Explosions 'n Stuff!
If you like seeing shit blow up, go have a look at this short video of the thermite reaction flash-boiling some liquid nitrogen (original temperature: -196 degrees C) and eating through various parts of a small French car on the excellent British TV show Brainiac (like Mythbusters but way cooler).
In the thermite reaction, aluminum metal is oxidized by the oxide of another metal (like iron oxide, or rust) to give aluminum oxide, the other metal (pure molten iron), and quite a lot of heat. The reaction takes an input of energy to start (like a lit fuse), but once it starts it is impossible to stop until almost all of the aluminum has been oxidized. Even dunking it in water won't work, since the oxygen required for the reaction comes from the iron oxide (or whatever oxide is used) and not from the air around the reaction. You don't want to start a thermite reaction unless you're sure of what's going to happen. Interestingly, I learned via Wikipedia that instead of using a fuse to initiate this reaction, you can use the oxidation of glycerin by potassium permanganate. You may remember that I have some experience with that reaction lighting things on fire.
The key to the thermite reaction being so cool is the fact that aluminum has a low melting point for a metal, but a very high boiling point. When the reaction starts, the aluminum rapidly melts, which means that the reaction is proceeding in the liquid phase (which is a better condition than the solid phase to get an extensive reaction). The high boiling point means that none of the aluminum fuel goes into the vapor phase as the reaction proceeds, so all the fuel sticks around and gets reacted. The result, as you can see from the video, is a very hot, very long reaction that's capable of eating through literally feet of solid metal.
Chemistry is cool!
Cross-posted at Nice Shoes, Wanna Fock?
Tags: thermite, Brainiac, explosion
In the thermite reaction, aluminum metal is oxidized by the oxide of another metal (like iron oxide, or rust) to give aluminum oxide, the other metal (pure molten iron), and quite a lot of heat. The reaction takes an input of energy to start (like a lit fuse), but once it starts it is impossible to stop until almost all of the aluminum has been oxidized. Even dunking it in water won't work, since the oxygen required for the reaction comes from the iron oxide (or whatever oxide is used) and not from the air around the reaction. You don't want to start a thermite reaction unless you're sure of what's going to happen. Interestingly, I learned via Wikipedia that instead of using a fuse to initiate this reaction, you can use the oxidation of glycerin by potassium permanganate. You may remember that I have some experience with that reaction lighting things on fire.
The key to the thermite reaction being so cool is the fact that aluminum has a low melting point for a metal, but a very high boiling point. When the reaction starts, the aluminum rapidly melts, which means that the reaction is proceeding in the liquid phase (which is a better condition than the solid phase to get an extensive reaction). The high boiling point means that none of the aluminum fuel goes into the vapor phase as the reaction proceeds, so all the fuel sticks around and gets reacted. The result, as you can see from the video, is a very hot, very long reaction that's capable of eating through literally feet of solid metal.
Chemistry is cool!
Cross-posted at Nice Shoes, Wanna Fock?
Tags: thermite, Brainiac, explosion
posted by The Disgruntled Chemist at
10:47 AM
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