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Is blowing up a balloon a great analogy for Avogadro's Law?

  1. Jan 4, 2015 #1
    I was learning about Avogadro's Law and trying to find some real-life example of it. It mainly states that:

    For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

    So let's say I have a balloon with X moles of air inside it which take up volume V. Then I pump it and add more air which result in the balloon having 2X moles and taking up volume 2V right? I think that the pressure is constant since it must adjust to the pressure of surroundings but I'm not sure about the temperature. So is it a good example to build up some intuition about the law or I misinterpreted something?
  2. jcsd
  3. Jan 4, 2015 #2


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    "Great?" No. "Good?" Not really. "So-so?" Depends on the balloon: rubber party balloons, not so good due to pressure difference required to stretch them though they do offer cylindrical or semi-spherical shapes that are fairly convenient for volume calculations; mylar bags, garbage bags, that inflate without deformation and are very low mass are okay, but it's tough to calculate a volume for very irregular geometry. A reasonable compromise for two rudimentary approaches ---- eehhh ----- better than no mental picture.
  4. Jan 4, 2015 #3


    Staff: Mentor

    I think the easier thought experiment apparatus is a piston and cylinder.You can think about the volume of the cylinder, the mass of gas contained, the temperature, and the force on the piston.
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