Facepalm Friday

I’m a Chemistry teacher, and I’ve started preparing my students for their exams. I get the students to do past papers, so that they can understand what’s expected.

A particular question asked the students to design an experiment that checked how solubility changed with temperature. Will more solid dissolve if the temperature goes up? How do you know? Prove it.

Anyhow, this student I teach understood they needed to pick a temperature, and add this chemical to a fixed volume of water till no more could dissolve, repeat 2 more times, then change the temperature, and repeat for this new temperature.

The scary thing was that this 18 YEAR OLD student didn’t grasp that the mass goes up when something dissolves. He genuinely asked “How will we know how much we’ve added?” I asked him to describe what we would do at a certain temperature, “We’ll dissolve a solid into a liquid till it can’t go in any more.” Then I asked about what dissolving meant. “It means the solid goes into the liquid in really small bits.”

It was at this point I waited for a sign of “Oh ah we’ll have more stuff so we can look at the mass”, but no. He looked at me as if to say “Ok… next step?” When I asked him to think about what we could measure now we know what he’s just told me, he carried on looking at me, clearly thinking “I’ve got nothing, help me out here.” I then changed tacks and asked “Is there more stuff in the test tube before or after?” and he continued to look at me as if to say “Seriously, I’ve got nothing, you’re going to have to help me out some.”

So I’m not sure who my facepalm moment is for, my student (who doesn’t realise mass goes up when some you dissolve something in a liquid), or me, who managed to get a kid to 18 (with great grades) and not know that.

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