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When boiling water, why is a kettle initially very noisy but then becomes quieter at boiling point?

If you’ve ever watched a video of a blacksmith making a sword or something, after he’s finished hammering it, he dips the red hot metal in the cold water, and you hear it sizzle, yes?

Same thing is going on here. Your electric kettle has a heating element, which gets very hot, about 2000 watts. The element is your sword.

Cold water + Hot Metal = Rapid heating on water molecules immediately around the element (sizzling noise).

Now those particles around the element are hotter than everywhere else, and they move away due to thermodynamics, and so now more cold water surrounds the heating element. Process repeats - cold water heats up rapidly, moves away, replaced by more cold water.

Now, once all the water has heated up to boiling point, there’s no more cold water to sizzle. Boiling water can’t get any hotter, so sizzling becomes the noise of boiling water.

Side note: Once your water is boiling at 100 Degrees C, your heating element will continue to heat, and the element will get hotter and hotter until the safety cut off turns the kettle off (by design).

/u/tgun782

(via sdsimple)

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