Comment of the Day: Robert Waldmann: Physical Chemistry:

Mass shouldn't affect boiling points...

What matters for a molecule in a liquid yearning to be breathable and free is momentum not velocity. The puzzle is why at STP is methane a gas while gasoline is a liquid and parafin a solid.

On Ammonia, come on, partial charges vary. It isn't as if charge is + 1 electron, + 0.5, 0 - 1, -2. Nitrogen is less electrophilic than Oxygen so the partial charges are smaller. HCL is a solid at STP because the partial charges aren't well partial.