Blog post: swansont: Physics in the News

Dry ice bombs were in the news, with two having gone off at LAX. A bit of a surprise that these haven't been on the radar much, seeing as they don't have a chemical signature that could be sniffed out, and have no moving parts. When they blow is not really controllable, but the mechanism is simple — the ice sublimates and pressure builds up. Since a mole of an ideal gas wants to take up 22.4L at STP, while the solid takes up negligible volume. Since the volume is restricted, the pressure builds as more gas accumulates, until the container fails. Boom.

What Is a Dry-Ice Bomb?

It's noted that such devices are illegal, but when I ran across a story about a teen getting in trouble for doing this in his backyard a while back, the law was stated (or perhaps paraphrased) in such a way that it would make any carbonated beverage illegal. I have to hope most laws are written better than that. It's rare, but soda bottles can explode, and small amounts of dry ice in containers can be interesting. Context, i.e. the amount of material, matters, much like how the dose makes the poison.
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