in reply to OT: Physical exitation of pressurised liquid gas.

My gut feeling is no, that it would not.

From chemistry, you have P*V = n*R*T, or P*V/T = n*R. (From Boyle's Law, Charles' Law, Avogadro's Hypothesis, Law of Combining Volumes, Ideal Gas Law, Gibbs' Phase Rule, etc.) Assuming a sealed pressure container, the volume will be constant. Therefore, P/T (the ratio of pressure to temperature) is proportional to n (the number of moles of gas). The pressure should then stay constant, unless the number of moles of gas or the temperature change. Assuming that the compound is not unstable, then P/n is proportional to T.

While shaking would likely add some energy to the system, I do not know if it would add enough to change the temperature (and thus the pressure) noticeably.

HTH.

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Re^2: OT: Physical exitation of pressurised liquid gas.
by BrowserUk (Patriarch) on Apr 11, 2009 at 11:04 UTC
    While shaking would likely add some energy to the system, I do not know if it would add enough to change the temperature (and thus the pressure) noticeably.

    The liquid/gas: butane. The pressure vessel: a disposable lighter. As the fuel runs low, so the pressure inside drops until you reach the point where the flame is very feeble. Out of habit or instinct, I tend to shake it for a few seconds, and try again. Frequently, the flame is stronger afterward, I got to wondering if this effect was my imagination or real.

    The likelihood is that any significant increase in pressure is due to the warming affect of my hand holding the lighter. But try as hard as I might to not grip the lighter whilst shaking it, so as not to cause it to be warmed by body heat. Still, shaking it does seem to produce a noticeable increase in pressure. Hence the question.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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[reply]
      I'm neither a chemist nor a physicist, but I doubt your disposable lighter is made of frictionless material. Hence, shaking the lighter will cause friction between the liquid (butane) and the vessel. Friction causes heat. So the liquid, and hence the gas, will heat up, regardless of the effect of your hand.

      But as soon as you open the lighter, pressure drops (as gasses escape). Gasses that rapidly drop in pressure cool. No idea how this offsets things.

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