# [Help] Expansion of air or due to formation of water vapour?

• dibilo

#### dibilo

Hi all,

I recently encountered this scenario.
I placed a (1 litre) glass bottle with water (about half filled) that is corked up near my stove.

My wife was cooking and the cork suddenly popped.
We discussed this over dinner and I said that it was due the air in the bottle that has become heated and expanded.

My wife said it is due to some water turning into water vapour and cause the build up in pressure. I thought that make sense but I am interested to know what really happens in that scenario. Is it mainly due to air expansion or water turning into water vapour that has caused the popping of the cork?

I vaguely remember what I learned in college about the bombardment of molecules but many years has passed and much has been forgotten.

I think there is not much to debate. If you heat up the bottle both the pressure of the air above the water and the pressure of the water vapors will increase.
You cannot say than only one of them popped the cork. It may be possible that one contribution will be larger than the other.

One of the tables in http://en.wikipedia.org/wiki/Vapour_pressure_of_water" [Broken] shows you how the vapour pressure of water changes with the temperature.
Around room temperature, the vapour pressure is not a lot but, of course, at 100C, the vapour pressure is 1 Atmosphere (100kPa). Warming water just from 20C to 30C changes the vapour pressure from 2.3kPA to 4.2kPa (an excess pressure in the bottle of 1.9kPa - assuming the cork was pushed in at 20C).
The change in air pressure for the same temperature change would be 100kPa times the temperature ratio (in K - because you have to refer it to absolute zero, -273K)
That would be 100X303/293 - or 103.4kPa- another 3.4kPa

The total excess pressure would be 1.9 + 3.4 = 5.3kPa or about 1/20 Atmosphere. Enough to push out a loose cork.
For a bigger temperature increase, the vapour pressure would start to dominate.

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Thank you both for you fast reply.

My wife and I are both Science lovers so whenever sure things happen, we will be excited and confused as well due to our limited knowledge.

We have learned something interesting today.

Thanks again!