Eli5: when the water is in a state of rolling boil, why do the bubbles appear to ascend from particular pinholes in the bottom.

Question

These said pinholes change from each boiling session.

In: 139

Answer 1

Nucleation.

The surface of the pot isn’t smooth. The bumps are where the bubbles form, grow, & rise from.

The same answer (nucleation) is why putting Mentos in soda/pop causes such a mess – CO2 under pressure is dissolved in the syrupy liquid, but takes advantage of the (microscopically) rough surface of the candy to come out of solution.