Physics thought question

Goldy

I thought up a little mind bender this afternoon and wanted to see what everyone thought the outcome would be.

If you had an airtight container with 0% humidity and you placed a bowl of water in it, what would the humidity in the air tight box after it reaches equilibrium?

I'll post what I think is the correct answer on Monday.

xmacro

Wouldn't it depend on the air temp?

dwayne3307

xmacro:

Wouldn't it depend on the air temp?

i was thinking this too

Joeyjoe21_8

i thought this too..but just to be a smart ass with a answer..ill just say 100%

sightunseen

Is it a vacuum inside?

stephen_hannibal

sightunseen:

Is it a vacuum inside?

+1

DSWarmack

Is there any circulation?

beatnic

To achieve 0% humidity, the air has to approach 0°C. The water would be frozen! And the RH would be 0%
The real question is how to get the bowl of water into the container without letting in ambient air?

bigharpoon

Intuitively I would have to go with 100%, unless it's a tiny bowl of water in an enormous box. Anything less than 100% the bowl would be empty and all the water would have been absorbed into the air and the air would still have potential for more moisture.

zoom6zoom

Schrödinger's humidor?

BlueRings

I am no physicist but at 100% humidity water vapor the tempature would need to be higher than the outside tempature which would cause condensation. Air holds more water the higher the tempature right!? It would not cause rain because of the need for mass and air flow however it would condense and cause the inside to sweat. Just my theory based on no fact.

YankeeMan

I've got a headache!!! Thank God I teach Criminal Justice and not physics!

cabinetmaker

Altitude also is a variable, as is temperature. There is a nice formula to predict it if you'd like, I remember doing a lot of it in physics in college. I don't miss it. Look up Goff-Gratch (I think)..

Goldy

Now that I think of this a bit more I think I screwed it up. I forgot to say that pressure cant change in this magical air tight container. If we have an air tight container with no changes in pressure at an average temp and average elevation what would happen?

beatnic

So the container is perfectly dry. No moisture at all. 0% humidity at a constant temperature and pressure.
Magically, a container of water appears in the container. What happens to the humidity of the air inside the container?
It would equalize immediately. The temperature would remain the same and the humidity would reach that level of the surrounding atmosphere. At sea level, that would be 1 atmosphere of pressure (atm), or 30 inches of mercury). So there would be 30"Hg humidity, the RH being dependent on whatever temperature in the container is.

I may be totally wrong, but I'm a DANCIN FOOOOOL. Frank Zappa.

Goldy

Alright, I cant wait till Monday.

Since dry air is more dense than humid air and your volume is fixed, I dont think the air could pick up any moisture and would remain at 0%. If P and V are fixed you can't change the density which means you can't change the humidity regardless of the temp. Right?

beatnic

In fantasy land, a cloud would form and it would start raining, the drops being absorbed by the air just as it reaches the surface. The volume increase in the air would equal the volume decrease in the water bowl.