Students got a treat on the day before Halloween. They strengthened their understanding of phase changes and expansion and contraction of matter as well as extreme boiling and melting points as they observed 10-15 demonstrations using dry ice, and liquid nitrogen as well as some expansion contraction demos with cans and eggs. The magic crystal ball was a new one to me, brought to me by a student who had seen it in a you tube video and payed close attention!
The magic crystal ball is made with dry ice (solid carbon dioxide in the bowl). As it sublimates (turns from a solid directly to a gas), the gas expands to form the bubble. We put a layer of soapy water over the top of the bowl to create the bubble and the CO2 is causing it to expand. Thanks to Hayden for showing me this one.
The water was heated in the flask and then the hardboiled egg was placed on top. I then set the flask in ice water and as the air contracted in the flask it created a vacuum and sucked in the egg.
http://vimeo.com/78320134
We heated this same bimetallic strip and it only bent one way. Blaine reminded me to try it with the liquid nitrogen and look how much it bends the other direction. If someone wants to do some video editing to show both directions in a shorter video, I’d greatly appreciate your help!
If you have any videos you took of the halloween show that show other demonstrations please let me know. I’d like to have a copy. Thanks!