Quote:
Originally posted by Giltwist
The molecules in hot water are moving at a much faster rate than the molecules in cold water. Also, the molecules are much further apart. That little change could easily change the sound.
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Not really.
The molecules are moving faster but the temp. difference is only about 70-90 degrees K. The cold water is still about 280 K so it's not a huge difference. K is proportional to the mean velocity squared so I think we're only talking about a 10-15% difference.
As for the molecules being further apart, that is negligible -- compare the volume of cold and hot water, it is nearly the same.
I think you need to start by thinking about where the sound is coming from. I don't think the water molecules themselves are emitting sound, but rather the pouring of liquid into a cylinder moving air around that creates the sound.
I am not certain but I think happymaan's theory is more likely.
A good way to test this would be to compare the sound of water at 10, 35, 60 and 85 degrees C. If Giltwist is correct, all four should sound different, whereas if happymaan is right, the 10 and 35 should sound very similar.