The surface tension of the interface between liquid and gas creates a pressure difference. For a soap bubble, the pressurized bubble of air is contained within a thin, elastic surface of liquid. When the bubble bursts, the difference in pressure causes an audible pop.

Why is the pressure inside a soap bubble higher than outside?

There are two free surfaces of soap bubble. Due to surface tension, the molecules on the surface film experience the net force in the inward direction normal to the surface. Therefore, there is more pressure inside than outside.

What is the pressure inside a soap bubble?

Pressure inside two soap bubbles is 1.01 and 1.02 atmosphere.