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: August, 2014

This is a collection of free, downloadable, interactive computer models 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. Note that these are not really simulations of particular commercial instruments. They are rather interactively manipulable mathematical models that are essentially sets of linked equations that describe various parts of or aspects of each system. Most of them produce graphs and charts that illustrate the internal operation of, or mimic the output generated by, these systems. Because they are just spreadsheets, it's easy for instructors and students to inspect the equations that drive these models. Unlike closed proprietary programs, the mathematical basis of these models is not hidden but rather easily accessible and can be viewed, modified, corrected, or extended by any instructor who is familiar with the basics of modern spreadsheet construction.

I originally designed these models for courses I used to teach in Instrumental Analysis (an upper-division undergraduate laboratory course) and Spectrochemical Methods (a graduate lecture course) at the University of Maryland. The spreadsheets 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 in PDF files, including all cell definitions and equations. Instructors are able to and are invited to modify these spreadsheets in any way for their students. See the unsolicited user comments below from actual users of these spreadsheets. 

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 Calc 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: Downloading the individual spreadsheet .ods 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.

Microsoft Excel Versions
Interoperability between Excel ".xls" and OpenOffice Calc ". ods" files have been improved in Excel 2013 and OpenOffice version 4, which can read and save in each other's formats, but there are still some problems relating to fonts, forms controls (particularly radio buttons, check boxes, and sliders), and named variables. I am gradually trying to fix those problems and provide customized xls version that have been tested in Excel 2013. If you don't find what you want here, let me know. I also recommend Scott Sinex's excellent collection of Interactive Excel Spreadsheets.

WingZ Versions
These models were originally developed in the early 90's in WingZ (.WKZ) format, the first 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 (but not unfortunately on 64-bit Windows). 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:

PC users: Click to download a basic set of WingZ models and the player application as a ZIP file (700 Kbytes)
Mac users: Shift-click to download a basic set of WingZ models and the player application as a SIT file (500 Kbtes)

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

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 



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?


Unsolicited Comments from Users at Other Institutions

"I came across your ďInteractive Computer Models for Analytical Chemistry InstructionĒ manual. Itís a remarkable piece of work, you have written."

"This stuff is really impressive work...."

"Iím happy I have found your site since it has some very valuable information relevant to the projects Iím currently working on."

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

"...my deep gratitude for the wonderful interactive diffraction grating models; they are in so many words instructive and indispensable."

"Iím happy I have found your site since it has some very valuable information relevant to the projects Iím currently working on."

"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 Ö 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...."

"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." 


References
1. Scott Sinex, Chemical Excelets:  Interactive Excel Spreadsheets for General Chemistry. (http://academic.pgcc.edu/~ssinex/excelets/chem_excelets.htm)
2. Chemistry - PhET Simulations (http://phet.colorado.edu/en/simulations/category/chemistry)
3. Brian Tissue, Spreadsheet Simulations for Analytical and Physical Chemistry (http://www.files.chem.vt.edu/chem-ed/simulations/spreadsheets.html)


View this page in Romanian courtesy of azoft
Created by T. C. O'Haver , Department of Chemistry and Biochemistry, The University of  Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu.

Copyright © 2014, Thomas C. O'Haver
 
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.


THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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