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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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