# Day 177: Chem Final Most Missed Question

The conceptual chemistry final was today. Question 41 was the most missed question — everyone got it wrong! Beside each choice is the percentage of students who picked that as their answer. (N=10)

What's going on here?

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I hope the 60% who got the previous question right weren’t the same ones who got this one wrong.

Hi Frank – can you post the original without your annotations (or email me a copy: brta@patana.ac.th)? I’ll try it out with my students to see if there is an international flavour to the leaning conspiracy!

The percent breakdown is the same for both questions. I wonder how many students chose the same answer for both. That would be informative. Were there other density questions? If so, how did they do?There are oodles of misconceptions around mass, volume, and density, and its not uncommon for students to use them interchangeably. Perhaps they just don’t quite get the "per" relationship. Did you do the volume and density graphing activities? When we graphed our density data, I always emphasized the relationship in my phrasing: "For every ___, there are ___" rather than "___ per ___."

I agree with 21stcenturychem on the verbiage used to describe the relationship. I also always go back to Eureka! and use lead and Styrofoam as an example. Huge differences in densities, so in order to get equal mass, you would need a really, really BIG block of foam. This would be a really cool in class demo. 1 kilogram of lead, versus 1 kilogram of foam peanuts.

I hear ya. This is the same question that gets most of my kids as well. Even after we watch the video, and do the demo, and create the graph, only a few of my kids really get it. It seems like this is one of those situations where kids can parrot back the definitions of mass and volume, but have no clear concept of what they actually are when asked to apply them.