A bubble’s skin composed of a thin layer of water molecules sandwiched between soap molecules. Water has a high surface tension due to intermolecular forces. This causes molecules to pull on one another, trying to minimise the surface area and be as flat as possible. Soap reduces this surface tension. However the effect of surface tension is still present which causes the bubble ‘film’ to be stretched. A sphere is formed because this shape is the shape with the least amount of surface area for its available volume
