities: Christine Wendt of UM and Rich Wiggins, Mick Giddings, and Tim McCaffrey of MSU were especially helpful.
chemistry, West Virginia Institute of Technology can provide no laboratory assistants, teaching assistants, or skilled graders. All instruction and virtually all grading falls directly to the individual faculty member teaching the laboratory section. Institutions with a graduate program may also find that a shortage of highly qualified graduate students may hamper their operations. Careful grading of a typical experiment, such as a Dumas molecular weight determination or perhaps determination of the equivalent weight of a metal by displacement of hydrogen, takes an average of some 10 to 15 min per student per week. This translates to a total of some 50 to 75 h per week to grade experiments for 300 students. Approximately 90% of this time can be eliminated by transferring the routine of checking calculations, significant figures, graphing accuracy, and comparison of experimental results with the correct d u e s for unknowns f r o d the personal attention of the grader to a microcomputer. A residual amount of hand grad:mgremains. Such things as answering questions, checking for use of a pen rather than pencil, and checking for appropriate scales for graphs, etc., are not conveniently performed on a computer. Use of the Apple I1 series of microcomputers for grading laboratory reports requires a convenient and accurate method of data entry and appropriate software for the grading process. Data entry is conveniently performed by use of appropriately designed and printed mark-sense cards hand marked by the student (see figure). Card-marking errors,
Table 1.
Computerized Grading ot Freshman Chemistry Laboratory Experiments Robert L. Myers West Virginla Institute of Technology Montgomery. WV 25136
Historically, there have been two common methods of grading freshman chemistry laboratories. The first has been to spend hours and hours meticulously checking all calculations and measurements. Although the advent of the programmable calculator has somewhat reduced the tedium of the process, it still remains a time-consuming chore. The other method for grading these reports has been either not to check the student's measurements and calculations, or to check only his or her experimental results against a supposedly accurate standard (regardless of experimental technique or accuracy in calculation), or not to grade this type of experiment a t all. Like most institutions without a graduate program in
I
I
I
I
GRAVIMETRIC OETERMINATION OF PERCENTSULFATE
I
Hardware Requirements
1 Apple Ii+ (or Ile) with two disk drives, monitor, and 64K memory. An 80column display is not necessary. 1 Card Reader with serial imerface (HEI, lnc., Victoria. MN manufacturers an acceptable reader). 1 Primer capable of at least 115 columns in an 8-in. widlh, 8 lines per inch. and varlabie formlengm (3.5 In. is very convenient). A higher printer speed (160 to 200 cps w more) will provide a significant overall speed increase (especially if the Accelerator card is used). Specially designed and printed mark-sense cards (Requirements vary between one and four cards par student per experiment. The cards for one experiment are not usable for another). Mark-sense cards for convenient mster entry (one per studem per s c mester). An Accelerator I1 card may be used to make even greater decreases in grading time. (Optional. Not necessary for the process, but will signifleantly increase speed.) A printer buffer may be used to Increase the through-put. (Optional. Not necessary. but will be of benefit. especially If the Accelerator card is availahla\
EXPERIME PLACE YOUR NAME ON THE OTHERSIDE OFTHIS CAR0
A typical data smry card, gravimetric sulfate determination.
Volume 63 Number 6 June 1986
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such as double-marked positions, can become a problem unless the reading process provides a means of quickly checking the card entries for proper data type (numerals, decimal points, and spaces). Each experiment requires its own set of cards. Some experiments, such as a gravimetric sulfate, require only one card. Other experiments such as the chemical equilibrium experiment require up to four cards to allow sufficient space for the necessary data. Some 35 to 36 different cards are necessary for the 14 experiments. Tables 1 and 2 give the hardware requirements and estimated cost for the grading procedure. Software (in Applesoft Basic) for a series of 14 different experiments requiring measurements and calculations has been written and tested over a period of three years. The software, occupying 18 disks, is adapted for use specifically with the laboratory manual in use at WVIT. The 14 experiments are very common experiments that are performed in many freshman laboratories nationally (see Table 3). Adaptation of the software and data entry cards for other lahoratorv manuals is nossihle hut mieht Drove somewhat tedious a n i , in the case of the redesigned cards, expensive. The eradine process varies somewhat from one experiment to the next b;t'approximates the following pattern; The first step in the grading process after completion of the experiment and all calculations by the student is for the studentproperly t o transfer his data, calculation results, and Table 2. 1 1 1 1 1
Estimated Budaet
Apple, twodlsk drives. monitor HE CadReader 8 intertaw Pmter (Okidata 92/93 is satistanoryl Interface card f w printer Accelerator ll(e) card (optional)
$1150 950 400 100 300 9000'
T/-
+/+I+/-
+/+/-
Card design, layout, and printing (1K)
d1om"nts. A total of 36 or 37 cards is needed by each ;idem t a iw JeGnoe ot 14 experimem~once initial wtep charges are pald, *is item bemmes much lowet.
Table 3.
Experiments for Which Cards are Available
1) Fundamental Masurements-measurement
of lenglh. volume, mass,
temperature, and density (with unknowns).
2) Semiquanlitative Estlmations-diiuting solutions, measuring volume and temperature, graphing data, reading a graph (with unknowns).
3) Definite Propwths-weishklg, heating. cwilng. catalculatlonof moleuler formula (MgO or W O d 4) Enthalpy Changes-simple caiwimeter. measuremem of temperature change, graphing, extrapolation, determination of water equlvaiem (heat capacity) of the calorimeter. calculation of heat of neutralization . of HCI and acetic acid. ~
5 ) Gravimetric Anaiysrs (Hydratetweighing, heating, caoling, calculation ot moles of water of hydration (unknowns). 6) Diffusion of Oases-Graham's Law. 71 Behavim of Gases, Boyie's Law and Charles' Law-measurement of gas volume, pressure, temperature. graphing, approximate absolute zero by exhapoiation.
81 Molecular Weight--Dumas Method (unknowns). 9) Equivalent Weight of a Metal-measurement of weight, gas volume by dispiacement above water, paniai pressures, gas law calculations (unknowns). 10) Freezing Point Lowering-cwling determinath (Wnowns). 11) aavimetric Sulfate-a
curues, molality, molecular weight
commonly performedexperimem (unknowns).
12) Aclbsase Titration-stsndardlzation acid sample (unknowns).
of NaOH solution, titration of an
13) Redox Titration-starddization of a permanganate s o l u t i i permanganate titmtion of arsenic(il1) oxide (unknowns, both permanganate and arsenic). 14) Chemical Equilibrium-colorimetry, diluiions, graphing, reading ormhs. calculation of souilibrium constant.
508
Journal of Chemical Education
experimental results, including an unknown if applicable, to a mark-sensecan1 tor set ofcards).Thecardsare returned to the instructor along with the student's data sheet on hisher report form. The instructor then does the irreducihle minimum of hand madine and arrives a t a total number of points to be deducted for that portion of the grading process,.rangine from 0 to99 ooints. Thisdeduction is then enteredon the &dent's card(;) in the position provided for this purpose. The cards are then read into the Apple under software control with the use of a card reader (HEI Card Reader). The Apple scans the data from the card, flagging any obvious errors such as douhle marks, rejecting these for correction. After the student's last card for the experiment has been read (the order of card entry is not important, except as convenience), the student's data are filed on disk in a random-access file. indexed bv the student's desk numher. which is part of the data on the card. After all the cards have been read and filed on disk. then the a .o ~ r o ~ r i a-eradine te program is run. The second maim step is the aradine process itself. Under software control,-the student's-long ;ring of data is read from the disk. The data string is separated into shorter strings that represent each individual measurement, calculation result, or experimental result. Where appropriate, these data are checked for the proper numher ofsignificant figures. Then each calculation reported by the student is checked for accuracy. The experimental results (at the option of the grader) may he recalculated from the reported initial measurements hefore being checked against the accepted value for the unknown. T h e results, recalculated or not. are then checked aeainst the unknown eiven to the student, the data for whGh are extracted from-another file containing that data. The deduction imposed by the grader (from the-earlier hand grading) is also iead frdm t h e card. Deductions are made for each error found, and a notation of that deduction along with the reason for the deduction is printed as hardcopy to he returned to the student. Deductions are also made for greater than acceptable deviations of the experimental results from the accepted value for the unknown. The erader-imposed deductions are also noted on the student's cardcopy sheet. The student's grade is then printed on the hardcopy and is also filed on disk in a grade file. The final step is to print (on the hardcopy to be returned to the student) the data as read from the student's card; thus, the student can check to see that the data he thinks he has reported are actually the data that the computer has for his experiment. The prbcess then repeats for the next student's report. At the end of a grading run, the grader runs a utility program to print a hardcopy of the students' grades. This step serves several purposes, not the least of which is that of hardcopy back-up should the disk with the grades become unreadable for some reason. All of the student's laboratory grades along with the running average are printed. Since grading ie. usually done by sections, the grades are printed for one section a t a time. Utility programs are used for the purpose of printing student grades, changing grades, entering unknown numhers and values, grading multiple-choice exams, setting u p the printer for the grading process, and so forth. These utility programs all were written expressly for use with the other programs of the package. They are provided for the convenience of the operator and allow (among other functions) rapid generation of gradesheets for each section containing the student's grades (to date) and his current lab average. Additional functions include the ahilitv convenientlv to change the student's grade for an experiment (which will he reflected in future eradesheets), to set the printer ~ r o p e r l v :or student report generation (aform length-of 3.5 ii., 8iinei per inch, 28 lines per form, and 15+ characters per inch make a maximum use of the least-expensive computer paper available). A
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Two utilities are intended primarily for the use of the individual in charge of preparing for the experiments. I t is his or her responsibility to see that the student's unknowns are available on time and that the computer has a record of exactly which unknown each student has and what the appropriate analysis for that unknown is. Programs have been written that allow unknown number entry on cards which are marked by the technician as he fills the student sample containers. The cards are read, the experiment number and unknown type are read from the cardsand a file is written to disk containing thestudent sample numbers for that experiment and unknown. A second program allows manual entry of correct analytical values for the unknowns. Both of these programs allow on-screen validation and correction of entry errors prior to actually writing the file on disk. The grading programs use these files for comparison with student reported values for unknowns. The two programs are accessed via the menus available a t hoot-up. An additional class of utility program is the file initialization ~ r o m a m sThese . oroarams are not accessible via menu. he; m i s t he accessed b y typing the appropriate command to RUN the programs. Since the function of these programs is to prepare an-empty file, properly dimensioned for later data entry, if these programs were to be inadvertently run, an entiresemester''w&th of data could be wiped out by a single careles~act. T o avoid this potential trap a control character has into the names. con- ~ . ~ been ~embedded ~ ~ - file ~ ~'Chis ~ trol character will not be seen when the catalog of the disk is ~~~~~
~~
~
~
read, and, if the disk is cataloged, the program FILEINIT is found, and the command "RUN FILEINIT" is typed (without the control character), the computer will respond "FILE NOT FOUND". These initialization programs are used for the roster file, the grade file, and all of the reported data files. Each is located on the disk appropriate for its intended use. The card-reading program, all of the grading programs, and the utility programs are all menu-operated and require virtually no operator training. Although an entire year's worth of experiments are, as yet, not available for use with the Apple 11, the experiments that are available are commonly performed experiments and can significantly reduce the amount of grading time required of graders and/or faculty. There are also advantages for the student. The computer, unlike human graders, does not get tired or irritable and is entirely consistent from one student to the next. Nor is the computer going to let personal likes or dislikes enter into the grading process. Grades may easily be returned by the next class meeting, not several weeks later, thus providing the student with better, more immediate feedback on his work. The principal disadvantage for the student is that the additional johof transferring data from the datasheet to the card isrequired. This operation is not difficult hut does takea few minutes extra for each experiment. The author welcomes requests for information and sample ~ student printouts.
Volume 63
Number 6
June 1986
509
