# Relative Density of Various Gases with Varied Temperature

Discussion in 'Community Discussion' started by kalisphoenix, Aug 8, 2006.

1. ### kalisphoenix macrumors 65816

Joined:
Jul 26, 2005
#1
Is there any way for a hypothetical gas to be lighter than air during the day (based on greater solar radiation, or maybe that solar radiation is greater than terrestrial radiation?) and heavier than air at night?

*ponders* I wouldn't expect that this is possible, but I thought I might as well ask.

2. ### Timepass macrumors 65816

Joined:
Jan 4, 2005
#2
yes it is possible. I dont know of any off the top of my head and the text books that I have where it could be possible for me to look it up are 600 miles away.

But for something to show why I know it is true is just look at those termonitors that have floating things in it for different temps. That is the density changes enough as it warms up to increase or decrease faster than the liquad it is in. Also for calcs and really study air and gases are just fluids and really should be thought as such. Only they have a very low density and no really vecoilitys but behave just like fluids for the most part.

3. ### mkrishnan Moderator emeritus

Joined:
Jan 9, 2004
Location:
Grand Rapids, MI, USA
#3
When you say hypothetical gas, how hypothetical? If you're talking about a chemical gas without a lot of unusual weak intermolecular interactions, isn't it going to be very close to ideal gas behavior at STP?

4. ### j26 macrumors 65832

Joined:
Mar 30, 2005
Location:
#4
Boyles Law might be of assistance.
Of course there are all sorts of mathematical equations to work out changes in volume, but if the container was sufficiently elastic to allow pressure to remain constant, them volume would be directly proportional to temperature and at a certain temperature the gas would displace more weight than the air surrounding it and becomes "lighter than air". However, it would have to be light enough to counter the weight of the container to be buoyant.

So it's hypothetically possible. As to practical examples, I dunno.