Bubbles naturally “want” to be round (or spherical rather). Why is this?
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.
Why Do Bubbles Hate Surface Area So Much?
Bubbles prefer the least amount of surface area because of a phenomenon known as surface tension.
A bubble is usually composed using a water and soap mixture. Water molecules are attracted to one another like magnets are attracted to one another.
The oxygen molecule’s nucleus is larger than the hydrogen’s so it attracts more of the water molecule’s electrons. This imbalance of electrons creates polarity, so the water molecules are attracted to one another. The negative charge of the oxygen molecule is attracted to the positive charge of other hydrogen molecules, and vice versa.
Because the water molecules on a bubble’s surface are always “pulling” on one another in this way, a bubble’s surface will minimize until the force of the air pressure within is equal to the “pull” of the soap film.
A sphere is produced as long as there aren’t any other forces at play, which is why bubbles are almost always round.
…almost, learn How to Blow a Square Bubble.