Why does the tea kettle go quiet before it starts to whistle?
In: Chemistry
As pressure climbs, the boiling point of a liquid like water increases. While your kettle isn’t airtight, it is capable of building up some pressure. That very brief span where the boiling rattle stops before the whistling starts is when the internal pressure of the kettle has risen just enough to suppress boiling, but isn’t great enough yet to escape through the whistle.
As kettle heats, the conditions for boiling exist close to the heat (the bottom) bot not higher. Vapor bubbles form on the hot bottom and collapse almost immediately. You’re hear the collapse (cavitation, as noted elsewhere).
When the water heats sufficiently, the conditions for boiling exist all the way through, the bubbles escape through the surface with very little noise.
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