Is there a solid with such a low density, it floats in air?

[Alex299792458]

Is there a solid that has a density of or below the density of air or any gas?

 

[A.T.]

Is there a solid that has a density of or below the density of air or any gas?

Not quite what you asked, but still fun:



If you allow foamy materials that enclose lots of air, you could eventually have them float in such a gas.

 

[berkeman]

Is there a solid that has a density of or below the density of air or any gas?

AFAIK, Aerogel is the lightest solid, and it is denser than air:

"Guinness Records Names JPL's Aerogel World's Lightest Solid". NASA. Jet Propulsion Laboratory. 7 May 2002
http://stardust.jpl.nasa.gov/news/news93.html

https://en.wikipedia.org/wiki/Aerogel

 

[rootone]

Which basically IS air, with another absolutely minimal amount of other stuff mixed into it so that electostatic forces hold the structure together.
'Frozen smoke' is an analogy which which seems good to me.
Light elements are obviously the best candidates, Carbon is I think one of them.
I don't know if Lithium might be able for the job, but seems like it could be.

 

[A.T.]

Light elements are obviously the best candidates, Carbon is I think one of them.

One could also try a lighter than air gas for the filling.

 

[Vanadium 50]

Do you consider a box of helium a solid? If so, there's your answer. If not, a helium filled aerogel isn't either, since it's essentially a number of such "boxes" that are attached to each other.

 

[anorlunda]

Hmm how about an H2O molecule? It seems to fit the following Wikipedia definition of a solid.

[A solid] is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does"
​

What do we call the state of matter when there are too few molecules to classify as solid/liquid/gas ?

 

[stedwards]

Is there a solid that has a density of or below the density of air or any gas?

Yes! there is. Thanks for the reminder. I've been waiting for someone to make some helium filled aerogel, but there is evacuated aerogel, instread. From https://en.wikipedia.org/wiki/Aerogel:

Silica
Silica aerogel is the most common type of aerogel, and the most extensively studied and used. It is silica-based, derived from silica gel. The lowest-density silica nanofoam weighs 1,000 g/m3,[14] which is the evacuated version of the record-aerogel of 1,900 g/m3.[15] The density of air is 1,200 g/m3 (at 20 °C and 1 atm).[16] As of 2013, aerographene had a lower density at 160 g/m3, or 0.13 times the density of air at room temperature.[17]
​

 

[nasu]

But this is not a "solid". Not more so than would be any vacuumed box. This may answer the OP need. Unfortunately he did not specify the goal besides "floating in the air".
A mylar baloon filled with helium may fit the description too. Mylar is pretty "solid".

 

[Redbelly98]

But this is not a "solid". Not more so than would be any vacuumed box. This may answer the OP need. Unfortunately he did not specify the goal besides "floating in the air".
A mylar baloon filled with helium may fit the description too. Mylar is pretty "solid".

But that is not mylar, it is mylar + helium. And the lower-than-air-density is due to the presence of the helium, a gas.

 

[nasu]

Yes. And the same can be said about these "aerogels".
My point was that IF these are considered to fit the description, we can have simpler solutions.

 

[jbriggs444]

But this is not a "solid". Not more so than would be any vacuumed box. This may answer the OP need. Unfortunately he did not specify the goal besides "floating in the air".
A mylar baloon filled with helium may fit the description too. Mylar is pretty "solid".

An evacuated hollow sphere manufactured from lead is more stylish.

 

[eifphysics]

Steel ships can float on water, but steel is definitely denser than water. Maybe we can borrow that idea.

 

[stedwards]

Aerogels, aerographenes included, are open cell solids by their very nature of manufacture. They are porous.

To make an aerogel a colloidal solution is made. Gelatinous, after meal deserts are a colloidal mixture made of a suspension of animal bone extract in sugar water. The usual aerogel is a silicate. Normally, through evaporation, your strawberry-tuna flavored Jello(R) will collapse, under the surface tension of the retreating water, into a very small, hard to consume solid.

Aerogels are created in a chamber of raised pressure and temperature. Either the fluid portion of the colloidal solution is raised to a regime of high pressure and temperature of superfluidity or another fluid is introduced under it's conditions of superfluidity. In this regime the fluid acts like both a fluid and a gas. Look it up. The fluid can be extracted from the mixture without the structure collapsing undergone the by long-abandoned plate of jello.

Here is a photograph of an aerographene supported by a few plant fibres.

http://data:image/jpeg;base64,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
Aerographenes have a density as low as 160 grams per cubic meter. By comparison, the density of air, at STP, is about 1225 grams per cubic meter. They are very porous, and in the photograph, surely full of air.

Evacuted aerographene, as I recall, will collapse like a sponge under atmospheric pressure, and not float. As far as I know, all the rigid, evacuated aerogels will shatter at STP.

Unfortunately, these fail to have the full, visceral appeal of an unadulterated solid floating in air, at STP. I guess we'll have to wait a little longer.

 

[CWatters]

In this vid at about 10seconds in they appear to float aerogel in a tank of nitrogen ...



Correction. I understand that this is SEAgel filled with Helium floating in Nitrogen.

 

[Redbelly98]

Yes. And the same can be said about these "aerogels".
My point was that IF these are considered to fit the description, we can have simpler solutions.

Agreed. At this point, the discussion seems largely a question of semantics. Do we consider a solid plus its enclosed lighter-than-the-surrounding-gas gas (or vacuum, if the solid part is strong enough not to collapse) to be a solid object?

In my opinion, it doesn't.

 

[TheCanadian]

Hmm how about an H2O molecule? It seems to fit the following Wikipedia definition of a solid.

[A solid] is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does"
​

What do we call the state of matter when there are too few molecules to classify as solid/liquid/gas ?

I would believe they are of no defined state since, as you imply, there needs to be a structure to the substance. When there are too few molecules, then no stable structure is produced. Besides quantifying their properties (which would not be very easy) like kinetic energy, I don't believe there is any classification of states for individual molecules (or very low numbers of them).

 

[Vanadium 50]

Do you consider a box of helium a solid? If so, there's your answer. If not, a helium filled aerogel isn't either, since it's essentially a number of such "boxes" that are attached to each other.

Agreed. At this point, the discussion seems largely a question of semantics. Do we consider a solid plus its enclosed lighter-than-the-surrounding-gas gas (or vacuum, if the solid part is strong enough not to collapse) to be a solid object?

In my opinion, it doesn't.

And we have come full circle.

 

[CWatters]

I suppose someone should ask what temperature air ;-)