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IGE INNOVATION ABSTRACTS 42:25
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THE LABORATORY PRACTICAL FINAL, OR AN ALTERNATIVE TO MORE OF THE SAME

A practical laboratory exam tests student skills in performing the procedures and operations learned in the
laboratory. The practical exam, while common in vocational courses, is less prevalent in chemistry and other
science courses, where written laboratory final exams (usually similar to the lecture exam) predominate.

I first used a practical exam for a laboratory final while coordinating the freshman chemistry labs at East
Texas State University (ETSU). It was our belief at ETSU that laboratory and lecture purposes differed: the
laboratory was an extension and supplement to the lecture. In the laboratury the student should apply the
concepts and theories introduced in the lecture while simultaneously developing laboratory technique. The
development of manipulative skills, planning operations and organization of lab time is expected to occur in
the science laboratories. Our purpose in using a laboratory practical was to evaluate the student skills
developed in the chemistry lab.

The laboratory practicals that I have used test students’ manipulative skills along with their application of
the data obtained. Over the past fourteen years I have used practical laboratory exams in both general
chemistry classes and chemistry classes for non-science majors at three very different institutions; a regional
college, ETSU; a rural community college, Northland Pioneer College; an urban community college, Pima
Community College.

The administration of a laboratory practical is cumbersome, and this has probably limited its use. The
practical exam should be limited to four to six exercises with twenty to thirty minutes allowed for each
exercise. Five exercises with twenty minutes per exercise has been the optimum. In my system, each cluster
is set up with three to six identical work stations. The students at the cluster will each do the same exercise,
then move on to the next cluster. Every twenty minutes the students at cluster I move to cluster II; those at
II move to III, etc., until each group has been at each cluster. In this manner, a laboratory with five clusters,
with six stations each, can accommodate a class of thirty students in 100 minutes. (The key to setting up the
practical exam is in preparing each station such that all the equipment needed for the exercise is present.) In
a typical final laboratory period of 180 minutes, one can conveniently administer the practical final and check
the students out of their lab drawers. This format has made the use of a laboratory practical possible as a
part of the normal laboratory schedule.

As a part of the practical final, I have used exercises such as, acid-base titrations, formula of hydrate,
densities, chemical reasoning, heats of solution, empirical formulas and others. The exams are prepared
with a minimum of explanation and are given as open-book exams. The students are expected to use their
experience and knowledge. In the acid-base titrations a double burrette apparatus is used; and usually more
than half the students will complete three titrations in a twenty-minute laboratory period. In the formula of
a hydrate exercise, the number of waters of hydration is determined by driving the water off and monitoring
the mass change. A chemical reasoning exercise is always included. This requires the student to use results
of chemical reactions to identify an unknown. Usually the students are not familiar with the specific
reactions that are used; however, they will have done one or two similar exercises during the semester. The
equipment is set up ready to do the exercise at each station. Equipment set up may be tested separately.
Each exercise is designed to measure a specific skill or set of skills. The exercises given are sufficiently
sophisticated to challenge the students, yet appropriate for a twenty-minute time slot.

I have received some personal satisfaction in finding that some students can use the skills and thought
processes learned in the laboratory for solving new problems. For example, attached to an exercise to
determine the density of a liquid was a question, posing a problem where one needed to know whether the

40} Community College Leadership Program, The University of Texas at Austin, EDB 348, Austin, Texas 78712