We had an awesome (to me) Young Men/Young Women combined activity last night. One of the advisors is a Chemistry professor at the good ol' "Y" and he gave us a great display of chemistry experiments. You know, color changes, explosions, colored fire, etc. The most amazing of those was using thermite to create iron. He also used a bell jar and vacuum to "inflate" a balloon and a marshmallow and showed us that you can boil water at room temperature if you remove enough of the air pressure.
Thermite is a combination of good old rust (iron and oxygen) and aluminum powder. I didn't know this, but aluminum "rusts" but its' "rust" is clear- infact, that's what sapphires are- aluminum rust. Aluminum happens to like oxygen even more than iron and when, the mixture is ignited, will "steal" the oxygen from rust and leave a blob of iron. The only thing is, it's occurs at a temperature of something like 2500 degrees F and there's no way to stop it until the reaction is complete. It burns so hot that they used to use it to weld train tracks together when building the railroads because it was easier to carry rust and aluminum powder out to the middle of nowhere than an acetylene torch. He showed us a small reaction (mix the two and then light it on fire)in the lab that resulted in a white hot blob of iron the size of my thumb in about 5 seconds. Then he showed us a video where two guys mixed a bunch together in a flower pot on a car hood. It burned through the pot and into the engine and a few seconds later the entire engine melted out the bottom of the car. It was amazing! They did it again over the fuel tank and the whole car exploded. That was the YM favorite part!
And now for the "cool" part. What I didn't know (or remember, anyway) is that you can actually boil water until it freezes solid. (This video is a bit on the dry side, but it was short and sweet. The other were too long.) Crazy! If you remove enough of the air pressure, the water boils. But, it still takes energy to change the water from a liquid to a gas state. In the closed system of the bell jar, the only energy available is the heat inside the jar. So, the longer the water boils, the colder it gets until it finally freezes. He said that's actually the reason astronauts have to wear space suits and not just warm clothes and an air mask out in space. It's not just that it's cold and they'd freeze or suffocate without air, it's that their bodies would start to "boil" first in the vacuum of space and then freeze if they didn't have a suit to keep their bodies pressurized. Hope that's not too graphic, I just thought it was a very interesting fact.
Science is SO cool! (Sorry, no pun intended!)