Why Does Ice Float in Water at 9°C?

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Discussion Overview

The discussion centers on the question of why ice floats in water at temperatures around 9°C, despite claims that ice is denser than water at these temperatures. Participants explore the relationship between the densities of ice and water, referencing density charts and questioning the conditions under which ice and water coexist.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that ice is denser than water when the temperature is above 9°C, questioning why it floats.
  • Others point out that the density of water at 9°C is approximately 0.9997 g/cm³, which is less than the density of ice at 0°C (0.9167 g/cm³), suggesting that ice should sink.
  • There are claims that ice cannot exist in equilibrium with water at temperatures above 9°C, as ice melts and water freezes at 0°C.
  • Some participants express confusion about the density chart provided, noting that it only lists water densities and does not include ice, leading to questions about the relevance of the chart.
  • One participant introduces the concept of super-cooled water, suggesting that it may be less dense than ice, indicating ongoing research in this area.
  • Several participants request clarification on the specific temperatures being discussed and the context of the density claims.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the relationship between the densities of ice and water at 9°C. Multiple competing views are presented regarding the conditions under which ice floats and the implications of the density chart.

Contextual Notes

There is uncertainty regarding the definitions of density in relation to temperature, and the discussion highlights the limitations of the provided density chart, which does not include ice densities.

pscience
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Please help. Ice is more denser than water when temperature of water ≥9°C. Then why ice doesn't sink in water at these temperatures? I greatly appreciate your help.
Density chart: http://www2.volstate.edu/chem/1110/Density_of_Water.htm
 
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Wikipedia said:
The density of ice is 0.9167 g/cm3 at 0 °C,[3]

I don't see the water density becoming smaller than that in the chart you linked to, at 9 degrees the water was at the 0.9997xx area.
 
pscience said:
Please help. Ice is more denser than water when temperature of water ≥9°C. Then why ice doesn't sink in water at these temperatures? I greatly appreciate your help.
Density chart: http://www2.volstate.edu/chem/1110/Density_of_Water.htm
Ice and water can't exist together at >9C (in equilibrium). Ice melts and water freezes at 0C and as soon as you drop ice into water, the water's temperature starts to drop until there is quickly an equilibrium (at least locally).

[edit]...er, yeah, and it looks like the density claim is wrong anyway. Ice's density is 0.917...
 
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ice float

Gullik said:
I don't see the water density becoming smaller than that in the chart you linked to, at 9 degrees the water was at the 0.9997xx area.

As per any density-Temp chart or graph I found online giving unique info and that is ice is denser than water at temperatures more than 9C. Please be specific about temperatures.
 
pscience said:
As per any density-Temp chart or graph I found online giving unique info and that is ice is denser than water at temperatures more than 9C. Please be specific about temperatures.

Where is ice listed in the chart in your link? All I see is water density numbers.

And as has been said already, ice does not exist at 9C...
 
Thank you for your time my friend. Do you think that water of any temperature is denser than ice?
For example which is more denser? ice(0C) or water(20C)
 
pscience said:
Thank you for your time my friend. Do you think that water of any temperature is denser than ice?

If ice has the density quoted or 0.917g/cm^3, and you look at your table, what do you think?

What is the context of your question?
 
No context my friend. I was reading a physics book and curious to know more about it. so, you think that ice is less denser than water of any temperature. Is that correct? thank you.
 
pscience said:
As per any density-Temp chart or graph I found online giving unique info and that is ice is denser than water at temperatures more than 9C.
Why don't you give the link to that reference so we know what you were looking at.
 
  • #10
pscience said:
No context my friend. I was reading a physics book and curious to know more about it. so, you think that ice is less denser than water of any temperature. Is that correct? thank you.

Maybe I'm getting a little out of the context of the question, but it's thought super-cooled water at the lower bounds is less dense than ice. There's still a lot of research and experimentation going on about the thermodynamics of super-cooled water.
 
  • #11
Yes, the same chart I posted above my friend. Water density at 9C is 0.999781 g/mL and at 0C is 0.999841 g/mL. So clearly ice denser as per that chart. So shouldn't ice sink? Thank you and sorry to bother you.
http://www2.volstate.edu/chem/1110/Density_of_Water.htm
 
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  • #12
pscience said:
Yes, the same chart I posted above my friend. Water density at 9C is 0.999781 and at 0C is 0.999841. So clearly ice denser as per that chart. So shouldn't ice sink? Thank you and sorry to bother you.
http://www2.volstate.edu/chem/1110/Density_of_Water.htm

No, that's all liquid water.
 
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  • #13
pscience said:
Yes, the same chart I posted above my friend. Water density at 9C is 0.999781 g/mL and at 0C is 0.999841 g/mL. So clearly ice denser as per that chart. So shouldn't ice sink? Thank you and sorry to bother you.
That chart only shows liquid water densities. No mention of ice. (Water can be liquid at 0°C.)
 
  • #14
Oh,Water can be liquid at 0°C. that makes sense. Thank you so muchhhhh.
 

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