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How do you change the volume without changing the pressure Charles law

  1. Feb 21, 2013 #1
    Hi,

    According to Charles gas law if you keep a certain constant pressure & moles of gas, you can relate the other 2 physical quantities (Volume & Temperature) in a formula: V/T=c




    If you increase T, V will increase because the temperature is directly proportional to the volume. The same happens if you decrease T, V will decrease.

    Now I cant understand how to start with V instead of T. How do you increase the Volume without changing the pressure ( because it must be constant) so that the temperature increases?


    Thanks in advance!!
     
  2. jcsd
  3. Feb 21, 2013 #2

    mfb

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    Re: How do you change the volume without changing the pressure Charles

    You have to provide some energy to increase the temperature anyway. As both V and T change at the same time, I don't think it is meaningful to separate those processes.
     
  4. Feb 21, 2013 #3
    Re: How do you change the volume without changing the pressure Charles

    Thanks, but the problem is how do we provide that energy? If I increase the Volume of a gas, it automatically decreases pressure(!). I dont want that to happen because the pressure must be the same if we want to explain this second gaslaw.
    I cannot even imagine how it would be possible to increase volume wihout the decrease of pressure so that the temperature increases.

    Is that even possible? Or am I making it way too difficult & should I just always start off with increasing temperature which will increase volume and not vice versa (This way pressure doesnt change)?
     
  5. Feb 21, 2013 #4

    mfb

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    Re: How do you change the volume without changing the pressure Charles

    With the usual methods to heat a gas: Put it in a hot environment, expose it to radiation, high-energetic particles, let it do chemical or nuclear reactions or find some other way to add heat.
     
  6. Feb 21, 2013 #5
    Re: How do you change the volume without changing the pressure Charles

    Ok So 1 more last question to make sure im getting it :p
    We start with raising the temperature which will raise volume. We do not start of increasing volume to increase temperature because that is impossible, right?
     
  7. Feb 21, 2013 #6

    mfb

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    Re: How do you change the volume without changing the pressure Charles

    At least not with a regular gas, right.
     
  8. Feb 21, 2013 #7
    Re: How do you change the volume without changing the pressure Charles

    Thanks for the answers :) It helped me a lot.
     
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