Your students think they are clean in the lab. They aren’t.
Every one of us, during the lab safety talk, mentions keeping a clean and organized lab space. And this is absolutely important. However, first year chemistry students lack the understanding of how easily chemicals can accidentally be spread around a lab station. The ring on the bottom of a beaker. Setting down a stirring rod. The drip that slowly rolls down the class’s stock container. Contamination is everywhere. Until the students see the impacts, they will have a hard time truly believing it.
In the past couple of years, I started using a very simple and dramatic process to remind students of the importance of lab cleanliness. I’m thinking of patenting my invention.
It’s called “Phenolphthalein on a Tissue.”
It is magical. I can walk around with a little bottle of phenolphthalein and a tissue and in seconds, give the students feedback about their lab processes. Here is how I did it.
We were doing an introductory mini lab where the primary goal is to teach the students how to filter a precipitate from the aqueous solution. I used a small amount of CuSO4 and had the students dissolve it in deionized water. Then they measured a small volume of sodium hydroxide and transferred it to a separate beaker. Then they combined the beakers to see the formation of copper (II) hydroxide. It is a neat looking reaction with bold blue color. Then they have to filter off the copper (II) hydroxide leaving the aqueous chemicals in the bottom beaker. It’s very simple. And they can spread sodium hydroxide all over their lab area. Even on accident, the NaOH gets around.
This is where “Phenolphthalein on a Tissue” comes in. I can walk around and ask the students about drips on their counter. Is that water? They are sure it is, until I pull out the tissue.
Oh, well maybe I should clean that up first.
Yeah, maybe you should.
I test the outside of their graduated cylinders, the base of the ring stand, their gloves. Everywhere I find NaOH, even in tiny amounts, BOOM, they see the pink color. I walked up to a group yesterday and before I even got there, they were explaining that they knew the drip was sodium hydroxide and that they were getting a paper towel, and they asked if they should also use vinegar. They were actually thinking and engaging.
Something as simple as a tissue in your hand with a little indicator and you wield the power to cut through the BS of them having “already cleaned up”. I found it a simple and effective way to increase the concern about chemistry while helping them learn to clean up and care for their environment and safety. And to think, I did it with a tissue.
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