What happens if you pour boiling water on a fire?
In: Chemistry
It’ll help put the fire out.
The water will still both cool the burning materials that are hotter than 100C, and will smother the surfaces to deprive them of oxygen for combustion. There would be very little observed difference in its effectiveness vs cool water.
Water needs a **LOT** of energy to go from 100C liquid to 100C gas. If you took a block of ice at just above absolute zero and heated it all the way up to 100 degrees C liquid you’d need to put in almost twice as much energy again to turn that 100 degrees C water into 100 degrees C steam.
The fire is weakened and the water evaporates. Because the boiling water is still water, it still does the job of cutting off oxygen to the fire, and because even boiling water is colder than fire, it still does the job of lowering temperatures, which both weaken a fire.
It should help put the fire out.
Will it help less than cold water? Yeah, a bit less. It won’t cool the burning material quite as much, and it’ll vaporize a bit more readily. But I don’t think you’d notice the difference, 99% of the time, as long as you don’t get any boiling water on yourself.
Even though the water is boiling it takes a substantial amount of energy to convert water at 100 C to gas at 100 C it is called latent heat. https://youtu.be/18pK7rPtAAk
It takes 3 things to make and sustain a fire. Oxygen, Fuel, and Heat.
Water takes care of two of those things. It can separate the Oxygen from the fuel and also absorbs a lot of heat (usually turning into steam) and causing the fire to go out.
Wood ignites at around 370°C, so even boiling water at 100°C is going to be much cooler and take away heat from the fire. The main key is that when water going from liquid to steam, it absorbs heat away from the fuel. So constantly dumping water with eventually put the fire out.
Now if your fuel is something liquid like grease or oil, and you put boiling water on it……run, run like hell and call the fire department (same goes for combustible metals like lithium cause water only makes it worse).
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