Structuring Lab Time
Introducing the Lab
It's helpful to think about planning your lab introduction around the questions that the students will probably have. These include:
- What is the purpose of the lab?
- What is the relevant background information?
- What are the materials we need for the lab?
- Where are these materials?
- What are the main steps in completing the lab (especially, what is the first step)?
- What follow-up work (if any) do we need to do and when is this due?
Of course, most of these questions will be addressed in the lab handout that you will have given students (or posted online) for them to read before the lab session. But even the most conscientious students will need a summary of the lab purposes, etc. at the lab time. This is also a good time to show any visual information (slides, maps, etc.) that helps put the lab work in context and cannot easily be included in handouts.
It's important to keep the introduction brief. After all, the lab session should be the time when students are learning by doing. However, it's worth adding a few words about what you expect to see and hear during the lab session (see Keeping the lab session running smoothly below). If you want students to work in groups, talk with each other, walk around the room and be active learners in other respects, you will probably need to make these expectations explicit, both in your lab handout and in your introductions to the labs.
How much material should be in a single lab session?
The answer to this question will depend on the purposes of the lab and the length of the lab period. For instance, if students are doing a series of experiments (for instance, varying materials and temperatures to study mantle convection or determining the activity of an enzyme under various conditions) they will be able to do different numbers of experimental runs in two hours, three hours or four hours. If the first run takes 45 minutes (because the equipment and materials are unfamiliar) and subsequent runs take 20 minutes each, students in a two hour lab period could do two or three experiments, students in a three hour lab could do five or six experiments, and students in a four hour lab could, conceivably, do even more. (You'll want to allow time at the end of the lab period for summarizing).
If the purpose of the lab session is to learn and review the propoerties of a set of samples (minerals, microscope slides of rocks or living organisms, insect collections, etc.), consider articulating for the students interim and final goals and giving them a low-stakes quiz towards the end of the lab period on some of the interim goals. For instance, an interim goal for a lab on rock types might be that students should be able to distinguish igneous, sedimentary and metamorphic rocks and explain why a particular rock specimen falls into one of these categories. (Perhaps a "final" goal would be facility with the names and properties of a set of diverse rock types). At the end of the lab period focused on rock properties, then, you could give students a quiz with a selection of three or four rocks, ask them to categorize the rocks and explain their reasoning. If you then end the lab period by discussing these rocks, students will leave with an understanding of what they've mastered during the lab and what they need to continue working on.
Keeping the lab session running smoothly
There are several techniques that you can build into the lab preparation, lab instructions (and your own expectations) that will help keep the lab running smoothly:
- "Test drive" all the components of the lab ahead of time to make sure the equipment works, you have enough samples and to give you an idea of how long different parts of the lab will take. Just remember that the students will need more time than you do.
- If the lab is meant to be done in a sequence (part 1 followed by part 2, etc.), make your written and verbal instructions clearly sequential. You might even want to consider distributing them in pieces, if necessary, to sidetrack the students who jump to the last page.
- If the lab has four different sections which can be done in any order, also make that clear in your instructions.
- Respond quickly to signs that students or groups of students have reached the end of one task and are waiting to move on. You can encourage them to take a short break, help them start the next part of the lab, or use this as a cue to summarize the previous section of the lab for everyone ("I know not everyone has finished drawing their cross-section. I'd like to take a few minutes now to have a couple of people show and explain their cross-sections using the projector and then talk about the next step.").
- If you're teaching the lab for the first time, cut yourself some slack. It's unlikely to be completely smooth sailing the first time around. Some groups of students respond well to a request to "please help me improve this lab by giving me your opinions about what worked and didn't for you." We've found that a good tactic is to carry a copy of the lab assignment with you and use it to make notes during the lab session - and then transcribe those notes into an electronic copy of the lab handout immediately.
You may also find two parts of the "field labs" site helpful in your planning: structuring time during field labs and suggestions on managing time during the field lab. An additional source of helpful information about structuring lab time is this module on studio teaching
A major issue with lab session pacing is that different students (individually or in small groups) will work through the lab at different paces. This is not only a matter of how quickly students pick up on ideas, concepts and technical skills, but also a matter of how clearly they understand the aims of the lab. For instance, a highly intelligent student with a perfectionist streak may be the slowest person in a lab section to finish a task like making a topographic cross-section because of the desire to achieve the perfect result. As the instructor, your idea in assigning this particular task may have been that students get a general idea of the procedure and a sketch of a final result, but unless you've communicated that clearly to the students, some of them will attempt to do everything carefully and perfectly.
Thus, you (and lab assistants, if you have them) will want to circulate around the lab, listening to students tallking with each other and watching them do the desired tasks. You will often be able to suggest something helpful ("try putting your hand lens closer to your eye and the rock closer to the handlens") or clarify some of the lab instructions ("Why don't you start by finding the highest and lowest points on the map along your line of section?").
Lab instructors will differ on the appropriate level of noise for a lab. We like the noise that comes with students engaged in the lab, talking over ideas with each other, responding to a particularly spectacular result. We have seen labs where students work individually with worksheets and materials and the lab assistants line the walls, occasionally calling out "Does anyone need help?" Apart from the access to specimens and other materials, the students might as well be in a coffeeshop or dorm room.
Organizing by different activities
If you have many shorter activities to cover in a lab period, you might consider setting up a number of lab stations that students cycle through during the lab period. For instance, a lab on Solar System Geology might include a station where students use an airgun to create craters, a station where students record numbers, sizes and morphology of craters from a lunar quadrangle map, a (computer) station where students explore Martian features using GoogleMars or Venus features using Magellan radar images, a station where students explore a geologic map from a terrestrial area, and others. Again, depending on the length of the lab period, you'd include fewer or more stations (or give students options).
Another reason for having different groups of students doing different activities during the lab session is a project that has many pieces, each of which is completed by a different group. For instance, if an experiment on an enzyme expression requires runs at ten different temperatures and four different pH values, you might have each of ten groups do four runs and then have students analyze the combined information from the whole class. In such a case, it's very useful to devise a uniform reporting system in advance (for instance, an EXCEL template) so that the results look consistent.
Summarizing at the end of the lab and explaining the post-lab assignment
Chances are that some of your labs will be open-ended, with extensive follow-up work, some will require students to do a small amount of writing or compiling after lab and others will be self-contained. Whichever kind of lab it is, you'll want to spend a few minutes summarizing what's taken place during the lab and what follow-up students need to do. Even those students most comfortable with self-directed learning and ambiguous results will appreciate having the ambiguities (and the points of clarity!) clearly described at the end of a lab.
If students are working in groups, you might consider having groups talk, choose a spokesperson, and then having that student summarize the group's findings. (A tactic like this one is particularly important if each group has been working on a separate piece of a larger puzzle for which everyone needs all the data). It's often more useful for you to hear students present at the end of the lab, because you can more easily discover where the misunderstanding and other sticking points occurred and then clarify these points during the next class or lab period.
The summarizing time of the lab is also the time to explain any follow-up assignments, such as "I expect you to plot your cross-section on a clean piece of metric graph paper and hand it in at the next class period" or "You'll find the research paper assignment and all the group data on the course web site. The paper is due in two weeks." These explanations need only repeat the important points of the paper or web-based assignment sheet.