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jinx
05-10-2004, 01:01 PM
Anyone in the states seen a preview for The Day After Tomarrow where the polar ice caps melt in one day? If not look here:

Still Frames (http://www.hollywood.com/photogalleries/gallery1/id/1751105)
and
Movie Trailer (http://www.hollywood.com/multimedia/detail/media/1746771)
The polar ice caps melt and the world floods. Well...doesn't water expand when it is frozen...? So if it melted it would contract? Is this one of holyywood's greatest flaw yet?

Magos
05-10-2004, 01:22 PM
Floating ice, yes, but the north pole has ice on land.

loopy
05-10-2004, 01:34 PM
I want to see this, I'm always interested in human endurance storys, this is a new storyline as far as I know.

Sang-drax
05-10-2004, 02:20 PM
Floating ice, yes, but the north pole has ice on land.No, floating ice doesn't affect the water level in any way.

Water expand when frozen, but the south pole (NOT the north pole) has vast amounts of ice on land. When this ice melts, the water level of the oceans will rise.

Magos
05-10-2004, 02:50 PM
No, floating ice doesn't affect the water level in any way.
That's what I said. Or at least meant...


Water expand when frozen, but the south pole (NOT the north pole) has vast amounts of ice on land. When this ice melts, the water level of the oceans will rise.
Oh, i thought it was the north pole that had land and south didn't. I knew one did and the other didn't...

XSquared
05-10-2004, 04:20 PM
>Well...doesn't water expand when it is frozen...? So if it melted it would contract?
Other way around.

jinx
05-10-2004, 05:30 PM
Okay X, get a bottle of drinking water and take the cap off and fill it completely full and stick it in your freezer and let us know what happens :eek:

scrappy
05-10-2004, 11:23 PM
Charles' Law
V1/T1 = V2/T2

If V1 = 10 L; T1 = 250 K; T2 = 300 K;

(10 L * 300 K)/(250 K) = 12 L

(Assuming water) Goes from freezing temp to liquid temp and expands. This is just a gas law I learned in chemistry, so I don't know if it applies to solids and liquids as well

RoD
05-10-2004, 11:41 PM
Water is peculiar. When most substances change from liquid to solid form, they shrink together, become denser, their molecules packed most closely together.

But when water changes from a sloshy liquid to solid ice, it expands, becomes less dense. Which is why ice floats to the top of your Coke, rather than sinking like a stone to the bottom.

At normal atmospheric pressure, molecules usually behave in predictable ways as their temperature changes. Molecules fly apart into a gas when heated, condense into a flowing liquid when cooled, and shrink into a frozen solid when chilled still further. The changes in state parallel changes in energy: from high energy to medium energy to barely jiggling.



http://www.word-detective.com/howcome/waterexpand.html


Normally, things expand when heated and contract when cooled. Water is an exception to this rule. Even though water does expand when heated and contract when cooled at most temperatures, water expands when cooled and contracts when heated between 4 degrees Celsius and 0 degrees Celsius.


http://www.physlink.com/Education/AskExperts/ae371.cfm

This is why PVC pipes (plumbing) explodes when you allow the water in it to freeze.

kermi3
05-10-2004, 11:46 PM
For all those who care, the movie is based on the book Coming Global Superstorm by Art Bell and Whit Steele (not sure on last name). They didn't write it as pure fiction; they based it on what they believe will happen at current rates and took one story out of that.

jinx
05-11-2004, 07:58 AM
Thank you RoD! I thought I had made it clear that water was the *only liquid that expands when it freezes! About the floating ice...yes it does effect water levels. Fill a glass COMPLETLEY full and put three ice cubes in it....duh. And, you only see ten percent of a glacier's body because the rest is under water. Does any one know what the highest point of ice is on the south pole?

Clyde
05-11-2004, 08:12 AM
water was the *only liquid that expands when it freezes!


Any liquid with reasonably strong hydrogen bonding will expand when frozen (e.g. ethanol).



About the floating ice...yes it does effect water levels. Fill a glass COMPLETLEY full and put three ice cubes in it....duh.


He means that if you melt floating ice the water levels do not change. So you partially fill your glass with water then add enough ice so that the water level is up to the rim of the glass then you melt the ice and the water level does not change.

loopy
05-11-2004, 08:23 AM
About the floating ice...yes it does effect water levels. Fill a glass COMPLETLEY full and put three ice cubes in it....duh.


I didn't know that! :eek: :cool:

ober
05-11-2004, 09:04 AM
I didn't know that! :eek: :cool:You're an idiot! :eek: :cool:

loopy
05-11-2004, 09:11 AM
I just found it interesting, I didn't want to start trouble.

adrianxw
05-11-2004, 11:01 AM
Water reaches maximum density at +4C, that is why ponds freeze from the top downwards.

>>>
About the floating ice...yes it does effect water levels. Fill a glass COMPLETLEY full and put three ice cubes in it....duh.
<<<

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.

jinx
05-11-2004, 01:33 PM
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?

Clyde
05-11-2004, 01:52 PM
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).

Sang-drax
05-11-2004, 02:45 PM
(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 (http://www.physlink.com/Education/AskExperts/ae389.cfm).

loopy
05-11-2004, 03:06 PM
What I don't get is, if water expands when frozen, then when it melts it must contract?

Clyde
05-11-2004, 03:36 PM
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.

loopy
05-11-2004, 03:54 PM
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. ;)