John Kolach, age 9, of Albany, New York, for his question:

How does water put out a fire?

A wad of dry paper needs only a match to make it catch on fire. But a wad of wet paper refuses to burn. When fire logs are left out in the rain, we have to wait for them to dry out before we can burn them. Wet wood and kindling either refuse to burn or need a lot of blazing hot kindling before they make a good fire, It stands to reason that a pail of water will soak the wood of a blazing campfire and douse the flames. Water has certain tricks that help either to put out a fire or keep it from starting.

Burnable materials must be warm enough to reach a certain temperature called their kindling point. Water cools things off. It lowers the temperature needed tokeep the fire burning. The fire also needs oxygen to keep blazing. It gets its oxygen from the air. When cold water hits a blazing fire, it warms up and some of it changes into steam. A thick cloud of dense steam tends to shut out the air and its oxygen. The fire chokes from a shortage of oxygen and dies because its water logged fuel becomes too cod to burn.