This is something I've observed when boiling water for tea.

I place the water in a metal pot and bring it almost to a boil. The water level is at about the middle of the height of the pot.

When the water is ready, I pour the water in the cup. Suddenly, when coming into contact with the side of the pot (that was not in contact with water beforehand), the water starts violently boiling and spraying around.

Clearly this suggests that the upper side of the pot is much hotter than the water itself. But why? After all, the water is in the pot, and the upper side of the pot is farther from the heat source than the water.

Why does this happen?

  • 3
    $\begingroup$ Why can’t the air next to the upper side of the pot be at >100°C, thus excessively heating the pot there where there’s no adjacent water to regulate the temperature? $\endgroup$ Oct 25, 2018 at 10:39

1 Answer 1


The lower half of the pot is in constant contact with the water, and so will never reach much above 100°C, even while the pot is being heated. The heat is constantly being carried away by the water.

The upper half of the pot is in contact with air, which is a poor conductor. As hot gases rise from your heat source (particularly if it's a flame), they can heat the metal above the water line to well above 100°C.


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