The ninth-graders are studying calorimetry this week in their online science class, so I did a little Googling and found instructions for making a bomb calorimeter out of a couple of tin cans.
A bomb calorimeter is basically a small can of water suspended in a big can with the bottom cut out and holes poked in it. You insert a needle into a cork, impale a piece of food on the needle, set fire to it, and set the calorimeter over it to see how much it raises the temperature of the water until it completely burns up. Our experiment called for burning peanuts, cashews, and almonds and comparing the results.
We didn’t have quite enough time to complete the entire experiment in a single 30-minute enrichment period (a cashew, as it turns out, can burn for a really long time), but we had fun setting fire to the nuts and watching the water temperature rise, and two days’ worth of enrichment periods yielded enough information for the kids to see that a cashew contains more energy than a peanut.
A few thoughts:
- I’d recommend this project for classes on a block schedule, as you could probably get the hang of the process and complete all the necessary trials in a couple of 90-minute class periods. On a more traditional 45- to 55-minute schedule, you’ll probably want to allow a week to do the experiment properly.
- To save time in class and reduce the likelihood of students stabbing, cutting, or smashing their fingers, you’ll want to cut the bottom out of the big can, punch the holes, and insert the needle into the cork in advance.
- A champagne cork, with its flared shape, makes a very stable base for the needle.
- Scorched cashews smell like burned popcorn, but a candle warmer loaded with a strong caramel-apple wax melt will fix that problem fairly quickly.
- If you need a ninth-grader’s full attention, letting him set things on fire will do the job.