--
no hugs have been detected in the last three semesters of use. Program LEWIS-Basic-Plus, 403 multistatement lines, 26 comments, no files. Students run LEWIS on any TEKTRONIX eranhics terminal. Execution reauires 13 K W h i t words on ~"PDP 11/70 minicomputer. students receive complete instructions a t execution time. Copies of the listing are available free from the author.
N2
---
0,
0
A Versatile Kinetics Simulation System B a r r y C. Finzel and J o h n W. Moore Eastern Michigan University Ypsilanti, M I 48197 The chemical kinetics simulation system described here accepts as input the series of elementary chemical equations that define the mechanism of areaction and the rate constant associated with each elementary process in the mechanism. The system outputs a table andlor graph of the concentration of each reactant, product, and intermediate as a function of time. Because innut of the reaction mechanism closelv "oar. allels the usual conventions for writing chemical equations, students having no expertise in computer programming can easily perform simulation runs. Instructors can use the system to generate concentration versus time data from which students can he asked to obtain rate constants and infer mechanisms. The svstem can also be used in research, with rate ronstmts ti,r given mechanism being adjtlsr~dto pnnide the hrst f ~of t simulated conrentration/rim~~li~ta t~~experimental observations. Since a numerical integration methbd is used, there is no requirement that a closed-form mathematical solution tothe ddferential rateequaria,ns+xist,or that common mechanistic siniplificarions such a+the steady-state approximation he empl~ryed.Indeed students cnn use the kinetic simulation svsrem tuexplor~.the relationshipamong mechanism. initial nmditions, aud accuracv u f a sim~lif'ication.In some cases, for example, the steady-state approximation can lead to erroneous conclusions, (4), which students can observe by doing steady-state calculations and comparing their results with data from a simulation. In principle the kinetic simulation system can accommodate any mechanism, but extremely complex mechanisms require a good deal of computer time. We have successfully simulated a pinp-pone mechanism in enzyme kinetics, reproducing the . .. experimental data of amm me sand Fasella ( 5 ) : ~ ehavealso duplicated the the solar flare example given by Edelson (6). A plot of the output from the latter simulation is given in the figure for comparison with Edelson's results. The input equations and rate constants from which Figure 1was obtained are aiven in Table 1. Note that when eouations are entered i n t i the computer, equals signs are used instead of arrows, there are no subscripts, superscripts, or lower-case characters, and ampersands are used instead of plus signs to separate different reactants or products. Plus signs are reserved to designate charged species. These conventions are close enough to standard chemical nomenclature that they can be learned easilv. The kinetic sidulation system follows the outline suggested bv Edelson (6). . . Program ENCODE handles innut of the elementary reaction equations and encodes subroutines that
a
-
-2
0
LOG (TIME/s)
2
4
LqWirnic plot of mncentrations versus time f a hsirnulatian definedin Table '.
calculate the derivatives and partial derivatives that are required for numerical integration. Program GEAR employs the Gear aleorithm (7) for inteeration of stiff systems of differential e&ations. GEAR accepts rate const&, initial concentrations, and parameters that control the numerical integration. I t produces a teleprinter plot and a table of concentration versus time data. If puhlication-quality graphic output of the sort shown in Figure 1is desired, program PAPPLT will produce it on a Calcomp plotter. The concentration/time data produced bv GEAR can he dotted directlv. .. with anv one or srwrnl species on the same coordinate axes. In addition selected functions (such as the logarithms shown in Firure 1) may be applied to any or all sets of values from GEAR'S output. Programs ENCODE, GEAR and PAPPLT have been written in FORTRAN but are not specifically designed for transportability. Use of disk files, graphics, and some local routines for packing characters into 36-bit words will require modification by other users. The three programs contain approximately 1980 statements, of which about 730 are comments. The nroerams are currentlv run from DECscone CRT 1 0 they , can also be r;n (with terminals on a 6 ~ ~ s ~ s t e m -and some loss of eleeance in the teleprinter olot) usine hard-coov terminals sue( as ~ ~ ~ w r i ~oc;me&ati& t e k includis samole executions and descriptions of local routines for gradhics and character manipuiation. Listings of ENCODE, GEAR, and PAPPLT will be supplied to anyone who sends e . decks a stamped, self-nddrersd 9 X i2-in. e n ~ e l ( ; ~Card cannot he supplied, hut listings and documentation along with an dOO H D.~KHCI)IC . version of the Droernms on \,our %track " magnetic tape are available a t a cost of $15 for postage and handlinr. Send a blank tane with a check made out to Dr. John W. ~ o & at e the addressabove. The authors acknowledee the assistance of Dr. K. Jeffrev Johnson who provided a working version of a subroutine for the Gear integration procedure.
.
.
-
P r e p a r a t o r y C h e m i s t r y and Physics: A CAI A D D ~ O ~ C ~
Table 1. Input for Ceslum Solar Flare Problem Equations
Rate Constants
028CS+=CS802 CS+8E-=CS CS=CS+8E02- = 0 2 8 E2 0 2 8 CS = cS02 8 0 2 028CS8N2=CS028N2 2028E-=02-802 028E-8N2=02-8N2
5.OE-8 1.OE-12 3.24~-3 0.4 1.0~-31 1.OE-31 1.24E-30 1.OE-31
Duli C. J a i n and T. Howard McGee York College, The City Uniuersity of New York Jamaica, NY 11451 This paper describes CAI programs developed for a preparatory or remedial course entitled Natural Science 100 (NS loo), for chemistry and physics students. CAI is ideal for alleviating several problems of a remedial course, namely: large class size, which limits individualization; varied backgrounds of students; the need for more individual drill than can he Volume 57, Number 4 ' - n f 7 W "
"53
provided in class or with normal homework assignments, and the need to maintain a hetter record of individual student progress. In contrast to other preparatory courses (8,9), the emphasis is on math concepts and the ability to apply them, not on knowledge and understanding of chemical and physical principles. Math concepts developed, however, are illustrated by examples from physics and chemistry and are specific to requirements of students in these areas. For example, logarithms are reviewed and applied to the calculation of pH and [H+]. Only the definition, pH = -loelH+l ". .and a brief description of [H+l is given, sufficient to perform the calculation -and see an appEcation of logarithms. Another topic is the conversion factor approach to problem solving. he student is taught to formulate a conversion factor and apply the proper factor to solve a problem. Again, emphasis is on using a given relationship to calculate a desired result and not on details of the chemistry or physics. The course as currently structured consists of two lecture hours, one recitation/lah~hourand a minimum of two hours of CAI per week. Eleven modules of CAI and eight laboratory exneriments have been develooed. The labs are keved to specific CAI modules and provibe experience with basic lab urocedures and instruments. Students are placed in NS 100 based on an exam that was developed internally and has been used successfullv for five vears. The compute; programs have been designed so that: (a) Students do not rewire much time to learn the use of the programs; programs b e uniform in structure. (h) Students are not reauired to refer to a text or depend on class instruction. (c) he computer "teaches" how to translate a verhal problem into mathematical language and apply the necessary mathematical techniaues to s d v i it. (d) ~-~~~~ . . Students are able to receive ample drill and tutorial assistance. (e) Students are able to proceed a t their own pace. (f) The computer maintains a record of student progress and achievement. To achieve these results a svstem of computer programs t (Table 2) wasde\.eloped it1 H A S ~ Clanguage. ~ h e s t u h e n runs O;C.AI.I.lJA(: to access CALLSIGN or the instructional modules. $CALLPAC (1) provides information on the modules, (2) searches the data file for record keeping, (3) chains to CALLSIGN which provides student indentification numbers, and (4) chains to the instructional modules as required. The instructional modules for NS 100 are listed in Table 3. Each module is divided into units representing aspects of the ~ e n e r amodule l touic or a eraduallv increasine deeree of diffiklty. One unit is imoduleuquiz. able 4 lists tKe &its for the module on loearithms and exponential functions. The units of module 1&rough 9 (except'the module quiz unit) are further subdivided into three segments: I. Statement and diwussion o f rhe neressary mnthematiral tcchniquer and phyiirnl ur rhemical concepts with sums illustrative rxamples. 11. Prarrirr t~rohlerns.111. Unit uuiz Thestudmts mavskin " . or repeat segments of each unit or an entire unit. The module quiz, as a minimum, must be taken to demonstrate competence. Assistance in the form of helpful hints is provided in segment I1 for students experiencing difficulty. Help is not provided for unit and module quizzes. All practice prohlems and auizzes are randomlv eenerated. U& of modules 10 an2 11 have segments I and I1 only. These modules include different types of problems designed mainly for student drill. Three options are available for solving prohlems of these modules: Code 0:The computer gives the solution. Code 1:The computer provides hints for solving the problem. Code 2: The student solves the problem without any assistance. The student may complete any number of units of a module during a CAI session. The system stures the module units completed and dirtbcts earh student where to start at thebeeiilnine ol'cach session. A feature named DESKCAL (which perfor& like a desk calculator) is built into the system. The practice problems, unit and module quizzes are graded
.--~-~~~ ~
~
~
~~
~
254 1 Journal of Chemical Education
Table 2. NS 100 Computer Program System
I. A master program: SCAUPAC. ii. A general purpose program: CALLSIGN. iii. Eleven instructional modules. iV. Three data files far each section of 30 stmdmh. Each data file is one file unit in ienath. Table 3. lnslructional CAI Modules for NS 100 1.
2. 3. 4.
5. 6. 7.
8. 9.
10. 11.
Direct proportions Percentages Scientific notation Conversions (physicalquantities) Conversions (chemicalquantities) Emoiricai formulasand simoie chemical eauntions .- Simple algebraic equations Quadraticequations and simultaneous equations Lwrithrns and exponential functions Trigonometric functions Vectors, their components and resultant
Table 4. Units of Module 9: Logarithms and Exponential Functions
Logarithms end antilogarithms Multiplications. divisions, cube roots, etc. (by using logs and antiiogs) Unit 3: pH and concentration of Hf ion Unit 4: Module quiz Unit 5: Natural ioaarithrns and exoonential functions lootional\ Unit 1: Unit 2:
-
bv the comnuter and immediate resoonses are orovided. students a&allowed three attempts to correctly solve practice ~rohlems.Thev can repeat a unit or a module auiz to im~rove their performance. he system maintains arecord df the performance of the students for three instructional modules. For modules 1 through 9, the system stores: the number of practice prohlems attempted, the cumulative score in practice prohlems, the number of attempts and scores in module quiz. For modules 10 and 11 the system records: the number of problems attempted, the cumulative score in problems, the number of prohlems of each type and of each unit solved with the score of 75%or hieber. This information for eachmodule can he printed out i n a tabulated form for all students. The CAI nroerams described have been comnleted and class tested. ~ h i d c . 4 1 approach has been henefirial iostudents and fitcultv. Studenr rweive extensive drill. tutorial assistance and proceed a t their own pace with attention paid to specific weaknesses and varied backgrounds, Faculty can accommodate more students in lecture and monitor individual performance. The detailed student records will pinpoint main weaknesses and allow modification of lecture and CAI materials to provide an increasingly effective course. Students successf~llycompleting NS COOcontinue in chemistry and physics with greater confidence, more attention to principles and less concern about mathematical fundament&. The system is installed in the CUNY IBM 370 computer. Each module has about 700 statements in BASIC (28Kbytes). Programs can he copied on magnetic tapes and an assortment of options of density, record length, etc., exists. Documentary flowcharts, sample listings and runs are available. Contact the authors for details. The authors are grateful to Profs. F. Pomilla and E. Levin for their suggestions and discussions. This work has been supported by a CAUSE grant # SER 77-05466 from the National Science Foundation. Literature Cited (1) Marron, M.T.. J.CHEM.EDUC.52.336l1975). (2) TRS-80 is a trademarkofthe Tandv Carporation. (3) Taylor, D. G.. Ph.D Lhwia, Univomityaf Virginia, 1979. (4) Farrow, L. A,, and Edolson, D.,Infern.J C h m . Ki%, 6,787 (1974). (5) Hammes, G. G.,and F a d l a , P., Bioehamkfry. 6.1798 (1967). (6) Edeison.D..J.CHEM.EDUC.,52.642 (1975). (7) Gear, C. W.. N u r n e ~ i dInifioi-Value Pmblams in OrdinaryDil~emNio1E q ' ~ t i i i , Prenfiee-Hall, Enpiewoal Cliffs, NJ, 1971,Chap. 11;Gear. C. W., Cornrn. ACM, 14.
, m (,a?', ,."..,. (8) 6eitinger.D. J..and Hsight.H.L.,J.CHEM.EDUC..54(12).729 11977). (9) Krannich, L. K., Patick, D., and Pevear, J.,d. CHEM. EDUC. 51 112). 730 (19771.
