Dry ice that's been super-cooled in liquid nitrogen is dropped in a container of water! How much fog will -that- make?
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: In an earlier experiment, we put dry ice in liquid nitrogen. We found that, while dry ice is cold, it's still a lot hotter than liquid nitrogen. The 'hot' dry ice makes the liquid nitrogen boil faster and the liquid nitrogen makes the dry ice colder.
Steve: Now, we all know what happens when you put regular dry ice in water. It makes a bunch of cool-looking fog. What'll happen if we use the super-cold dry ice instead?
Well... It doesn't look that much different than the regular dry ice. So, why doesn't cooling the dry ice make it make more fog?
Joanna: Because cooling it is not the thing to do. Dry ice is normally at its sublimation point, the temperature at which it changes from a solid to a gas. The cold gas then mixes with the surrounding air, cooling it enough to form fog.
The super-cold dry ice starts off too cold to sublimate, but the water rapidly warms its surface to the sublimation point. Once the outside gets that warm, it doesn't act any different than regular dry ice.
Steve: If your goal is to make a lot of fog, don't cool down the dry ice. Heat up the water. Then, the dry ice sublimates faster, so it gives off more gas. And, the air above the water contains more water vapor, so it's easier to make the fog.
Joanna: Thanks for watching! I hope you'll join us again soon for another experiment!
Awww... Spilling dry ice isn't nearly as fun as spilling liquid nitrogen...
For the scientifically curious: You might have noticed a brief period of rapid boiling when the super-cooled dry ice was first placed in the water. If it's too cold to sublimate, what caused the boiling?
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