Interactive models for Analytical Chemistry Instruction

Interactive Computer Models for Analytical Chemistry Instruction

Tom O'Haver
Professor Emeritus
Department of Chemistry and Biochemistry
The University of Maryland at College Park

http://www.wam.umd.edu/~toh/models/

A Links²Go Key Resource Award in the Simulation Models topic
First version created in 1991
Last updated: September, 2006

This is a collection of interactive computer models and simulations of common analytical instruments and techniques. Most have a point-and-click interface; you click buttons and drag sliders to control variables and the model responds dynamically, usually faster than real time. I originally designed these models for students in my courses in Instrumental Analysis (an undergraduate laboratory course) and Spectrochemical Methods (a graduate lecture-based course). They were designed to be used by individual students either as homework assignments, for in-class use in a computer lab environment, or in the laboratory for the analysis of student-generated data. Some can be used by the instructor in lecture-demonstration environments. Student assignment handouts are attached to most of them. The mathematical basis for each model is described, including all cell definitions and equations.

PC users: Click to download a basic set of models and the player application as a ZIP file (700 Kbytes)

Mac users: Shift-click to download a basic set of models and the player application as a SIT file (500 Kbtes)

These model collections include a "player" application that will allow you to run the models and make changes to the parameters. Make sure that ALL of the files in this download are kept in the same folder. Put any separately downloaded model files (.wkz files) in the same folder. To run a model, first launch Wingz.exe, then open the desired models files from within Wingz (File --> Open). Note: It is best to download the basic set of models initially, to make sure that you have all the pieces needed, then check back here occasionally for new models, which can be downloaded individually. Individual models are listed here:

Spectroscopy Instrumentation and methodology

Color Temperature of a Blackbody Source	Animated Diffraction Grating	Photomultiplier Light Measurement System

Error propagation in Analytical Calibration	Multiwavelength Spectrometry	Lock-in Amplifier	Wavelength modulation system

Molecular spectrometry

U.V.-Vis. Photometer	Dual Wavelength Spectrophotometer	Instrumental Deviations from Beer's Law	Fluorescence Spectroscopy

Atomic spectrometry

Signal and Photon SNR of Atomic Emission Spectrometer	Effect of Slit Width on Signal-to-Noise-Ratio	Line Wing Overlap	Spectroscopy of Atomic Absorption

Classical and electrochemical methods

Calcium Ion Selective Electrode model	Resolution of Capillary Chromatography	Discrete Equilibrium Chromatography Model

Triprotic Titration Data Analysis	Monoprotic Titration Curve model

If you have suggestions for other models like these that you would like to see developed, please email me at toh@umd.edu

What do the students have to say about these models?

How can I develop my own models?

Developing new models such as these is not hard because they are merely spreadsheets. I used WingZ 1.1, a 90's vintage spreadsheet. There is a brief WingZ tutorial on the Web, at Introduction to Spreadsheets. In most respects (cell equations, functions, math expressions, cell formatting) WingZ is like most other spreadsheets. The major differences are in the use of control objects: see the sheet "controls.wkz", included in the above downloaded zip file, for more information and examples of control objects and their use. There are also some differences in plotting and curve fitting (see "MultipleYPlotDemo.wkz" and "LinearCurveFitDemo.wkz" in the downloaded zip file). The "player" application included in these model collection downloads, although it is stripped-down compared to the later and more highly developed versions of WingZ, will allow you to edit these models and even develop your own; just select New from the File menu to get a new sheet to work with. Don't forget that you can Copy and Paste control objects and scripts from my sheets into yours, then modify them to suit your application.

How these models were Developed

These models were created using WingZ, a 90's vintage object-oriented spreadsheet with a built-in macro language that used to be available from Informix and Investment Intelligence Systems Corp. No knowledge of WingZ is required to operate the models. The advantage of WingZ, as compared to more popular spreadsheets such as Excel, is that WingZ 1.1 requires much less computer capacity - needing only about 1 MByte of RAM and 700K of disk space to run. It's also faster than Excel on small, older machines. The models themselves are quite small - about 10 to 40K bytes each; several can be open at once if desired. The disadvantage of WingZ is that it is not Excel and hence is doomed to obscurity.

Why didn't I write these models in Java or Flash ActionScript, so they would run directly on the Web pages? Several reasons. First, I have not found an an easier way of programming this type of equation-driven simulation than a spreadsheet. Second, I have not found a programming system that produces products that can run more quickly that WingZ (especially critical for the computationally intensive real-time models such as fluorescence spectroscopy and the lock-in amplifier). Third, a Web browser requires a larger and faster computer than WingZ 1.1; you can run most of my models on those old 486's that are too slow for recent Web browsers. Fourth, and most important, my models are just spreadsheets, which are much more easily understood and modified by instructors. You don't have to know programming to make simple changes in a spreadsheet. Some of these Web pages include specific suggestions for aspects that can be readily customized by the instructor. The bottom line is that I am more interested in creating models than in programming; as far as I am concerned, the less programming the better.

Description of the WingZ program

Unsolicided Comments from Users at Other Institutions

"Let me congratulate you on a fine web page! I'm a technical support engineer for Wingz ... and I rarely run across such sophisticated use of our products."

"I was able to get everything working nicely and can promise you they will be helpful with my students."

"Today I had the first simulation experiment and the students were excited... The lab was much more interesting than the lecture, this is for sure!...I had very good feedback from students..."

This page is maintained by Prof. T. C. O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Created 1991. Last updated September, 2006. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu.