Ask A Scientist Chemistry Archive

Question:
Why does dry ice squeal when you put a flat metal object against it?
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Answer:
The surface you touch is considerably warmer than the dry ice
(which, I believe, is normally at around 60 below zero,
Fahrenheit) and causes the dry ice to sublimate rapidly to
CO2 gas.  Since you're pressing the ice against the metal,
there will be places where gas is momentarily trapped between
the two surfaces, and when released through a small opening tends
to "whistle," which has a characteristic sound when coupled with 
the resultant vibration of the metal plate.
--WORD!!