Bubbles and Bubbles

Bubbles are usually made of soapy water that has been shaped into a thin film. The film catchs air in the center, causing the bubble to keep its round form until it pops. The adding up of soap to the water is significant. The cause why bubbles only really hold their shape when made with soapy water is that the soap stabilizes the outside of the bubble. The soap reduces the bubble's surface tension, which lets it to enlarge and hold its shape.

When the soapy solution is expanded across a surface (the end of a bubble wand, for example), it forms a thin, filmy sheet with quite low surface tension. As air fills the sheet, it takes on a spherical shape. This is because, as the solution stretches and the surface concentration of the soap drops, the surface tension rises. To recompense for this increase in surface tension, the bubble forms into a shape that puts the least amount of stress on the surface layer. For any given volume, spheres have the lowest possible surface area. This means that the surface layer has to stretch the least when forming into a sphere.

Why they pop?
The addition of soap to the external layer of the bubble reduces evaporation that plagues bubbles that are formed from water alone (such as bubbles blown in a drink with a straw). However, even soap bubbles burst in the end. This is can happen for a couple different reasons. The first is that soap bubbles are automatically drawn to other objects and bubbles. Generally, when they touch these objects, the bubbles pop.

Bubbles also achieve their most capability rather quickly, particularly if they are large. This is because, as the soap in the solution extends out, it's in nature drawn to the feebleest spots in the bubble. Though the soap stabilizes these feeble spots, it also tends to avoid them from enlarging any further. When pushed away from their limits, these areas explode.

Source:ehow.com

Watery Wednesday