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Old 12-09-2018, 10:57 AM
SigMan SigMan is offline
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Unique properties of water

Water is plentiful and much needed to sustain life. Water is made up of two simple elements, Hydrogen and Oxygen. Two gases that combine to create a liquid that we call water.

Elements expand when heated but not water. It expand when cooled instead. This brings a question I have in mind.

let's say we hollow out a cannon ball where we have an inch thick shell. Fill it full of water and seal it good like a screwed in plug.

Freeze the ball.

Now will the water bust the ball open?

Last edited by SigMan; 12-09-2018 at 10:58 AM.
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Old 12-09-2018, 11:10 AM
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Water expands when heated (expansion of the ocean water due to global warming is a large part of the reason for rising sea levels). Except for a narrow range where it expands when cooled from 4 C to 0 C, and when it freezes. Whether freezing water would burst your sphere depends on the strength of the sphere. Surely you've had the experience where an accidentally frozen bottle of liquid cracked open? Glass isn't very strong in tension but iron or steel is stronger.
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Old 12-09-2018, 11:15 AM
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Water expands and contracts with changing temperatures just like any other material. You can make a water thermometer. However, it also expands a lot as it freezes, about 9%. I think this has been discussed numerous times before. As I recall, it can produce over 30,000 psi as it expands. So your cannonball would have to be able to withstand that much pressure. And be truly filled with water, no air pockets.

If it was solid enough to resist that much pressure, the water converts to one of its other forms of ice that does not expand any further.

Dennis
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Old 12-09-2018, 11:24 AM
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If it was solid enough to resist that much pressure, the water converts to one of its other forms of ice that does not expand any further.
Beware of creating ice IX!
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Old 12-09-2018, 11:32 AM
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My youngest was gifted and very curious. When he was about 6, I observed him making a hollow sphere from clay; it had a hole which he used to fill the interior with water. When it was completely full, he carefully sealed the hole, and then placed the sealed sphere in the freezer. Several hours he returned, took the sphere out, looked at it (it was cracked with ice extrusion from the cracks) and muttered to himself.."So water really does get bigger when it turns to ice."

As a note, water does shrink when it gets colder. It is only with the phase change to ice that the volume increases. That is why cold water sinks, and ice floats. Handy, because otherwise lakes would freeze solid, and life probably wouldn't exist on earth.
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Old 12-09-2018, 11:50 AM
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As a note, water does shrink when it gets colder. It is only with the phase change to ice that the volume increases.
Not quite true. As I noted above, water's maximum density is at 4 C. Cooling from a higher temperature to 4 C causes water to contract, but continue cooling between 4 C and 0 C causes expansion. Freezing causes even more expansion.
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Old 12-09-2018, 12:41 PM
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Note that expanding when freezing is not a unique property of water. Bismuth, silicon, gallium, antimony and germanium are elements that do the same. And there are of course many compounds that do likewise.
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Old 12-09-2018, 01:03 PM
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Yeah, there aren't very many other substances with that property, but there are a few.
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Old 12-09-2018, 02:10 PM
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Funny, I was so sure that water don't expand when heated but the ocean part explained it did. Looks like I need to go back to my science classes again.

There are really other elements that expand when cooled? I thought water only do that.
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Old 12-09-2018, 04:40 PM
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An amazingly high heat capacity and being the "universal solvent" due to it's polarity are two properties that I haven't seen mentioned above.

The heat capacity of water higher than any other common substance.

Last edited by rat avatar; 12-09-2018 at 04:41 PM.
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Old 12-09-2018, 05:21 PM
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An amazingly high heat capacity and being the "universal solvent" due to it's polarity are two properties that I haven't seen mentioned above.

The heat capacity of water higher than any other common substance.
This is what I was going to say (heat capacity). It really is amazing.
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Old 12-09-2018, 06:50 PM
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Water's heat capacity isn't all that remarkable. All substances have close to the same heat capacity, if you look at them on a per-molecule basis (or per-mole, if you're allergic to scientific notation) instead of per-mass. Water just stands out because it has a low molecular mass (i.e., a lot of molecules per mass), and most other things with molecular masses that low are gases.

As for being a universal solvent, it dissolves both kinds of substances, country and western polar and ionic. Which is already pretty far from "universal", and even as far as that goes, there are other polar substances, like alcohol, which dissolve pretty much anything that water does and then some.
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Old 12-09-2018, 07:39 PM
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I remember about the high heat capacity of water. The microwave oven was a good example. Normally it take 3 minutes to bring it to boiling temp. Run it for 5 minute and you have a dangerously super heated water!
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Old 12-10-2018, 12:49 AM
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Water expands and contracts with changing temperatures just like any other material. You can make a water thermometer. However, it also expands a lot as it freezes, about 9%. I think this has been discussed numerous times before. As I recall, it can produce over 30,000 psi as it expands. So your cannonball would have to be able to withstand that much pressure. And be truly filled with water, no air pockets.

If it was solid enough to resist that much pressure, the water converts to one of its other forms of ice that does not expand any further.

Dennis
How much would the contraction of the iron cannonball add to the pressure caused by the expansion of water?
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Old 12-10-2018, 02:04 AM
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Is there a nice simple explanation for WHY water has a higher density in its liquid phase?
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Old 12-10-2018, 03:27 AM
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The molecules can pack up more. I know, it's kind of "no shit Sherlock". But get a bunch of V-shaped items and bunch them up willy-nilly; see how much space they occupy. Now take the same items and arrange them in neat cubic positions: it takes up more space.
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Old 12-10-2018, 04:39 AM
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I see that my question was much too simplistic and naive. Ice-VII is much denser than liquid water and occurs naturally on Earth among inclusions found in natural diamonds !
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Old 12-10-2018, 08:11 AM
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The molecules can pack up more. I know, it's kind of "no shit Sherlock". But get a bunch of V-shaped items and bunch them up willy-nilly; see how much space they occupy. Now take the same items and arrange them in neat cubic positions: it takes up more space.
It's more of a hexagon-based shape. (Think snowflakes.)

The "V"s can fit together a little tighter when part of one "V" can fit into the notch of another "V". When freezing happens they want to form a ring-shape due to polarity and the "V"s make it a hexagon. See here. (That person sure loves ice. Lots of interesting info.)
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Old 12-10-2018, 08:26 AM
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let's say we hollow out a cannon ball where we have an inch thick shell. Fill it full of water and seal it good like a screwed in plug.

Freeze the ball.

Now will the water bust the ball open?
Depends how cold you get it. If pressure keeps the water from expanding, the water won't freeze. I put a bottle of beer in the freezer once, and took it out thirty minutes later. It was still liquid, but when I opened it (relieving the slight pressure that the bottle was able to bear), the beer turned to slush and started slowly erupting out of the bottle.

The flip side of the above assertion is that if you confine water and cool it to a very low temperature, you can generate very large pressures. Many years ago I saw still photos from the exact demonstration you described, i.e. a hollow iron sphere was filled with water and sealed. But they didn't just put it in the freezer, they put it in a bowl full of dry ice (-109F). At that temperature, the water developed enough pressure to shatter the iron sphere in an explosive fashion and immediately freeze once the pressure was relieved.
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Old 12-10-2018, 09:02 AM
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The heat capacity of water higher than any other common substance.
I am sure that the heat capacity of baked potatoes must be higher. This thing has been on my plate for 5 solid minutes and still burnt the #$%& out of my tongue!
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Old 12-10-2018, 09:17 AM
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That's the water in the baked potato.
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Old 12-10-2018, 10:33 AM
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Many years ago I saw still photos from the exact demonstration you described, i.e. a hollow iron sphere was filled with water and sealed. But they didn't just put it in the freezer, they put it in a bowl full of dry ice (-109F). At that temperature, the water developed enough pressure to shatter the iron sphere in an explosive fashion and immediately freeze once the pressure was relieved.
Wait, are you saying that ice continues to expand as it's cooled below 0 C? So the same quantity of water has a larger volume at -75 C than it does at -1 C? I don't think that's true, but I'm not positive about that. Cooling the sphere in dry ice would cause the water to freeze FASTER than just putting it in an ordinary freezer, but I don't think the pressure would be any higher.
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Old 12-10-2018, 11:18 AM
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Wait, are you saying that ice continues to expand as it's cooled below 0 C? So the same quantity of water has a larger volume at -75 C than it does at -1 C? I don't think that's true, but I'm not positive about that. Cooling the sphere in dry ice would cause the water to freeze FASTER than just putting it in an ordinary freezer, but I don't think the pressure would be any higher.
I am not saying solid ice expands as it cools further and further below zero.

I am saying that if you constrain (i.e. hold constant) the volume of a body of liquid water as you cool it further and further below 0C, the liquid water will exert greater and greater pressure against its containment; the liquid water is trying to expand to achieve the volume it needs in order to become solid ice. Assuming a constant-volume container (a cast-iron sphere is a good approximation of this), the pressure of the liquid water at -75C will be much greater than at -1C. The phase diagram for water shows you what's happening. at 101 kPa and 0C, you're at the boundary between liquid and solid. As you lower the temperature, the water remains in its liquid phase, provided the pressure is high enough. And that elevated pressure is what the cast-iron sphere provides, at least up to its strength limit. Cooling this cast-iron sphere in your kitchen freezer (to -15C) won't make the liquid water generate enough pressure to crack it. But if you cool it to the temperature of dry ice, it does generate enough pressure; as soon as the cast-iron sphere cracks, the liquid water expands and becomes solid ice.
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Old 12-10-2018, 11:27 AM
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My youngest was gifted and very curious. When he was about 6, I observed him making a hollow sphere from clay; it had a hole which he used to fill the interior with water. When it was completely full, he carefully sealed the hole, and then placed the sealed sphere in the freezer. Several hours he returned, took the sphere out, looked at it (it was cracked with ice extrusion from the cracks) and muttered to himself.."So water really does get bigger when it turns to ice."
That's awesome! Mythbusted by a six-year-old!
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Old 12-10-2018, 11:44 AM
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The phase diagram for water shows you what's happening. at 101 kPa and 0C, you're at the boundary between liquid and solid. As you lower the temperature, the water remains in its liquid phase, provided the pressure is high enough.
Ok, I understand what you're saying now. Your last clause is the key though. Even fairly high pressures don't reduce the freezing point all that much. Even at 100,000 kPa, the freezing point drops only to about -9 C (cite), well within the range of a typical household freezer. I'm not sure how to calculate the actual pressure that would be produced in this situation.
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Old 12-10-2018, 12:15 PM
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Ok, I understand what you're saying now. Your last clause is the key though. Even fairly high pressures don't reduce the freezing point all that much. Even at 100,000 kPa, the freezing point drops only to about -9 C (cite), well within the range of a typical household freezer. I'm not sure how to calculate the actual pressure that would be produced in this situation.
Presumably by "this situation", you mean cooling a bomb full of water down to -77C. I don't know either, but based on the pictures I saw so many years ago, the pressure was more than a thick-walled cast-iron sphere could withstand.

There's a better phase diagram here. The nearly-vertical line rising up from (273K, 1 bar) is what we've been talking about, and shows that enormous pressures result in small decreases in the freezing temperature. Once the pressure gets high enough, it's going to become solid ice even at freaky high temperatures; it'll just have a different crystalline structure.

At temps below -20C, it looks like you'll have solid ice regardless of pressure, but the density for each of those solid phases is still substantially less than for liquid water.
The table further down that page shows the change in molar specific volume (inverse of density) for each of the phase changes; each of those solid phases is less dense than the liquid phase.

For more interesting reading, check out this Gizmodo article:


What Happens When Water Freezes in a Box So Strong It Cant Expand?
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Old 12-10-2018, 12:43 PM
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Wait, are you saying that ice continues to expand as it's cooled below 0 C? So the same quantity of water has a larger volume at -75 C than it does at -1 C? I don't think that's true, but I'm not positive about that. Cooling the sphere in dry ice would cause the water to freeze FASTER than just putting it in an ordinary freezer, but I don't think the pressure would be any higher.
The link I gave earlier gives a coefficient of thermal expansion of ice as ~ 50 x 10-6 deg-1. That's a little higher than gold. But it's positive, so colder=smaller.

OTOH, it's not a constant. Once you get sort of close to Absolute Zero it goes negative. Then it's expanding as you get colder.
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Old 12-10-2018, 12:45 PM
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That really got interesting. I never read that article or any other about the inch thick cannon balls but there it is, the very thing I was asking about in my OP.
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Old 12-10-2018, 01:06 PM
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So from Machine Elf's link, we learn that the highest attainable pressure of freezing water is over 43, 500 psi, at which point it becomes Ice II. That's the chamber pressure of a modern rifle cartridge. So if the container does split, watch out.

Dennis
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Old 12-11-2018, 06:38 AM
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Depends how cold you get it. If pressure keeps the water from expanding, the water won't freeze. I put a bottle of beer in the freezer once, and took it out thirty minutes later. It was still liquid, but when I opened it (relieving the slight pressure that the bottle was able to bear), the beer turned to slush and started slowly erupting out of the bottle.
Actually, the beer wasn't kept liquid by the pressure, but merely by the absence of a suitable crystallization nucleus---the freezing process needs a kind of 'starter', and if you cool a liquid carefully enough, it will go below its freezing temperature, but remain liquid, entering a 'supercooled' state.

Any physical disturbance then is likely to induce rapid freezing, such as you observed. The process releases heat; that's how those sodium acetate heating pads with the disk you click work.
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Old 12-11-2018, 07:28 AM
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Not quite true. As I noted above, water's maximum density is at 4 C. Cooling from a higher temperature to 4 C causes water to contract, but continue cooling between 4 C and 0 C causes expansion. Freezing causes even more expansion.
This property of water is one of the fortunate properties that helps life. Ponds & lakes would freeze solid much easier if this didn't happen. As it is as water gets colder it sinks to the bottom, mixing the water, till that temperature is reaches at which time the coldest water stays near the top, and will freeze over, insulting the water below.
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Old 12-11-2018, 08:41 AM
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Water's heat capacity isn't all that remarkable.
...
As for being a universal solvent
...
I suspect that this is a situation where "common" is the operative word, along with engineering practicality in an industrial environment.

Those two attributes of water were very specifically identified in navy nuclear power school as key stand-out features. I suspect that a scientist in a laboratory would have very different opinions of the awesomeness of water alongside its competition.
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Old 12-11-2018, 10:33 AM
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I believe the beer didn't freeze because of the alcoholic contents. Alcohol has a lower freezing point than water. It's why we use alcohol in anti-freeze/coolant for our cars.
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Old 12-11-2018, 10:58 AM
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I believe the beer didn't freeze because of the alcoholic contents. Alcohol has a lower freezing point than water. It's why we use alcohol in anti-freeze/coolant for our cars.
It did freeze, once I popped the cap off. Half Man Half Wit's explanation - that I had achieved a supercooled liquid state - is plausible, with newly-formed CO2 bubbles (when I relieved the pressure) perhaps serving as the nuclei that started the freezing process.

See How to Instantly Freeze A Beer (includes video demo) they claim that it's the act of striking the bottle on the counter than generates bubbles, but I'm pretty sure the bubbles happen as soon as you open the bottle. I wish they had also done a "control" bottle, i.e. one that they had opened without striking on the counter.
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Old 12-11-2018, 11:52 AM
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This is interesting. Seeing that it has 5% alcoholic content I can see how that happened. I remember the therapist told me to mix alcohol with water in a bag to have super cold packs without freezing for my back aches.
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Old 12-11-2018, 03:58 PM
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Water doe certainly have some interesting properties which can often be useful, and it's also extremely common, at least on this planet, and very safe for the lifeforms native to this planet. So if you want a big tank of something to soak up heat, for instance, you're likely to use water instead of (say) ammonia (which has an even better heat capacity), just because it's really cheap and easy.
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Old 12-11-2018, 05:10 PM
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Old 12-11-2018, 05:48 PM
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Water doe certainly have some interesting properties which can often be useful, and it's also extremely common, at least on this planet, and very safe for the lifeforms native to this planet. So if you want a big tank of something to soak up heat, for instance, you're likely to use water instead of (say) ammonia (which has an even better heat capacity), just because it's really cheap and easy.
Ammonia does not have a higher heat capacity at the temperatures water is liquid, even if we switch to your non-standard but requested mole based numbers.

@ 1 bara and 17 C:
Water: 75.4 kJ(kmol *K)
Ammonia: 36.9 kJ(kmol *K)
You need to move up to 50-100 bara for the isoberic heat capacity for Ammonia to be higher. So I am guessing you are looking at or calculating isochoric heat capacity which as it would be gaseous and under pressure is a bit of a trivia point when I was mentioning common materials. Unless you consider 1000psi to be a common I guess.

Last edited by rat avatar; 12-11-2018 at 05:52 PM.
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Old 12-12-2018, 02:12 PM
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Yes, he fact that water expands below 4C is why we get crusty solid surfaces on bodies of water. But, in summer the surface layer stays warn and does no mix with the lower levels, since it above 4C and hence warmer means less dense than lower levels.

IIRC it is around 0F /-17C that ice stops expanding as it gets colder and starts contracting. I heard once that the reason warmer ice is slippery is because the pressure can cause the fine surface layer to melt (expanded ice to less expanded liquid) providing lubrication. Once ice is cold enough that compression does not bring on melting then ice is no longer slippery.

Last edited by md2000; 12-12-2018 at 02:13 PM.
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Old 12-12-2018, 02:45 PM
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IIRC it is around 0F /-17C that ice stops expanding as it gets colder and starts contracting. I heard once that the reason warmer ice is slippery is because the pressure can cause the fine surface layer to melt (expanded ice to less expanded liquid) providing lubrication. Once ice is cold enough that compression does not bring on melting then ice is no longer slippery.
That explanation has been around for a long time, but according to Wikipedia, it's incorrect:

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Originally Posted by Wikipedia
A skate can glide over ice because there is a layer of ice molecules at the surface that are not as tightly bound as the molecules of the mass of ice beneath. These molecules are in a semiliquid state, providing lubrication. The molecules in this "quasi-fluid" or "water-like" layer are less mobile than liquid water, but are much more mobile than the molecules deeper in the ice. At about −250 F (−157 C) the slippery layer is one molecule thick; as the temperature increases the slippery layer becomes thicker.

It had long been believed that ice is slippery because the pressure of an object in contact with it causes a thin layer to melt. The hypothesis was that the blade of an ice skate, exerting pressure on the ice, melts a thin layer, providing lubrication between the ice and the blade. This explanation, called "pressure melting", originated in the 19th century. This, however, did not account for skating on ice temperatures lower than −3.5 C, whereas skaters often skate on lower-temperature ice. In the 20th century, an alternative explanation, called "friction heating", was proposed, whereby friction of the material was causing the ice layer melting. However, this theory also failed to explain skating at low temperature. In fact, neither explanation explained why ice is slippery when standing still even at below-zero temperatures.
This claim in the first paragraph is backed up with cites, although I'll admit I haven't looked at them.
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Old 12-12-2018, 03:55 PM
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IIRC it is around 0F /-17C that ice stops expanding as it gets colder and starts contracting.
See the chart in this link that I gave earlier. There's no such "hump" in that range.
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Old 12-12-2018, 05:39 PM
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But ice isn't slippery at very cold temperatures.
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Old 12-12-2018, 09:52 PM
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Another cool thing about water is how much energy it can transfer to the Earth’s atmosphere when warm, moist air gets trapped below cold, dry air (e.g. leeward of the Rockies in N. America). This instability can result in a very rapid phase change from gas to liquid and release a ton of energy.
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Old 12-13-2018, 07:34 AM
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But ice isn't slippery at very cold temperatures.
Indeed, if the explanation at Wikipedia is correct, then ice should be pretty damn grippy as we get toward -250F. In reality, the temperature at which good grip can be achieved (even with ordinary shoes, as opposed to skates) is much higher. It's been years since I experienced outdoor temperatures much below 0F, but ISTR ice on the sidewalk being not terribly hazardous at those temps.

The thing is that ice is slippery at temperatures below what is predicted by the pressure-melting/friction-heating theories.
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Old 12-13-2018, 09:54 AM
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The angle of the molecule itself...104.4775 deg...just happens to be the optimum angle to tessellate 4-space.

Water could be used to construct a four dimensional hyper-object.

Like a time crystal?
https://en.wikipedia.org/wiki/Time_crystal
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Old 12-13-2018, 05:21 PM
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Location: The Eastern Watershed
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Wikipedia:
A tessellation of a flat surface is the tiling of a plane using one or more geometric shapes, called tiles, with no overlaps and no gaps. In mathematics, tessellations can be generalized to higher dimensions and a variety of geometries.
And..
A normal tiling is a tessellation for which every tile is topologically equivalent to a disk, the intersection of any two tiles is a single connected set or the empty set, and all tiles are uniformly bounded. This means that a single circumscribing radius and a single inscribing radius can be used for all the tiles in the whole tiling; the condition disallows tiles that are pathologically long or thin.[23]

Is water a normal tiling?

Last edited by EastUmpqua; 12-13-2018 at 05:22 PM.
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