Center for Teaching and Learning

Conducting Labs

class in Physics Astronomy Building. Led by Grad student.Labs provide students first-hand experience with course concepts and the opportunity to explore methods used by scientists in their discipline. As a TA in a lab, you will need to know and review the experiment, plan clear explanations, and create questions to stimulate student thinking. In addition, it is your responsibility to ensure that safety standards are followed. Below you will find further information to help you in teaching your lab section and student comments about what makes a lab TA effective.


Preparing to conduct a lab

The best way to prepare for labs is to conduct the experiment yourself with the students’ lab manual in hand. You’ll discover whether directions are clear and if students have the skills necessary to complete the experiment. Jot down notes as you proceed, so you can tell students how long the experiment should take, clarify confusing passages, and demonstrate new or difficult procedures. If you know what problems students are likely to encounter and what questions they may ask, you will be able to make much better use of your time and make the lab itself more effective for student learning.

You should also know exactly what materials and equipment you will need. Order the lowest possible volume of chemicals needed. Maintaining lower volumes of chemicals in storage is good safety practice and leads to reduced hazardous waste disposal costs. You are responsible for the proper packaging and labeling of chemicals for collection and disposal according to the UW Hazardous Waste Management Guide. Familiarize yourself with the hazards and clean up procedures of chemicals before you use them in the laboratory. Courtesy is also important in the lab; be sure the workspace is clean and ready for the next users before you leave the lab session.


Supervising the experiment

At the beginning of the lab, review the purposes and procedures of the experiment. Even if labs are designed primarily for independent student work, most students will appreciate a brief overview at the beginning of the period. You might deliver a brief lecture on how the experiment relates to recent class lectures and/or to current issues in the discipline, or you might briefly discuss any other assignment you have given the students in order to prepare them for working through this experiment. Ask for questions, clarify any ambiguities in the lab manual, and demonstrate special procedures at the beginning of class rather than interrupt the experiment later.

If both you and your students are well prepared, you will be free to guide the students as they do the experiment. Try to talk with each student at least once during the experiment. Technical and procedural matters can be handled quickly in a few words of advice. Ask questions to help students master the steps of scientific inquiry: recognizing and stating a problem in order to explore it; collecting data; forming and testing a hypothesis; and drawing a conclusion. It is best to refrain from giving outright answers or advice. If lab partners ask, “Why can’t we get this to come out right,” try asking a series of questions, which lead them to discover answers, rather than simply explaining why the experiment failed. Although it is tempting to help students by saying, “I see where you went wrong,” your students will learn more if you challenge them to figure out the answers on their own.


Assessing students’ performance in labs

As in evaluation of other types of student work, it is important to match the assessment to the goals of the course and to the objectives of the individual assignment. Measurement of student achievement in labs is often based primarily on completion of the lab and a written lab report. However, it is possible to assess other aspects of lab performance, including:

  • Students’ preparation for lab.
  • Students’ ability to perform lab techniques.
  • Students’ understanding of the lab procedures.
  • Students’ observance of safety standards.

Whatever the professor and TAs decide to assess, it is crucial to establish clear grading criteria and also to communicate them in writing to the students. It is also important to keep accurate records, particularly when assessing non-written aspects of student performance.


Safety procedures

UW’s Laboratory Safety Manual – All staff in UW laboratories are required to have access to this manual. ¬†Bookmark it!

Safety is an important issue when you are directly responsible for the health and well being of 25-30 laboratory students. Although dramatic incidents are rare, small accidents can be commonplace in a laboratory setting.

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. Anyone teaching or working in a lab is also expected to attend the laboratory safety seminar offered by Environmental Health and Safety (543-7262 or http://www.ehs.washington.edu). Sessions are offered just prior to the beginning of Autumn Quarter and throughout the year.

During the first few weeks of the quarter, you should demonstrate the proper techniques for decanting and mixing liquids, handling glassware, organizing a work area, using burners and other equipment such as gloves, goggles, face shields, etc. (i.e. all of the precautionary measures you now perform almost unconsciously, but which have not yet become familiar to your students).