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Q & A: Bubble Shapes

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Most recent answer: 10/22/2007
Q:
What is the scientific reason that when a three dimensional object is dunked into soapy water the bubbles don’t stay on the sides but connect into the middle?
- Meredyth Boaz (age 11)
Bloomington, Il, McLean
A:
Meredyth -

The reason that this happens is because of something called surface tension, which you can think of as the force within a surface that is "streched".

Among other things, the fact that we have surface tension means that when you have a thin film of liquid, it will try to have the lowest surface area possible. That is, it will try to become the smallest sheet that it can given where its edges are. By connecting in the middle, the total area of the soap film is much smaller than if there were separate films for each side.

This is the same reason a balloon is spherical; this shape gives it the smallest surface area, thus causing the least amount of "streching".

-Tamara

(published on 10/22/2007)

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