Is there any liquid that is lighter than a gas?

I would think that by definition a gas has to be less dense than a liquid.

Even if they're different substances?

Yes. The forces that hold a gas together are very weak, therefore there is a LOT of space in between the individual gas molecules. In a liquid, no matter what liquid it is, there is a large attracton between the individual molecules and very little space. The more space between the molecules, the less dense it is. There is no gas in existance whereby the space in between the molecules/atoms is smaller than in any liquid.

well, it should be noted that the volume of a gas depends on a number of factors.

Yes, but you will never find a gas that is physically denser than a liquid. You can take a gas and compress the living hell out of it, but guess what, it's no longer a gas now.

Ah, yes, that's almost certainly the case, but swansont said by definition. There's nothing inherent in the nature of gases and liquids that makes it impossible that some gas could be compressed to the point of being denser than some other liquid without itself condensing. Now, just because there probably is no such gas doesn't make that any less true. That is, unless I'm missing something.

Ah, yes, that's almost certainly the case, but swansont said by definition. There's nothing inherent in the nature of gases and liquids that makes it impossible that some gas could be compressed to the point of being denser than some other liquid without itself condensing. Now, just because there probably is[/i'] no such gas doesn't make that any less true. That is, unless I'm missing something.

I agree with this. It is imaginable that a gaseous compound with an icreadibly large molecular weight has a larger density than the least dense liquids and solids. But from a practical point of view, I indeed do not know of any gaseous compound, with these properties.

Ok, I just thought that since many solids are lighter than many liquids the same might apply to gases and liquids.

Ah, yes, that's almost certainly the case, but swansont said by definition. There's nothing inherent in the nature of gases and liquids that makes it impossible that some gas could be compressed to the point of being denser than some other liquid without itself condensing. Now, just because there probably is[/i'] no such gas doesn't make that any less true. That is, unless I'm missing something.

 

 

I interpreted your question in a different way. I was assuming it was the same substance - I didn't realize you were looking for any gas that was denser than some other substance is as a liquid. So my answer needs to be taken in that context.

You could always heat and compress a heavy gas ... past it's critical temp, it's going to be a gas despite further compression. A light liquid might be less dense, in this case.