Why soap bubbles are spherical?
The skin of a bubble is composed of a thin layer of water molecules sandwiched between two layers of soap molecules.
Water on its own has a high surface tension due to intermolecular forces causing molecules to pull on one another, trying to minimise the surface area and be as flat as possible.
Soap reduces this surface tension, but the effect of surface tension is still present in a bubble, causing the bubble 'film' to be stretched. A sphere is formed as it is the shape with the least amount of surface area for its volume.
(Surface tension is the tendency of fluid surfaces to shrink into the minimum surface area possible.)
