# Boyle's Law, does it hold true in a non finite container ?

1. Aug 12, 2011

### karen_lorr

If a gas will expand to fill the available space (container) does this still hold true if the "container" is the atmosphere?

Assuming the gas(es) can escape (either in molecular or in subs - atoms) from the area around the earth containing our atmosphere this means that the gas is not contained so Bolye's law is not applicaable as the this makes the contain non-finite (not contained).

If this is the case (non-finite area) ?? then does Boyle's law hold for, for example water evaporation, where it could (although not likely) escape the system.

Thank you

2. Aug 12, 2011

### Studiot

Good morning Karen.

No, Boyle's law does not apply to the atmosphere.

But that is not because of its size.

Boyles law states that PV = a constant.

In order to apply this you have to have one pressure (and one volume) to represent the whole mass of gas.

The pressure in the atmosphere is not constant - it varies generally with altitude and also from place to place.
This is because there is another agent acting, that is not included in Boyles law. That is gravity.

In fact Boyles law excludes any body force, of which gravity is an example.

You can, however, apply the law locally to a small enough volume to discount the effect of gravity.

Can you think of any other body forces?

3. Aug 12, 2011

### karen_lorr

If Bolye's is not applicable due to the PV <> a constant
then (just wondering here)
is the same true of the Le Chatelier principle (basically a gas will expand to fill the space) - if the space is non-finite or (as you point out) there are other forces involved

If we assume a given volume of H2O the Le Chatelier principle will take too long to achieve anyway - as the H2O isn't "up there" long enough away, so it would never occur -, but is the general principle still valid - the water will spread out (assuming nothing else, eg, gravity, wind, etc) until it was evenly distributed over the entire space (to relieve the pressure in the volume)

??

Last edited: Aug 12, 2011