Suppose you have a glass of water with ice in it. The ice melts. so, has the water level of the glass increased, decreased, or neither?

I think it should remain constant, with very small error margins considering the increase in the volume of the water its self its mean temperature increases or decreases.

But, what do you think?

Neither. Do I get a check plus?

Suppose you have a glass of water with ice in it. The ice melts. so, has the water level of the glass increased, decreased, or neither?


It decreases. An easy test of the reverse effect is to
Put an unopened, flimsy half-liter bottle of water in your freezer for a quick chill down
Forget that you have done so
Yell "Eureka! I have found it" when you come across it the next day, and Clean up the mess made by the the exploded bottle.

The water level decreases as the ice melts because ice is less dense than water. Freezing water makes the volume occupied by it increase.

Decrease. Water increases in volume as it freezes, becoming less dense. So the total volume of ice + water is greater than the volume of water after melting. This is why ice floats and also why things tend to break when the water they contain freezes.

Expanding during the transition liquid -> solid is rather unusual. Water is one of the few common substances that do this. More common is contraction liquid -> solid.

>>edit. Actually, if the ice is floating in the glass in the op's scenario then the liquid level might remain very close to unchanged. The water from the ice above the liquid level should about compensate for the decrease in volume of the ice melting below.

You are both wrong. Sigh.

DH is wrong because you have the ice FLOATING in water. The ice displaces it's weight in water, even if it is less dense.

kevinalm, we aren't talking about volume, but the level of the water.

Yeah, I caught that after I posted. See edit.

Neither. I tried it once.

Hector Berlioz is correct. Floating ice does not cause a practical change in water level.

My only real experimentation has been with Scotch and ice.

I have discovered that the liquid vanishes before accurate measurement has been made.

You guys are confusing Buyouncy with volume. The volume of the water is the same and does not change unless the water begiins a "change of state" which i am sure most of you already know ;). So if an ice cube already in place when the measuremnt of volume was taken, the water level would only change slightly between 2^ and 6^ Celsius. after it reaches the point of just water in th eglass the Level would be the same disregarding minor evaporation of atoms jostling each other and eventually jumping out of the glass (seriously)

Good to know.

You are both wrong. Sigh.

DH is wrong because you have the ice FLOATING in water. The ice displaces it's weight in water, even if it is less dense.

kevinalm, we aren't talking about volume, but the level of the water.How do you figure? kevinalm is right. Water expand when it becomes ice because of the cofiguration of the hydrogen bonds. The question asks about the volume: total volume. That would include the volume of the ice above the surface of the water line. When it melts: the total liquid water volume has to increase. Sigh.

imo the water level would remain the same. the part that sticks out of the water makes up for the contracting ice

if you take one cup of water... and you freeze it.. the water expands...

when it liquifys its volume is slightly less...

the point? i dont know...

but if we could get water to rapidly freeze and liquify in volume, we would have a unique power source.. since the ice, when freezing will generate tremedous pressure if it was contained in a limited space..
thus.. a small volume of water might lift great weights... if only a few milimeters...
but then.. when it liquifys.. that weight must fall, and if attached to a pully..
it could generate power. (assuming it was very large and heavy.)

ice floats cause it is less dense than water.

What i want to know.. is why do you ask the question?

-MT

How do you figure? kevinalm is right. Water expand when it becomes ice because of the cofiguration of the hydrogen bonds. The question asks about the volume: total volume. That would include the volume of the ice above the surface of the water line. When it melts: the total liquid water volume has to increase. Sigh.

actually the question was about the water level.

It doesn't change.

What i want to know.. is why do you ask the question?

-MT

hector asked the question in the op.

water is a very complex substance - the highest density is at 4 degrees celsius ...
if you warm water from that temperature it actually expands very slightly ....
if you cool it from that temperature it expands - and it especially expands when turning into ice, creating lower density - which is why ice floats ....

So theoretically , you could have an example of a glass of water with floating ice - when it is warmed up the ice will melt and the water from ice contract - but some of the ice was above the waterlevel (floating), so that counters it .... however if you warmed it up from 4 degrees celsius to lukewarm the waterlevel would rise very slightly - probably so little that you could not see it, but still risen .....

glass also tries to expand when warmed - but the crystalline nature of glass counteracts it - that is why a glass breaks when beeing put into scolding hot water and the energy of expanding is stronger than the energy in the crystalline bindings ....

but if we could get water to rapidly freeze and liquify in volume, we would have a unique power source.. since the ice, when freezing will generate tremedous pressure if it was contained in a limited space..
thus.. a small volume of water might lift great weights... if only a few milimeters...
but then.. when it liquifys.. that weight must fall, and if attached to a pully..
it could generate power. (assuming it was very large and heavy.)
-MT

I guess if you would calculate the energy required to "rapidly freeze and liquify in volume", and all the losses in efficiency -- transfering forces to pully... etc.. It wouldn't be practical.

water is a very complex substance - the highest density is at 4 degrees celsius ...
if you warm water from that temperature it actually expands very slightly ....
....
ah insane? i believe you have it backwards

ah insane? i believe you have it backwards

Do I ?
Well let´s see - water has is its highest density at 4 degrees celsius (actually it is precisely 3.97 degrees celsius) - water above and below that temperature has a lower density - that is a fact from my chemistry book ....

density = mass/volume

For a constant mass of water :
the higher the density the smaller the volume..
the lower the density the bigger the volume

water warmed above 4 degrees = lower density = bigger volume = expanding

Actually I think I´ve got it right, Leo

i will be more observent in the future

No problem, Leo , I make mistakes all the time myself ......

if you warm water from that temperature it actually expands very slightly ....if you cool it from that temperature it expands - and it especially expands when turning into ice, creating lower density - which is why ice floats ....

So theoretically , you could have an example of a glass of water with floating ice - when it is warmed up the ice will melt and the water from ice contract - but some of the ice was above the waterlevel (floating), so that counters it .... however if you warmed it up from 4 degrees celsius to lukewarm the waterlevel would rise very slightly - probably so little that you could not see it, but still risen .....

glass also tries to expand when warmed - but the crystalline nature of glass counteracts it - that is why a glass breaks when beeing put into scolding hot water and the energy of expanding is stronger than the energy in the crystalline bindings ....This is absolutely correct. When the ice melts, all other factors being held constant, it will not increase the overall volume of the liquid.

This is easy to prove. Place a can of uncarbonated soda in your refrigerator (I say "uncarbonated, because carbonated beverages have a tendency to expand soo much that they burst and create a mess). Let the can freeze and you will clearly see a bulge expansion in the can from the liquid water expanding as it turns to ice. Then take the can out of the refrigerator and let it warm up for a day. When you open it, there will be the exact same amount of liquid there as when you started.

Now for a larger scenario: you have vast amounts of ice and even vaster amounts of water. When the ice melts what happens to the water level. We'll say 620,000 km^3 of floating ice and 1.37x10^9 km^3 of water. The density of ice is given as 0.931g/cm^3 and water is clearly 1g/cm^3. (As stupid as it would be to assume uniform density of water with that much water... if it's easier, try it that way).

Good grief: Think about buoyancy and use some logic !! An object which floats in water displaces a volume of water equal to its weight of water. The ice cube weighes X ounces, it displaces X ounces of water. When it melts, it still displaces X ounces of water. Therefore, the water level remains essentially the same when the ice melts.

The above is not precisely correct due to slight changes in water density with temperature.

So, this begs the $64K question: Why would the melting of polar ice caps cause any global flooding? Melting of free-floating ice wil not change the water level one bit. (Though melting of ice on land will).

Anartica has land under the ice, so melting at the Sourth Pole should raise the water level. I am not sure about the situation at the North Pole.

I think there is a lot of permanent ice on land in Northern Canada and other Northern land massws. If the Artic ice melts, so will this ice.

Global Warming is also causing glaciers to melt on land in Alaska, Canada, Greendland, Norway, Siberia, in the Alps in Europe, and - I don't know - maybe in the Himalayas too.

Also, if 1/7th of an iceberg is above the ocean surface? Also, ice sheets freeze solid in the Arctic, but then snow and ice piles above it. No more of that - all raises the oceans' levels.