# Question about the structure of ice

sonhouse
Posers and Puzzles 27 Sep '07 20:42
1. sonhouse
Fast and Curious
27 Sep '07 20:42
Does anyone here know how many molecules of water you have to have frozen together before you can call it ice? Like I know the density of ice goes down but how many molecules does it take for an increase in volume and therefore a decrease in density? 2? 20?
2. AThousandYoung
All My Soldiers...
27 Sep '07 22:46
Originally posted by sonhouse
Does anyone here know how many molecules of water you have to have frozen together before you can call it ice? Like I know the density of ice goes down but how many molecules does it take for an increase in volume and therefore a decrease in density? 2? 20?
Just 2.
3. coquette
27 Sep '07 23:491 edit
1 (at zero degrees Kelvin, it would just sit there "frozen" . . . . ice
4. slappy115
Slappy slap slap
28 Sep '07 00:26
Originally posted by coquette
1 (at zero degrees Kelvin, it would just sit there "frozen" . . . . ice
But isn't the problem with getting to absolute zero that the volume would equal zero and, therefore, not exist?
5. sonhouse
Fast and Curious
28 Sep '07 01:26
Originally posted by slappy115
But isn't the problem with getting to absolute zero that the volume would equal zero and, therefore, not exist?
C'mon, you guys are being silly, whoever said 0 degrees Kelvin?
I am just asking about ordinary ice at 0 degrees Celsius. How many molecules does it take to be called ice?
6. slappy115
Slappy slap slap
28 Sep '07 01:44
Originally posted by sonhouse
C'mon, you guys are being silly, whoever said 0 degrees Kelvin?
I am just asking about ordinary ice at 0 degrees Celsius. How many molecules does it take to be called ice?
I was just questioning the one response.

I don't know too much about this but I would say 2. That should form the crystal lattice. You know what? Maybe it's 6.
7. sonhouse
Fast and Curious
28 Sep '07 01:55
Originally posted by slappy115
I was just questioning the one response.

I don't know too much about this but I would say 2. That should form the crystal lattice. You know what? Maybe it's 6.
I was just thinking about it and trying to visualize where that conversion to ice happens, I don't think 2 molecules would do it, don't know why I think that, it just doesn't seem to fit somehow. If two molecules could convert to ice, I would think it would happen at a lot higher temp. Then I got to wondering if ice has a crystal structure or is random or semicrystalline, whatever you call thatðŸ™‚
8. slappy115
Slappy slap slap
28 Sep '07 02:05
Originally posted by sonhouse
I was just thinking about it and trying to visualize where that conversion to ice happens, I don't think 2 molecules would do it, don't know why I think that, it just doesn't seem to fit somehow. If two molecules could convert to ice, I would think it would happen at a lot higher temp. Then I got to wondering if ice has a crystal structure or is random or semicrystalline, whatever you call thatðŸ™‚
I honestly think it is 6 because when the crystal lattice is, I think, a hexagon. That would form 1 "crystal" of ice.
9. 28 Sep '07 04:30
How many do we want it to be? Let's make the definition ourselves.
Because this is only a matter of definition, nothing else.
If you say 2 water molecules or 6 or whatever, I'm sure that this has no practical consequence.

If we put the same question about liquid water, does any answer make any sense? Or how many molecules do we need to call water a gas?

I you want to call n number of cold water molecules to be ice, then no one can argue that, whatever n is (if sufficiently small).

10. 28 Sep '07 05:13
Originally posted by FabianFnas
How many do we want it to be? Let's make the definition ourselves.
Because this is only a matter of definition, nothing else.
If you say 2 water molecules or 6 or whatever, I'm sure that this has no practical consequence.

If we put the same question about liquid water, does any answer make any sense? Or how many molecules do we need to call water a g ...[text shortened]... ice, then no one can argue that, whatever n is (if sufficiently small).

Fabian's right.

It's a case of a bloody arbitrary definition of "how small do you want it to be?".
11. AThousandYoung
All My Soldiers...
28 Sep '07 07:20
Originally posted by sonhouse
I was just thinking about it and trying to visualize where that conversion to ice happens, I don't think 2 molecules would do it, don't know why I think that, it just doesn't seem to fit somehow. If two molecules could convert to ice, I would think it would happen at a lot higher temp. Then I got to wondering if ice has a crystal structure or is random or semicrystalline, whatever you call thatðŸ™‚
To increase the density via making ice, you need the molecules to orient themselves in a rigid hydrogen bonded way instead of packed tightly. That difference, including the change in density, could be done with only two I think.
12. wolfgang59
28 Sep '07 10:03
Interesting question and interesting answers. I think it probably does (to some extent) depend on definitions but I was thinking ...

Does a single molecule of water have a state? (is it gas, liquid or solid or 'none of the above'?) In other words can you call a single molecule below 0degreesC a solid? Can you call a single molecule above 100degreesC a gas? Does 'pressure' even have any meaning to a single molecule ...

(Sorry - all questions and no answers!)
13. PBE6
Bananarama
28 Sep '07 14:26
Originally posted by EinsteinMind
Fabian's right.

It's a case of a bloody arbitrary definition of "how small do you want it to be?".
I don't think it's arbitrary. The question seems to be really asking how many water molecules need to be grouped together to exhibit the properties of ice. I'm guessing it's at least 10^6, the same number of molecules you need to get a decent temperature reading (since temperature is a measure of the average kinetic energy, you need a certain number of molecules to make sure the reading really is a well-formed average).
14. AThousandYoung
All My Soldiers...
28 Sep '07 14:39
Originally posted by wolfgang59
Interesting question and interesting answers. I think it probably does (to some extent) depend on definitions but I was thinking ...

Does a single molecule of water have a state? (is it gas, liquid or solid or 'none of the above'?) In other words can you call a single molecule below 0degreesC a solid? Can you call a single molecule above 100degreesC a ...[text shortened]... e' even have any meaning to a single molecule ...

(Sorry - all questions and no answers!)
No. A single molecule has no state. The state is about it's relationship with other molecules.
15. 28 Sep '07 14:42
We try with one molecule of water. Is this ice? No, we can all agree that there is no meaning talking about one molecule of ice.

The fun starts when we try two molecules of water to see if it can be considered as ice.

How do we attach the two molecules together?
Where do we have them to begin with? In some ind of vacuum not to be disturbed by other molecules of various kinds?
What temperature do we have? In vacuum? Well, they can have a termal energy. The higher temp the probability is lesser that they stick together, the lesser temp the higher prob that they stick.
When the two molecules stick together they use electrostatic forces (and other forces as well?) But this (these) forces is (are) very weak, compered with the thermal energy. So to make them stick and continue to stick, we have to have pretty low temp.

These are only a few of the problems how to make two molecules of water become ice.

Another problem is that - In water there is not only H2O (even when the water is completely pure. Water should be scripted H2O, H+, and OH- mixed. This means that a water molecule may be splitted in two ions. That's the reason that even destilled water is not a perfect restistor. If we have two H2O in the form of ice, they may split and then we have no ice anymore.

So how about 3 molecules of water? Or 4 or, whatever... Then we should talk about probability and statistics only.

The answer has no real meaning.

But I couldn't resist thinking about the question, I find it really interesting. It' will be a future topic to discuss over a beer with some good friends.