Posted on 08/09/2018 1:36:31 PM PDT by Sub-Driver
displacement3. Physics.
b. the weight or the volume of fluid displaced by a floating or submerged body.Compare Archimedes' principle.
The only water displaced by ice is that which is below the water line. 10% of its volume is above water and ice is only 9% greater in volume than the water it is formed from in liquid form.
I'm sorry but djs12345 was mistaken in his statement that "the displacement of ice (frozen water) in water greater than the equivalent in liquid water."
Rather than being mistaken, I think he just stated it poorly.
b. the weight or the volume of fluid displaced by a floating or submerged body.
Two things. You have left out that (b) depends on the weight of the floating or submerged body. If the weight is less than the amount displaced, it floats. If the weight is more, it sinks. If he weight is the same then it would move up and down under the surface, mostly due to currents.
The fact that 10% of the iceberg floats above water proves that the TOTAL volume of the iceberg weighs less than the exact same TOTAL volume of water, which is what dhs12345 was trying to say.
He is saying the same thing you are, just in a different way.
Still with us...
Ya. Thanks everyone. Good analysis.
No offense to either of you but that is definitely a clumsy way to state it.
A mass of ice of equal volume to a mass of liquid water would contain less water thus the lower density. Put another way; one cubic foot of ice has less water than one cubic foot of water.
The reason ice has a lower density than water is because it has expanded its volume making a given weight (mass) of ice more voluminous than its equal weight of liquid water.
His statement still can't be correct.
"the displacement of ice (frozen water) in water greater than the equivalent in liquid water."
It isn't clear from that statement which "equivalent," volume or mass, is being compared but in either case ice displaces less water than liquid water.
Without knowing if it has risen or subsided or eroded that is meaningless.
Isn’t displacement based on mass or weight. And you add density of ice vs liquid. Volume is the key variable, greater volume consumed by ice means higher water levels because frozen water or ice displaces the liquid water.
Yes, but volume is taken into consideration too.
DENSITY is defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume.
And you add density of ice vs liquid.
Ice is less dense than water by volume.
..greater volume consumed by ice means higher water levels because frozen water or ice displaces the liquid water.
That would only be true if all of the ice were displacing water. 10% of the volume of ice remains above water yet the ice only increased in volume 9% over its liquid state.
It's a wash. One pound of ice displaces almost exactly the same volume of water as the volume of one pound of liquid water.
Actually, I think it works this way...
For example: 1 liter of water.
Frozen, it consumes 1.09 liters of volume.
Liquid, it consumes 1 liter.
Mass doesn’t change. Only volume.
Displacement doesn’t change either. 1 liter is one liter frozen or liquid.
That means that 9% of the ice cube is above the water surface and not below the surface where it will displace the water causing the surface to rise.
Exactly! Displacement does not change. That is what I've been saying.
1 liter is one liter frozen or liquid.
No. If you freeze one liter of water, as you said, it expands to 1.09 liters. If you take one liter of ice and let it melt you will have less than a liter of liquid water.
Mass doesn’t change. Only volume.
Density also changes as it is defined by both mass and volume. That is why ice floats and 10% of it will be above water.
To add. If there is a lid on the container right at the surface preventing the ice cube from floating above the surface and forcing it below the surface, then yes, volume of the frozen cube would be a factor and that volume of the frozen water (1.09%) would be displaced however there would be a constant force to try to push it upward towards equilibrium.
However, if the ice cube is allowed to float above the surface, then equilibrium is achieved and 9% of it will poke out of the surface of the water.
This probably varies with water density. For example: water density at 0 feet, at the surface, is different from water density at 1000 feet, etc.
Remember that mass is constant.
1 liter of water = x grams.
1.09 liter of ice = x grams.
Whether frozen or liquid, whatever 1 liter of water weighs is displaced.
Not to be too nit-pickey but 10% of the volume of ice is above water.
Of course changes in the density of the water the ice is floating in would alter the equation. Salt water for example has a different density than fresh water. If the ice was formed from salt water it would have a different density too. For simplicity the figures given were derived from fresh water at sea level and the volume of water at room temperature. (as stated in the link)
Yes, as I stated several times with proofs.
A liter of liquid water displaces one liter of water. If you freeze the liter of water it will have the volume of 1.09 liters but it will only displace 1 liter of water.
Also, the air above the surface is not a vacuum and the air will be displaced too. So it is probably not exactly 9% but some percentage of the percentage. Maybe more like 7% or 8%.
You could compute it by figuring out the ratio of the density of water at the surface to the air right above it at a certain temperature.
Of course, temperature is a factor, too. Water probably behaves different than air (nitrogen, oxygen, CO2, etc.).
If 10% of the volume of the iceberg is above water I suspect that would be the amount of air displaced.
Ya. Thanks.
Just coming up to speed. Been busy the couple of days that this discussion has been going on.
Lol.
But air is not a vacuum so the amount of air displaced will create a force downward onto the ice and into the water. Probably small in comparison to the water (or salt water).
Of course, air density is not a constant but it is denser at sea level. Probably the densest.
I think that that is how it works.
Archimedes' principle of Buoyancy
At any rate, it has already been established that 10% of the volume of an iceberg is above water. That is not in question.
Iceberg
Because the density of pure ice is about 920 kg/m3, and that of seawater about 1025 kg/m3, typically about one-tenth of the volume of an iceberg is above water.
Not as dense as it is below sea level. ie Death Valley. :)
I suspect that all oceanic icebergs are at sea level.
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