Black Haired Girl Making Soap Bubbles Down By The Lake

Physics
Surface tension and shape
A soap bubble can exist because the surface layer of a liquid (usually water) has a certain surface tension, which causes the layer to behave somewhat like an elastic sheet. Soap film is extremely flexible and can produce waves based on the force exerted. However, a bubble made with a pure liquid alone is not stable and a dissolved surfactant such as soap is needed to stabilize a bubble. A common misconception is that soap increases the water's surface tension, soap actually does the opposite, decreasing it to approximately one third the surface tension of pure water. Soap does not strengthen bubbles, it stabilizes them, via an action known as the Marangoni effect. As the soap film stretches, the surface concentration of soap decreases, which in turn causes the surface tension to increase. Thus soap works by selectively strengthening the weakest parts of the bubble, preventing any one part of the bubble from stretching excessively. In addition, soap reduces evaporation, making the bubbles last longer; but this effect is relatively small.