The round shape of a bubble is due to the competing forces of the air within, and the liquid surface of the bubble, which prefers the least amount of surface area. A sphere is the shape with the least amount of surface area for the volume within. So, when air or gas is forced inside of a liquid shell, a sphere is naturally formed.You may have noticed that when you’re getting ready to blow a bubble with a bubble wand, the soap film will create a flat plane.
This is also the shape with the least amount of surface area for the amount of volume. In this case, however, the volume of air contained by the liquid just happens to be zero.