Kitchen Sink Science

Have you ever noticed that boiling water is quieter than cold water?

Over the years, I have noticed that when pouring boiling water into the sink (for example, when draining pasta), the noise is noticeably quieter and softer than when I pour cold water.

I always pour into a stainless steel sink, not a plastic or ceramic one.

To me it makes sense because the density of water at 100oC is 958 kKg/m3 versus 999 or 998 Kg/m3 for water at 10 or 20oC respectively.

That makes boiling water about 4% less dense than cold tap water, or ... maybe I am the one who is dense because no one else ever seems to hear the difference.

As usual, I have no published science to back this up. It is something I have never seen documented anywhere. But it is something I have observed and this is my best explanation.

You can explore the density of water at various temperatures and salinity here.

Image nabbed from here.


KayMac said…
ok, i am going to try this at home tonite. i will have my daughter listen as well....will let you know our observations (audservations???).
can't say that I've ever noticed..we don't have pasta very often! Not much hot water would be dripping through and at a slow speed as opposed to regular cold water taps being full force and perhaps at a faster rate. Would speed and volume of water/second be factors?

Our plumbing is weird and old. Every time we do laundry, which is right below our kitchen sink in the basement, we hear loud gurgling glugging in the sink pipes. I expect clothes to come up through thr sink!
Barbara said…
I've never listened to water (warm or cold) as I poured it down the drain. I will observe and report back. You have such a scientific way of observing things!
Richard said…
kaymac: the problem of course is in eliminating observer bias. Humans are pretty good at tricking themselves - sometimes to notice things, other times to ignore things. I think it is pretty obvious. Your daughter may have better luck, young people's hearing is better (assuming they haven't destroyed their hearing with loud music). Let me know the results.

MOI: you can easily replicate and control the conditions. I know I have. Fill a kettle with cold water and pour it out into the sink. Next fill the kettle and bring to a boil. Pour the boiling water out into the sink. I hear a difference. The boiling water makes a quieter and softer sound.

barbara: I just noticed it sounded different. Of course, there are many times I don't notice things at all.
b said…
interesting. when i read this, i immediately thought that i have noticed the difference between the two...and then i read your comment to kaymac about observer bias and laughed. maybe not.
Richard said…
breal: it can only be observer bias if I have prejudiced you about possible outcomes.

If you think you heard a difference, without having been prompted to hear it, I would say there is a good chance you definitely heard something different.

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