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I know that surface tension plays a key role in the formation of a bubble. I guess a bubble contains air inside it. Now how is it so that a soap bubble contains air both inside it and outside it?

I will be grateful to an answer donor if he explains me the various stages of bubble formation. In brief "How to make a bubble from a glass of water, what are the various processes that take place during the bubble formation"??

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2 Answers

The air inside is at a slightly higher pressure than the air outside, so the surface tension times the change in surface area is equal to the difference in pressure times the change in volume under an infinitesimal defomation, by the principle of virtual work.

The processes that make a bubble are

  • monolayer formation when you extract the wand, with a thin sheet of liquid separating two soap monolayers.
  • Expansion of the monolayers when you blow on the wand, until they come close.
  • Bilayer separation and rejoining, which makes a topological change in the surface of the bubble, when the two bilayers touch.

None of these three processes have been studied in quantitative detail as far as I know.

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Thanks a ton. Your reply seems quite interesting. –  Primeczar Sep 4 '11 at 5:08
I hope you will be glad to attach a reference. –  Primeczar Sep 4 '11 at 5:10
I've also heard that a soap bubble has a very interesting property of self-regeneration. Don't know the details, but it's related to the fact that the water surface tension is much higher than that of soap, so that if the soap layer thickens in some location this leads immediate arrival of more water, change in the surface curvature, which in turns attracts more soap. –  valdo Sep 4 '11 at 12:10
@primeczar: I don't know a reference. –  Ron Maimon Sep 4 '11 at 15:09
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remember that a "soap bubble" is basically a very thin film of soap water that forms a hollow sphere, and exhibits iridescent surface. Soap bubbles usually last only a few seconds and then explode by themselves or by contact with another object.

The bubble is a thin layer of water trapped between two layers of surfactant molecules, often soap. These "surfactants" have hydrophilic heads and hydrophobic tails. The hydrophilic heads are attracted to the thin layer of water and maintain intact pump

The bubbles in the background and physical termios are a type of "container" gas and gas law says that "all gas pressure is constant and equal anywhere inside the body that contains it," ie, pressure is equal at any point within the container, what happens is that this contenerdor is not "solid" is flexible and dynamic is normally comes even balance between the force that the gas (air) that is exerted on the inner walls bubble by trying to expand and outside the bubble kept closed.

So why is spherical? that the force of contraction of the bubble is the same everywhere on the inner wall of the bubble, and the expansion of the air force is also the same in any part of the inner wall, both are dynamic,

So if you have a body which exerts a thrust force equal in all directions and one that contains fuerxza of contraction exerting the same in all web addresses ... the only way that can meet those conditions is the sphere, (Vector) talking.

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