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busk31
724419.  Wed Jun 30, 2010 5:23 am Reply with quote

Lots of cool facts.

The poles are not normally ice covered. The reason for this is that
we are currently in the middle of an ice epoch (longer than an ice age) which has lasted millions of years.

The thickest layer of ice is found in the Antarctic; in one spot the ice is 4,770 meter thick

The oldest ice ever probed and examined was found in the Antarctic and is ca. 750,000 years old.

As the Alpine glaciers are constantly retreating a number of archaeological findings of all sorts have surfaced - among them tzi, the mummified corpse of a bronze age man, and an entire German plane that crashed in 1941

Ice is considered a mineral.

When ice melts, it absorbs as much energy (heat of fusion) as it would take to heat an equivalent mass of water by 80 C, while its temperature remains constant at 0 C.

Until recently, it was widely believed that ice was slippery because the pressure of an object in contact with it caused a thin layer to melt. For example, the blade of an ice skate, exerting pressure on the ice, melted a thin layer, providing lubrication between the ice and the blade.
This explanation is no longer accepted. There is still debate about why ice is slippery. The explanation gaining acceptance is that ice molecules in contact with air cannot properly bond with the molecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These molecules remain in a semiliquid state, providing lubrication regardless of pressure against the ice exerted by any object

In 400 BC Iran, Persian engineers had already mastered the technique of storing ice in the middle of summer in the desert. The ice was brought in during the winters from nearby mountains in bulk amounts, and stored in specially designed, naturally cooled refrigerators, called yakhchal (meaning ice storage). This was a large underground space (up to 5000 m) that had thick walls (at least two meters at the base) made out of a special mortar called sārooj, composed of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, and which was known to be resistant to heat transfer. This mixture was thought to be completely water impenetrable. The space often had access to a Qanat, and often contained a system of windcatchers which could easily bring temperatures inside the space down to frigid levels on summer days. The ice was then used to chill treats for royalty on such occasions.

The solid phases of some other substances are also referred to by the term ice: dry ice is a popular term for solid carbon dioxide.
A "magnetic analogue" of ice is also realized in some insulating magnetic materials in which the magnetic moments mimic the position of protons in water ice and obey energetic constraints similar to the Bernal-Fowler ice rules arising from the geometrical frustration of the proton configuration in water ice. These materials are called spin ice.

 
mckeonj
724515.  Wed Jun 30, 2010 8:57 am Reply with quote

Why did my tongue get stuck to an iron railing in 1947?

 
tetsabb
724575.  Wed Jun 30, 2010 12:22 pm Reply with quote

Had the iron railings been put back by then, John?
I thought many were sacrificed in the war effort.
Oh bugger, is that a *klaxon* I hear?

 
Ion Zone
724620.  Wed Jun 30, 2010 3:32 pm Reply with quote

Having just come from the magnets thread, I'm wondering what would happen if you froze a suspension of iron filings and wrapped wire round it....

Could you crack the ice with a high enough voltage, or would it just be a brief novelty magnet?

 
Efros
724646.  Wed Jun 30, 2010 5:13 pm Reply with quote

You would have a magnet for a bit until the resistive heating started to melt the ice.

 
Spud McLaren
724674.  Wed Jun 30, 2010 7:11 pm Reply with quote

The density of water increases as temperature decreases, until 4 deg C. It then begins to decrease again, which is why ice floats - its density is lower than that of the surrounding water. Also for this reason, water of a temperature of 4 C will always accumulate at the bottom of fresh water lakes, irrespective of the temperature in the atmosphere.

 
Efros
724677.  Wed Jun 30, 2010 8:04 pm Reply with quote

As water freezes the water molecules begin to organize themselves into one of several different structures dependent upon the conditions, they can do this as the amount of kinetic energy each of the molecules has is insufficient to prevent the formation of a non-transitory hydrogen bond. The structures have voids in them which liquid water does not, consequently this results in an increase in volume for a given mass of liquid water, producing the same mass but higher volume of ice, density is mass/volume so ice has a lower density than water.



representation of one form of ice

The bluish connectors in the above structure are hydrogen bonds, not true chemical bonds but a fairly strong intermolecular force of attraction, and it is these that are responsible for the formation of the structure and hence voids in ice.

 
Jenny
724851.  Thu Jul 01, 2010 11:44 am Reply with quote

Shame we've already done Pykrete in the F series, though I gather the prototype ship was initially made out of pure ice.

 
mckeonj
724874.  Thu Jul 01, 2010 2:06 pm Reply with quote

On the question raised: does pressure on water ice cause it to melt? i.e. the narrow edge of an ice skate.
The answer is, yes it does, in the real world, whatever the physicists say.
See this in action:
http://press.exploratorium.edu/cutting-ice-into-one-november-2009/
or better still, do it yourself in the kitchen with a block of ice and a weighted cheesewire.

 

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