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Old 10-22-2004, 07:33 PM
Peter3 is offline
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What is the sound of a tea kettle not boiling?


Before a kettle of water begins to boil it makes a popping and high pitched sizzling sound. I've looked inside and there isn't any boiling going on yet (no bubbles). So is the sound coming from the expanding kettle or the water or somewhere else (like my fragile psyche). Please tell me so that I might look even smarter in front of my wife.
Thank you,
Pete3
Frederick, MD
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Old 10-22-2004, 07:46 PM
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Microboiling.
Long before the bulk of the water in your teapot hits 100C, the bottom of the pot will be heated to over the boiling temperature of water. Water in contact with it will briefly flash into steam, but the resulting small bubbles will quickly collapse as they transfer their heat to the surrounding cooler water. If the bubbles are small enough (have a large surface to volume ratio), the collapse can be fast enough to make a popping or sizzling sound. This can happen even when the bubbles are too small for you to see.
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Old 10-22-2004, 08:38 PM
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What is the sound of a tea kettle not boiling?
WAG The same as the sound of a cow not mooing.
Squink has right idea. This will not happen unless the teakettle or pot/pan has several inches of water in it. The principle is the same as the explanation of how geysers work long prior to the eruption.
Old Faithful
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Old 10-22-2004, 09:30 PM
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Quote:
Originally Posted by spingears
Squink has right idea.
Do I get extra points for not mentioning any possibility of producing thermal neutrons in the collapsing cavities, when you replace the H2O with D2O?
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Old 10-22-2004, 09:33 PM
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Quote:
Originally Posted by Squink
Do I get extra points for not mentioning any possibility of producing thermal neutrons in the collapsing cavities, when you replace the H2O with D2O?
Absolutely!
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Old 10-23-2004, 08:25 AM
vetbridge is offline
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Quote:
Originally Posted by Peter3
What is the sound of a tea kettle not boiling?
If there is nobody in the kitchen to hear it, you could argue that it doesn't make a sound. When it isn't boiling.
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Old 10-23-2004, 09:13 AM
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"Subcooled nucleate boiling" will probably sound more impressive to the spouse than "Microboiling".
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Old 10-23-2004, 10:36 AM
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Cecil calls it "cavitation."
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Old 10-23-2004, 08:28 PM
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I don't think cavitation is the right word.

Granted "microboiling", "subcooled nucleate boiling" and "cavitation" are all involving tiny little regions of water who have a vapor pressure above the local vapor pressure (thus causing the water to turn into gas) and then the resulting gas moving to an area of higher local vapor pressure causing the gas to turn back into liquid, "popping" the bubble.

Cavitation is generally used to refer to an object moving through a liquid and causing low pressure cells in its wake. I.E. the bubbles form due to the lower local vapor pressure.

Microboiling and subcooled nucleate boiling result from the water on the heated surface being heated faster than convection or conduction can carry the heat away. So the water on the surface warms until it begins to boil. I.E. the bubbles form due to higher water vapor pressure.
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