Water expands and decreases in density upon heating. So does it mean that an object with high temparature that has water in it will float better than if the object was cold.

And does this effect also apply to living organism.

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goatharper t1_ixay9th wrote on November 22, 2022 at 2:06 AM

Strictly speaking, yes, but the expansion of water with temperature is so small that for all practical purposes the effect is negligible.

https://antoine.frostburg.edu/chem/senese/javascript/water-density.html

The densest possible liquid water is 4% denser than water a degree short of boiling. In living organisms, the difference will be far less.

So "negligible" is le mot juste I think.

m4rc0n3 t1_ixb2v9n wrote on November 22, 2022 at 2:41 AM

I wouldn't call 4% negligible. And even with only a small temperature increase, thermal expansion is a major factor in sea level rise according to https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/thermal-expansion

jellyfixh t1_ixb5pve wrote on November 22, 2022 at 3:03 AM

Keep in mind that for sea creatures their bodies are made largely of water and usually have body temperatures a few degrees above ambient so they would expand as well albeit not as much.

SBreacher t1_ixbmfqy wrote on November 22, 2022 at 5:38 AM

I can vouch for that. As a former competitive swimmer the water temperature has a meaningful impact on buoyancy and viscocity. Warmer water always negatively affected the "grip" you had on it.

Chemomechanics t1_ixbqxcm wrote on November 22, 2022 at 6:29 AM

> As a former competitive swimmer the water temperature has a meaningful impact on buoyancy

This part strains credulity. How were you able to gauge a <0.5% difference in buoyancy?

[deleted] t1_ixcgfcw wrote on November 22, 2022 at 12:07 PM

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fliguana t1_ixb01he wrote on November 22, 2022 at 2:20 AM

Water expands very little with temp, but gases do.

A feverish animal with fart bubbles inside will have higher buoyancy than identical colder animal.

Fart jokes aside, blubber in marine animals changes density with temperature.

https://www.researchgate.net/publication/287491270_Blubber_density_depends_on_lipid_composition_and_temperature_in_three_deep-diving_odontocetes

left_lane_camper t1_ixdp2dk wrote on November 22, 2022 at 5:46 PM

While the density change is only ~4% for liquid water between its minimum and maximum (under standard conditions), this can be noticeable if the floating thing is very close to neutral buoyancy.

For example, the Galileo thermometer works by having objects of (relatively) fixed density suspended in a water column. The objects densities are slightly different and such that they are all very near neutral buoyancy, so that the more dense objects will only float when the water is colder and more dense as well. This can be made into a thermometer by carefully selecting the densities of your suspended objects!

[deleted] t1_ixaynka wrote on November 22, 2022 at 2:09 AM

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[deleted] t1_ixb2kub wrote on November 22, 2022 at 2:39 AM

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[deleted] t1_ixblzde wrote on November 22, 2022 at 5:33 AM

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[deleted] t1_ixc57e4 wrote on November 22, 2022 at 9:43 AM

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opopkl t1_ixcyvdm wrote on November 22, 2022 at 2:48 PM

Can I ask a related water temperature question? As a kayaker, I feel that water seems to be much more viscous at low temperatures (4C) than at even slightly higher temperatures (15C). Is this just my imagination?

Chemomechanics t1_ixdahne wrote on November 22, 2022 at 4:10 PM

A search for water viscosity temperature will immediately give you many versions of the same table/chart showing the relationship. From that, you can quickly estimate the percent change across that temperature range and decide if the hypothesis makes sense. (There are actually two types of viscosity, but that’s a nuance that can be ignored in this context.)