What makes bubbles pop?

The sudden release of tension energy from the bubble occurs as a sound. The energy had to go somewhere, so it comes out as sound energy (vibrations). :)

I don't know if this is what you were looking for but I believe that gravity makes bubbles pop. The soap bubbles skin keeps the air enclosed until gravity pulls enough of the skin to the bottom stretching the rest of the surface of the bubble to the fracture point.hope this helps