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12 Dec 09
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This may seem a strange question but has anyone else noticed that the pouring of very hot water into a cup sounds a little different to doing the same thing with cold water. Maybe I'm imagining it, but to me there is a difference. Anyone here have a possible explaination?
13 Dec 09
Originally posted by divegeesterMaybe it is because boiled water has less air in it? let the hot water cool off, see if it still makes the sound of hot water.
This may seem a strange question but has anyone else noticed that the pouring of very hot water into a cup sounds a little different to doing the same thing with cold water. Maybe I'm imagining it, but to me there is a difference. Anyone here have a possible explaination?
13 Dec 09
Originally posted by David113Another aspect of hot water: Take a cup of water, put it in the microwave, set it on high and let it rip for a couple three minutes, then put in a teabag, when that happens, the water will boil furiously even though before there would have been only a few bubbles forming. What's up with that?
Maybe it is because boiled water has less air in it? let the hot water cool off, see if it still makes the sound of hot water.
13 Dec 09
Originally posted by sonhouseBubbles need a rough surface to form on.
Another aspect of hot water: Take a cup of water, put it in the microwave, set it on high and let it rip for a couple three minutes, then put in a teabag, when that happens, the water will boil furiously even though before there would have been only a few bubbles forming. What's up with that?
13 Dec 09
Originally posted by mortisdeadMake up a cup of hot chocolate, or instant coffee. Then take your teaspoon, put it in the cup and repeatedly tap it on the bottom. The pitch of the tap will go up and up and up.
Slightly lower density too so sound travels differently through the water.
--- Penguin
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13 Dec 09
Originally posted by PenguinInteresting, but why? And is this the same explaination as to why poured hot water sounds different?
Make up a cup of hot chocolate, or instant coffee. Then take your teaspoon, put it in the cup and repeatedly tap it on the bottom. The pitch of the tap will go up and up and up.
--- Penguin
13 Dec 09
Originally posted by AThousandYoungbut the water is at 101 degrees C, past boiling point, in the same cup on a stove it would bubble first while boiling, but in microwave, bubbling is delayed till the teabag touches it. I don't think it has to do with roughness. Maybe nucleation centers like what causes CO2 to bubble out of beer or soda, needs nucleation centers, bits of dust or some kind of debris to start building up bubbles on. Maybe the same thing in H2O.
Bubbles need a rough surface to form on.
14 Dec 09
1 edit
Originally posted by divegeesterI think it is to do with the difference in fluid density between hot water (or milk) with particles mixed in it and the same fluid with the particles disolved.
Interesting, but why? And is this the same explaination as to why poured hot water sounds different?
I did here an explanation on a podcast (the Naked Scientists, I believe) but wasn't paying enough attention for it to stick in my sieve-like mind.
Maybe a physicist here could provide a better explanation?
--- Penguin.
14 Dec 09
Originally posted by divegeesterI've never noticed that particular case, but sound has been a large part of fluid dynamics since its inception. In fact, people actually used to be trained to listen to pipes to determine whether the flow was laminar, transitional or turbulent, and to try and find strange eddy currents that could damage the pipes. Astounding!
This may seem a strange question but has anyone else noticed that the pouring of very hot water into a cup sounds a little different to doing the same thing with cold water. Maybe I'm imagining it, but to me there is a difference. Anyone here have a possible explaination?
15 Dec 09
Originally posted by PenguinSimply that the liquid becomes denser as it colds, waves can propagate through it more easily so the pitch goes up.
I think it is to do with the difference in fluid density between hot water (or milk) with particles mixed in it and the same fluid with the particles disolved.
I did here an explanation on a podcast (the Naked Scientists, I believe) but wasn't paying enough attention for it to stick in my sieve-like mind.
Maybe a physicist here could provide a better explanation?
--- Penguin.
21 Dec 09
1 edit
Originally posted by sonhouse"Nucleation Center" is what I meant by "Rough Surface".
but the water is at 101 degrees C, past boiling point, in the same cup on a stove it would bubble first while boiling, but in microwave, bubbling is delayed till the teabag touches it. I don't think it has to do with roughness. Maybe nucleation centers like what causes CO2 to bubble out of beer or soda, needs nucleation centers, bits of dust or some kind of debris to start building up bubbles on. Maybe the same thing in H2O.
Stoves heat differentially, while microwaves do not - or if they do it's not in the same way.
22 Dec 09
Originally posted by mortisdeadIf it was just the cooling, then it would work for all liquids. I am pretty sure I have tested it with tea and there was no rise in pitch (I will do another test with my next cup). I believe it needs to be a hot liquid with granuals disolving within it, such as hot chocolate or instant coffee but not tea, plain water or filtered coffee.
Simply that the liquid becomes denser as it colds, waves can propagate through it more easily so the pitch goes up.
Some more testing required, methinks.
--- Penguin.