Computers in Introductory Chemistry Laboratories

Introduction:

• 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

• 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

• 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)

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

• 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)

• a graphics calculator is used to collect, display, plot and process experimental data
• an accessory (about the size of another calculator)
  • accepts various probes (temperature, pH, pressure...)
  • makes readings as often a 10 reading per second
  • sends the results to the calculator for processing
• Size is much more promising
• Cost is also much more encouraging
  • calculator is $100
  • interface device is $200
  • probes are $30-75 each
• There is software that can let the calculator then transfer information to a conventional PC

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

• 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

• 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

• 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

• The Casseopia Classroom Model
• This was actually developed for classroom use (mostly in mathematics)
• it looks like a tiny laptop unit.
• It opens up to show a screen (about 6 x 3 inches)
  • it's monochrome (a drawback)
  • it's the same resolution as standard PC displays but only half as tall (640 x 280 pixels)
• It has a full keyboard
  • tiny, but usable for simple data entry
  • membrane type keyboard (so relatively well protected from occasion spill or splatter)
• It has a touch sensitive screen
  • for operation in a menu driven mode
• It has a sizable memory for these type of units
  • enough to load and store programs and then collect results
  • unit does not have any disk drives
• It has several interface ports
  • serial (important, the way to connect sensors)
  • IR (also very useful to us as way to load programs, transfer to printers)
• The cost is between basic PDA and laptop units
  • about $400 per unit
  • we'd need to add about $250 in accessories to handle lab data

• The university has not, in recent years, showed any evidence of supporting instructional laboratory developments.(The administration talks the talk, but we haven't seen them deliver.)
  • It's taken several years to get several older PC's for instructional labs in chemistry
  • at that rate we'd need a decade or more to do this project
• Projects like this that require $30,000 or more are beyond the resources of the department
• External funding agencies like the NSF are the most promising source of funds
  • NSF is national Science Foundation
  • NSF will only pay 50% of equipment cost
  • Still, that's enough money to get university to provide matching funds
• However, the NSF has its own goals
  • they do not view themselves as a source of funds for conventional projects
  • they want their funds to evaluate promising techniques, new ideas, to lead to improvements in a larger number of schools
  • they are eager to exploit developing technology
    • standard PC's and Laptops have been used in teaching labs for many years
    • the HPC are a promising developing technology

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 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

• time to focus on interpretation and calculations
• time to include a calibration run
• time to make several runs and comparisons

Titrations

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.

• 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

• 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

Titrations

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

• would be too tedious to collect many data points
• would need to do more slowly and heat loss is more of a factor then

• 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

• Computer can collect relatively large number of data points for smoother curves
  • conventional experiment would collect 10 -15 points, then plot
• Computer can also display derivative or slope (which is the rate of reaction)
  • very unlikely to manually determine slope other than initial slope
• Computer can also try conventional test plots to examine order (plot log and inverse)
• Can set up runs with lifetimes of 1-5 minutes
  • easy to do multiple runs
  • vary initial conditions and see effect
    • begin with visual comparisons
    • then do quantitative treatment

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

Important concepts to be examined:

• Can we keep the experiment focused on the chemistry and not on the computer and the data collection mechanics.
• Does introduction of computers improve student morale
  • makes the work seem more modern and relevant
  • provides better quality experimental results
  • bypasses some of the tedium in multiple data points and multiple calculations
• Can we use this to introduce additional computer familiarization
  • e.g., the use of spreadsheets
• Are these miniaturized versions adequate to the task?
  • Keyboard is tiny and data entry is awkward, error prone
  • Screen is small, harder to read than standard PC (especially for students with vision difficulties
  • These are slow realtive to today's expectations; is that a problem?
  • In the absence of disk drive, progrram and data storaage is limited and probably inconvenient
  • The units are just specialized enough that we are unliekly to to have many persons who will maintain the software.
  • As a non-standard unit, there is the risk that the device will cease production (suddenly) and/or be replaced with models that are quite different. Five years is a very long time in this market, but five years is a minimum to recover instructional investment in development work.