# Vacuum and temperature relationship

### How does one determine the temperature of a vacuum?

A vacuum doesn't affect temperature, as such. If there were a compete vacuum, there would be nothing in it to contain energy. Therefore, no. Dearest Vacuumologists, There's been a recent windfall of vacuum orientated questions recently and I felt the need to add my own? See this. If you want, though, you could choose to only call that a vacuum if the temperature is zero. By the way, the third law of thermodynamics says nothing can ever get.

But, wouldn't that imply that there always has to be at least one particle within an arbitrarily defined box?

Can there be empty space? Doesn't temperature require the presence of energy? Isn't temperature always the temperature of a collection of particles and not of space itself? If there are no particles, how can there be temperature?

If you count photons as particles as we ordinarily do then there are indeed particles in any otherwise perfect vacuum.

This is a bit different from the situation you might be picturing, in which temperature is a property of some fixed collection of particles. The temperature here accounts for the existence of the particles.

Cooling things down would leave fewer photons in the space. If i were to create a simple vacuum in a jar by means of a vacuum pump, what would the temp. Would it be equal to the surroundings room temp. And if i placed water in that vacuum would it boil or would i have to supply a little more heat? The water will start to boil when the pressure gets low enough. If the pump is good it will get the pressure low enough for the remaining water to freeze before boiling stops.

## Does A Vacuum Affect Temperature ?

The water will continue to evaporate until it's all gone, with the pump sucking the water vapor out. When the water is all gone, the temperature will drift back up to room temperature. Cooling a computer in a vacuum Q: If i created a partial vacuum maybe 20 Torr and placed a computer inside therefore a heat source and left the pump running would the vacuum help cool the computer? Or would the temperature increase just like it would in 1 atmosphere, perhaps even faster because of the lack of convection?

### Does A Vacuum Affect Temperature ? | Naked Science Forum

As you suggest, it would probably be harder to cool a computer in a partial vacuum. They can't function in a vacuum. If you want to cool a computer more effectively, air can only do so much.

You can do better by using something with a higher heat capacity, like liquid water. In a liquid-cooled computer, water is pumped in through tubes so that it passes near the hot components of the computer. Then the hot water is pumped away, cooled with a fan, and re-circulated.

You can even cool a computer by completely immersing it in a cooling liquid. Water is conductive, so it would short out the electronics and ruin the computer—but mineral oil has similar cooling properties and does not conduct electricity. Rebecca Holmes Follow-Up If temperature is the movement of particles, and absolute zero is zero movement, then if there are no particles to measure the movement of, is there any temperature at all?

I don't think so, personally. In school people sometimes say that "temperature is the movement of particles". Sometimes that's pretty close to a good definition, but in general it isn't.

Zero temperature means that some system is in the quantum state with the lowest possible energy. As we said above, if you define a vacuum as having no particles in it at all, including particles of light, it can only exist at zero temperature. Nothing real, however, can reach zero temperature. So the more common definition of vacuum is space that has no particles like atoms and molecules.

It does have some electromagnetic radiation in it, at a temperature of about 2.

Lets take a bell jar and put a thermometer under it. So before starting the evacuation, the pressure under the bell jar is the atmospheric pressure and the thermometer shows the current room temperature. When we now start the evacuation process an finish at a very good vacuum, which temperature will the thermometer show us?

Does the temperature decreases slightly caused by flowing air out of the bell jar or is there a temperature drop caused by the evacuation which causes a pressure decrease? So the boiling will essentially take place uniformly in the whole liquid. Phase transition from liquid to gas absorbs heat, and that is what will cool the water very quickly, as it evaporates. My guess is also that the energy loss will cool the water down to sublimation temperature solid-gas transition before it all evaporates, so that some parts of the liquid may be cooled down to freezing before they have time to evaporate.

But as boiling takes place everywhere, it actually breaks the remaining water into tiny fragments that cristallize, and possibly also collect some of the vapor to grow. Anyway, you apparently get snow. But the cooling is due to evaporation, which is very fast, much more than to radiation which has hardly any time to take place. Numerical evaluation We analyze what becomes of available heat to understand whether some water freezes directly.

This is a very rough approximation as the figures used are actually somewhat variable with temperature, but I cannot find the actual values for the extreme temperature and pressures being considered. The specific heat of water is 4. So my hypothesis that there is not enough heat available to vaporize all the water is correct, as only about one sixth of the water can be vaporized with the available heat.

The ratio between the two part is inversely proportional to the specific latent heat for freezing and vaporizing. These figure are very approximate. The ratio divides the remaining 4.

And it all happens rather quickly.