Why did this ice explode? After watching this video of molten copper poured on a block of ice, the whole thing kinda exploded.  What would cause ice to explode when subjected to molten copper?
 A: First, I think there's some interesting physics to that question and I don't think the dry ice bomb comparison works because a dry ice bomb is a sealed system.  Pouring hot metal onto a block of ice shouldn't create a seal because any escaping hot water vapor should be able to fly out the hole that was created by the copper that was poured in, even as part of the copper solidifies the combination heat and liquid water around the hot metal and hole it made going in should allow gas to escape and never create a tight seal.  That's true unless the block of ice is cold enough to re-seal after entry, but I don't think that's the case here.
What happens in that video is basically the same thing that happens when you drop icecubes into a warm drink and the ice-cubes crack.   Ice's density drops with temperature.  As ice grows colder it grows more dense and as it warms it expands.  This is called differential expansion.
When that guy in the video poured molten copper into the block of ice, the same thing happened, only the expansion happened from the inside out, so ice was expanding from the inside, when the outside of the ice wasn't, and ice, not being very elastic, once the pressure reached a certain point -  kaboom.   It's logical to think expanding gas created the explosion, but I don't believe that's the case, I think it was the expanding solid ice from the inside which created the explosion, loud noise and flying bits of molten copper, and most important, 3 million views.
Graph here on how much ice expands by temperature.   
