Welcome Hiarthbeorn to the Black Tower!

[Mrs. Cindy Gill]

you forgot your ministry of silly posts font

[Wren of the Brown]

OH!  That's what I did wrong!

I guess I have to fill out a correction form.  In triplicate.  Drat and double drat.  Apologies without contingencies, one and all, for my ineptitude.  I had not realized silliness was such a serious thing!

*trods off to face the Black Tower Bureaucratic Corps*

[Mrs. Cindy Gill]

I'll prepare the comfy chairs

[Shadar Alantin]

I'll get the popcorn.

 

Oh in triplicate.

 

Sillyness is a most serious of issue. And it requires butter.

[Panchi]

What chances does Hiarth have of surviving Bureaucratic Corps?

 

They are trollocs

[Wren of the Brown]

Dearest Panchi, I work for a large corporation and I enjoy it.

 

Bureaucrats are nothing to me.

[Leyrann]

 

Yeah.

 

And you think that's the real meaning?

 

I guess you're going to have to show me where that post was made in sincerity.  With the disembodied organs farting and belching their way to glory, I had assumed a /silly tag was not necessary.

 

Goodness!

 

 

I didn't read the full post.

[Mrs. Cindy Gill]

skimmer tut tut

[Panchi]

Long posts and spam generally do not go together

[Leyrann]

Long posts and spam generally do not go together

 

They don't.

[Shadar Alantin]

 

 

Long posts and spam generally do not go together

They don't.

But I thought they were a match made in heaven.

[Panchi]

In Pit of Doom maybe >.>

[Shadar Alantin]

[Shadar Alantin]

[Panchi]

Shady, why would hot water cool a fire faster than cold water?. My book says it is because it gets converted to steam faster. Which makes no sense. My friend and I think it should be the other way round.

[Panchi]

Shady, why would hot water cool a fire faster than cold water?. My book says it is because it gets converted to steam faster. Which makes no sense. My friend and I think it should be the other way round.

[Leyrann]

When water vaporizes, it requires an extra boost of warmth, so I could see that actually working.

[Panchi]

So, it absorbs heat at a faster rate?

[Panchi]

Or it would continue to absorb heat at the same rate?

[Shadar Alantin]

Well water has a specific heat capacity, but transitions take more I think. So then when it is vaporizing, or melting, you have to put enought heat to keep it the same temperature, which is what happen for any phase transition. The temperature stays the same until all of the liquid is turned into steam.

[Panchi]

I went through the chapter again and got these results from a graph

14 J of heat energy were absorbed per second while water was heated

25.4 J were absorbed per second while water was converted to steam.

But graph was supposed to be constant heat supplied graph (at least so it was with other temperature time graphs).

 

 

Btw, give more explanation. I am not in eight grade you know (as much as I wish otherwise) and can understand things like latent heat (even an eight grader can)

[Leyrann]

Well, my brother (who has studied physics at university) was like "cold water works better", but he talked about the amount of water you'd need. Maybe you can do it faster with hot water. I'm not sure.

[Panchi]

So, my book was wrong? (quite possible)

[Mrs. Cindy Gill]

this is physics and that's almost math so ouch.

 

I googled and got many contradictions and reasoning for completely different answers.

 

this one made the most sense to me, but again, OUCH!

 

To sustain a fire, you need three factors: fuel, oxygen, and heat. Take away one of the three and the fire goes out. Water removes heat. Most of this "removing heat" is the evaporation - roughly 540 calories / gram, so 7x more heat than is needed to get water from 20°C to boiling (with a tip of the hat to @Jasper for pointing out erroneous value in earlier revision of answer). So using hot water is "a bit" less efficient for cooling (per unit mass of water added), but not as bad as you might think. And warm water will create (relatively) more vapor which will actually improve its role as an asphyxiant (pushing away atmospheric oxygen).

 

In certain kinds of fire, using water will not work well (or "at all"). That includes fires with liquid fuel - force of water can disperse the fuel into the air and thus the cooling doesn't happen where the fire happens (actually this can make things worse, since many droplets of fuel can now burst into flame away from the base), chemical fires (you might cause additional reactions, or just speed up the reaction by dissolving the components), and fires in which the fuel would react with water - for example certain kinds of metal fires (e.g. magnesium shavings, alkali metals, and the like). You also don't want to add water when there are other risks related to its use (for example high voltages present).

 

This is why many "general purpose" extinguishers tend to be of the "deprive of oxygen" kind - foam, powder.

 

Afterthought based on BeastRaban's answer: when water becomes vapor, it is lighter than air, with an atomic mass of 18 vs 29 for the usual oxygen/nitrogen mixture - but being generally cooler than a flame (most vapor will be around 100°C), it may slow down the rate with which fresh air is being drawn into the fire. As such, it is not only a coolant of the fuel (which slows down the rate of the exothermal reaction taking place), but also an asphyxiant, pushing away oxygen (or at least slowing down the rate at which it is being replenished).

so I think maybe they're saying that when you consider the smothering effect of the steam against the negligible difference in the efficiency of cold over hot water to remove the heat.... maybe hot water is a wee bit better. though I woukd factor in the time it takes to get hot water, that's not science.

 

tl;dr

 

the correct answer for you in this class is what your book and your teacher say is correct.

 

which may or may not be objectively correct but which will affect your grade.

[Panchi]

One teacher said one thing, another said another thing.

 

Thanks! It was a lot of help.