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Q & A: Boiling Water - Mystery Bubbles

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Most recent answer: 11/09/2015
When water boils, it bubbles. Where on earth do the bubbles come from? The air above the water? The water itself? The bottom of the pot?
- Eryn (age 15)
Kamloops Christian School, Kamloops, B.C., Canada
Eryn -

Strange though it may sound, the bubbles actually come from the water itself. When a liquid boils, it literally turns into a gas. For water, that gas is steam. As the water at the top of the pot evaporates (boils), the gas can go straight into the air. But when it evaporates (boils) at the bottom of the pot, it forms bubbles that have to float up to the top.


(published on 10/22/2007)

Follow-Up #1: trapped air bubbles

Some of the bubbles can also come from trapped air from the bottom of the pot due to the surface tension of the water and the space between the water/pot, right?
- Thuan Ly (age 27)

Yes, but those will soon be cleared out. Almost all the gas in the bubbles of boiling water is just water vapor.

Mike W.

(published on 11/09/2015)

Follow-up on this answer.