Hot/Cold with CO2 Cartridges
Today a student asked me, "If you use a CO2 cartridge to propel a toy
the cartridge will feel cold. But if you use a rocket engine with
solid propellant, it will feel hot. If both are expelling gases, then
why is one hot, and the other cold?"
Because one is simply the expansion of compressed gases -- perhaps with
a phase change (which absorbs heat) while the other is a chemical reaction
to produce the gases -- one of the products of the specific chemical
reaction used is heat.
gregory r bradburn
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Update: June 2012