Homework Help: How do you change the volume without changing the pressure Charles law

1. Feb 21, 2013

mcfaker

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. Feb 21, 2013

Staff: Mentor

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.

3. Feb 21, 2013

mcfaker

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)?

4. Feb 21, 2013

Staff: Mentor

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.

5. Feb 21, 2013

mcfaker

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?

6. Feb 21, 2013

Staff: Mentor

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

At least not with a regular gas, right.

7. Feb 21, 2013

mcfaker

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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