edited by: John W. Moore, Eastern Michigan University
Computer-Aided Instruction with Microcomputers
John W. Moore,' George Gerhold,' R. Daniel B i ~ h o pJohn , ~ I. Gelder,4 Gilbert F. ~ o l l n o w , ~ and G. Scott Owene
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K Systems and applications, comparison and evaluation
This article continues the description of microcomputer systems and applications in chemical education begun earlier (I).We conclude with a comparison of a number of microcomputer systems. Though n i t all-inclusive by any means, this comparison will he valuable to anyone considering purchase of a microcomputer system. In addition to material presented in this and the previous article, several reviews of popular microcomputers have appeared recently (2-6). A Disk-Based TRS-80 System by R. Daniel Bishop
Our school recently purchased two Radio Shack TRS-80 microcomputers to be used as teaching aids in our undergraduate chemistry program. One of these is the standard IGK-RAM microcomputer with cassette storage ($890 currentlvl: ... diskette . . the other has 32K RAM with a single floupv drive for disk storage, an expansion interface unit (required for disk operations), and electronic dot matrix quick-printer ($2400).A very short "monitor" program on the disk system allows the student to see the titles of all the programs on the disk and to select the desired program merely by tapping a single numeral key. At the conclusion of each program, the program title and the student's name, computer usage time, and scores are recorded on the disk. The computer then reverts to the monitor Droeram . .. and waits for the next student. The programs that are included on our first complete diskette, GENCHEMIONE, are listed in Table 1. Each program is also individually available on cassette for use with the 16K non-disk microcomputer. These programs were developed entirely "in-house" by the author. Our tutorialldrill programs pose a prohlem for the student and, following the student's response, show the correct answer and allow the student the opportunity to select a program sequence showing exactly how the problem should have been worked. In some cases. the student also has the option of seeing - worked examples a t any time during the program sequence. The Charles' Law and the density programs are computer simulations of laboratory experiments that are designed to teach concepts rather than manipulative skills. For this type of experiment a computer simulation can save much student time as well as the cost associated with actually performing eraohics the exneriment. Extensive use of " . not onlv adds to the realism of the simulation, but also enhances student interest in the exercise.
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Eastern Michigan University, Ypsilanti, MI 48197. Author to whom correspondence should he addressed. 2 Western Washington University, Rellingharn, WA 98225. "chuol of the Ozarks, Pt. Lookout, MO fi5726. Oklahoma State University, Stillwater, OK 74074. "University of Wisconsin-Oshkosh, Oshkosh, WI 54901. "Atlanta University, Atlanta, GA 30314.
The Charles' Law simulation displays the apparatus on the video n ~ r n ~ t u.ith o r thr mercury plug in thr glass tube positioned apprc~pri:ttelyl.,r wnate\er tcampt.ratllrr the student hi14 . ~. ri. e..~ t e~Filr ittldrnt then mensuws the length ,d - I. l ' h ~ of the trapped air column directly from the screen. ~ f t eart least four trials a t different temperatures, the student may entl:r h t ; pc)int< ~ frrm which the computw yrdplli the line of t ~ wl i t and prinrn rhr throrct~culvalue 811 s l ~ r l ~zt:ru ~ t cd ~ tainrd i n m thc student's data. The >tntibt~val~ ~ ~ a l vcan sis easily he deleted from the program if desired. students readily ~erceivethe value of selecting the widest possible range of ~ ' of using more than the temperatures (-15 to ~ o o ' cand minimum number of data points. The density program (Fig. 2) simulates an experiment in which the volume of a solid is determined by displacement of ~
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Table 1. Brief Description of Programs in GENCHEMIONE Prooram Set
Cas~ene Load Time Program Name
Density Simulation
Description Simulation of
experimental determination of the density of a solid. (Graphics) Charles' Law Simulation of the Charles' Law determination of absolute zero. (Graphics) Elementary Solution Tutorialldrill in making Chemistry a given volume of solution of desired concentration. Advanced Solution Tutorialidrill in converting solution Chemistry concentration9 from one unit to Other units. Dilution Chemistry Tutorialldrili in calculating volume and concentration relationships involved in solution dilutions. Tutorialidrill in Tem~erature Conversions calculating temperature conversions ( O F and
IS
Memory Required /bytes
60
6K
65
6K
110
8K
155
1ZK
90
8K
110
8K
'C only). Uses
graphics and game routine with timer for additional intmrc4
Volume 57, Number 2. February 1980 / 93
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Y O U H A V E BEEN G I V E N A SOLUTION OF POTASSIUM HYDROXIDE THAT H A S A M O L 4 L I T Y O F 12.3862. THE D E N S I T Y OF T H I S SOLUTION 1 5 1.4103 G l M L CALCULATE THE !+EIGHT PERCENT AND TliE MOLE F R A C T I O N FOR T H I S S O L U T I O N .
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SOLUTION
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h E ARE G I V E N T H A T THE SOLUTE IS P O T A S S I U M H Y D R O X I D E AND THAT I T S N O L A L I T I I S 1 2 . 3 8 6 2 . THE D E N S I T Y OF THE S O L U T I O N 1 5 1.6103 6 1 N L .
Figure 1. Screen display for Charles' Law simulation. (TPS-SO)
~. OBJECT XEITWT:
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h E llErO TO TI00 T*E A P P R O P W I A T L YMLULS COR ( l i T H R O U G X i H 1 . M O L A L I T I C l Y E S U S 1 Or MOLLS LIT i O L U T L PLR MC. O r SOLVENT. T b i U I c1>=12.1862 HOLES Ano D=iaOO G R A M S . HOLES T I M E S M.*T. GIVES
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(8): ~ e b y equation e KC 1 ---+ AR. M-P(OI
P C T ~T W E N
2A2C
Figure 7. Screen displays from program for determining molar mass a1 a polymer by light scattering. (a) Zimm plot: (b) summary at results. (Tektronix 4051)
in excpss of that due tosolvent. is the ratio of the corrected -~~-~~~ ~
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FPUH PEFEREHLE r 3 i
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light intensity (per unit volume of solution per unit solid angle a t the detector a t scatterine..angle . 0) to the incident intensity. AR,, has dimensions of length-'. The particle scattering factor P(0) is a function of the shape and dimensions of the scattering particle, as well as the scattering angle 0 (8).In the limit of H = 0, P(0) = 1. For small, positive scattering angles and dilute solutions, Zimm (9) has shown that the Debye equation hecomes:
Here B,Z is the z-average mean square radius of gyration for randomly coiled polymers, and A, is the wavelength of incident light; the scattering ratio KCIARo is a linear function of C and of sin2 ((112).Mmcan be obtained from a Zimm d o t . in which the scattering ratio is plotted against sin2 (HI$) k c (where k is an arbitrarv constant) and the data are extrapolatedto~=~agH=b. Numerically, M,, A2. and S: can be adjusted to minimize the sum of the squares of the differences between observed and calculated values of the scattering ratio. Solution of the normal eauations is " eiven bv Collins. Bares. and Billmever (10) along with standard error equations for the regression coefficients and the resulting errors in the molecular parameters. These equations have been combined with a plotting routine in a BASIC Droaram for the Tektronix 4051. Samole screen displays are s h o k in Fig. 7 for the data provided in reference (10) (and contained within the program for verification). In Figure l a the two line segments from the scattering envelope corresponding to C = 0 and R = 0 have been drawn, as well as the exoerimental noints. A documented listing of the light-scattering program is available from G . F. Pollnow a t no charge. Alternatively, for
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a service charge of $20 to cover postage and handling, the program will he loaded onto your 3M DC300A tape cartridge and returned. This work was supported by the UW-Oshkosh Faculty Development Program and by National Science Foundation Grant No. SER-16644. Comparison 01 Systems
By George Gerhold
Which microcomputer is best depends on a variety of circumstances: the specific application for which the machine is to be used; whether a wide variety of applications will be attempted; whether the manufacturer of a given system will continue to support it (or even stay in business); availability of software and peripherals; and price. Price enters the decision in two ways: there may be abudget limit beyond which you cannot go; and there is the costlbenefit question of whether a $2500 microcomputer provides three times the educational benefit of an $800 system. Obviously you must base your decision on your specific circumstances, and we cannot recommend a single system or machine as best. Nevertheless, some comparison of features such as we have provided in Table 2, is useful. We can state two generalities: first, the microcomputer market is very competitive and so you usually get what you pay for; and second, certain features listed in the table may be essential for one application hut totally useless for another. Comparisons themselves are colored by the author's biases, and their value is deoendent on the breadth of the author's exprriencci u,ith a rarwty of computer;. 'l'm dim compari sans are c,r "the (omrwvr I h;rw .elected and have with all thc others I rejected anddon't have." Thus one should always find out something about the experience of the author with the machines in question. T o that end, I have used the following microcomputers extensively: TRS-80, Apple 11, SwTPC Volume 57, Number 2,February 1980 1 97
680016809, North Star Horizon, and the TERAK. I have a little experience with the PET, and the remaining portions of the comparison are secondhand. Brief amplification of some of the phrases used in Table 1 is in order. Some manufacturers have dealers in most medium-sized cities (dealer network a virtue), while others are primarily mail-order firms (dealer network a weakness). Not all dealers are equipped to service their products so a service network is usually separate. Graphics resolution has been defined previously (11, I). The term "square array" means that horizontal and vertical spacing between dots is the same: four adjacent dots for a square. Not all micros allow complete superposition of text and graphics. Memory-mapped displays offer the advantage of speed (sufficient for animation in some cases) at the cost of flexibility; a memory-mapped display and a particular microcomputer must be used together. Color is a mixed blessing: the advantages are obvious, but many of the displays currently available are sufficiently less stable and less sharp than black-and-white displays in that they are very fatiguing in extended use. For most systems a reduced number of lines below the 24 on standard display screens is less serious than a reduced number of characters per line below 80. A great deal of programming is required to adapt a program that assumes 80-character lines to 64 or fewer characterslline. Limitations of uppercase-only displays are obvious to chemists;
on the plus side, a user-definable character set allows one to show chemical notation nf any ctmplexity. Quality of construction and packaging includes items such as adequacy of power supply and ventilation, memory speed (use of substandard chips at less than design speed is a cost saver), and component interconnecti
