One of the few things I remember from middle school science is making Flinkers - objects that neither float nor sink in water, but rather stay suspended in between. Since we just finished our unit on density, I decided it was a good idea to have our 1st Annual Flink Off. The 6th graders were put into teams, given corks, styrofoam peanuts, pennies, paper clips of different sizes, and were challenged to make the best Flinker possible. At the end of the second day of designing Flinkers we had a competition to declare a winner. Even I entered a Flinker in the Flink Off, which seemed to raise the stakes as far as the students were concerned.
I've been trying to do these hands-on, problem-solving, group activities on a weekly basis this semester and so far they've been great. We had a lot of good cooperation and clever engineering going on during the last two days, and my hope is that, like me, they will never forget making Flinkers.
Check out the video of the Flink Off Finals. Not the best quality, but hopefully you can get a sense of how much fun we had as a class.