Why do bubbles coalesce?

1. Apr 7, 2017

joshmccraney

Why do bubbles coalesce? I imagine it has to do with surface tension and pressure. The Young-Laplace equation states a bubbles pressure is inversely proportional to its radii. Higher pressure implies higher potential energy, so maybe bubbles coalesce to form a bigger bubble with bigger radii, and hence smaller pressure and less energy?

2. Apr 7, 2017

Khashishi

The surface tension tries to minimize the surface area. One big bubble has lower surface area than two smaller bubbles.

When two smaller bubbles touch, there's a seam between them. If a tiny hole develops in the seam, connecting the two bubbles, then you have a narrow choke between the two spheres. In the choke, the radius of curvature is very small, so it is very unstable. The Young-Laplace equation refers to a static situation, but gives the idea that the pressure is instantaneously not equal everywhere. Pressure will quickly equalize, which means the bubble needs to reshape itself into a sphere.

3. Apr 7, 2017

sophiecentaur

All the best (and most reliable) arguments are based on energy. "Good on yer!"

4. Apr 7, 2017

joshmccraney

Since energy is proportional to surface area, this is why surface area is minimized, right?