Remember the microwave question (could the water really explode <yes> and would it help to put a piece of wood in the cup <yes> because it starts the bubbling process <no, I am not a scientist> - because the water was heated uniformly and didn’t rise from convection <I think!>)?
(So, in this context of uniformity of temperature…)
Well, also, somewhere in there it is said that water could be less than 32 degrees and still be liquid. So, lets say the the water is 30 degrees and still liquid (or 31.9 or whatever is plausible) and you had a cubic foot of water all at that temp - when it is ignited to freeze (or whatever was holding it back is removed suddenly) - is it a virtually instantaneous thing? I mean, BANG - solid block of ice? In one split second?
Is colder ice stronger? Is older ice stronger than fresh ice? When “cracking” ice cubes to put in a cocktail shaker, it seems that the colder ice is more brittle and easier to crack - have I had one too many at this stage, or is it true?
I know that salt water freezes at a lower temperature than pure water, but I think I remember something about water not freezing under high pressure, but I also remember learning that liquids cannot be compressed. Now I regret not having paid attention in chemistry class.
We must blame them and cause a fuss before somebody thinks of blaming us.
Sheila Broflofski
The process of cooling a liquid below its melting point is called “supercooling” (creative, eh?). I believe pure water can be uniformly cooled to -40 degress Celcius at least, but I can’t remember what the physical limit to supercooling is. At some point, the liquid you’re cooling will simply solidify without a “seed” to start the process. You can certainly introduce a seed into the liquid before this point is reached, and it’s quite likely you’ll observe a dramatic freezing of the liquid. So yes, BANG, and you have a solid peace of ice. It’ll be fast, but I can’t say if it’s under a second or not for any given amount of water.
I have no idea how much resistance to compression or shear ice has at various temperatures. I think it’s safe to say that temperature will change it’s resistance, but I doubt it’s something you can observe from a cocktail shaker. More likely than not, the strength of your ice cubes is mostly attributed to the condition in which it had frozen (which heavily influences its internal structure).
Colder ice is definitely harder; so it becomes more brittle, but more difficult to flex (and crack). I seem to recall that the hardness increases “faster” with lower temperatures than the brittleness does. - MC
When supercooled water begins to freeze, it requires a point of crystallization, or seed. One is enough, though, and the ice that forms on that point will serve as a point for continuing crystallization, by other molecules. The phase shift will surrender some energy into the liquid, so, unless the entire container is very far below the freezing point, only a portion of the water will freeze. The process is rapid, and dramatic, and will shatter the vessel in which it takes place in some cases.
Likewise a container of superheated water must have nucleation centers for the phase shift to gas for the water, and a small bubble of steam is sufficient for later molecules to evaporate as well. The phase shift in this case absorbs energy from the system, so only a portion of the liquid will become steam. If the liquid is in a tall container, though, it can well be possible that liquid water, as well as steam will be ejected out of the top of the container. Steam at one atmosphere occupies 1700 times the volume as it does as a liquid. One percent of the liquid changing to gas would provide enough pressure to spray scalding hot water (99°C) over someone’s hand, or face.
<P ALIGN=“CENTER”>Tris</P>
Experience keeps a dear school, but fools will learn in no other.
– **Benjamin Franklin **
According to my college physics book, “Very pure water can be cooled several degrees below the normal freezing point under ideal conditions: when a small ice crystal is dropped in, or the water is agitated, it crystallizes very quickly.”
I assume this means crystals form quickly, since the water is only a few degrees cooler than the normal freezing point, and it takes the equivalent of about 80 times as much energy to freeze a unit of ice as it does to cool it a degree, perhaps 4% of the water would crystallize. It would still be very impressive though. If you could indeed get the temp to -40 without freezing then half the water would crystallize. Perhaps under extreme pressures this could happen, I don’t know. On a related note, ice under sufficient pressure is fluid.
Ice under pressure is liquid? Does that have anything to do with how ice skates work or does the pressure and friction in that instance work to HEAT the water?
Can water be condensed? I remember from high school that you could not take any amount of water and crush it into a smaller amount. Didn’t sound true at the time - is it?
Freezing rain is the result of super-cooled water. What happens is that rain either originates or passes through a mass of air that is warmer than freezing. As the droplet gets closer to the ground, the temperature drops below freezing and the droplet cools as well–but a falling droplet undergoes some turbulence and the water molecules have difficulty crystallizing. When the droplet hits the ground, it spreads out and instantly freezes. It will stick to anything it touches. Huge amounts of ice can build up on roofs, trees, power lines or other odd surfaces because NONE of the precipitation runs off (rain) or falls off (snow). That is why a little freezing rain is much worse than a little snow storm.
I don’t know if it’s true, but I read in an encyclopedia that it can–but not much, and it takes a lot of pressure.
It said something like “under a pressure of 20K pounds per sq in, water compresses about 20%.”
This version (mid 50s) version of the encyclopedia also showed, under the heading of “Negro” a picture of a porter with a caption that read something like “Pullman porters are known for their smiling faces and good personalities.”
Just remembered: “World Book” encyclopedia. That’s the one
It seems counterintuitive but there is no conflict. Putting a liquid under pressure does not reduce it’s volume as with a gas but pressure is still exerted against the vessel.
As an example this property is used to test compressed air tanks in relative safety. An air tank filled to 125psi has about 8.5 times its volume of atmosphere pressure air squeezed inside. If it ruptures or cracks it can explode like a bomb because all the air still has to get out.
The same tank can be filled with water then the by adding a tiny bit more liquid the pressure increases dramatically. Forcing in a little grease with an ordinary grease gun is an easy way to do this. If the tank ruptures the pressure drops so fast that nearly all the water just pours out at atmosphere pressure.
I’m no chemist or physicist, but here’s my opinion.
It may depend on how far below freezing the water temperature is. Supercooled water was demonstrated on a “Scientific American Frontiers” show hosted by the MIT prof “Woody” Flowers. His water was probably relatively close to the freezing temp because ice crystals formed with a slow yet visible speed, and the entire amount of water didn’t freeze.
This also happened to me once. I got the last few ounces of water out of a water cooler. Ice crystals began to form in about the same way as the in the tv show.
As to whether a large amount of supercooled water could freeze completely in a second or less, well, I’m not sure. Those warming packs that you hit to release the heat (and can recharge by putting them in boiling water) contain a solution of water and some chemical - sodium acetate, I think. This solution “wants to be” solid at room temperature, but will reliably supercool. The pack will solidify completely, but it takes a few seconds.
Since the solidifying process releases heat into the remaining liquid, this could slow down the solidification.
Wow, I think I have the same set. They are weather damaged from being in a shed but I managed to keep my mother from throwing them out. It’s like having a time capsule to another era.
Sure water compresses, everything compresses given enough pressure. The metric for compressability is called the bulk modulus.
in units of 106 atm (I know that’s ugly, I don’t know how to do the fancy stuff) water has a B of 46.4, mercury is 3.8, lead is .08
To get the percent of compressibility, let’s assume 200 atmospheres of pressure,
Dv = -(46.4 * 10-6) * 200 * V
Dv = -.00928 * V
Converting to percent, .928 percent decrease in volume. Not much, but some. If I screwed that up, sorry, but you get the idea.
When a slight amount of pressure is exerted upon ice, it will melt. If one were to examine a three-phase diagram for water, one would find that a slight increase in pressure causes the transition. This IS the heart of the reason why ice skates work so well. it is also the reason why packed snow with form into ice.
Liquids are in fact compressible. They’re just not VERY compressible. Neither are solids (things that you think of as solid that are compressible are generally spongy, with lots of trapped air, and THAT’S what’s getting compressed).
With some things, if you put sufficient pressure on them they’ll reform into a different “phase”. Ice has several different phases (at least seven of them) which occur at various temperature and pressure ranges. However, you’ve got to get to at least a thousand atmospheres or below -50 degrees C before you see anything besides ice I, so I doubt that’s an explanation for your “strong ice”.
Along of the line of Powers’ OP, does anyone know how it is possible for ice (H2O) to sublime in your freezer? Only one chemistry book I have found makes mention of this as being possible with no further explanation.
