# Polar Ice Caps Obviously...

This is a discussion on Polar Ice Caps Obviously... within the A Brief History of Cprogramming.com forums, part of the Community Boards category; Water reaches maximum density at +4C, that is why ponds freeze from the top downwards. >>> About the floating ice...yes ...

1. Water reaches maximum density at +4C, that is why ponds freeze from the top downwards.

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About the floating ice...yes it does effect water levels. Fill a glass COMPLETLEY full and put three ice cubes in it....duh.
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The point with that experiment is that you have a full glass but are adding water to it, frozen or not is immaterial, if you add liquid water, it will still overflow.

A better experiment would be to take a full glass of water and freeze it. Since water at 0C is less dense then water at 4C, it will expand, and either rise above the rim of the glass or break the glass, (depends on the geometry and smoothness of the glass). In the interval between +4 and zero, the expansion will be enough to make some of the water overflow the glass.

Actually - for a complete truth, it depends on the definition of "full". If the water level in the glass is exactly level with the top of the glass, surface tension will allow the level of the water to rise above the top of the glass without spilling, simple analogies like this suffer from these kinds of failings.

As to the film, never let the facts stand in the way of a decent special effects budget.

2. RECAP

So.....

Make a glass full of liquid water and its full (DUH).

Fill a glass with water and ice to the top, the ice will melt and leave a lesser level than full.

Fill a glass full of solid ice and it melts and leaves a lesser level than full.

Fill a glass full of water and freeze it it expands fuller than before (i.e. it expands)

Okay. Now I've stated the obvious stuff... But back to the ice caps now? But what about salt water in the ocean. I know that it must be able to be frozen somehow even it it must reach 0k (zero kelvin - absense of tempurature where molecular activity stops). Is this a paradox though? An object couldn't reach zero degrees kelvin unless it was in a vaccum and void of any molecular contact (i.e. suspended in zero gravity). Is this right? I read in PopSci about some superconductor expirements that got *close to 0k, but not there. Anyone know more about this here?

3. fill a glass with water and ice to the top, the ice will melt and leave a lesser level than full.
I don't think it will, i think the level of fluid will remain constant. Atleast according to my back of the envelope calculation it will.

but what about salt water in the ocean. I know that it must be able to be frozen somehow even it it must reach 0k (zero kelvin - absense of tempurature where molecular activity stops). Is this a paradox though? An object couldn't reach zero degrees kelvin unless it was in a vaccum and void of any molecular contact (i.e. suspended in zero gravity). Is this right? I read in PopSci about some superconductor expirements that got *close to 0k, but not there. Anyone know more about this here
Salt water will freeze, the saltier the solution the lower the freezing point, but even a supersaturated solution will freeze way above absolute zero.

It is impossible to reach absolute zero, we can get very close, but we cannot (and i'll wager never will) actually get there. (Doing so would violate thermodynamics).

4. Originally Posted by jinx
(1) Make a glass full of liquid water and its full (DUH).

(2) Fill a glass with water and ice to the top, the ice will melt and leave a lesser level than full.

(3) Fill a glass full of solid ice and it melts and leaves a lesser level than full.

(4) Fill a glass full of water and freeze it it expands fuller than before (i.e. it expands)

(5) Okay. Now I've stated the obvious stuff
(1) Correct.
(2) Once again, NO. The water level will remain _exactly_ constant.
(3) Correct.
(4) Correct.
(5) No.

EDIT: Since you probably won't believe me just because I say so (that's wise btw), I leave it to Yasar Safkan, Ph.D to answer here.

5. What I don't get is, if water expands when frozen, then when it melts it must contract?

6. It does but ice floats which means not all the ice is submerged. As you melt the ice, you end up increasing the amount of liquid but you decrease the volume of submerged ice, the two cancel out so that the overall level of the liquid does not change.

7. Originally Posted by Clyde
It does but ice floats which means not all the ice is submerged. As you melt the ice, you end up increasing the amount of liquid but you decrease the volume of submerged ice, the two cancel out so that the overall level of the liquid does not change.
Thats interesting, I must have known that, but it was never solidified as knowledge, I guess you learn something new everyday.

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