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 Posted: Fri Aug 10, 2007 7:51 pm
This was something very random that appeared in my head, but which state of matter, if any, heats up faster than the other states of matter?
Of course, I mean a single element. Other elements may differ in how fast they heat up in relation to their states of matter.
For instance, does 100 grams of pure solid water heat up faster than 100 grams of pure liquid water?
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Posted: Fri Aug 10, 2007 8:20 pm
You mean temperature change per unit energy put in? Yeah, liquid water at 25C heats up more slowly than ice at 0C, which heats up more slowly than water vapor at 100C.
The concept you're looking for is specific heat capacity, which is dependent on all sorts of factors such as temperature and pressure, so the state of the material doesn't exactly determine the rate of heating.
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Posted: Fri Aug 10, 2007 9:49 pm
But what if pressure and the rate of energy put in are constant?
I think I understand the general concept now, thanks, but...
I'm really trying to look at this down to the smallest particles.
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Posted: Fri Aug 10, 2007 11:47 pm
Well, suppose that the pressure is constant. Then, in a gas at least, when you increase the temperature, the volume has to increase, in accordance with the gas law PV = nRT.
So you have to specify that the pressure remains constant, because if you want the volume to remain constant, then you get a different specific heat capacity. A gas forced to remain at the same pressure will heat up at a different rate than a gas forced to remain at the same volume.
Both of them are dependent on the current temperature; the rate of temperature increase relative to energy increase is not linear, so we can't just say that it's a particular number; how fast something gets hotter depends on how hot it already is.
The problem with trying to look at it from a particle perspective is that temperature, and all of thermodynamics, isn't about particle behavior, but rather about the behavior of large groups of particles interacting with each other; it's all about emergent effects, things that can't be easily predicted or even understood at the individual level.
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Posted: Sat Aug 11, 2007 8:30 pm
Yeah, I know... I've studied a lot on gas laws with temperature and pressure.
That's kinda what I meant, sorry. Keeping one constant at a time.
I just want to experiment with this. i'm trying to find a way to keep one of the constants while changing the temperature. Then switching it up a bit so I can test the pressure, while keeping the temperature constant...
It all came back to me now, just in time for college... again... domokun
Ok, so let's say H2O (solid) is at -30 degrees C. I heat that up 30 degrees with constant energy. record time.
H2O (liquid) at 10 degrees C. Heat that up 30 degrees with constant energy. record time.
(same with gas, but that may be a bit hard to experiment because of its excitement. biggrin )
So, both have been heated up the same constant rate of temperature, and the same amount of degrees. So, which one would reach the 30-degree limit first? second? third?
and why would liquid (water) be the slowest of heating, like you said?
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Posted: Sat Aug 11, 2007 11:59 pm
Water's funny, and I'm not quite sure why because I'm not a chemist. All I know is "hydrogen bonds...um..." Most other substances are relatively sane, with the gases heating up more quickly than the liquids which heat up more quickly than the solids.
As I am not well-versed in thermodynamics either, I can only make conjectures at this point. Take it all with a grain of salt, and perhaps a glance at Wikipedia.
For non-water substances, the solid form has the least freedom; everything is attached specifically to everything else, and if something moves, the rest of it has to move. Hence, since it is difficult to get everything to move together, getting it to move at all is difficult. Hence solids take longer to heat up.
Gases, in contrast, have almost completely disconnected molecules, each completely free to move, so the temperature can increase more easily.
I'd imagine that plasmas would heat up even more quickly than gases, and that Bose-Einstein condensates would heat up even more slowly than solids. Liquids are in the middle, having middling properties.
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Posted: Sun Aug 12, 2007 2:47 pm
Talking about a grain of salt, why is it that ice melts faster if you put salt on it.
I know its true, but I've never understood why.
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Posted: Sun Aug 12, 2007 9:24 pm
Dewdew Talking about a grain of salt, why is it that ice melts faster if you put salt on it. I know its true, but I've never understood why. It's not just putting salt on it that helps, it's putting salt in it. Or more specifically, dissolving salt in the liquid water on the ice. Dissolved particles prevent crystals from forming by getting in the way of the bonds being formed, and thus prevents liquid water from turning into ice. Since "solid ice" is constantly turning from ice into liquid water and back along the surface, when salt is present then it dissolves into the liquid water and the liquid water gets trapped as liquid, instead of turning back into ice. Hence the ice melts faster.
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