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Re: [Phys-l] fizz-ics



SOME CO2 escapes with even a 'normal' container being opened.
When a fluid mixture is shaken - a semi-permanent (meta-stable) froth is left on the top surface.
If the container has froth on top instead of clean CO2 - then this froth with spray out and the accompanying turbulence MIGHT stir up more liquid.

Many years ago my students told me that a shaken can of soda could safely be opened IF it was rolled carefully across a SMOOTH surface a few times.
Others claimed that it was sufficient to gently tap the side of the can a few times.

Either of these exercises will in fact greatly reduce the amount of froth that will spew out upon opening.

Clear plastic bottle are now used to test these methods.

A carbonated beverage is in a metastable state. Add salt or mentos to kick it out of equilibrium.

Further serious research requires extensive consideration of several glasses of freshly drawn Guinness.


On Jan 9, 2008, at 10:27 AM, Anthony Lapinski wrote:

I have heard conflicting stories about what happens when you shake/ open a
can of soda.

I have gathered that shaking a can of soda does NOT increase the internal
pressure. The system is still in equilibrium. This can be felt by
squeezing the can. However, the soda will spray out when you open the can.
Is this because the CO2 bubbles are forced out of solution (after shaking)
and thus are more likely to come out of the can when it is opened?

If you do this with a 2L bottle (shake, open, recap, shake again), the
internal pressure appears to increase (felt by squeezing the sides).

Can anyone offer a simple physics/chemistry explanation of what's going on?

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