Bubbles in drinks

[AndiFlatland]

When you open a bottle of beer, soda pop or champagne, there is an immediate rush of bubbles to the top of the liquid. But they keep on coming for many hours, and I was wondering if there is any reason why they do not all come out at once. What mechanism determines whether a bubble will appear instantly the bottle is opened, or whether it will appear 8 hours or so later?

[theprof]

It’s all because of the surface tension of the carbonated liquid and the energy contained in it. This effectively keeps some of the gas bubbles in the carbonated liquid.

So what’s surface tension? Well, under normal circumstances, these carbonated liquids resist the expansion of bubbles. This happens because all water molecules attract each other strongly which results in them forming a tight mesh around each of the gas bubbles. Energy is required to push these water molecules away from each other to either allow a new bubble to form or to further expand an existing bubble. This energy requirement to separate the liquid molecules from each other during the bubble formation is what is called surface tension.

When a tiny bubble begins in a carbonated liquid, the energy needed per molecule of carbon dioxide in the bubble is comparatively large. This means that it’s pretty difficult to get started. However, once that tiny bubble is formed, a much smaller amount of energy is needed to expand the bubble. When you shake a bottle or can of carbonated liquid, lots of small bubbles are formed, which join together to form larger bubbles. These energy laden large bubbles escape very quickly from the carbonated liquid causing lots of fizz.

A carefully handled carbonated liquid in a still state in a wide-mouthed container is able to retain some of the gas for many hours as bubbles are formed at a very slow rate, have little energy to escape and held back by the mesh of molecules. Obviously, most of the get through in time causing the carbonated liquid to eventually go “flat”.

For more information on this Google “Mentos and Diet Coke” which shows the fun side of this phenomenon.

[vascop]

NOOOh that's rubbish! Gasses can be dissolved in liquids at low temperatures (depends on the gas and liquid) and as the temperature of the liquid rises the dissolved gas becomes gas again and forms a bubble. By keeping the liquid under pressure, more gas can be dissolved than normal. So when you open the bottle, the pressure drops suddenly and a lot of gas escapes (that which was dissolved due to the pressure on the liquid). Then, as the liquid warms the rest of the gas slowly come out as described above.

[theprof]

Vascop, you might find it beneficial in future to read the original question carefully before you reply. Your lack of appreciation of what happens at a molecular level has doubtless led you to use simplistic phrases such as "dissolved gas becomes gas again and forms a bubble" and "the pressure drops suddenly and a lot of gas escapes" which are what one might expect from a year ten school pupil. If you really wish to challenge my answer at least do me the decency of using the correct scientific terminology and substantive arguments as then I will listen to you.

Whilst temperature is important from a physical chemistry standpoint, it is not so in this particular case as careful reading of the question should have shown you. AndiFlatland did not ask about the gas/temperature solubility relationships - he was asking about carbon dioxide behaviour at normal room temperature. Don't complicate matters unnecessarily.

I note that you have avoided answering the final sentence of AndiFlatland's question. If you don't know the answer, let me know and I'll explain it to you in more detail.