Ice Question

Agent Phrank

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Suppose you have a 3 ounce ice cube in a glass of 9 ounces of water. When the ice melts, will the water level increase or decrease, and by how much?

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Snape Uchiha

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It decreases, because solid Ice is less dense and has more volume than liquid water.
 

SRShock10

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Water level decreases or remains the same since ice is less dense than water and adds to more volume, initially, with 8% remaining exposed to the air, above the water line... however, once the ice melts, you will have 12 ounces of water, since you have conservation of mass and oz's are a measure of mass (not volume or density)
As far as determining how much water level changes, we can't determine unless you give us the volume and height (or bottom area) of the container the water sits in, as well as the initial temperatures of water and ice, since density decreases in water as you increase temperature from 4C.
 
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SRShock10

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Okay, I decided to do it, since I did the MCAT recently... Just say it's the same... Let's take a look
the relative density of ice is 0.92 (in comparison to water), right?
Plug it into m*g... m=density times volume.
So. If we have 3 oz of ice and 9 oz of water, that would mean there's volume being displaced by the ice to raise water level. Given the relative density is 0.92, 8% of the ice will remain out of the water.
Without converting to grams/L (note don't use these numerical values bc they aren't converted)
3=0.92V. V=3/0.92. So 92% of the ice's volume, which is displacing the water, is about "3". The other 8% (or 0.26 if you were to calculate) is not in the water. DON'T CONFUSE WITH OZ.
For the initial water, we've got 9 oz
m=pV, 9=1V, 9=V,
V(ice, submerged)+V(water)=3+9=12
Leaving total volume taken up by water (and the added ice), aka water level to "12".

In the end, all of the ice is melted. So, now we have to say m=12
12=1V, V=12.

The water level doesn't change.
It would decrease IF the ice cube were sunken and kept on the bottom while have the same specific density, by physical force
 
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Agent Phrank

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It will either decrease or remain the same.
Okay, I decided to do it, since I did the MCAT recently... Just say it's the same... Let's take a look
the relative density of ice is 0.92 (in comparison to water), right?
Plug it into m*g... m=density times volume.
So. If we have 3 oz of ice and 9 oz of water, that would mean there's volume being displaced by the ice to raise water level. Given the relative density is 0.92, 8% of the ice will remain out of the water.
Without converting to grams/L (note don't use these numerical values bc they aren't converted)
3=0.92V. V=3/0.92. So 92% of the ice's volume, which is displacing the water, is about "3". The other 8% (or 0.26 if you were to calculate) is not in the water. DON'T CONFUSE WITH OZ.
For the initial water, we've got 9 oz
m=pV, 9=1V, 9=V,
V(ice, submerged)+V(water)=3+9=12
Leaving total volume taken up by water (and the added ice), aka water level to "12".

In the end, all of the ice is melted. So, now we have to say m=12
12=1V, V=12.

The water level doesn't change.
It would decrease IF the ice cube were sunken and kept on the bottom while have the same specific density, by physical force

Correct, the water level will remain the same. Archimedes's Principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. In this case, ice upon water. The volume has already been dispersed; when it melts, it only changes its physical state. Counter intuitive, indeed.

All of you get a cookie.

Here are a few vids:






And this is a TED video on how Archimedes conceived this principle; these Greek scientists were really ahead of their time.

 
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