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60

Suppoose you put an ice cube into water, then it's going to float with about 92% of it underwater. This is shown in diagram (a) below: But now suppose I make my ice cube a different shape. I'm going to shape it like a disk with a hole cut out of the centre, or you could describe it as a flattened doughnut. When I put my oddly shaped ice cube into the ...


39

Apparently this is a simple question with a not-so-simple answer. I believe the general consensus is that there is a thin layer of liquid water on the surface of the ice. This thin layer and the solid ice below it are responsible for the slipperiness of ice; the water easily moves on the ice. (Well, why is that? Perhaps another SE question.) However, this ...


33

Good question. Assume we have one cube of ice in a glass of water. The ice displaces some of that water, raising the height of the water by an amount we will call $h$. Archimedes' principle states that the weight of water displaced will equal the upward buoyancy force provided by that water. In this case, $$\text{Weight of water displaced} = ...


28

Here is an explanation that needs no explicit equations. Consider the following diagram, in which part1 and part2 represent the ice. The displaced water volume equals part2 volume and has as much mass as (part1+part2) Now look at what happens when both part1 and part2 melt: their mass does not change, it is (part1+part2) it becomes water. And we just ...


17

One boring Monday morning in the lab a group of us did the experiment, and to our surprise we found that the hot water (in sealed containers) did freeze faster. On closer examination we discovered that the shelves in our freezer were covered in frost, like I imagine most freezers, and the hot water was melting the frost and creating a good thermal contact ...


17

I don't think John's explanation is sufficient. If 3 feet (90 cm) of ice is floating, it should leave about 7 cm of gap (according to the 92% number) - that is not what was described in the question, which was "the same level as the surface of the ice". But I think there is another explanation. Water level in bodies of natural water is subject to change, ...


14

Yup, this is true that the pressure is too small, but the true explanation is not justified yet. Nevertheless the common sense is that there is a lubricating film of water or at least anomalous ice. For an overview, see: http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf


11

In simple terms, there isn't any space in the ice crystal lattice for the extra atoms and there is no way to plug either of the ions (or the whole salt molecule) into the growing pattern. So more and more water joins the frozen mass, leaving a more and more concentrated brine until essentially all the water is frozen and the salt remains behind. As ...


9

It's certainly possible for ice to sink in water under the right conditions. The diagram this section of Wikipedia's ice page will show you the conditions under which the various types of ice can form. Most of the "exotic" ones such as XII will form only at pressures greater than around 200MPa. These high-pressure forms are all denser than water, so they ...


8

Water is an unusual substance in that it expands when it freezes. Evidently this expansion wasn't enough to burst the bottle in your case, but it left the bottle's contents under pressure. After you'd defrosted it for a while there was, presumably, some ice and some water in the bottle. Because the ice was taking up more volume than it did when it was water, ...


8

@MartinBeckett's already gave an excellent answer: Salt is excluded from ice because there is "...no way to plug the ions... into the growing [ice] pattern." This unusually long answer -- a mini-tutorial really -- is an expansion on his answer. I've added a long background section that uses informal, easily visualized analogies to define a number of related ...


8

This isn't the definitive answer that DumpsterDoofus was hoping for since I can't point to any scientific publications - they must exist but a quick Google failed to find anything from a reputable journal though there are loads of blog articles. Anyhow, although in soda the carbon dioxide solution is supersaturated there is an energy barrier to creating a ...


8

Due to the crystal structure of the solid phase of water, the molecules arrange themselves in a rigid, ordered fashion and end up being, on average, farther apart from each other (than they are in the liquid phase), and thus less dense. Less dense things float because of buoyancy.


8

I don't think the question can be answered because you don't say how the orbital energy is to be dissipated. However it's quite interesting to compare the orbital energy with the energy required to boil the ice. Let's suppose our ice supplied is aboard the International Space Station, so they are at an altitude of $h$ = 300km and moving at an orbital ...


7

I don't think that this question is still fully resolved, water is a fascinating molecule! But here are some thoughts. Clearly, if ice is lighter than liquid water it is because it doesn't pack as well. Its an example of how a random-ish packing can be more efficient than an ordered packing of a "weirdly" shaped molecule. Imagine throwing LEGOs into a box, ...


7

It's not a disturbance, the liquid isn't supercooled in this case. It's right about at 0 degrees, though. It isn't the pressure drop directly, because you can give an upper-bound estimate to how much cooling the pressure drop directly does based on the observation that the pressure is not more than a few atmospheres. That means that space the gas in the ...


6

Salt lowers the melting point of water. When you throw it on snow (in not-too-cold weather), it causes some of the snow to melt, and the snow surrounding it will melt until the concentration of salt is low enough that the melting point of the salt water is above the ambient temperature. This will form a layer of ice. You can achieve roughly the same ...


6

When water freezes, you get ice. Ice, like many solid materials, forms a crystalline structure. In the case of water, the crystalline structure may be attributed to the hydrogen bond, a special kind of an attractive interaction. So a big chunk of ice will have a crystalline structure - preferred directions, translational symmetry, and some rotational ...


6

I think what is happening in rough qualitative terms us that the water freezes around the sides and the top first leaving a hole in the centre. Ice expands by 4%-9% when freezing so as the water below freezes it forces the remaining water up through the hole where is freezes around the edge. The hole shrinks as the water freezes and rises around its edge ...


6

There seems to be an impression floating around that water is somehow rare and special in the universe. This is just plain false. Water is a rather natural thing to expect whenever there are both hydrogen and oxygen around. Now hydrogen is the most common element in the universe, and oxygen is the third most common, depending on how you count. Wikipedia has ...


5

The video was taken at the the EMO (which translates as "Machine Tool World Exposition") in Hannover at the booth of the company Huettinger. They have a video on their website where they show how its done: As already suspected, there is a metal piece inside the ice that is heated via induction. Towards the end of the video you can see that the glow comes ...


5

Decrease of the melting temperature with pressure increase is not enough to explain skating (I conducted the calculation myself, but please see http://scitation.aip.org/content/aapt/journal/ajp/63/10/10.1119/1.18028). AFAIK, skating can be explained by ice melting due to heating caused by friction. EDIT(10/22/2013): OK, so let us use the Clausius-Clapeiron ...


5

Well I would mostly dismiss the concern of the type: Adding ice to the planet wouldn't remove energy from the planet, it would just add matter to the planet. Sure, it increases the mass of the biosphere, but it would (in a cursory look) also decrease the temperature since the added water is lower energy than the average. We need an additional ...


5

Hypothesis Ideally, the ice and water should reach an equilibrium at zero celsius. But this equilibrium might take a long time to happen, based on the exact setup. Looking at a typical setup of yours, the ice will float at the top of the container and there is water (but no ice) at the bottom. Water is densest at $\sim 4$ degrees celsius, and such water ...


5

I'm answering my own question. Apparently this is one of those rare cases when the physicist must doubt what he observed -- or what he thought he observed -- and believe the numbers his theory yielded instead. From further experiments I've noticed that the ice tends to form thin plates inside the supercooled water once the crystallization process starts ...


5

This depends on contact area between bottle & ice/snow, and consistency of snow. If there is not much air in the snow, it should have bigger contact area with bottle, and thus heat will be transferred faster. Ice will contact with the bottle mainly at shards edges, so contact area is small. PS. Adding water will change everything, as contact area ...


5

It's because a bunch of people are standing around on the ice looking at the hole. You are floating ice with people and cars, not just plain ice.


4

The unusual thing is the really high absorption of microwaves by bulk water, whereas the ice behaves more normal like most solids and liquids. In liquid water we have an effect of relaxation of orientational polarisation. The polarisation is achieved not by rotation (not possible in liquid water) but by shift of hydrogen atoms along the hydrogen bonds. ...


4

Adding salt to water makes it freeze at a lower temperature. This fact is being used in two different ways in the two scenarios you mention. Dissolving sodium chloride in water is slighly endothermic, but this effect is small and to the best of my knowledge isn't important in the drink cooling process. Putting salt on the highway is quite straightforward: ...


4

Fluid inclusion analysis techniques are used by geologists to gather information on the pressure, volume, and temperature conditions during the crystallization of the mineral (here ice) containing the inclusion. There are three assumptions that usually made in dealing with fluid inclusions: • The composition of the trapped fluid has not changed since ...



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