LABORATORY SECTIONS

Laboratory sections offer students who are taking lecture classes a hands-on experience linking the theories explored in the lecture class with the actual practice of the discipline. It is often in a lab section that vague or confusing concepts become concrete, clear, and credible.

As a laboratory teaching assistant, you have three goals:

As with any type of teaching, be enthusiastic and share your excitement about lab work with the students.

SAFETY PROCEDURES

Safety takes on special importance when you are directly responsible for the health and well being of 25 or 30 laboratory students. Window shattering explosions are rare, but it is not uncommon for students to break beakers of acid, cut themselves while inserting glass tubes into rubber stoppers, or ignite their class notes with a Bunsen burner.

If your department’s orientation does not cover safety procedures, the professor or lab coordinator in charge of the course will probably take responsibility for describing departmental policies. During the first few weeks of the semester you should demonstrate to the students the proper technique of decanting and mixing liquids, handling glassware, organizing a work area, and using burners and other equipment as well as other techniques appropriate to the type of lab that you will be teaching. Keep yourself informed of all necessary safety precautions, warn students of any hazardous material they might be handling or of any other risks they might encounter, and make sure that safety goggles and other protective clothing are worn when appropriate.

For more on safety issues, visit the University of Pittsburgh's Department of Environmental Health and Safety web site.

FIRST CLASS PREPARATION

Before the lab section meets for the first time, make sure that you know where equipment is stored and acquaint yourself with the lab’s emergency facilities (first aid kit, eye wash stand, respirator, safety showers and fire extinguishers). You do not want to waste time looking for lab equipment during class nor do you want to be unsure of what to do should an emergency arise. If you have not already spoken to your supervising instructor or the lab coordinator about safety, you should do it immediately.

Familiarize yourself with the classroom layout. The number of "stations" available will determine the size of lab groups; the space between desks and tables will determine how easy it will be for you to move around, observe your students, organize discussions or offer help. The layout will also determine where you will have to stand when you lecture or demonstrate so that the full class can see you.

Finally, if the class for which you are conducting a lab has a recitation section (and you are not the instructor) speak to the recitation teaching assistant. He/she will have a good idea of what you can expect your students to know and what you will have to demonstrate during a lab.

On the first day of class, introduce yourself, learn the names of students, familiarize your students with the equipment in the lab, and demonstrate how and when safety equipment should be used. If appropriate, note the location of fire exits, explain to students what clothing is appropriate for lab work (open toed shoes, shorts and contact lenses are often prohibited), and ask students to report (confidentially) any health problems that may be exacerbated by the experiments you will be conducting.

WEEKLY PREPARATIONS

Each lab recitation also requires some preparation. The following checklist may help you to get ready for class:

SUPERVISING EXPERIMENTS

At the beginning of the lab, review the purposes and procedures of the experiment. "It is essential that before you send your students to work on a lab demonstration they understand its objectives, its relationship to matters introduced in lecture, and the methods they are to use in the lab. Your introduction or the lab manual should also point the students to the kinds of analysis and evaluation they are expected to make in the lab. The point, after all, is not the lab itself but the results (correct or incorrect) which lead to various interpretations." [14] Ask for questions, clarify any ambiguities in the lab manual, and demonstrate special procedures now rather than interrupting the experiment later. If the students are using equipment that they have not used before, you should demonstrate its proper and safe use. You may also want to provide them with an example of a well-written lab report that they can use to model their own conclusions.

Try to move around the classroom watching your students as they do their work and speak to each student at least once during the experiment. Technical and procedural matters can be handled quickly with a few words of advice or a very brief demonstration, but your primary role is to help students master the steps of scientific inquiry. You want to help students recognize and state a problem, collect data, form and test a hypothesis, and draw a clear conclusion. This is not an easy task. You can tell students to "hold the stopper between their index and middle fingers while they’re pouring," but teaching them to discover the theoretic underpinnings of an experiment is a bit more difficult. There are a variety of ways to help students solve problems for themselves. Here are a few:

Encourage students to ask questions. Invite students to ask questions whenever they are unsure of the correct procedure or the underlying theory. Questions reduce error and help you to be an effective instructor.

Hold a discussion. If a student asks a question or if a number of students seem to be struggling with a concept or idea, bring the issue to the attention of the full class. Allow the students to compare their results, to review the material covered in the lecture, and to search for their own answers. Discussions are a great way to develop students’ critical thinking skills, and they also help to dispel both the antiquated idea of the lone genius scientist and the misplaced ideal of scientific objectivity.

Ask questions of your students. When students ask "Why can’t we get this to come out right?" don’t simply answer their question. Try asking them a series of questions that will lead them to discover for themselves the reasons the experiment failed. Of course, sometimes the reason will be relatively simple—they used hydrochloric instead of nitric acid; however, just as often the reason will be more substantial—a matter of timing, sequence, proportion, or interpretation. Allowing them to solve the problem on their own will help them to develop the skills they will need to succeed later in the semester.

ENCOURAGING STUDENT PREPARATION

Those who have only a hazy recollection of Wednesday’s lecture usually follow directions mindlessly and complete the experiment, but those who have reviewed the lecture notes and the lab manual often develop a deeper understanding of the experiment’s importance and the theoretical concepts underlying it. Devise some means to ensure that students are familiar with the lab before they come to class. Some instructors feel that grades on lab reports are enough incentive while others require students to submit a statement of purposes and procedures or an explanation of why and how the experiment is performed.

NON-TRADITIONAL LABS [15]

As a lab teaching assistant you may have little say over what experiments are run or how the lab period is structured. However, if the course instructor is open to suggestions, you might consider running an "open-ended" lab. "Open-ended laboratory classes can be broadly defined as classes where the students are encouraged to design their own experiments or devise their own experimental strategy, rather than required to follow a rigid set of experimental guidelines specified elsewhere as in a lab manual, for example." [16]

Teaching Fellows in the Engineering School at the University of Wisconsin have identified three different ways in which a laboratory experiment can be made "open-ended." First, students may be allowed to design their own experiment setup given a set of assigned goals. Second, the experiment design can be left up to students. In this case, students are given equipment to work with but must "brainstorm" to determine what (related to the class objectives) the equipment might be used to study. If they come up with more than one use, students must determine how best to allocate their resources. Finally, data analysis and report writing might be made "open-ended" so that students can develop their own means of expressing the results of experiments they have conducted. For example, in a chemical engineering class students were asked to create their own experimental design concerning heat transfer using a large cylindrical tank with heaters and baffles. The teaching assistant led the students through a brainstorming session, helped them to rank their ideas for practicality and usefulness, and then oversaw groups of students as they performed their novel experiments. [17]

Teaching assistants who have used "open-ended" labs have found that the students find the work more rewarding and are more likely to explore the theoretical importance of the experiment. However, be warned, opening up the classroom often takes additional planning, may take additional lab time, and requires the constant supervision of the lab leader. For more information, follow the link to Wisconsin’s Strategies for Effective Teaching (This is an Adobe PDF file that requires a free viewer to read).

EVALUATION

Be sure to follow the instructor's guidelines when evaluating laboratory experiments and lab reports. However, the following factors usually are taken into consideration: (1) how well the students followed proper procedures; (2) how clearly they stated the purposes and conclusions of the session; (3) how adequately they gathered the data; and (4) how appropriately they drew conclusions from these data. [18]

BROADER ISSUES RELATED TO SCIENCE

Seek opportunities both in and out of the lab sessions to discuss social, philosophical, and ethical issues related to science. In chemistry lab, for example, students may be concerned about public policy regarding toxic wastes. In a biology lab, students may be concerned about the origins of individual life and the morality of abortion. In physics lab, students may be interested in philosophical implications of relativity. Recognition of the social values that underpin science is a valuable part of your students' scientific and liberal education. Express interest in addressing the students' concerns when they raise questions, help them to reflect responsibly on the scientific material being covered, and raise questions yourself whenever possible. [19]

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