Can dry ice be used as a explosive chemical? I am intrigued by this chemical dry ice and seen various experiments with it, and seems to have potential to be a explosive.
So can dry ice explode?
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9$\begingroup$ I've seen (no reference at hand) dry ice in a coca-cola plastic bottle explode. But there's a difference between deflagration and explosion. The former one is subsonic, the later one supersonic. Dry ice doesn't come anywhere near supersonic. $\endgroup$– Gyro GearlooseCommented Feb 12, 2016 at 21:53
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2$\begingroup$ And beside, it wouldn't be a chemical reaction. $\endgroup$– Gyro GearlooseCommented Feb 12, 2016 at 21:55
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2$\begingroup$ I've done this myself. The bottle gets ripped open with great force (DON'T TRY IT AT HOME!), but as @GyroGearloose correctly noted, this is certainly not a chemical explosion. $\endgroup$– Ivan NeretinCommented Feb 12, 2016 at 22:04
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$\begingroup$ @GyroGearloose - is sublimation, a phase transition, not chemical? I guess one could argue that it is physics, but the thermodynamics of phase transitions would seem to straddle the two disciplines. $\endgroup$– Jon CusterCommented Feb 12, 2016 at 23:18
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$\begingroup$ I toned this back a bit as to avoid any appearance of malfeasance :) $\endgroup$– jonscaCommented Feb 13, 2016 at 0:14
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2 Answers
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Actually, you are close. While technically not an explosive (and really, it's liquid CO2 vs solid CO2), charges containing liquid CO2 that are heated can be used as blasting agents for mining and tunneling. They make up for relatively low shock/energy output by being very safe and also breaking material via tension instead of compression. A well-known example is Cardox, which is used in coal mining. Or see this.
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Chemicals used as explosives are those which, by some reaction/state change, can produce a large pressure (and thus usually volume) change very quickly.
While dry ice (solid carbon dioxide) is much more dense than in its gaseous phase, at room temperature the change happens very slowly, and is just unstable rather than stable but reactive, so can't be left and triggered later.
This makes it pretty useless as a working explosive.
Since it can exert a significant pressure while it sublimates, however, it can make other things explosively fail -- like the dry ice in the soda bottle demonstration. A quick search suggests that soda bottles are rated to withstand a pressure difference of around 100 psi (~6.8 atm, 0.69 MPa), and the increasing pressure won't stop the carbon dioxide subliming/boiling (since at that point it'll be a liquid) until ten times that.
Now, there is a market for things that slowly expand with a lot of force ("non-explosive demolition agents"), but they're solids that you mix into a slurry and pour into a cavity, since these can trivially exert orders of magnitude more pressure -- a common brand-name one, Dexpan, is rated at 18000 psi -- and they also turn from a slurry or solid into another solid. If you tried this operation with something that turned into a gas, you'd need to seal the cavity to stop the gas just escaping, whereas with solid-to-solid reactions, gravity and the solid itself will do the job for you.
