In the Classroom
Designing New Undergraduate Experiments Min J. Yang and George F. Atkinson* Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
An eager teaching assistant approached me, “I’ve been asked by Professor X to prepare an experiment using the new instrument, and I want to do a good job of it. Can you help me?” We spent an initial half-hour together, which I won’t detail here, and agreed to meet again. Thinking about the conversation, I realized how difficult it is for a beginner, whether a TA or new faculty member, to find a convenient outline of the task of preparing an experiment for undergraduates. Hence this paper. What is offered here is not an exhaustive description, but a series of checklists of points based on experience and observation. They are often overlooked, which creates problems when the experiment is used in the lab. It is primarily about designing experiments for existing instruments in a laboratory. Lists 1 and 2 are for getting started and for some logistic matters. Objectives As Mager reminds us, if you’re not sure where you’re going, you’re liable to end up someplace else (1). If the new experiment is to be resource-effective in both cost and time, the designer must from the beginning have a clear picture of the intended lab course outcomes. Some possible outcomes might be those in List 3. It may be helpful to think about a specific concrete example. Let us assume we are introducing into a typical undergraduate instrumental analysis lab one of the new GCMS instruments and that the course goal is understanding the optimization of instrument operation. Now we can look at desired outcomes for this new experiment. At this point, context intervenes. For example (academic): are students required to perform a GC experiment before using the GCMS? If they are, the starting point for new learning of lab skills and new grasp of theory is different. For example (logistic): how many hours can we allow each student to use this machine? Considerations like these bear upon questions like those in List 4. Reasonable expectations will vary if a student or student group can be offered three hours to use the machine or if only one hour is available. Learning theory indicates that information overload may now become important. Johnstone and Letton (2) suggest that to develop a richly interconnected memory bank from which many different stimuli will trigger appropriate recall of an item, new items must not be presented in a flood, but at a measured pace. The message in this for the experiment designer is that how much can be learned while actually performing the experiment is limited by a principle of diminishing returns, or of saturation. Several strategies are available for avoiding such overload.
*Deceased.
Before the Lab Period The long-term strategy of stressing the cumulative nature of knowledge can be developed throughout the lab program. We are expecting what was learned last week or last year to still be useful and required for use (List 5). What shall we do with the students who fail the turnkey test? One suggestion is to exclude them from the lab session and give them a prepared library assignment on the topic, which if well done can earn them half the marks available for the experiment. Another, depending on the overall scheme of the lab course, is to let them continue with other work such as sample preparation for other experiments, and reassign the proposed experiment to a later lab session. In this case, to avoid students’ manipulating the system it is probably desirable to impose a moderate grading penalty on the deferred experiment, possibly of multiplying the mark earned by 0.9 or 0.8. Doing the Lab When we began, we established a target: what should the student be capable of doing after completing this experiment? At this point, we have established a starting point for students doing the experiment. The remaining task, deciding what the students should do while performing the experiment, is usually not seen as problematic, but our beginner may benefit from a few checklist questions like those in List 6. Knowing the Cost We should be able to assume that before the department bought the new instrument, the cost of operating and maintaining it was assessed, accepted, and built into the budget. The designer of an experiment may or may not have been party to that decision, but even if the designer is a graduate teaching assistant, she or he should estimate the cost per student or per group of performing the new experiment by looking at its requirements for reagents, samples, and any other consumable supplies. More senior persons may have to List 1. Getting Started 1. Are you thoroughly familiar with the operation of the instrument? • Have you read all of the instruction manual? • What puzzled you, what did you do slowly (or even wrong) when you first used the instrument? • How did you overcome these difficulties? 2. What experiment would be a typical use of this instrument in a non-teaching, real-world lab? 3. What candidate experiments have been published? • In textbooks or manuals already in use (which are often overlooked)? • In this Journal or similar journals?
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In the Classroom
List 2. Logistics 1. How many students are going to be in the course, or in one lab section? 2. After allowing for check-in, mandatory safety talks, tests, and other occasional events, how many working hours of lab time, in blocks of what size, does the course have? 3. Is it necessary for every student to perform every experiment? If not, is it necessary for every student to perform this experiment? 4. Is this experiment a permissible first experiment for some students, or can it only be started in a later lab session? If so, for what number of lab periods will it be usable? 5. How long does it take a beginner to perform a measurement with this equipment? 6. How closely can this equipment be supervised during the lab session? 7. How easy or difficult is it for a beginner to damage, decalibrate or contaminate this equipment while trying to use it? 8. Can two or three students effectively work together on this experiment? (i.e., can you postulate a reasonable division of necessary activities that doesn’t reduce one student to a “gofer” role?) 9. Is there actual space at the instrument for two or three students (and occasionally a teaching assistant) to both see what is going on and not get in each others’ way? 10. In a worst-case scenario, based on an accident either at this or at a neighboring work station, how will students get access to room exits, service shutoffs, or emergency equipment?
List 3. Possible Course Outcomes 1. Students have experienced operating the instruments and interpreting either their own results or “good” results obtained by an instructor or technician. 2. Students are proficient operators of the instruments. They do not cause damage to equipment. Their operation is at a technician’s level. 3. Students obtain reproducible results from their measurements using prescribed operating conditions; i.e., precision is under control. 4. Students obtain valid results (qualitative or quantitative) from their measurements; i.e., accuracy is under control. 5. Students understand the relative impacts on results of adjusting various operating conditions; i.e., optimization of instrument operation is being understood. 6. Students can begin to decide when this instrument or method is best suited to a new measurement task; i.e., the role of a professional analytical chemist is being introduced.
make decisions about trade-offs between cost and educational effectiveness, but no one should propose a task without looking at the question of costs. Designing the Write-Up In 1930, Kenrick (4) proposed that for students there is a problem of “lab work”—really doing the experiment you think you are doing, and a problem of “word work”— describing what really happened instead of what should have happened as proposed by theory. Defining the write-up expected must be part of developing the experiment. While the write-up is written by someone who per-
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List 4. Possible Experiment Outcomes That Might Be Emphasized 1. Regardless of whether a prior GC experiment is required: • Students can verify purity of GC peaks by mass sampling early and late in a peak. • Students can identify a peak from its mass fragmentation pattern. • Students can relate selected ion monitoring output to the corresponding gas chromatogram. 2. If no prior GC experiment is required we might also emphasize: • Students have observed and can predict the effect on the chromatographic separation of varying both carrier flow rate and column temperature separately or together. • Students can suggest (although they may not be able to try) changing columns to improve separation. List 5. Possible Useful Preparation 1. Remind students to ask themselves before each experiment, “What have I learned before that I will need for this task? Need I review it?” 2. Occasionally, ask students to list in point form the facts and skills required by the assigned experiment. 3. Require a pre-lab visit to simply observe the equipment. This may be arranged by appointment with an instructor when the lab is not in operation, or it may be simply the requirement to drop by during an earlier lab period and spend a few minutes watching another student or group at work on the instrument. 4. Include in the lab manual or instruction sheet, which can be read at leisure, labeled photographs not copied from a textbook or manufacturer’s operating manual, but of the actual installed equipment in your lab. A locally made videotape of the experiment being done by students may also be useful. 5. Require students to “fill in the blanks” in the lab manual, with information which can be found either in the course textbook or in reference material in the library. (An example from one of our electroanalytical experiments required students to complete a small table of half-wave potentials and related standard reduction potentials for the system to be investigated.) Local custom and experience will show how often such activities must be varied to discourage mindless and effortless copying from previous students’ notes. 6. Require a turnkey test, which students must take successfully to be allowed to operate the equipment. The more expensive and fragile the instrument, the more demanding this test must be. This may be the appropriate point to use a well-designed computer-based emulator of the equipment. Henry Bent’s comment is relevant: we are more inclined to award marks for listing points about an activity than for actually doing it (3). In the interests of the department, the students being tested, and their fellow students who will suffer if the equipment is disabled, both listing and doing must be covered. Note that effective use of turnkey tests while obtaining maximum benefit from the equipment requires having another user or user group “on deck” who can be offered use of the vacated equipment if the scheduled users fail the test and are denied access.
formed the experiment, it is usually marked by someone who at best was only present for a part of the working time, and who may have not been there at all. Inescapably, therefore, a diary-style notebook must be kept by each student. This
Journal of Chemical Education • Vol. 75 No. 7 July 1998 • JChemEd.chem.wisc.edu
In the Classroom
List 6. Are These the Right Tasks? 1. At a practical level: • How long will it take a beginner to perform the operations required? • How rapidly will the typical minor operating problems that arise with this equipment be fixed? • How much time for note making? (We don’t want lab books written up from memory after students go home!) • How much time will be consumed by TAs questioning or helping the students? • Therefore, will this work usually be completed successfully in the available time? 2. At a broader level: • Will the students have time to think about what they are doing? • Is this the right way to perform this task, or a “quick and dirty” expedient shortcut which requires a sophisticated eye watching for problems? • By doing this, are the students learning how to perform useful tasks which they may either do or prepare technicians to do after graduation? • By doing this task, are the students being given a technician’s outlook on the work, or a professional chemist’s outlook? • Therefore, is this work contributing to the expected outcomes of the whole degree program for the students? If so, in what explicit way or ways? If not, why not?
record should be full enough to inform the nonobserver of “what really happened”. Students may need some reminder in the instruction sheet of what to include in the diary, such as settings of various instrument controls or reasons for aborting or discarding some measurements. It is easy to fall into the bad habit of recording only “good” information. The diary should be available to the marker on request. If a report beyond the diary is to be submitted, local custom will likely dictate its nature and extent. The important consideration here is to require a report that can be written by students and graded by markers in a realistic length of time and that does not encourage students to “adjust” the facts from their lab work to conform more closely to expectations from theory. Lord Kelvin said, “The saddest sight in science is a beautiful theory killed by an ugly fact.” Recent major scandals remind us that a fact invented or amended to support a beautiful theory is worse. In Conclusion This paper does not attempt to detail all the specific points needing attention in designing a particular new undergraduate experiment, but instead raises some general questions that are sometimes overlooked until resulting difficulties have been experienced. Attention to these may improve both the cost effectiveness and the educational effectiveness of the considerable effort expended by enthusiastic young instructors on preparing and revising experiments. Literature Cited 1. Mager, R. F. Preparing Instructional Objectives, 2nd ed.; FearonPitman: Belmont, CA , 1975; Preface. 2. Johnstone, A. H.; Letton, K. M. IUPAC International Newsletter on Chemical Education 1990, No. 34, 14–18. 3. Bent, H. A. J. Chem. Educ. 1977, 54, 462–466. 4. Kenrick, F. B. Can. Chem. Met. 1930, 14, 45–46.
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