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goatharper t1_ixay9th wrote

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.

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m4rc0n3 t1_ixb2v9n wrote

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

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jellyfixh t1_ixb5pve wrote

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.

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SBreacher t1_ixbmfqy wrote

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.

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Chemomechanics t1_ixbqxcm wrote

> 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?

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left_lane_camper t1_ixdp2dk wrote

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!

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opopkl t1_ixcyvdm wrote

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?

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Chemomechanics t1_ixdahne wrote

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.)

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