John Barry, age 16, of Toledo, Ohio, for his question:

HOW HOT MUST WATER BE TO BOIL?

Boiling point is the temperature at which a liquid bubbles and turns into a vapor. This bubbling is called boiling.

At sea level, where the atmospheric pressure is 14.7 pounds per square inch, water will boil at 212 degrees Fahrenheit. At higher altitudes, where atmospheric pressure is lower, water boils at lower temperatures.

The boiling point is about one degree Fahrenheit lower for each increase of 550 feet in altitude. At lofty heights, the boiling point of water is so low that food cannot be cooked in open vessels.

Not all liquids boil at the same temperature.