When students first come into a designated chemistry class, that is, not a chemistry unit of a science/physical science class, but a “Chemistry” class, students often do not have the knowledge of the various glassware used in a chemistry lab. Most often or not, their prior experience with laboratory glassware is simply using a beaker or two for measuring / holding liquid, but the actual purpose of each glassware is not completely clear.

During the first week of my usual chemistry classes, aside from the usual routine of lab safety, I get my students to measure a specific volume. I usually get the students to be in pairs, and write a number “50ml” on the board for them measure out.  I tell them that they are allowed to use any type of glassware in the lab as long as the volume is 50ml.  The next part becomes the most entertaining because you can see the pairs struggle to figure out which glassware is the best/accurate in measuring out the 50ml.  Most often, the students will resort to their prior knowledge of using a beaker even though beakers are by far the most inaccurate from them all.

Once the students have their “50ml” all measured out, I get them to pour into a 50ml graduated cylinder and have them see which glassware (beakers of different sizes, Erlenmeyer, even graduated cylinders) are the most accurate in their measurements. The beakers usually are the most inaccurate, and I would ask them why they would think so and what they notice from the surface areas of beakers, to Erlenmeyers, graduated cylinders, to a volumetric flask. There is also a % error on each of the glassware that I prompt to calculate the error difference of a 1000ml beaker to a 1000ml volumetric flask.

The glassware activity can eventually elude to sig figs as most students will memorize the rules of determining the correct number of sig figs but the actual purpose of sig figs is often lost.  “How sure are you of your measurements in a 250ml beaker? Are you sure that the volume is 125.5ml? 130ml? or 126ml?” What about if you were to use a 1ml pipette? How sure are you with your measurements? Are they 1.0? 1.1? 1.01?

Hopefully after this lesson, students will not use beakers to measure out any volume as that is my biggest pet peeve as a chemistry teacher!