From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: Shaking up a Coke can
Date: 29 Nov 1995 20:15:31 GMT
Organization: Consulting Chemist
Lines: 36

In article <30badfd2.13411696@pubnews.demon.co.uk>,
Oz@upthorpe.demon.co.uk (Oz) says:

>crs <chucksz@ultranet.com> wrote:
>
>>Query:  Take two cans of Coke - same amount in each - shake one - don't shake the 
>>other.  Is there a difference in pressure?
>
>Yes, try it with a polybottle of coke and detect the
>pressure by feeling the tension in the bottle sides.
>
>Standard technique when opening polybottles handed to you by
>'innocent' children with a "can you open this please daddy".
>
>NB Also applies to larger children too, and even adults on
>occasion.

Shaking a bottle of soda does not increase the maximum pressure
in the bottle, it merely accelerates the attainment of 
equilibrium pressure if the bottle has been vented recently.  
If you allow the container to sit for a while after it has been 
opened and reclosed, it will no longer become firmer on shaking.

Agitation merely creates bubbles which act a nucleation sites
for the carbon dioxide and thereby increase the rate of 
diffusion from condensed phase to gas phase and vice versa. The
relative rates remain constant.

Jerry