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MERLOT II


    

Peer Review


Spectrophotometry Simulation

by Gary Bertrand
 

Ratings

Overall Rating:

4.25 stars
Content Quality: 4.5 stars
Effectiveness: 4 stars
Ease of Use: 4 stars
Reviewed: Feb 19, 2009 by Chemistry Editorial Board
Overview: An interactive simulation of a spectrophotometric experiment involving the quantitative analysis of a mixture of two dyes is given. The student is able to simulate the generation of calibratrion curves, plotting of spectra, and calculation of the concentrations of unknowns.
Learning Goals: The simulation enables the student to become very familiar with the operation of spectrophotometric quantitative analysis prior to going into the lab. The simulation also enables the student to determine such things as the optimum sampling wavelength for two different analytes.
Target Student Population: First year chemistry students and 1st year analytical chemistry students will benefit from the speed of this simulation, gaining valuable background knowledge and dry-lab experience before going into the actual experiment.
Prerequisite Knowledge or Skills: The students should understand why molecules absorb light and that the absorbance of a sample is proportional to the concentration of the analyte (Beer's Law) and the extinction coefficient of the sample at the wavelength selected.
Type of Material: This site is an interactive simulation of a spectrophotometer.
Recommended Uses: 1. This simulation could be used as a pre-lab exercise for students doing quantitative spectrophotometric analyses.

2. Students could use it to investigate beers law, interference effects in measurements, solution concentration, calibration and operation of a spec 20.
Technical Requirements: 1. Program works fine with IE and Netscape, but does not open with Opera

2. It is helpful if the user has excel or another spreadsheet program available for plotting of the data.

Evaluation and Observation

Content Quality

Rating: 4.5 stars
Strengths: 1. The simulation is quite marvellous. The students can select the wavelengths, zero the absorbance of the spectrophotometer, generate calibration curves and scan spectra.

2. The background content is perfectly appropriate for the experiment and well written, but if this module is going to be used for students to uncover relationships, it might be better to leave this out.
Concerns: The instructions are a little bit complex. Students will have to pay fairly close attention the first time they use the applet.

Potential Effectiveness as a Teaching Tool

Rating: 4 stars
Strengths: 1. Straightforward module, common technique and equipment, widely used in high school and introductory courses, allows students to explore data acquisition. After spending 15-20 minutes with this simulation a student could be very efficient in lab.

2. This is a perfect simulation for teaching about the quantitative use of spectrophotometry. The use of two different dyes causes the students to think about the optimum wavelengths, the use of calibration curves etc. The use of unknowns and verification of the calculated values is a clever idea.
Concerns: 1. The module would be a much more effective teaching tool with lessons designed for guided inquiry experiments. This application could be a very useful tool for helping students develop an understanding of several important concepts such as calibration, interference, and solution concentration.

2. When the student calculates the wrong value for the unknown, there should be some sort of feedback telling them how close they were and requesting the wavelengths they used. From the wavelengths they used, feedback should be given regarding the appropriateness of that wavelength choice.

Ease of Use for Both Students and Faculty

Rating: 4 stars
Strengths: It is terrific to be able to mix up any combination of the analytes, measure the<br/> absorbance, scan the spectra. It is a very clever simulation indeed. Dumping the solutions is easy to do. The scan data is readily accessible for further manipulation in a spreadsheet package etc. This is a great way to get the timid student used to using equipment.
Concerns: 1. The module is simple enough but with minor modifications users would not need any instructions. Suggestions to help with this include: -Add text to main screen with basic steps to set up spec 20. This would allow exploration of the module without looking at the instructions. The operations section is clear, but some minor changes in the page layout might make this section much shorter or even unnecessary. This would make the module much easier to use. For example, if the blank and the two samples are labeled, then the first paragraph of the operation section would not be necessary. If the red, blue and water dispensers were labeled and indicated it was mL added, it would be more obvious how to mix solutions. The steps for operation could be shortened and included on the page. With these modifications the operation would be much more obvious. -Include volume added and labels to the three solutions (red dye, blue dye, and water). -Add some text to clarify steps for making up new solutions.

2. It would be useful if the instructions included some links to online spreadsheets (which can be made active) into which the data could be posted to instantly generate the spectrum.

Other Issues and Comments: It took me a few minutes to figure out what I was doing on the simulation. As a prototype student, I didn't read the instructions first. But then I learned after a few experiments.