Is methane gas heavier than air?

Is methane gas heavier than air? No! Methane gas is known as "the lift gas". It is also explosive.
Does this answer your question? Tom

No. It is actually lighter than air.
You can work this out from the fact that a gas's density is proportional to its formula mass.
If we take the atomic masses of Carbon (C) as 12, Hydrogen (H) as 1, Oxygen (O) as 16 and Nitrogen (N) as 14 then:
Air contains Nitrogen (N2) - 78% and oxygen (O2) 21%. The equivalent 'formula mass' of air is therefore just slightly more than 28 (2 x14)
Methane's (CH4) formula mass is 12+ 4 or just 16 - so it is lighter than air as the formula mass (and hence density) is less than 28.
Carbon Dioxide (CO2) has a formula mass of 44 (12 + 16 + 16) so it is much more dense than air.
Hydrogen (H2) with a formula mass of just 2, is much lighter than air - in fact it is the lightest gas of all.

Hi chefpierce...

Having a chemistry and biology background myself I can really appreciate the answer given!

Thanks for posting the answer... ;)

Mark