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## Computers in Introductory Chemistry Laboratories

### A Proposal Submitted to NSF in June 2000funded May 2001-April 2003

In June 2000 we submitted to NSF a proposal to purchase computers and laboratory interfacing for the introductory chemistry laboratories. This document is an attempt to show the logic of that request.

edited: January 21, 2001 (This is being revised, August 2004)
comments to: Paul Endres
file: nsf/nsf5_HPC.htm

### Introduction:

For some time we have been trying to find a way to bring computerized data collection to the general chemistry course. There are some serious problems that need to be resolved.
• cost (purchasing computers, but also developing software and maintenance)
• space (including where computers are placed)
• security (from theft, but also from laboratory chemicals which are tough on electronics)
• accessories (30-50% of the cost of a typical installation is devoted to sensors and interfacing with the computer.)
• actual experiments designed to intelligently use computers
One approach is to have computers around the perimeter of the lab
• students take experimental materials to the computer work site
• we have up to 60 students in these labs
• 60 computers is unrealistic
• working individually on alternate weeks would require 30 computers
• basic cost-- about \$2500 for computer and lab interfaces (about \$75,000)
• each standard computer needs about 4 ft of table top
• we'd need about 120 feet of space around the room
• there isn't that kind of space available in the general chemistry lab
Another approach is to place a computer at the lab bench
• we still need about 4 ft of bench space
• that's over half of the area for one student work station
• we might build a stand to keep most of the computer off the table top
• however, we need to keep the computer safe (from water, reagents, ring stands)
It's difficult to see a way to use conventional desktop computers in this environment.

We could, of course, use fewer computers

• have students work in groups of two or four
• to have computer use limited to 20 minutes/lab so same machine can be shared by 2-3 groups
• This can be done, but it severely limits the role of the computer in experiments
We then examined the prospects for lap tops or similar units
• space needed per unit is much smaller
• cost is generally higher than for standard PC's
• (\$1500-2000 for computer; \$250 accessories)
• laptops are generally easier to damage, harder to get repaired
• laptops are harder to keep secure (easier to steal)
• laptops might be harder to keep safe (easier to move into a region of chemical danger)
At the other extreme, there are calculator based labs developed and a company called Vernier Software In March 2000 we got local funds for one of the Vernier / TI systems to evaluate the system.

We were not satisfied with this approach:

• programming is extremely awkward
• dumping data to a PC is possible, but not convenient
• data display is tiny
• computational options are surprisingly limited
• students familiar with computers would see this as a very backwards technology
One other option is the use of smaller computer devices
• PDA-- Personal Data Assistant like the Palm (TM) devices
• HPC-- Handheld Personal Computers
• Obviously these are smaller and fit our space well
• They are portable and could be kept relatively secure when not in use
• They are generally designed for a somewhat more rugged environment than PC's and laptops
• They are considerable less expensive than PC's (\$100-500)
• They have communication features that we could use effectively
Most of the PDA's pose serious problems
• They have no commercial software that can handle laboratory situations
• They are programmed using a specialized programming language
• We could expect a steep learning curve and a long preparation time before we could use such devices in the lab.
• Most students would be unfamiliar with the specific device and would have to learn its operation
• Most PDA's actually have a tiny screen with modest capability
However, a few of the HPC units operate under Microsoft Windows-CE
• this means the screen has the look and feel of conventional computing activity
• a programmer can develop software using standard computing languages like Visual Basic
• the screens generally have larger size and better resolution than most PDA's
In particular, we evaluated a unit made additional feature has to do with funding All of these factors led us to write a proposal for computer based experiments in the introductory chemistry labs based on the HPC approach.

Let's look at some typical applications. Let us also ask some very specific questions.

• 1. What are the (chemistry) concepts that the experiment develops?
• 2. In what way does the computer change the experiment?
• 3. How do you focus on the chemistry rather than the computing?
• 4. What other factors (pro and con) enter the picture?

### Calorimetry

• Dissolve a metal (Ca, Mg, Zn, Fe) in acid
• Measure the temperature rise
• store temperature vs.. time data
• display temperature vs.. time graph
• Compute the Enthalpy change in the reaction.
The calculation depends only on the overall temperature rise. It would be cheaper and easier to use a thermometer to make that measurement. What advantages are there to using the computer?
• The real time graph shows additional information
• student gets experience extracting information from graph
• actually see the rate of the reaction
• could examine the effect of surface area
• compare time for large pieces vs granualar metal samples
• can see heat loss
• can see cooling after the reaction
• due to both heat losses (insulation) and to evaporative cooling
• this would probably not be noticed with thermometer
Process is rapid (5 minutes)
• time to focus on interpretation and calculations
• time to include a calibration run
• time to make several runs and comparisons

### Acid-Base Titration Curves

We do this now with conventional glassware and pH meter.

• typically make 10-20 additions of titrant
• read and record pH
• then plot graph
• finally interpret graph
• each run typically takes 30 minutes
• students likely to get 2-3 runs in a period.
using computer to log and plot pH
• allows many more data points to be collected, leading to smoother and well defined graphs
• minimizes tedium and transcription errors
• data appears in real time
• experiment provides data initially as a visual image
• student is free to focus on data, to try to predict remainder of the curve
run is much faster
• could be a 2-4 minute run
• it would be realistic to do 5 (or even 10) different runs for comparison
• strong and weak acids, strong and weak bases
• with good graphics, endpoints of weak acid-weak base can be determined
• polyprotic acids
• mixtures (bicarbonate, carbonate), (HCl and acetic acid)
• Again, comparison of runs begins with a visual image (curve) with clear qualitative differences

### Other than Acid/Base by pH

Could monitor temperature during an acid base titration curve

• can actually use both temperature and pH probes and plot both
• this is rapid process
• results show up immediately as visual image
Not likely to do with conventional equipment
• would be too tedious to collect many data points
• would need to do more slowly and heat loss is more of a factor then
Could monitor electrical conductivity during a titration
• complexing reagents, precipitates, neutralization

### Kinetics

Can expect to monitor concentration of one species throughout a reaction

• typically be colorimetry or spectrophotometry
• could also use a species selective electrode
• can monitor heat produced by reaction
Again, the history of the reaction is displayed in real time as an image

### Vapor Pressure of a Liquid

• Simple pressure sensor can record pressure vs.. time.
• Small amount of liquid added to a closed flask connected to the probe
• As liquid evaporates, pressure rises
• Pressure levels off when the equilibrium vapor pressure is reached
• Again, process produces a real time visual image (graph)
• Process is rapid (2-5 minutes)
• Could be one part of a larger experiment on gases
• Could be run at several temperature to determine enthalpy of evaporation
• Could be done with conventional equipment
• pressure measurement is more difficult and slower
• of course, same probe could be set up for a voltmeter
• would only get a few data points
• would rely on initial and final values, not on curve