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Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Obivously not just steam, but also hydrogen wich gets trapped inside the block and it blows the block up.
From here
wikipedia wrote ... If thermite is ignited underwater, the molten iron produced will extract oxygen from water and generate hydrogen gas in a single-replacement reaction. This gas may, in turn, burn by combining with oxygen in the air.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
That quote from wikipedia makes sense provided that there is air underwater.
Since water expands roughly 1500 fold when it boils I think a steam explosion is perfectly reasonable. I have seem (years ago) video of a pot of molten copper being poured into water. The explosion is pretty substantial and has nothing to do with hydrogen.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Yep; but this is ice, wich has lot of air bubbles trapped inside wich can ignite with produced hydrogen. When this happens in a closed space it gets quite mad.
Steam could also have played a role here, but I don't know would just it detonate so violently. rather than just 'popping' thermite from the top.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Someone needs to try it with a block of dry ice to see if hydrogen is a factor. Personally I don't think molten metal is hot enough to dissociate water much, and even if it was, it just burns back into water and doesn't release any more energy than you had to start with.
So I think with dry ice the bang would be bigger.
PS, this thread on the sciencemadness forum seems to suggest that it's purely a steam explosion, and works with liquid water too. The last post in the thread brings up an interesting point, if droplets of molten metal are mixed with water, the rate of heat transfer could run away as the mixture boils and shakes itself around.
Registered Member #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
yeah steve is right. they explain it in the video.
the thermite is more than 3000degrees hot. when the thermite comes into contact with the ice block the ice gets so hot that it changes into steam within a few microseconds causing this huge explosion
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Yeah, but to do it properly someone would need a clear area without anything flammable, some huge blocks of dry ice and large amounts of thermite. I don't know how would experiment scale down well!
Lots of steam is definitely produced very rapidly, along with hydrogen.. 50:50 for now?
I somehow felt that steam explosion would need better ''sealing'' for pressure buildup, but I might not be right...
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
"Yep; but this is ice, wich has lot of air bubbles trapped inside wich can ignite with produced hydrogen. When this happens in a closed space it gets quite mad.
Steam could also have played a role here, but I don't know would just it detonate so violently. rather than just 'popping' thermite from the top."
It's still mainly ice. I'm not sure that a H2 +air explosion would propagate through a mesh of ice and water- after all a copper mesh will stop an acetylene flashback. You seem not to wish to believe that molten copper certainly detonates when dropped into water; why not?
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10 Ways how NOT to play with Thermite . . .
