6
$\begingroup$

I was recently reading the satirical, fictional book Cat's Cradle by Kurt Vonnegut. In this book, one of the major subplots is the invention of a mythical polymorph of ice called ice-9 in the book. In the book, it is described that if this polymorph of ice were to touch actual water, all the water, inevitably touching through oceans, rivers, lakes, etc. would freeze into this polymorph of ice which is purported to melt at a temperature over 100 degrees Fahrenheit.

This raises two questions for me:

First, would something like this actually happen? I know, for instance, a method people use for purifying crystals is to create a supersaturated solution and disturb the substance and it will crystallize quite dramatically. Could something similar happen here in the sense that the mythical ice-9 structure would be introduced into liquid water (which to ice-9 is a supersaturated solution of water) and create a massive crystal out of all water?

Second, and more in reality, is there any solid that is like this? A solid which has two stable crystal structure that exist at temperature reachable in everyday life at about atmospheric pressure? And if so, can you actually convert one crystal structure to another easily? And would one of the liquids behave as a supersaturated solution of the crystal?

Sorry if that is a little unclear. I am sincerely interested in this and can clarify if there is any confusion.

Anything interesting along those lines would be considered relevant in my mind.

$\endgroup$
  • 1
    $\begingroup$ This is probably more suited at Worldbuilding.SE $\endgroup$ – user15489 Sep 4 '15 at 23:09
  • 1
    $\begingroup$ There is no creative or world-building element to this since it's a question inspired by a book that's already written.... The question of forming a crystal using a seed-crystal is very much a chemistry question for which I am only interested in a chemistry answer. I'll edit the second part to make it more appropriate to Chemistry.SE though. $\endgroup$ – jheindel Sep 4 '15 at 23:19
  • 2
    $\begingroup$ The only I way I see for water to solidify like in Vonnegut's novel is if all liquid water on Earth is in a false ground state (a metastable state), blocked from the true ice-9 ground state by a kinetic barrier, so that once a small portion crystallises, the released energy prompts the conversion of the rest of the Earth's water into ice-9 (strong parallels can be made with a vacuum metastability event). $\endgroup$ – Nicolau Saker Neto Sep 5 '15 at 1:08
  • 1
    $\begingroup$ Should my previous comment be the case, then there's an argument which is very interesting for its simplicity, which I have previously heard used as a quick dismissal of a quack theory in chemistry (hydrino theory). Basically, the Earth has had large liquid bodies of water for over 4 billion years, subject to all sorts of conditions. That's more than enough time for water to have found its true ground state one way or another, so we can only infer that liquid water is stable under the present conditions. $\endgroup$ – Nicolau Saker Neto Sep 5 '15 at 1:10
  • $\begingroup$ Interesting. More generally, do you know of any crystal which commonly exists in a metastable state just out of curiosity? Or is this quite rare? $\endgroup$ – jheindel Sep 5 '15 at 2:43
8
$\begingroup$

A precise physical argument against the existence of an Ice-9-like state of water is probably not trivial (ab initio methods required?). However, there is a simple but powerful argument against it; we haven't found anything like it yet. Water is a very common substance, and humans have been applying the scientific method to it for hundreds of years, humans have manipulated it for hundreds of thousands of years, but most importantly, the entire Earth has been churning massive amounts of water around for billions of years. If an Ice-9-like state of water did exist, we should have seen it by now.

To be clear, superficially this argument may seem to be a fallacious argument from ignorance. However, we can qualitatively back it up with a bit more knowledge. Assuming that Ice-9 is the true ground state of water, and that all liquid water on Earth is currently in a false ground state, separated only by a kinetic barrier, and realising that the conversion of liquid water to Ice-9 is autocatalytic, we must ask ourselves, if it only had to happen once, why hasn't it happened yet?. The only reasonable conclusion is that, if it can happen, then the kinetic barrier to conversion must be enormous. The interconversion of diamond to graphite is a chemical process with a famously large kinetic barrier (around $\mathrm{540\ kJ\ mol^{-1}}$), yet we have plentiful evidence of it happening many times in geological time scales (and we can do it in the lab too!). Thus the kinetic barrier for conversion between liquid water and Ice-9 would have to be even larger, which is unlikely. There's also a limit to how high we can expect chemical kinetic barriers to be, which we can put very generously at $\mathrm{100\ eV \approx 10\ MJ\ mol^{-1}}$. Water molecules on Earth have had many, many, many interactions at energies way higher than this, as they have been incessantly exposed to cosmic radiation, nuclear decays, lightning strikes, high temperatures, etc. In short, the collective history of all water molecules on Earth has explored a vast region of the space of allowed states, and not once has an Ice-9-like state been found. It is thus fair to assume it simply does not exist.

Regarding your second question, I just remembered a great example: pure tin. At ambient pressure, solid tin can exist in two different polymorphs, and the transition between the most stable form is conveniently close to room temperature. Above 13.2 ºC, tin is most stable as a ductile metallic material, called white tin, whereas below 13.2 ºC, the most stable form is a brittle non-metal called grey tin. It is possible to sustain white tin below 13.2 ºC for a period of time, creating a metastable system, much like a supersaturated solution. However, an adequate disturbance will cause the white tin to fall to its ground state. Like Vonnegut's Ice-9, this transition is autocatalytic; once conversion begins, there's no stopping it below 13.2 ºC, creating the so-called tin pest. There are actually several great videos showing the process, which you can easily find on YouTube, such as this one.

$\endgroup$
  • 2
    $\begingroup$ I forgot to mention, but not long after Kurt Vonnegut published Cat's Cradle, there was a lot of commotion in the scientific community over the possibility of water being able to polymerise, forming a substance called polywater, which could conceivably have had the ability to convert liquid water as we know it into a new form with different properties. It turned out to be a messy mistake, though, and there are several interesting accounts on the web about how polywater developed from its first reports to the final nails in its coffin. $\endgroup$ – Nicolau Saker Neto Sep 5 '15 at 5:08
  • $\begingroup$ Polywater is a great example. Considering all the work (both theoretical and experimental) into the structure of water and various ice polymorphs, it's extremely unlikely that there is a more stable ground state. $\endgroup$ – Geoff Hutchison Sep 5 '15 at 14:36
2
$\begingroup$

Just to offer a counter to arguments based on energetics...

However, there is a simple but powerful argument against it; we haven't found anything like it yet

But the same could be said for replicating, living organisms outside of the one known case here on Earth.

Even though the necessary components were present and the kinetic barrier to the formation of the key ingredients was relatively moderate, the probability of it happening is (apparently) extremely remote. Catalysts, such as the chiral face of a crystal and special magnetic and electrical events may have been simultaneously required to bring about the first chiral organism (or its inanimate, chiral precursor). The odds of all of this being in the same place and happening at the same time may be incredibly small.

Perhaps the same could be true for ice-9 formation. Maybe a crystal face with a very specific morphology is required to catalyze the transformation of water into ice-9. Even if the mineral is known on Earth, perhaps the specific crystal face\morphology does not presently exist on earth. However, it's conceivable that it could be formed on a planet with extreme temperatures and pressures not found in Earth geology. Maybe this planet, in some remote corner of the galaxy, has since been destroyed through a collision and a resulting planetary fragment containing crystals with the alien morphology is now headed towards Earth.

$\endgroup$
  • $\begingroup$ You are, of course, entirely correct. The problem with my qualitative argument is that, though it suggests water in Earth has explored a large state space, there is no information provided about the full size of the permissible state space (is there even a way to know this?). It could be that there are many more configurations for water that have not yet been reached (and indeed, that may never be reached in the entire future of the Universe!). In the end, all I can do is put some weak constraints. Sorry I can't do any better! $\endgroup$ – Nicolau Saker Neto Sep 6 '15 at 2:22
  • 1
    $\begingroup$ No, on the contrary, your arguments are very persuasive. I'm just offering an equally unprovable point of view. $\endgroup$ – ron Sep 6 '15 at 2:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.