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I was sitting watching my G&T which had a slice of lime in it, when I noticed that the lime sank to the bottom of the glass, and then rose to the top again, it then continued to repeat this cycle for some time. What is causing this behavior?

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Pieces of lime are slightly denser than a mixture of water and alcohol, and so they will naturally sink at first. However, they also encourage carbon dioxide gas to come out of solution and form bubbles by making the liquid around the fruit more acidic (and thereby reduce the amount of dissolved CO2 that it can hold). Unlike bubbles that form on the side of a glass and then detach, these bubbles will stick to the fruit and cause it to float to the surface. When sufficient bubbles have burst, the fruit sinks to the bottom again, and the cycle is repeated until no more CO2 will come out of solution.

  • Thank your for your answer, I am nearly there, however what is a nucleation point? – dougal 5.0.0 Mar 30 '17 at 16:22
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    It's a piece of dust/dirt or a defect (e.g. scratch) on the wall of the glass. Anywhere that the glass is not perfectly smooth, dissolved gas will come out of solution and form bubbles (nucleate). I'm not sure why this happens, but I suspect that it's something to do with surface tension. – Mick Mar 30 '17 at 16:26
  • Ah well, I'll never confess to the dirt/dust, but will confess to maybe a scratch or two on the glass itself! Thank you. – dougal 5.0.0 Mar 31 '17 at 3:40

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