## Conceptual Physics (12th Edition)

Your instructor pumped a lot of air out of the (very thick-walled) flask before handing it over. A partial vacuum can drop the boiling point for water to well below $100^{\circ}C$. The instructor pumped just enough air out so that the water was just short of boiling (i.e., the boiling point was just a hair above room temperature). The heat from your hand is sufficient to boil the water under this reduced pressure.