🧵 Help me understand pressure and temperature.
Anonymous at Thu, 6 Jun 2024 22:43:29 UTC No. 16218238
This isn't homework. If you have a sealed tank of water at room temperature, and half of the water in the tank ceases to exist and is replaced with vacuum, after the water spread into the vacuum, what would the pressure be inside, still at room temperature. I swear this isn't homework.
Anonymous at Thu, 6 Jun 2024 23:23:21 UTC No. 16218330
>>16218238
take a fucking gas instead of water.
fluids like water are nearly incompressible, if suddenly half the water in a sealed tank ceases to exist, the only way for the rest of the water to spread into the resulting vacuum is to change into a gaseous phase.
but probably not all of it because liquid to gas water doesn't change at a 2:1 expansion ratio, but a lot higher, so in the end you end up with the sealed tank having a bunch of liquid water aswell as a bunch of gaseous water and your pressure would be all over the place because for the liquid pressure you need to consider how much of a mass of liquid is above you pressing down.
You wouldn't end up with 1 single p value for your container.
Now to your actual question, lets replace water with helium, and lets assume ideal gas law.
you have p*V/T = n R
left side is pressure, volume and temp, shit that you usually change
right side is amount of particles and gas constant, shit that always remains constant if you don't change the amount of particles.
Now in this case you actually magically take out half the particles, while leaving the volume and temperature exactly the same in your sealed tank.
so on the right side you have a new factor of 0.5
since temp and volume remain the same on the left side, the only thing that can change is pressure, which also gets halfed.
so the answer to your question using actually sensible examples, you'd have half the pressure inside if suddenly half the (helium) in a tank of constant volume and temperature ceased to exist.
Anonymous at Thu, 6 Jun 2024 23:27:09 UTC No. 16218345
>>16218238
"Pressure inside at room temperature" would just be vapor pressure, assuming isothermal not adiabatic. Just look up vapor pressure at room temp, or use Antoine equation for water.
Anonymous at Fri, 7 Jun 2024 03:08:17 UTC No. 16218744
>>16218238
What're you friggin' makin' this thread for, you're just gonna die.