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Thermite vs ice = explosion

Madalch said:
Dried steam? Superheated steam, I could see, but dried?
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Dried steam is run through a set a baffles called a steam dryer that has the goal of removing all droplets that almost universally are in steam right from the boiler. Steam right from the boiler is usually called saturated steam. Superheated steam is also necessarily dried steam.
 
Lye water in a pop bottle, slide in some rolled up tin foil, and snap a condom over the top- instant hydrogen balloon. Attach a wick. Light it and let her go. Watch for the utility company trucks after the old lady next door calls them to report flashes on the overhead wire.

Careful, it's an exothermic reaction, the bottle will melt the rubber.

Anyway, I don't think mere aluminum and water will make hydrogen, it takes lye in there. Other wise we couldn't cook in aluminum pots, or have aluminum around boats.
 
casebro said:
Anyway, I don't think mere aluminum and water will make hydrogen, it takes lye in there. Other wise we couldn't cook in aluminum pots, or have aluminum around boats.
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Actually, the lye is only there to make the reaction product (aluminum hydroxide) soluble. If you put a piece of perfectly clean aluminum in water, it instantly becomes coated with a layer of aluminum hydroxide, which prevents the water from reaching and reacting with the rest of the aluminum. But aluminum hydroxide is amphoteric, and will dissolve nicely in strong base or strong acid, so aluminum will react readily with these solutions.

If you put water into molten aluminum, you will get a fire in addition to the steam explosion, since aluminum hydroxide can't coat the surface of a liquid.

ETA: What BenBurch said.
 
casebro said:
Lye water in a pop bottle, slide in some rolled up tin foil, and snap a condom over the top- instant hydrogen balloon. Attach a wick. Light it and let her go. Watch for the utility company trucks after the old lady next door calls them to report flashes on the overhead wire.

Careful, it's an exothermic reaction, the bottle will melt the rubber.

Anyway, I don't think mere aluminum and water will make hydrogen, it takes lye in there. Other wise we couldn't cook in aluminum pots, or have aluminum around boats.
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Well aluminum general has a coating of aluminum oxide preventing it from reacting more, but liquid aluminum would not have this and be more reactive.
 
You know, from appearances, it looks a lot more like a steam explosion than hydrogen combustion. A violent phase change can produce this can't it?
 
Travis said:
You know, from appearances, it looks a lot more like a steam explosion than hydrogen combustion. A violent phase change can produce this can't it?
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I didn't watch the video, but it sounds reasonable to me.
 
Travis said:
You know, from appearances, it looks a lot more like a steam explosion than hydrogen combustion. A violent phase change can produce this can't it?
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Wouldn't be the first time they have tested an explosion where the combination of extreme heat and extreme cold results in a disaster. The other scenario is the frozen turkey in the deep fryer.
 
Cuddles said:
I assume it's what Jamespatterson said. If you produce lots of gas in an enclosed space, you get an explosion once the pressure is too great to contain.

Why were they looking at this anyway? The interaction between thermite and ice hardly seems like a common topic of discussion that they'd be interested in investigating.
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Mythbusters gets a TON of the silliness ideas from game-playing children, and occasionally will try to make sense of a made-up "myth".
It's hardly a situation anyone would ever encounter.
I failed to pay much attention to the episode, but it has generated hundreds of messages on their forum.
 
Travis said:
You know, from appearances, it looks a lot more like a steam explosion than hydrogen combustion. A violent phase change can produce this can't it?
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It can, yeah... but not usually so suddenly without containment.

My own pure speculation is that it's a hydrogen effect, not just ice -> water -> steam. The report was pretty impressive, and it threw chunks large and small for hundreds of feet. I'm guessing the blast qualified as a low-order explosive, though it's hard to tell without a pressure measurement.

What could happen is if enough water was cracked, and possibly oxygen bound up in the iron as well, it would generate a hydrogen plume mixing unevenly with ambient air. Ignition source is right there, obviously. When this plume approached the right ratio, BOOM! Nice deflagration with a clear flame, something that fits the audio and video evidence.

But maybe not. I suppose it could also be the ice puddled, containing enough liquid water that a large chunk of it superheated and flashed to steam all at once. Seems unreliable, but who knows?

Jamie's observation was that the ice/water/steam might somehow trigger "aerosolizing" the thermite. I don't see that being reasonable, but it is possible that some similar effect is going on -- steam somehow helps melt or strip oxide coating from the metals and speeds up the already ongoing thermite reaction. I'd call this a long shot.

What would be interesting is to retry this (1) in an inert atmosphere, which would eliminate my leading hypothesis if nothing happens, and (2) in the presence of dry steam instead of ice, which if it does BOOM eliminates the second. Also might be worth trying with a regular bucket of water to see what happens. Better calorimetry, too, to see if atmospheric oxygen is contributing, will help a lot.
 
R.Mackey said:
It can, yeah... but not usually so suddenly without containment.

My own pure speculation is that it's a hydrogen effect, not just ice -> water -> steam. The report was pretty impressive, and it threw chunks large and small for hundreds of feet. I'm guessing the blast qualified as a low-order explosive, though it's hard to tell without a pressure measurement.

What could happen is if enough water was cracked, and possibly oxygen bound up in the iron as well, it would generate a hydrogen plume mixing unevenly with ambient air. Ignition source is right there, obviously. When this plume approached the right ratio, BOOM! Nice deflagration with a clear flame, something that fits the audio and video evidence.

But maybe not. I suppose it could also be the ice puddled, containing enough liquid water that a large chunk of it superheated and flashed to steam all at once. Seems unreliable, but who knows?

Jamie's observation was that the ice/water/steam might somehow trigger "aerosolizing" the thermite. I don't see that being reasonable, but it is possible that some similar effect is going on -- steam somehow helps melt or strip oxide coating from the metals and speeds up the already ongoing thermite reaction. I'd call this a long shot.

What would be interesting is to retry this (1) in an inert atmosphere, which would eliminate my leading hypothesis if nothing happens, and (2) in the presence of dry steam instead of ice, which if it does BOOM eliminates the second. Also might be worth trying with a regular bucket of water to see what happens. Better calorimetry, too, to see if atmospheric oxygen is contributing, will help a lot.
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They're always doing retests of old myths. Perhaps I should go over and suggest this on their forum.
 
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