• Question: Why do Bubbles go upwards in a fizzy drink?

    Asked by cathkidston to Martin, Rob, Suzanne on 22 Mar 2012. This question was also asked by courteney4.
    • Photo: Suzanne McEndoo

      Suzanne McEndoo answered on 22 Mar 2012:

      Because the bubbles are lighter than the liquid of the drink. They form at the bottom or sides of the glass because they use the roughness of the surface to collect together and form, then once they’re big enough they just let go and float up. They also get bigger the higher they go, because the pressure from the water is less when they’re less liquid above them.

    • Photo: Robert Thompson

      Robert Thompson answered on 22 Mar 2012:

      Yes the simple answer is the bubble is less dense (its lighter), it’s exactly the same with helium balloons floating up or hot air balloons, The helium or hot air are less dense than normal air so they rise.

    • Photo: Martin Zaltz Austwick

      Martin Zaltz Austwick answered on 23 Mar 2012:

      It’s also to do with how pressure works – because pressure gets higher as you get lower in the drink, there’s more pressure on the bottom of the bubble pushing up than the top of the bubble pushing down. So the bubble rises!