Interactive Computer Models for Analytical Chemistry Instruction

Tom O'Haver
Professor Emeritus
Department of Chemistry and Biochemistry
The University of Maryland at College Park
toh@umd.edu

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

Last updated: December, 2011
(I am currently revising and updating these models: send your comments and suggestions, and corrections to toh@umd.edu)

This is a collection of free, downloadable, 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, often much faster than real time. I originally designed these models for students in my courses in Instrumental Analysis (an upper-division undergraduate laboratory course) and Spectrochemical Methods (a graduate lecture course). They were designed to be used by individual students either as homework assignments, for in-class use in a computer lab environment, in the laboratory for the analysis of student-generated data, or as a temporary replacement for unavailable laboratory equipment. They can also be used by the instructor in lecture-demonstration environments. Student-assignment handouts and suggested experiments are included for most of them. The mathematical basis for each model is described, including all cell definitions and equations. These spreadsheets make extensive use of named cells (variables), which makes the equations easier to understand (as compared to the standard spreadsheet row-colunm references). Instructors are able to and are invited to modify these spreadsheets in any way for their students. 

OpenOffice Calc Versions
All of the new models and the updated versions of the original models are being developed in the Open Document spreadsheet format using OpenOffice Calc, part of the OpenOffice Suite, which students and faculty can download and use without cost, from OpenOffice.org for Windows, Macintosh, and Linux. To run these spreadsheets, you have to first download the OpenOffice installer (download from openoffice.org), then install it (by double-clicking on the installer file that you just downloaded), and then download my spreadsheets from this site.  Once OpenOffice is installed, you can run my spreadsheets just by double-clicking on them.   The OpenOffice suits also includes a full-featured word processor, a presentation program, and other components.  There is no need for students to buy the expensive Microsoft Office suite; the latest version of OpenOffice is always available for free download.

Note 1: Don't use version 3.1. There is a bug in OpenOffice 3.1 that causes bad x-axis scaling on some of my graphs.  The problems does not occur in versions 3.0, 3.2, or in the most recent version 3.3. 

Note 2: Downloading these files with some versions of Interent Explorer will change the file types from ".ods" to ".zip"; you will have to edit the file names and change the extensions back to ".ods" for them to work properly.  This problem does not occur in Firefox or in Chrome.

WingZ Versions
These models were originally developed in the early 90's in WingZ (.WKZ) format, an object-oriented spreadsheet with a built-in scripting language called HyperScript. This is still a useful format, because the HyperScript language has some has some unique capabilities that are useful in this sort of simulation and because the WingZ player program has a very modest memory footprint and runs very quickly even on older, smaller, or slower computers. I am gradually re-writing these models in the industry-standard, non-proprietary Open Document format (using OpenOffice Calc), but until that work is complete, some of them will be available only in the original WingZ format. To open the WKZ files you'll need the "player" application that  is included in the following file archives for both PCs and Mac:

How to open WKZ files: Both of the file archives above include the WingZ player application that is needed to open the WKZ files. 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 WKZ files from within Wingz (File => Open). (To get WingZ to launch when you double-click a WKZ file, you'd have to enter WKZ as a new file type in Tools => Folder Options => File types). 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 and then moved into the folder with wingz.exe.

Spectroscopy Instrumentation and methodology

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

Comparison of Analytical Calibration Methods	Multiwavelength Spectrometry	Lock-in Amplifier	Wavelength modulation system

Molecular spectrometry

U.V.-Visible Spectrophotometer	Dual Wavelength Spectrophotometer	Instrumental Deviations from Beer's Law	Calibration Curve Fitting Methods in Absorption Spectroscopy

Signal-to-Noise Ratio of Absorption Spectrophotometry	Effect of Slit Width on Signal-to-Noise Ratio in Absorption Spectroscopy (Version 2)	Scanning Fluorescence Spectrometer	Fluorescence Spectroscopy Signal-to-Noise Ratio

Atomic spectrometry

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

Classical, electrical, and computational methods

Worksheets for Analytical Calibration Curves	Calcium Ion Selective Electrode model	Resolution of Capillary Chromatography	Discrete Equilibrium  Chromatography Model

Triprotic Titration Data Analysis	Monoprotic Titration Curve model	Introduction to Signal Processing	Interactive Simulations of Basic Electronic Circuits

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?

Unsolicided Comments from Users at Other Institutions

"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..."

"...I have found [your worksheets] of great use whilst working on my current project."

"Wow! Nice work … and lots of it. Your stuff is wonderful!"

"What I like about your grating demo is that it clearly shows how increased dispersion causes the different wavelengths to have to travel different distances to the sensor...."

"Your models and write ups are excellant. It is an outstanding contribution for students and faculty members from developing countries."