A soap bubble is an extremely thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface.
What fluid dynamical process occurs during the popping of a soap bubble?
[Physics] the physics behind a soap bubble
bubblesfluid dynamicssoft-mattersurface-tension
Best Answer
A bubble, while it still exists, is balanced by three factors:
1) Surface Tension of the soapy water.
2) Internal Pressure applied by the air inside the bubble on the surface.
3) Atmospheric Pressure.
When any of these are imbalanced, one force is greater than the others and this causes the bubble to pop.
If you're talking about why do they burst in practice? Well the bubble's surface is made out of soap water. Soap is lighter than water so when you create a bubble, the water is pulled towards the bottom of the bubble - pushing the soap upwards - due to gravity. Surface tension of water is higher than that of soap, so the upper part of the bubble is getting weaker as more soap is concentrated at the top. Soon, the internal pressure will be enough to break the bubble, causing it to burst.
Another reason is that the water gets evaporated, leaving it with a more concentrated solution of soap which - as mentioned above - has a lower surface tension.