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  #1  
Old 09-30-2006, 04:25 PM
psychonaut psychonaut is offline
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Which chemicals are denser as liquids than solids?

It's well known that water has the special property that its liquid phase is denser than its solid phase, allowing solid ice to float in liquid water. I always thought that this property was unique to water, but Wikipedia claims otherwise:
Quote:
A simple but environmentally important and unique property of water is that its common solid form, ice, floats on its liquid form. This solid phase is not as dense as liquid water, due to the geometry of the strong hydrogen bonds which are formed only at lower temperatures. For almost all other substances and for all other 11 uncommon phases, the solid form is denser than the liquid form… Almost all other chemicals are denser as solids than they are as liquids, and freeze from the bottom up.
(emphasis mine) So, which other chemicals are denser as liquids than as solids? Are any of them suitable solvents for sustaining life on other worlds?
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  #2  
Old 09-30-2006, 07:15 PM
Bob Scene Bob Scene is offline
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Liquid gallium, a metal that melts near room temperature, is denser than the solid. If any living things are using gallium as a solvent (unlikely, of course), they're going to be pretty different from us.
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  #3  
Old 09-30-2006, 07:34 PM
yabob yabob is offline
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You can turn up a few others, as well as water and gallium. Bismuth, Antimony, Germanium, Silicon and Acetic Acid according to a couple sources. All of those except acetic acid are metallic or semi-metallic elements. How you are going to get oceans of glacial acetic acid, and what kind of life processes they could support, I don't know.
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  #4  
Old 10-01-2006, 11:37 AM
jackdavinci jackdavinci is offline
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Quote:
Originally Posted by psychonaut
For almost all other substances and for all other 11 uncommon phases, the solid form is denser than the liquid form
(hijack)... what's an "uncommon phase"?
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  #5  
Old 10-01-2006, 12:04 PM
bibliophage bibliophage is offline
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Quote:
Originally Posted by jackdavinci
(hijack)... what's an "uncommon phase"?
I think it's a reference to ice II through ice XII, which have different crystaline structures than the familiar ice I. See http://en.wikipedia.org/wiki/Ice#Phases_of_ice
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  #6  
Old 10-01-2006, 01:34 PM
threemae threemae is offline
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Quote:
Originally Posted by psychonaut
So, which other chemicals are denser as liquids than as solids? Are any of them suitable solvents for sustaining life on other worlds?
Okay, although you don't explicitly make the connection between this phyiscal porperty and their appropriateness for use as a biological solvent, by asking the questions together I get the distinct feeling that in your mind the two are linked. I don't believe that they are in any way. Other biological solvents could exist where the solid form was denser and that wouldn't affect their suitability for use in an organism.
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  #7  
Old 10-01-2006, 01:43 PM
Crescend Crescend is offline
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Quote:
Originally Posted by bibliophage
I think it's a reference to ice II through ice XII, which have different crystaline structures than the familiar ice I. See http://en.wikipedia.org/wiki/Ice#Phases_of_ice
And things like supercritical fluids.
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  #8  
Old 10-02-2006, 08:20 AM
FluffyBob FluffyBob is online now
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An Interesting point that Crescend brings up.

One of water's problems as a biological solvent is that because the solid phase is less dense, the freezing process is dangerous to cellular life. For life based on a different solvent, the liquid to solid phase change might not be such a problem.

The property of ice to float on water comes with its own costs.
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Old 10-02-2006, 08:22 AM
FluffyBob FluffyBob is online now
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Quote:
Originally Posted by FluffyBob
An Interesting point that Crescend brings up.

One of water's problems as a biological solvent is that because the solid phase is less dense, the freezing process is dangerous to cellular life. For life based on a different solvent, the liquid to solid phase change might not be such a problem.

The property of ice to float on water comes with its own costs.
Arrgh. I mean threemae's point.
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  #10  
Old 10-02-2006, 09:40 AM
Quercus Quercus is offline
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Quote:
Originally Posted by FluffyBob
One of water's problems as a biological solvent is that because the solid phase is less dense, the freezing process is dangerous to cellular life.
Is this true? I always read that the reason you can't thaw out and revive Ted William's frozen head was because the ice crystals' hard pointy edges poked too many holes in the cell membranes. This seems different than a mere volume change. But I'm eager to be enlightened. (After all, I need to perfect the technique before embarking on the planned Big Papi Ice Preservation Project of 2030).
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  #11  
Old 10-02-2006, 10:47 AM
Lumpy Lumpy is offline
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I'd heard that the alloy commonly used for producing metal type expands when it solidifies, to preserve the dimensions and sharpness of the type.
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Old 10-02-2006, 11:51 AM
bouv bouv is offline
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Quote:
Originally Posted by Quercus
Is this true? I always read that the reason you can't thaw out and revive Ted William's frozen head was because the ice crystals' hard pointy edges poked too many holes in the cell membranes. This seems different than a mere volume change. But I'm eager to be enlightened. (After all, I need to perfect the technique before embarking on the planned Big Papi Ice Preservation Project of 2030).
It's both. Yes, the crystals are sharp, so even if the volume change was like most materials and became denser, they still might poke holes, but the swelling itself does burst membranes too. And, if they didn't swell, then the sharp, pointy, edges wouldn't be pressed up so tight against the cell membranes.
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  #13  
Old 10-02-2006, 04:57 PM
Chronos Chronos is online now
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Quote:
I'd heard that the alloy commonly used for producing metal type expands when it solidifies, to preserve the dimensions and sharpness of the type.
The idea is to get it to remain as close to constant volume as possible. And they achieve this by including antimony (mentioned by yabob in the third post) in the alloy (as well as other metals which more conventionally shrink on freezing).

Back in high school chemistry class, we were all assigned a random element, and had to write a report about that element, its physical properties, its common uses, etc. I got antimony, and I still remember that type metal is its major application.
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  #14  
Old 10-02-2006, 05:05 PM
yabob yabob is offline
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I'm still intrigued by the thought of acetic acid oceans. The vinegar planet ... probably inhabited by scorpions ... when the Titanic hit the vinegar-burg and sank, it would be pickled and preserved for future historians.
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  #15  
Old 10-02-2006, 05:33 PM
Lemur866 Lemur866 is offline
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Just remember that the most common elements in the universe are hydrogen, helium (inert), carbon, nitrogen and oxygen. That means that the most common compounds in the universe would statistically be H2, CH4, NH3, and H20. And indeed when we look out at our solar system we see abundant hydrogen, methane, ammonia, and water. So any "ocean" not composed of one those four substances would be pretty unusual, there just isn't that much gallium in the universe to form oceans.

And while CH3COOH is composed of common elements, it is likely to break down into CO2 and H20, which are lower in energy. There would have to be some sort of biological process constantly generating gigantic amounts of vinegar to produce vinegar oceans, just like on earth there is a massive amount of photosynthesis generating atmospheric O2, a most unlikely compound to find floating around free.
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  #16  
Old 10-03-2006, 09:24 AM
Jake4 Jake4 is offline
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Intracelluar ice is bad, yes. But the environmental effect is not 'bad' for life. Ice layers on top of bodies of water protect the life below. Fish do okay. Things that burrow into the soil under the pond are okay. Ice bridges form, allowing land animals to migrate. If the liquid freezes from the bottom up you don't necessarily get those effects, or they're radically changed.

But there's no reason a solvent with 'normal' density characteristics wouldn't support life AT ALL.

I agree that an acetic acid meduim for life is an interesting question, but like Lemur866 don't know whether that's 'naturally' possible. It still could be fun to play god w/ a vat of vinegar.
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  #17  
Old 11-05-2013, 08:46 PM
wernervh wernervh is offline
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Floating Ice

I know this isn't exactly on topic but...

The fact that ice is less dense than water and floats happens to be important in that this world would have quickly frozen solid after sufficient cooling if water didn't have this property...and we wouldn't be here discussing it.
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  #18  
Old 11-05-2013, 09:28 PM
njtt njtt is offline
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Quote:
Originally Posted by Crescend View Post
And things like supercritical fluids.
Oh, I hate them! They never stop nagging at you.

Yes, I do know it's a zombie.
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  #19  
Old 11-06-2013, 02:08 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by yabob View Post
I'm still intrigued by the thought of acetic acid oceans. The vinegar planet ... probably inhabited by scorpions ... when the Titanic hit the vinegar-burg and sank, it would be pickled and preserved for future historians.
On vinegar planet, they might pickle things in water (if it was impossible for things to live in it)
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