greenyppols
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which substance heats fastest?
Hi all
Been awhile since I perused the board. my ol' lady posed a question to me, which stumped me after thinking about it awhile.
Which substance heats up the fastest? water, soil, ice, air or granite? And why?
Dammit, she's been goin' to school lately and I have no idea where she got this from... my guess was ice..'cause I figured the molecules where
closer..but then I thought granite...then I figured I'd just ask the illuminati here!
Thanks!
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anotheronebitesthedust
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I would guess air, but that it also cools the fastest. ???
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BromicAcid
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Search specific heat capacity to see the actual amount of energy required to heat the substance of your choosing. As for the reason why, it varies
from substance to substance but it always has to do with a combination of physical and chemical properties unique to the substance.
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greenyppols
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I have no clue...I thought about it then lost my trains of thought in a wreck. lol. And when I asked about what conditions, like...are they in an
oven? in sunlight? under a UV light? She just told me to "just answer the question." So..I think Im about to get burned, then I'll never hear the
freakin' end of it.
Dammit, its getting harder to argue with her, too!
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greenyppols
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Bromic,
You mean the latent heat energy it can absorb or hold?
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Magpie
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How fast something heats not only is determined by its heat capacity but also by the mechanism(s) of heat transfer: radiation, convection, and/or
conduction.
Assuming this question is based on the surface condition of the earth, then radiation from the sun is probably the intended mode. In that case I
would guess air, as it has such a relatively low specific heat capacity.
[Edited on 10-9-2009 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Sedit
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Im more then likely wrong but my educated guess says water would heat the fastest under sunlight due to its fluidity, transparency, and density making
radiative heat more effective per square inch over air...... But then theres Ice that shares these simular properties and is already very low in
temperature an wants to equalize to ambiant temperatures..
Ouch.... that place where my brain is suppose to be hurts....
So does your wife know the answer and just testing you?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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greenyppols
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Here's what I found,
j/(g*k)
Ice 1.012
granite .790
water 4.1813
ice 2.05
Couldnt find anything on "soil". too many variables there I think...sand, muck, big rocks in it, dog poo, the dirt in my yard..I dunno.
Magpie - so if the lowest heat capacity determined which heated the fastest, that would be granite, wouldn't it? But...well, if its molecules are
close, I guess that would make some sense..I had thought of air, but couldnt find out if it was "pure" air, smoggy air, or water-vapor laden air...
Sedit - she's sitting just smirking at me. Im beginning to doubt SHE knows the answer and just wants to drive me nuts.
She thinks Im working on a history lesson I have to give tomorrow. lol. No scientist am I...
[Edited on 10-9-2009 by greenyppols]
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Sedit
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Water has the highest number so I win!
No but seriously you have Ice on there twice.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Magpie
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I'm thinking my first answer was wrong. Stone has about the same specific heat capacity as air, ~0.2 BTU/lb-F. But granite surely has a much higher
absorbtivity of sunlight than air. So, now I'm thinking granite would be the highest.
This is also backed up by common experience, ie, basking in the sun by a marmot (or a person) on a granite boulder on a cold morning. 
[Edited on 10-9-2009 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Sedit
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Yes Magpie but that is also just surface heat due to resistance of the substance to spread the heat through out.. Since we have no idea and I think
this guys wife if fucking with him  we have no other choice but to assume its
speaking of the whole of the substance reaching a stable temperature. With that I would have to assume that a "transparent" object able to allow more
collisions of photons per inch2 would win the battle. It sucks because the more I think the more it seems like Ice would win this race.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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merrlin
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The speed with which a material heats up is related to its thermal diffusivity = (thermal conductivity)/(density)(specific heat). Overall, it is hard
to beat diamond due to its relatively low density and high thermal conductivity. For the materials listed, I would guess ice.
[Edited on 10-9-2009 by merrlin]
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Sedit
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Low density compaired to what a blackhole?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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merrlin
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Compared to Ag, Cu, and Au, the metals that are closest to diamond in thermal conductivity. At 3.5gr/cc, diamond is less dense than most metals.
What's your point?
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greenyppols
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sedit - my first "ice" number was supposed to be air, I dont know why I mistyped it..prolly cuz my brain was shorting out...
Im gonna stick to my first thought, "ice." I dont really know why...
I did find out it was a question from her meteorology class...dont know what kind of meteorology class asks that though.... when I find out the answer
and they why, I'll let ya know.
Thanks everyone, glad it wasnt just me boggled by this. I guess I'll just to suck it up and live with defeat by my wife. lol. I guess its not so
bad...
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barbs09
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Greenyppols,
According to the specific heat capacities in your earlier post Granite is the winner at 0.790 j/(g*k) units. Ice at 2.05 j/(g*k) units requires over
twice the amount of energy to reach the same temperature (if I am understanding the physics correctly)
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Magpie
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As merrlin pointed out I don't think heat capacity tells the whole story. This is a very interesting and important question and I think must be
viewed in terms of the context in which it was asked, ie, meteorology, we later find out.
I hope greenyppols will sweet-talk his wife into giving us the textbook answer, and the reasons why.
The single most important condition for a successful synthesis is good mixing - Nicodem
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greenyppols
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Well, the ol' lady got the answer from her professor..It was granite.
Didnt get a more specific answer, though.
Thanks all!
now Im never gonna hear the end of it from her. dang it. 
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Sedit
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Do I win a prize for being the furthest off?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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merrlin
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I've seen thermal diffusivities published over the range of 1.1 to 1.7 square mm/sec for ice, and it appears that the thermal diffusivity of granite
can vary considerably (see attached). I suppose heating due to conduction could go either way. If the heat is provided largely by radiation, the
reflectance, absorption coefficient and dimensions of the materials would have to be considered, as well as the air speed and temperature. Internal
radiation absorption would favor ice under cold, windy conditions. I would normally expect ice to to be more reflective than granite, but I've read
that some impurities can greatly reduce the reflectance of glaciers. It seems that an unequivocal answer requires more information on the materials
and modes of heat transfer. I suggest you offer your wife a draw, or have her get more information from the professor.
Attachment: Thermal_properties_of_granite.pdf (94kB)
This file has been downloaded 631 times
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