[Daniel Migneault]

Daniel Migneault  asked the Naked Scientists:
   
Hi Naked Scientists,

yesterday my daughter blew some soap bubbles in her younger sister's warm bath, and some bounced on the surface of the bathwater. They actually made contact with the water and bounced back in the air, like a birthday balloon. Why would they not pop or sit on the surface?

Daniel from Ottawa, Canada


What do you think?

[RD]

Not just bubbles, droplets bounce too ...

[David Cooper]

That's beautiful. I'm guessing that there's some kind of weak bonding going on in surface tension (not molecular bonding, but left-over forces tend to make molecules stick to others) and that you require a water molecule in the right place to be sticking out a bit to form a connection with the other water surface so that they start to merge. There would then be some kind of unzipping process where the join between the two surfaces spreads outwards from there. If all the molecules are sticking maximally to the ones around them in their own surface, they aren't going to stick to the other surface anything like as strongly, so the bubble or water drop can bounce off again.

[wolfekeeper]

I think a lot of it is that there's a thin layer of air between the bubble and the water surface that can't get out of the way in time, so the bubble distorts and then bounces off.

Also dust on the surface of the water can help, or depending on the details, can act as a bridge and cause the bubble to pop.

[David Cooper]

Yes, that sounds more likely.

[Brook]

I too have noticed this effect at a hot spring i blew bubbles and was amazed as i watched the ones that hit the surface of the spring would bounce and roll on the surface of the water most only popping after they made it across

[Colin2B]

I suspect answer is similar to #3 but a layer of hot air or water vapour provides a separation.

[chris]

We did a kitchen science experiment on anti-bubbles a little while ago, which makes for an interesting read and has a nice video too:

https://www.thenakedscientists.com/sites/default/files/media/antibubbles-top.mp4