system
Given the following post, respond as if you're commenting on Reddit:
human
What about water puts out a fire?

Is it blocking off the fuel from making contact with air? Stealing away the activation energy? Something else? All of the above?
gpt
Mostly, it steals away the energy from the area. The evaporation of the water requires a lot of energy, and thereby results in reducing the temperature. Hopefully below the ignition point of the fuel, so the fire is contained or even put out. Most everyday things will only burn if the heat is concentrated. Like a single log will not burn on its own, since it radiates too much heat away. You need to build a fire that concentrates the heat at the center to sustain the fire. Robbing it of just a little bit of that heat, and the fire is no longer sustainable.

But the steam produced also lower the oxygen density of the air around the fire. And the water no doubt also simply washes some of the combustible gasses out of the air, before it can reach any free oxygen.