Thread: Lady Thatcher to be Honored with State Funeral

Originally Posted by DaveRobin

Originally Posted by Whiteshiva

Originally Posted by DaveRobin

Originally Posted by Whiteshiva

Originally Posted by DaveRobin

.... the paras then tabbed 50 km across bog at 3C with full kit. water starts to turn to ice at 4C.

Amazing - in the rest of the world, water starts to turn to ice at exactly 0 deg C.......

But as DD said - don't let facts ruin a good story......

Liquid water is most dense, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the temperature drops to 0 °C. IE between 0 and 4 C water is slush.

Basic stuff mate.

A bit too basic, apparently. Ice forms at 0 deg C, not 4. The expansion of water when cooling from 4 to 0 is due to the molecular structure of water (or more specifically the hydrogen bond), and has nothing to do with ice crystallizing.

If you don't believe me, chill a glass of water to, say 2 deg C and see how many ice crystals you find.

I wrote that water starts to turn to ice at 4 C. It does. It may not be a solid until 0 C but that's not what I said but that's what are trying to say I said. You said it starts to turn to ice at 0 C and that's incorrect. You are suggesting that at 1 C water has no ice crystals but drop 1 C to 0 C and suddenly it's a solid - baa. Extremely frustrating talking with beneficiaries of Thatchers Care in the Community

From the Department of Energy United States Government:

"From about 4 C to water's freezing point at 0 C, the
molecules are no longer able to so easily slip past each other as they
did in the liquid phase. They begin to really "feel" the intermolecular
attraction of hydrogen bonding which occurs between the hydrogen atoms
of one water molecule and the oxygen atoms of nearby molecules. Thus,
they begin to take on an orderly crystalline arrangement that we
recognize as ice."

Link: http://www.newton.dep.anl.gov/askasc...9/gen99817.htm

Interesting that you left out the sentences which followed immediately after your quote, part of the same paragraph actually:

The ice latticework simply takes up more space than the slightly more compact and disordered liquid state. Water expands when it freezes.
Water is unusual in this regard. Most substances shrink when they pass from the liquid to solid state.

The description above basically refers to the transition that takes place at 0 degress C.

When water cools it is a 100% liquid until it reaches 0 deg C. At that point ice crystals will start forming, and no matter how much heat you remove from it, the temperature will remain at exactly 0 deg C until all the water has turned to ice. Hence any mixture of ice and water will be at exactly 0 deg C. This is elementary physics, dude!

This is probably too complicated for you Dave, but if any readers should be geeky enough to be interested, here is a typical phase diagram (water shown as a green dotted line, most other mediums will have characteristics as the normal green line). Critical point for water is 374 deg C and 217 atm (bar), the triple point is 0 deg C and 6 mbar (0,006 atm). In other words, a phase transition from ice to water to steam (or the other way around) at atmospheric pressure would be a straight horizontal line just above Ptp on the graph below.


The transition from one phase to another, at a given pressure, takes place at one temperature only. Notice that there is no shaded transition zone - it happens at a particular temperature, which can be determined with great accuracy. For water at atmospheric pressure, the solid-liquid transition happens at 0 deg C and the liquid-vapour transition happens at 100 deg C.