– Why does putting the top on a pot of boiling pasta make it frothy and boil over?
In: Chemistry
Possibly the equilibrium is reached in the small section between the liquid level and the lid. This could either allow gas bubbles to re-entrain in the liquid and form an emulsion like layer of bubbles (once you start making bubbles there will be a chain reaction.)
Alternate the gas bubbles rising the the top cannot escape the liquid because equilibrium has been reached (gas/liquid phases) and no More gas can enter the gas phase and so are forced to develop a bubble under the liquid surface
Once the lid is removed the whole room above is unsaturated gas (air) and can absorb all the highly saturated gas vapour (eliminating the bubbles)
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