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Thanks Michael.

MrPloppy

Member
Try boiling the kettle with the lid off/open (if it has one) - it's a lot quieter as the sounds isn't as contained
I'll try that tonight. In the interests of fair science, I'll boil a pan with water in it and the lid ON. It will still be quieter! Why is that?

Also, in the interests of fair experimentation., I will be partaking in lots of scrumpy
Cider to help the evening along. Heck, I may even forget about the kettle and pan... ;)
 

Sandholme

Member
I'll try that tonight. In the interests of fair science, I'll boil a pan with water in it and the lid ON. It will still be quieter! Why is that?

Also, in the interests of fair experimentation., I will be partaking in lots of scrumpy
Cider to help the evening along. Heck, I may even forget about the kettle and pan... ;)
I suspect that there is more energy going into the kettle per unit time as kettles tend to boil quicker than pans, therefore the boiling will be more violent and noisier.
 

raydon

Well-Known Member
The water in the kettle is not all at the same temperature at the same time, not even when it is boiling. In particular when most of the kettle still is cold, but the element is getting hot enough to produce bubbles of steam, a bubble will suddenly explode into existence, creating a sound. However, what with the cold water all around it, it almost immediately condenses again into water, and thereby creates something pretty close to a vacuum. The surrounding water collapses into the space, typically fairly symmetrically. This means that the collapse ends abruptly at the centre of the bubble, creating something of a hammer effect. This makes a louder noise than the original steam explosion, which had ended comparatively gently.

In isolation the noise made by such bubbles is not particularly loud, but in a suitable kettle, particularly a metal one, the collapsing bubbles create the hammer effect directly onto the metal. Hammering on metal makes a loud noise, as you can tell by tapping your fingernails or a teaspoon against your metal kettle, or if it is not metal, tapping against the metal element inside the kettle.If you watch what happens on the element as the water heats up, you can see the bubbles forming and collapsing against the hot parts of the kettle while the noise is at its loudest.
When the boiling begins in real earnest, the surrounding water is pretty well at boiling point, and so it does not cause the steam to condense and collapse the bubble. Instead the bubbles of steam rise to the top and collapse with a gentle plop.
 

MrPloppy

Member
An excellent description, raydon! This describes the changes in sound as the water reaches boiling point. However, the question was about why a pan of water *doesn't* make a sound.

Shirley, its the same process going on! :)
 
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