You’ve had this question before.
“Should I have weighed my filter paper before I started filtering?”
Duh. Of course, you should have. Should you weigh a different one and assume it’s the same? No. But do it anyway. Sheesh. It’s enough to make you crazy.
I stumbled upon one little step in my lab instructions that might just help solve this problem. I was trying a coffee cup calorimetry lab in a way I had never done it before. I didn’t have a handout yet, because I wanted to see how it worked before I invested the time. Basically, I had two known metals that they calculated the specific heat capacity for. Then there were two unknowns. They had to choose the identity of the unknowns from a standard list of specific heat capacities.
Instead of an instruction sheet, I just instructed them using a lab map. If you haven’t read about how I use lab maps, you can here. After I laid out the lab map, I asked one important question.
“What should you measure and record?”
Since they didn’t have the data table produced on the paper in front of them, they actually had to think about it. They got with their lab group and discussed what measurements would be required. Then we came back as a group and discussed the needed measurements in terms of q=mcspΔT.
The next, forehead-slappingly easy step is the one that I will use from here on out. I had the students highlight on their own lab maps everywhere they would need to record a measurement. You may already do this, but it was an epiphany to me. Their drawings had five or six highlights drawn throughout the process. They knew exactly where they would be recording a measurement. And even more importantly, they knew why they needed that measurement. Throughout that lab, I answered so few questions about measurement and recording, it was amazing!
It seems so obvious, but having the students think about the measurements, talk about the measurements, and then highlight the measurements. It seemed to engrain in their brains not just what measurements should be taken, but why. If your students enter a lab knowing why they need to collect each of the measurements they will be far more engaged, focused and precise.
And let’s be honest, do you really feel like answering, “Should I have measured that?” one more time? No. No, you do not.
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