Invisible <voi### [at] devnull> wrote:

> On the other hand, what the HELL volume of methane gas weighs 1 kg? ;-)
>

That is actually a trick question.

The mass-part is easy enough: pure Methane consists of one C-atom (at 12g/mol)
and 4 H-atoms (at 1g/mol) for a total of 16g per 22.4 liter. Thus at regular
temperatures and pressures, you need 1400 liter of methane to get 1kg of
*mass*.

However the *weight* has to take into account buoyancy. Given an atmosphere that
consist mostly of N2 (weight 28g per mol) the buoyant force on a volume of
methane will exceed its gravitational force, i.e. it has a negative weight at
any volume.

I. e. it doesn't weigh anything - it rises up.

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