Why do the water drops on the lotus leaf become small water drops? It turns out that the molecules on the surface of water droplets are attracted by internal molecules and tend to move inward. So that the surface of the water droplets will be as small as possible. To what extent? As we know, the size of a water drop is constant, and its surface is the smallest only when it becomes a sphere. So the water droplet becomes a spherical water droplet.
Let's take a look at the soap bubbles that children love to blow. Soap bubbles are filled with air, and the two liquid levels inside and outside the soap bubbles will shrink continuously until the air inside is pressed as small as possible, and it will no longer shrink. At this time, the soap bubble turned into a ball.
Molecules on the liquid surface are attracted by internal molecules, which makes the liquid surface shrink, which will cause the adjacent parts of the liquid surface to attract each other. This mutual attraction is called surface tension in physics. We can observe this surface tension through a simple experiment.
Use a wire frame with a thin cotton thread that is not taut. Soak it in soapy water, and there will be a thin and tight soap film on the wire frame. If you try to puncture the film on one side of the cotton thread with a needle, the film on the other side will shrink immediately. Because the cotton thread loses the surface tension produced by one film, it presents a curved arc under the surface tension of the other film.
The surface of any liquid has surface tension, and under the action of this surface tension, the surface of the liquid seems to be covered with a dense film. In summer, there are often many bugs running around freely on the water, relying on the tight water film on the water.