We had a full day of liquid nitrogen demonstrations today. Merged 2-3 classes of 8th graders all day in the auditorium for observations and inferences of the following demonstrations:
1. “Fried Balloons”.
Prep: Pour a 3 cm layer of LN2 into a very large styrofoam container out of sight from the audience. Inflate and tie off 10 latex balloons, and store them in a very large garden trash bag. Before students enter the room, place the styrofoam container onto a table with the lid on the container. As students come in, do not draw attention to the box. (There will be some noise of LN2 bubbling and it’s best if students don’t notice.)
The “Patter”: “You know, the math department at our school has told us they’re very concerned that people just don’t understand basic geometry any more. They’ve asked us to incorporate some math lessons into our science, so here we go: look carefully at this balloon (hold it up), and estimate how many balloons of this size could fit into this box.” Depending on the size of your styrofoam container, people will typically respond anywhere from 2 to 6.
“OK, let’s see.”
Lift the lid slowly and slowly place the first balloon into the box. Try to do this without swirling the vapors over much. Hold the balloon down in the LN2 until it has shrunk to about half size. Repeat until you’ve got at least 8 balloons inside. You can push them down with your bare hands, just be careful not to let the liquid nitrogen drip onto your skin.
More “patter”: “I forgot to eat breakfast this morning, so I think I’m going to need to fry up something to eat. Hmm…. what do I have around… OH! I know! I’ll just use this NICE, HOT table (pat the surface of the table) to FRY some balloons!”
One by one, pick the balloons out of the container and ‘stir fry’ them on your table surface.