# What gas is heavier than air? **URL:** \ **Category:** Factual Questions\ **Created:** [March 17, 2001, 3:50am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334 "2001-03-17T03:50:28Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 9, 2013, 10:21pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/21 "2013-03-09T22:21:32Z")
> [@RM\_Mentock](#): > > My favorite demonstration experiment is to fill a bucket with carbon dioxide (dry ice, or vinegar/soda), and then blow soap bubbles gently above the bucket. The bubbles are heavier than air, so they gradually descend, but the ones that land in the bucket will float upon the carbon dioxide in the bucket. They bounce, and just rest there. It’s fairly dramatic. Now that sounds like one kewl experiment. Here’s the one I saw demonstrated in my 8th grade science class: Fill a small bucket with CO[sub]2[/sub] gas. It’s invisible, so you just have to take it on faith that the CO[sub]2[/sub] will just sit there in the bucket, and not instantly completely dissipate. Now, light a candle. Hold the bucket about a foot above the candle, and pour the CO[sub]2[/sub] out of the bucket. The candle will go out, thus demonstrating that you can pour CO[sub]2[/sub] through air. Just a little safe-n-sane demo of the Lake Nyos incident. ---
**Author:** ![Chessic\_Sense](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)\ **Post date:** [March 9, 2013, 11:06pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/22 "2013-03-09T23:06:57Z")
> [@zXMonsterz](#): > > Sulfur Hexafluoride > [@Senegoid](#): > > :dubious: Uh, and DID he self-asphyxiate? [Nah.](http://www.youtube.com/watch?v=u19QfJWI1oQ) ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [March 10, 2013, 1:42am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/23 "2013-03-10T01:42:39Z")
Fill a ballon with R12 and it will drop straight to the floor. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [March 10, 2013, 2:14am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/24 "2013-03-10T02:14:58Z")
Sulfur Hexafluoride is heavier than xenon, and about the densest gas that’s inert enough that you’d want to play with it. There are things like tungsten hexafluoride that are heavier but god-awful reactive with air, water and chemistry teachers. ---
**Author:** ![penultima\_thule](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/penultima_thule/32/3833_2.png) [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)\ **Post date:** [March 10, 2013, 2:23am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/25 "2013-03-10T02:23:00Z")
> [@DaveRaver](#): > > What gas is heavier than air? As those in the Flanders trenches in The Great War would verify, chlorine gas (Cl2) is heavier than air. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [March 10, 2013, 3:55am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/26 "2013-03-10T03:55:02Z")
> [@Senegoid](#): > > :dubious: Uh, and DID he self-asphyxiate? Who did the CPR to revive him after he spent several minutes standing his head to drain his lungs out? In [this thread](http://boards.straightdope.com/sdmb/showthread.php?t=668335) we discussed the heavy-gases-will-pool-in-your-lungs belief, a bit. I believe the chem teacher stood on his head quite unnecessarily. ---
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [March 10, 2013, 4:53am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/27 "2013-03-10T04:53:38Z")
> [@Lumpy](#): > > Sulfur Hexafluoride is heavier than xenon, and about the densest gas that’s inert enough that you’d want to play with it. There are things like tungsten hexafluoride that are heavier but god-awful reactive with air, water and chemistry teachers. If you want to up the temperature some (168 F), xenon hexafluoride is quite the heavy gas with a molecular weight of 245. I’m guessing a balloon filled with that would hit the floor pretty quickly. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [March 10, 2013, 5:49am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/28 "2013-03-10T05:49:18Z")
In Israel during Gulf I (Scuds from Iraq War), the entire populace learned something about heavier-than-air gas, most of whom never gave the matter much thought beforehand, I’m guessing. It became Topic A in that, by all common sense and proved by experience, War/Missiles=head for bomb shelter. But everyone was lectured over and over again that whatever anticipated gas released from the Scuds would sink. So ixnay on the shelters. It was all the more unnerving to be sitting ducks that way. Towards the end of the war rumors got out that high defense staff were saying Fuck this, I’m staying in the shelter, and people started following suit. Hell, that’s when Scud versus Patriot viewing parties were going on. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [March 10, 2013, 5:52am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/29 "2013-03-10T05:52:12Z")
Nm. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 10, 2013, 6:48am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/30 "2013-03-10T06:48:30Z")
> [@snailboy](#): > > If you want to up the temperature some (168 F), **xenon hexafluoride** is quite the heavy gas with a molecular weight of 245. I’m guessing a balloon filled with that would hit the floor pretty quickly. It must take quite some laboratory trickery to create xenon hexafluoride, xenon being an inert gas. I know some inert gases can be coaxed into molecules with other atoms by sufficiently contrived laboratory procedures. But it this possible with the heavier inert gases, or only with the lighter ones? And are such compounds stable, or do they decompose promptly? ---
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [March 10, 2013, 7:00am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/31 "2013-03-10T07:00:32Z")
> [@Senegoid](#): > > It must take quite some laboratory trickery to create xenon hexafluoride, xenon being an inert gas. I know some inert gases can be coaxed into molecules with other atoms by sufficiently contrived laboratory procedures. But it this possible with the heavier inert gases, or only with the lighter ones? And are such compounds stable, or do they decompose promptly? > **[Noble gas compound](https://en.wikipedia.org/wiki/Noble_gas_compounds)** > > In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 8 or 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon. > From the standpoint of chemistry, the noble gases may be divided into two groups:\[citation needed\] the relatively reactive krypton (ionisation energy 14.0 eV), xenon (12.1 eV), and radon (10.7 eV) on one side, and the ... There appears to be more compounds with the heavier noble gases than the lighter ones. There are none for helium or neon. As I recall (and my link probably talks about this but I haven’t read all of it), they are quite difficult to make but once made, they’re very stable. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 10, 2013, 7:13am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/32 "2013-03-10T07:13:03Z")
> [@Senegoid](#): > > :dubious: Uh, and DID he self-asphyxiate? Yes, and turned into a zombie. As to the rest, I’m guessing exhaling normally would clear the lungs enough to allow normal breathing, but the headstand is to ensure that _all_ the xenon is gone. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 10, 2013, 7:28am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/33 "2013-03-10T07:28:07Z")
> [@snailboy](#): > > [Noble gas compound - Wikipedia](http://en.wikipedia.org/wiki/Noble_gas_compounds) > > There appears to be more compounds with the heavier noble gases than the lighter ones. There are none for helium or neon. As I recall (and my link probably talks about this but I haven’t read all of it), they are quite difficult to make but once made, they’re very stable. Ignorance fought. It appears there are a LOT of Xenon compounds, in particular. The linked wiki mentions one that’s even easy to create: > [@](#): > > Xenon difluoride can be produced by the simple exposure of Xe and F[sub]2[/sub] gases to sunlight; while the mixing of the two gases had been tried over 50 years before in an attempt to produce a reaction, nobody had thought to simply expose the mixture to sunlight. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [March 10, 2013, 7:33am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/34 "2013-03-10T07:33:00Z")
> [@Malacandra](#): > > As to the rest, I’m guessing exhaling normally would clear the lungs enough to allow normal breathing, but the headstand is to ensure that _all_ the xenon is gone. But I don’t think it is necessary. Probably not even helpful. Gases in the lungs mix pretty well with every breath, so any xenon in your lungs should be quickly diluted and expelled, assuming you’re breathing normal air again. In [this thread](http://www.thenakedscientists.com/forum/index.php?topic=15771.0) I linked to in that previous discussion here, **Bored Chemist** links to [this MRI image of xenon in lungs](http://www.lbl.gov/Science-Articles/Research-Review/Magazine/1997/extra1.html), which shows that the xenon is evenly distributed throughout the lungs. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [March 10, 2013, 7:47am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/35 "2013-03-10T07:47:17Z")
> [@RM\_Mentock](#): > > My favorite demonstration experiment is to fill a bucket with carbon dioxide (dry ice, or vinegar/soda), and then blow soap bubbles gently above the bucket. The bubbles are heavier than air, so they gradually descend, but the ones that land in the bucket will float upon the carbon dioxide in the bucket. They bounce, and just rest there. It’s fairly dramatic. > > Then, you can scoop out carbon dioxide to change the level, or you can lower lit matches into it and watch them be put out at the same level as the bubbles. > > It makes the invisible carbon dioxide gas “visible,” by indirect means. Kids’ imaginations go wild That’s a really neat way to demo it. The less dramatic way was to pour it over a lit candle to put it out. Seeing it as a boundary layer of gas makes it stand out. ---
**Author:** ![Tangent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tangent/32/3098_2.png) [@Tangent](https://boards.straightdope.com/u/Tangent)\ **Post date:** [March 10, 2013, 10:09am UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/36 "2013-03-10T10:09:09Z")
> [@Malacandra](#): > > As to the rest, I’m guessing exhaling normally would clear the lungs enough to allow normal breathing, but the headstand is to ensure that _all_ the xenon is gone. Plus, it’s more dramatic! “Mom, my chemistry teacher inhaled this heavy gas that made his voice sound really deep.” vs. “Mom, my chemistry teacher inhaled this heavy gas that made his voice sound really deep, and then he had to stand on his head to exhale all the gas so he wouldn’t die!” ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 10, 2013, 12:01pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/37 "2013-03-10T12:01:16Z")
> [@chorpler](#): > > But I don’t think it is necessary. Probably not even helpful. Gases in the lungs mix pretty well with every breath, so any xenon in your lungs should be quickly diluted and expelled, assuming you’re breathing normal air again. > > In [this thread](http://www.thenakedscientists.com/forum/index.php?topic=15771.0) I linked to in that previous discussion here, **Bored Chemist** links to [this MRI image of xenon in lungs](http://www.lbl.gov/Science-Articles/Research-Review/Magazine/1997/extra1.html), which shows that the xenon is evenly distributed throughout the lungs. Understood - my point was that even if it didn’t work this way, your lungs wouldn’t be full of xenon after breathing out once, and any reduced lung capacity would be a nuisance rather than life threatening. Interesting to note, while I was looking up how expensive this stunt might be (xenon being pretty scarce stuff) that xenon’s actually an effective anaesthetic, and not merely an asphyxiant. That’s kinda counter-intuitive for a noble gas. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [March 10, 2013, 12:43pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/38 "2013-03-10T12:43:33Z")
So are there any liquids lighter than the heaviest gas? Could I have a bucket with a light liquid floating on a heavy gas? ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 10, 2013, 12:49pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/39 "2013-03-10T12:49:08Z")
No - there’s about two orders of magnitude difference between liquid densities and gas densities (at standard temperature and pressure); that is, you’re weighing liquids in hundreds of grams per litre, minimum, and gases in grams per litre. ---
**Author:** ![eltro102](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@eltro102](https://boards.straightdope.com/u/eltro102)\ **Post date:** [March 10, 2013, 1:10pm UTC](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334/40 "2013-03-10T13:10:05Z")
> [@DaveRaver](#): > > Is there a known planet where a balloon filled with air from planet Earth would float? not a planet, but on titan the air is a lot denser than on earth, so any balloons would float up (and the gravity is a lot lighter too, so you could conceivably float using a bunch of earth air balloons) the venusian atmosphere is a lot denser too, but the balloons would probably cause the air to combust and/or be crushed by pressure pretty much the same thing on jupiter/saturn/neptune/uranus below certain altitudes [Previous page](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334.md?page=1) [Next page](https://boards.straightdope.com/t/what-gas-is-heavier-than-air/58334.md?page=3)