Question

Upon opening a bottle of beer, you notice a cloudy haze that forms in the neck of the bottle above

the level of the beer. This cloud was not there before the cap was removed. Please explain quantitatively.

Hint: Beer is mostly water; most mass-market beers seem to be entirely water. The pressure inside the

neck of a bottle of beer is approximately 2 atm (about 2000 mb). Compute how high the RH could get in

the neck of a beer bottle immediately after the cap is removed. (The expansion is adiabatic.)

Answer 1

We know that , the pressure inside beer bottle is about 2 atm that is double of atmospheric pressure. Fizziness in beer is created by dissolved carbon diaoxide (CO₂).

When we open the bottle , the pressure inside the bottle reduces immediately. And the pressure in the neck drops very quickly to be equal to surrounding's pressure ( atmospheric pressure -1 atm). As we know that temperature is directly proportional to the pressure. So drastic decrease in pressure causes drastic decrease in temperature. And the water vapours in the neck condenses into a cloud and hence a cloud is formed at neck of the bottle when cap is removed. The dissolved CO₂ also forms bubble at the bottle surface.