MadSci Network: Physics

Re: it posible to make soap film or bubbles in vacuum ?

Date: Mon Apr 2 14:36:35 2001
Posted By: Richard Bersin, Other (pls. specify below), Senior Technical Staff Member, Emergent Technologies
Area of science: Physics
ID: 985682351.Ph

The ordinary soap bubble solutions are made of chemicals which evaporate 
rather quickly.  What this means is that when you blow a soap bubble with 
them in the air, the thickness of the film is very small and you note that 
in a minute or less normally the bubble breaks.  That is because as the 
film evaporates if becomes thinner and thinner and less weak, so that it 
then breaks under the stretching force of the higher pressure air inside 
the bubble.  If the bubble were blown in vacuum (if possible to do) the 
film would evaportate very much more quickly because there is not air 
present on the outside to slow down the evaporation and so the life of the 
bubble would probably be very very short.

However even more complicated, blowing such a bubble in a vacuum would be 
very difficult.  Remember the bubble grows because the air pressure inside 
the bubble is greater than that outside the bubble and this higher 
pressure causes the bubble skin to stretch out.(normal air pressure).
The easiest way to envision making such a bubble is to first imagine that 
you have a vacuum chamber with a pipe going through the chamber wall into 
the room, and with a valve on the room-end of the pipe.   Then you can  
inject a drop of soap-bubble liquid into the pipe through the valve. 
valve.  The liquid would be drawn through the tube towards the vacuum and 
when the drop reached the end of the tube it would form a film over the 
end of the tube and a bubble would form there.  The bubble would begin to 
form immediately and grow in vacuum depending upon the rate of evaporation 
of the liquid on the inside of the pipe.  It's life would depend on how 
fast the liquid evaporates away from the outside surface of the bubble 
into the vacuum.

In this way you should be able to make bubbles in vacuum but their 
lifetime may be very short!

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