Pizza and the (Cartesian) Devil

I brought some fun stuff with me to an outreach event for the Science Factory this past Wednesday at Cosmic Pizza (really good pizza, by the way). My demons are thick crust pizza slices with extra sauce, extra cheese, black olives and red onions. My devil is a little bent straw with a rubber band and a few paper clips partially submerged in a soda bottle of tap water dyed red. This is the coolest little science toy. I made one to keep at home.

The Devil’s apparatus (and how it works): I explain in the video, increasing pressure on the sides of the bottle reduces volume inside the bottle, increasing pressure on the water (Pascal’s Law), which increases pressure on the air bubble inside the devil. This air bubble maintains neutral buoyancy (Archimede’s Principle) when the bottle is at its normal state (un-squeezed). When pressure on the bubble increase from squeezing the bottle, the volume of the bubble compresses, making a smaller bubble. This smaller bubble isn’t large enough to maintain neutral buoyancy, and instead, the devil becomes negatively buoyant, or it sinks. Releasing the sides of the bottle allow the volume of the bottle, the liquid, and the air bubble to expand again, and the devil becomes neutrally buoyant.

I also brought along some self-inflating exploding balloons! I put small amounts of dry ice into normal latex balloons, tied them off, and then placed the balloons into bowls of warm water (the warmer the water, the better the effect). The dry ice inside the balloons sublimated, creating carbon dioxide gas, which filled the ballons and inflated them. If there was enough dry ice in the balloon, and the water was warm enough, the carbon dioxide gas would fill the balloons so quickly, it would exceed the maximum volume capacity of the balloons and the balloons would pop! Sometimes this took a while and the balloons popped after we had forgotten about them. That scared some of the kids. Don’t worry. They were scared in the way where they wanted me to do it again.


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