View Full Version : [OT] Trick Question.
Dribble Joy
06-12-05, 00:33
What is the freezing point of pure liquid water?
What is the freezing point of pure liquid water?
I dunno - teh liquid bit suggest none. Ice would be frozen... I dunno. Curse joo!
Dribble Joy
06-12-05, 00:45
OK, if you take pure liquid water and cool it, at what temp does it freeze at?
Well technically isn't nothing truly frozen till absolute zero? Although pure water is 0 C (or is that tap and pure is like -1 to -10?)
Although I'm guessing I've missed something :p
OK, if you take pure liquid water and cool it, at what temp does it freeze at?
Freezing point is 0 degrees C, but that seems too easy.
wait
pure freezes more easily doesn't it? Not sure.
Curse you sir Dribblesworth.
DarkPhoenix
06-12-05, 00:48
0 deg. C?
Dribble Joy
06-12-05, 00:48
Things will truely freeze before absolute zero, but no 0 celcius is incorrect.
Well I'm stumped...
While were talking about water and such, did you know liquid water is more dense than frozen water?
Hang on...at 0 it is ice, so is it 0.0000000000000[and on and on]00001 C?
Got it - It freezes once it returns to zero after dropping below it.
http://wwwchem.csustan.edu/chem1112/mwfpdep.htm
check the curve.
Unless...
what molar? IIRC that has a bearing somewhere here...
or am i getting too sciency?
Dribble Joy
06-12-05, 00:52
Yes, densest water gets is at around 4 C.
Here's a hint, what really causes something to freeze?
//edit, still wrong, they aren't using pure water.
Yes, densest water gets is at around 4 C.
Here's a hint, what really causes something to freeze?
//edit, still wrong, they aren't using pure water.
whoops - EDIT
Loss of energy.
Either that or summat to due with teh solvents in a liquid...
O_o
You DO realise i'm no longer able to sleep now. :mad:
Dribble Joy
06-12-05, 00:57
OK, and where will that loss of energy occur?
No, nothing to do with solvents.
OK, and where will that loss of energy occur?
stop it - I'm going to bed.
Is this a specific latent heat question? As the energy is freed up from the transformation from liqiud to solid?
Dribble Joy
06-12-05, 01:54
Due to the laws of thermodynamics, systems move towards equilibrium.
Where those places of equilibrium lie, and the boundries between states lie is the key.
Zero Degrees C is the "triple point" of water - where all three phases - liquid, solid and gas can coexist - at atmospheric pressure.
Now, water forms a solid because thats the lowest energy state - however at higher temperatures the thermal activity of the molecule means they dont stay still enough to remain as a solid.
Cooling back to a solid, there is a point where tempreture will not change, because of the "activation energy" required to form the ridig solid structure, even though the final energy state is lower.
In short, I don't see the trick to this question, but can talk around it really well :P
Dribble Joy
06-12-05, 02:08
It's all about where and when and why water looses enough energy to become solid.
OK, unless you know this, you won't get it, or at least it's unlikely. You have to know more about the mechanics fo materials.
Transformer
06-12-05, 02:52
It's all about where and when and why water looses enough energy to become solid.
OK, unless you know this, you won't get it, or at least it's unlikely. You have to know more about the mechanics fo materials.
i do'nt know much but lemee just put the obvious out there and say that when water is changing in states its due to the molecules either increasing or reducing in speed, in this case reducing....my answer is thus whenever all of the pure water molucules stop moving.
In 1742, Anders Celsius defined the Celsius temperature scale with the freezing point of water at 100 degrees and the boiling point at standard atmospheric pressure at 0 degrees. The scale was reversed in 1744.
Dribble Joy
06-12-05, 02:55
The point being is that the freezing point does not determined by the internal energy of a substance.
Are you talking about crystal seeding ?
i.e. In a *perfectly* pure liquid you don't get the initial cubic lattice seed that the rest of the crystal can grow from
What is the freezing point of pure liquid water?
Well once it's frozen it's technically liquid anymore :p So "frozen" "liquid" water is an oxymoron. My guess is the freezing point of pure water is 0 celsius, but pure liquid water can't freeze or else it's pure frozen water or ice.
When the entire system including surroundingss has reached a temperature in which the water is beginning to change state and stays there at equilibrium?
Yes, i am a shite chemistry student [edit] and im tired.
Dribble Joy
06-12-05, 03:01
Are you talking about crystal seeding ?
i.e. In a *perfectly* pure liquid you don't get the initial cubic lattice seed that the rest of the crystal can grow from
Winnar.
Ultra purified water freezes at about -40 C :p.
If you add particulates to this, the water will freeze immidiately and the temperature will rise to 0.
Are you talking about crystal seeding ?
i.e. In a *perfectly* pure liquid you don't get the initial cubic lattice seed that the rest of the crystal can grow from
/e salute.
Dribble Joy
06-12-05, 03:08
Ice forms around solid particles (be that allready present ice crystals, ions or other impurities), as the energy required to reach the lower energy state of a solid is higher there.
Remove all the particles so that the biggest things around are the water molecules, and you only get freezing when nuclearisation occurs around them themselves, which requires you to lower the internal energy significantly.
The process is used the other way round in metal forging so that you get a finer grain structure.
This also applies to boiling, as an aside.
Dribble Joy
06-12-05, 03:19
The mechanics of boiling are slightly diffrent, and impurities don't play as much a role (if any afaik, any particulates will 'cause' boiling to acellerate, but that's mostly due to the surface/area ratio they provide. The actual internal energy require to vaporise is dependant on pressure - desperately tries to remember more stuff from thermo lectures).
The issue is similar, if not the same process - to get the boiling going, you need to "cavitate" - create air pockets. However, in pure water on smooth surfaces, the vapour pressure involved means the cavaties get absorbed back into the bulk again before they can grow again. Adding "boiling chips", or aerating the water can help alevitae this.
So erm yeah, its a differnt process, but similar issue.
Dribble Joy
06-12-05, 03:29
Boiling is a point where the internal energy of a substance for a given pressure reaches a point where it will change state, whether that occurs on the surface or within the liquid is irrelevant.
Bah, anyway, more later, maybe
bed
Asurmen Spec Op
06-12-05, 03:34
What is the freezing point of pure liquid water?
From what I remeber, if you use pure water and a pure container it wont freeze till disturbed....
I think I heard something like that from my physics teacher...
Don't confuse boiling with evaporation.
vashtyphoon78
06-12-05, 04:32
Zero Degrees C is the "triple point" of water - where all three phases - liquid, solid and gas can coexist - at atmospheric pressure.
Now, water forms a solid because thats the lowest energy state - however at higher temperatures the thermal activity of the molecule means they dont stay still enough to remain as a solid.
Cooling back to a solid, there is a point where tempreture will not change, because of the "activation energy" required to form the ridig solid structure, even though the final energy state is lower.
In short, I don't see the trick to this question, but can talk around it really well :P
Woot for talking circles around DJs question :p
Winnar.
Ultra purified water freezes at about -40 C :p.
If you add particulates to this, the water will freeze immidiately and the temperature will rise to 0.
Gah - I was on the right track with my solvent thinking...
OMG DANGEROUS ;) (http://www.dhmo.org)
Bugs Gunny
06-12-05, 14:05
As a scubadiver i know that there is no inbetween for 4°c and 0°c water underwater.
It's either 4 in liquid state or 0 and below in frozen state.
If this wasn't true then all the bottoms of the oceans would be covered with ice, since there hardly ever gets any light down there.
Asurmen Spec Op
06-12-05, 14:58
As a scubadiver i know that there is no inbetween for 4°c and 0°c water underwater.
It's either 4 in liquid state or 0 and below in frozen state.
If this wasn't true then all the bottoms of the oceans would be covered with ice, since there hardly ever gets any light down there.
Remember, hes talking about pure water
Bugs Gunny
06-12-05, 15:13
Same thing.
It's not like some dirt and grime changes a lot.
In the oceans the salt changes some true, but the same thing aplies.
To add to the special things about liquid and solid:
Do you guys know what the state of glass is?
Same thing.
It's not like some dirt and grime changes a lot.
In the oceans the salt changes some true, but the same thing aplies.
To add to the special things about liquid and solid:
Do you guys know what the state of glass is?
Hi-viscosity liquid.
yes it does. The sea is a solution - look at the cooling curve for solutions.
http://wwwchem.csustan.edu/chem1112/mwfpdep.htm
See if you can name a Subliming solid by the way :)
It's like word association but with chemistry!
Dribble Joy
06-12-05, 16:34
Don't confuse boiling with evaporation.
The physical process is the same. The difference being that boiling can occur other than the surface of a liquid.
Remember that water will boil explosively when exposed to a vacuum.
Even distilled water is by no means pure, there are smal ice particles, dust and othe rimpurities. You have to filter water through about 200nm mesh to get it to freeze below -30C. So yes, grime and dirt can make a big difference.
Glass is a super cooled liquid btw.
WHooooooooooooooooooooooossssssssssshhhhhhhhhhh
See that fly over my head :confused:
You guys :lol:
See if you can name a Subliming solid by the way
Dry ice
Ahh thought so when i clicked the link, no point to this topic. :P
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