Why American Education is Failing: Not Enough MacGyver

Meg is teaching her third graders a unit on energy and needed an example scenario to test their knowledge of what happens to heated particles, namely that they expand to take up more space. She had a test question that was worded very oddly and involved how far capillary action would draw fluid up a straw if the water was cold or hot. She asked me to come up with an alternative thought experiment she could use to retest her students. My original thought was to eliminate water from the equation because of it’s tricky phase change/density issues and instead ask a question involving a steel pipe and a steel ball that just barely fits through the pipe when both are at room temperature. She decided that was too complicated. The experiment she came up with involved two measuring cups with 1 cup of room temperature water in each. One is heated, but not boiled, the other cooled, but not frozen. What difference would be observed between the two measurements after this temperature change occurred? She was looking for the warm cup to measure slightly more, and the cold cup to measure slightly less. Turns out some tricky parents decided to ACTUALLY TRY THE THOUGHT EXPERIMENT and found there was no change. Perhaps the water got below 4 degrees C and started down the odd shift that water has that causes ice to float, perhaps the warm cup wasn’t boiling, but enough evaporated to prevent any noticeable change, perhaps there was a change but kitchen variety measuring cups aren’t exactly graduated cylinders.

This is why I hate thought experiments involving water. (also: lead, uranium, neon and silicon also do some tricky things when cooled so they should remain out of the realm of third grade thought experiments) Here is my original thought experiment:

You are a secret agent and need to plant an explosive to blow up an enemy facility. Due to a mix up back at headquarters, you weren’t given the normal remote controlled detonation system for your explosives. Instead, you were sent a self-lighting welding torch, 6 inches of steel pipe 1 inch in diameter, a steel ball that just barely fits inside of the pipe and a pair of barbeque tongs. Without your remote controlled detonator, the only way to set off the explosives is by pressing the half inch wide button on top of the explosives, but that doesn’t give you any time to escape the explosion yourself. Using only the supplies you received how can you set off the explosives without blowing yourself up? Explain your solution in terms of adding energy to particles and what happens when a heated item cools over time.

If a parent actually helps a kid actually try the experiment they should win just for having the needed supplies.