Absolute Zero

V

Votorx

Still egotistic...
Valued Senior Member
Well I don't know where to put this so I guess the mod can change it if I'm wrong.

Since it's impossible to reach absolute zero by cooling an object is it possible to reach it through pressure? If so is it known how much pressure is needed to get to absolute zero?
 
CAn you explain your reasoning a little more?
At the moment, if I recall correctly, they can get very close to absolute zero in part by using a laser to cool groups of atoms. But I cant see how pressure would make a difference.
 
Votorx said:
Well I don't know where to put this so I guess the mod can change it if I'm wrong.
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:confused:

It’s not always obvious in which section a post should be placed, but at least an educated guess can be made. Putting a pressure-temperature thread in Biology/Genetics over Physics/Math or General Science is a bit silly..... :D <P>
 
You can decrease the temperature of a gas by increasing the volume, ie PV=nRTsquared. Which is the ideal gas equation (not needed it since I left University) and says that basically the pressure times the volume is equal to the number of moles of gas times the ideal gas constant times the square of the temperature. FOr the explanation of how it works you'll have to wait until I can remember how it does.
 
Putting a pressure-temperature thread in Biology/Genetics over Physics/Math or General Science is a bit silly.....
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Lol true, I wasn't thinkin...

Wouldn't pressure increase the energy in a system?

Wouldn't it therefore not be easier to create absolute zero in a vacuum????
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I don't know that's why I'm asking. I know very little about pressure other than basic facts, I'm just using logic. My understand is if you add enough pressure to a liquid then it can become a solid. But maybe this is where I'm gettin confused, even though the liquid is now a solid due to the pressure, does its over all temperature actually change? Now that I think about it, I guess it wouldn't
 
spuriousmonkey said:
Wouldn't pressure increase the energy in a system? Wouldn't it therefore not be easier to create absolute zero in a vacuum????
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The idea for using pressure to lower temperature is what your air conditioner or refridgerator uses. First you compress a gas. Using the PV=nRT formula, we use Kelvin because it's an absolute temperature, unlike Celsius or Fahrenheit. Or you could use the Rankin scale, which is also absolute, but most people are unfamiliar with that.

Anyway, room temperature is about 300 Kelvin. Put the squeeze on, say 1,000 atmospheres, and the temperature tries to rise to 300,000 Kelvin, 50 times hotter than the surface of the sun. Oh, wait a minute, you want to cool something off, not melt the emblem off of Superman's costume. Ok, let your squeezed gas sample stand still, radidiating all that heat until it returns to room temperature.

Uncork it.

The temperature of the gas snaps down a thousandth of room temperature, or 0.3 Kelvin, just three tenths of a degree above absolute zero.

You won't actually get all the way to absolute zero with this method, but you can get close.
 
Maddad said:
The idea for using pressure to lower temperature is what your air conditioner or refridgerator uses. First you compress a gas. Using the PV=nRT formula, we use Kelvin because it's an absolute temperature, unlike Celsius or Fahrenheit. Or you could use the Rankin scale, which is also absolute, but most people are unfamiliar with that.

Anyway, room temperature is about 300 Kelvin. Put the squeeze on, say 1,000 atmospheres, and the temperature tries to rise to 300,000 Kelvin, 50 times hotter than the surface of the sun. Oh, wait a minute, you want to cool something off, not melt the emblem off of Superman's costume. Ok, let your squeezed gas sample stand still, radidiating all that heat until it returns to room temperature.

Uncork it.

The temperature of the gas snaps down a thousandth of room temperature, or 0.3 Kelvin, just three tenths of a degree above absolute zero.

You won't actually get all the way to absolute zero with this method, but you can get close.
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Something in that description reminds me of the big bang, somehow. Expansion/cooling. Our expanded universe now is pretty cold compared to the incredibly hot compressed beginning.
 
Do to one of those chemistry laws, if absolute zero is reached, there would be 0 volume, which is impossible.
 
Emmveepee said:
Do to one of those chemistry laws, if absolute zero is reached, there would be 0 volume, which is impossible.
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This assums that the gas remains a gas at these very low temperatures. It does not, so you never get a zero volume because liquids and solids do not follow the ideal gas laws.
 
This assums that the gas remains a gas at these very low temperatures. It does not, so you never get a zero volume because liquids and solids do not follow the ideal gas laws.
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I don't get it, why would it still be a gas?
 
Substances can be gases as long as the molecules are far enough apart that electromagnetic forces can't interact. According to PV=nRT, when the temperature goes down, either pressure or volume must. In an ideal world we can fix one and varry the other, but usually volume goes down along with pressure. So the molecules get closer together, the forces interact and they become liquid.

This reminds me: there's no chemistry section.
 
Indeed there isnt, but most chemsitry type questions fit into sveral forums, though it might be worth petitioning for one.

And welcome to sciforums!
 
Votorx said:
I don't get it, why would it still be a gas?
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A gas is a state of matter as would be a liquid or a solid. It is generally dependent on the temperature. The gas has the highest temperature; the solid the lowest. Gasses usually revert to a liquid and then to as a solid as the temperature drops.
 
Electrons 'jiggle'. The lowest energy state is not zero, and they cannot truly stand still. Hence the temperature cannot reach zero, either, since that's what our sensors pick up as 'temperature'.

That's roughly what 'the book' says if I remember correctly.
 
A gas is a state of matter as would be a liquid or a solid. It is generally dependent on the temperature. The gas has the highest temperature; the solid the lowest. Gasses usually revert to a liquid and then to as a solid as the temperature drops.
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Yes I realize that, but that wasn't my question. If something was able to reach absolute zero or atleast get near it, then how could it still be a gas? I can't think of anything that would still be a gas anywhere near that temperature.

Now lets say somethin did reach absolute zero, why would there be no volume? And no one has answered this yet, does pressure increase the over temperature or decrease it. I know that if there is enough pressure the matter can go through a phase change and an increase can change a liquid to a solid.But, logically the temperature of that substance would decrease as well, is that true or not?
 
Hence there are such things as latent heat, eg. when you are freezing water, you can draw a chart of the temperature of the water, looks like a big curve running from say +5 degrees C at teh top left down to -5 degree on the bottom right. except for a flat point at 0 degrees, where it changes from being a continuously changing curve to a flat line as the energy is taken out of the water to make it freeze. Or thats roughly how it looks, again, its years since I did anything like this.

What your looking for is information on Thermodynamics, there are quite a lot of websites that explain it.
 
guthrie said:
Hence there are such things as latent heat, eg. when you are freezing water, you can draw a chart of the temperature of the water, looks like a big curve running from say +5 degrees C at teh top left down to -5 degree on the bottom right. except for a flat point at 0 degrees, where it changes from being a continuously changing curve to a flat line as the energy is taken out of the water to make it freeze. Or thats roughly how it looks, again, its years since I did anything like this.

What your looking for is information on Thermodynamics, there are quite a lot of websites that explain it.
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It takes 4.2*10^3 Joule for each degree of temperature but it takes 3.3*10^5 Joule to convert ice to water without temperature rise.
 
spuriousmonkey said:
Wouldn't pressure increase the energy in a system?

Wouldn't it therefore not be easier to create absolute zero in a vacuum????
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As pressure increases, volume decreases (Boyle's Law). As volume decreases, temperature decreases (Charles' Law). Pressure and temperature rise and fall together (Gay-Lussac's Law of Pressure and Temperature).

So technically yes, because energy and heat are basically the same thing.
 
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