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Monthly Archives: February 2017

Stoich Speed Dating

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Kinda based on the idea by Kate Nowak, I had my students Speed-Date (is that a verb?) stoichiometric practice problems. It’s a little different in format, and it’s in groups… on whiteboards… okay, maybe it’s a lot different.

My students normally sit in pods of three or four. They’re super familiar with the whiteboarding we do (which is at least weekly). After one practice/review stoich problem, I had them clear the boards. We picked some random numbers, and I added “grams” to each (something like, kids shouted out 5, 17, 207, and 73, so I would declare 20.75g and 17.73g). I posted a list of chemical equations on the document camera. Each group picked a random 2-reactant equation from the posted list of equations and started the stoich process (balancing the equation, filling out the BCA table, good sig figs, etc.). For example, if they chose the combustion of hydrogen, then using our random numbers, the stoich problem they worked on started with 20.75g H2 and 17.73g O2.

Now for the speed dating part: Every 2 minutes, I yelled “ding!” and each group moved to a new board to continue whatever the last group had left.

The first “ding!” usually happened just after getting molar masses calculated, so a lot of groans came out, but they knew approximately the step to work on for the next board. The second switch came part way through the BCA table, which really bothered some perfectionists. Some groups found mistakes and had to correct them. Four cycles usually got the boards completed and double-checked.

What I liked:

  • Even in a large class (10 groups), nearly every board had a different equation, so switching meant some big changes but the same process. It’s actually quite a bit of practice.
  • Limiting reactants were not always in the same place/order from one board to the next.
  • Students improved in figuring out the sequence of steps in stoich because they had to repeat/check and see the status of the new board.
  • Struggling kids were able to see how a particular step changed when equations changed (I may have “ding”ed intentionally when I saw a half-fast/slow group getting too comfy).
  • I was able to help one particular kid while everyone else worked through switching boards and checking each other.

What I need to improve/think about:

  • This worked for one round, but wasn’t interesting enough for two.
  • I did not check/grade the boards, but relied on students to check themselves.
  • For the groups that found mistakes, I’d like a way of discussing the mistake with the previous group. I don’t want them making the same mistake on the next board(s).
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