Charles' law and absolute zero

[joeyjo100]

According to Charles' law, volume decreases with temperature. Extrapolating down towards absolute zero, and the volume of the gas will be zero.

How can this be possible? Surely any amount of gas will still have to take up some volume in space. Can multiple gas molecules really occupy zero volume?

 

[TobyC]

In practice no, probably not, although I'm not sure what weird quantum effects set in.

But when you have an 'ideal gas', you model the individual particles making up the gas as being point particles of zero volume which collide with each other. The overall volume of an ideal gas is therefore entirely due to the motion of the particles preventing them from all being squashed down to a single point, it doesn't depend on the size of the particles at all, and that is why at absolute zero, with no motion of the particles, the volume of an ideal gas is zero.

In practice no gas is 'ideal', so you're query is probably completely right, but the ideal gas law is still a very good approximation for the behavior of most gases when they are far from their vaporisation point. The size of each gas atom is negligible compared with space between adjacent atoms, so the volume of a gas at absolute zero (when the gap between atoms is zero) is also negligible.

 

[AlephZero]

There are no gases at absolute zero. Charles' law does not apply when the gas has liquified or solidified.