PIRA: 4C30.10

This demonstration requires a boiling flask, a stopper, a Bunsen burner, a heating stand, a pair of protective gloves, some water, and a tray for catching water.  The flask is filled roughly half-full with water and placed over the Bunsen burner.  Once it has been boiling for a half minute or so, long enough for the air inside to be displaced by steam, the stopper is inserted into the flask.  While wearing the gloves, turn the flask over in the stand and put the stand in the water tray.  Cool water is then poured over the flask.  This cools the steam inside, causing it to condense, leaving the inside of the flask at relatively low pressure.  Since water boils at lower temperatures with lower pressure, the water inside will begin to boil again.