How does water extinguish fire?

[MR]

How does water extinguish fire? My 5-year-old brother asked me, and now I'm really curious.

 

[imabug]

Fire needs two things: oxygen and fuel.

Water cuts off access to oxygen, and cools the fuel to below combustion temperature.

 

[MR]

OK, now I'm feeling REALLY ignorant...
What's combustion temperature?
Also, I've heard a number of times of using water as a cooling agent (especially in nuclear reactors), but why does water cool things down so well?
Thanks!

 

[imabug]

Also, I've heard a number of times of using water as a cooling agent (especially in nuclear reactors), but why does water cool things down so well?
Thanks!

water has a high specific heat, meaning it takes a lot of energy/heat to increase the temperature of 1 gram of water by 1 degree Celcius

 

[russ_watters]

Fire needs two things: oxygen and fuel.

Water cuts off access to oxygen, and cools the fuel to below combustion temperature.

Make that 3 things: oxygen, fuel, and heat. Your description has all 3.

MR, when you strike a match, you are using friction to increase the temperature of the phosphorous on the match head above its ignition temperature - the temperature at which it starts to burn. After it starts to burn, it expends more energy than is needed to keep the fuel burning - so it stays lit.

Welcome aboard!

 

[imabug]

Make that 3 things: oxygen, fuel, and heat. Your description has all 3.

right, heat. i always make that mistake. I figure if you're talking fire, heat's pretty much a given.

 

[MR]

Thanks, people...This is so cool!