Have you ever been obsessed with beautiful soap bubbles? Do you know why soapy water can blow bubbles, but ordinary water can't? What plays a key role here is the surface tension of the liquid.
Magical "surface tension"
The distribution of molecules on the surface of the liquid is different from that inside the liquid. It is thinner than that inside the liquid. The interaction between molecules is mainly "surface tension", which makes the surface of the liquid shrink like an elastic film. In summer, some insects crawl on the water like walking on flat ground. The surface tension of water is one of the reasons. In addition, the shrinkage trend of this "elastic film" will "pull" the surface area of the liquid to the minimum, so the dew is "pulled" into a sphere. Of course, this is also the reason why soap bubbles are spherical. So, soapy water can blow bubbles. Is the surface tension of soapy water larger or smaller than that of ordinary water?
Try it yourself
Wash two identical cups, pour soapy water and ordinary water respectively, and add them drop by drop when the cup is almost full, so that the liquid level is higher than the edge of the cup. At this time, you will find that the bulge formed by ordinary water at the mouth of the cup is higher than that formed by soapy water. In other words, the surface tension of soapy water is less than that of purified water. It is precisely because the surface tension of ordinary water is too large, it is difficult to be blown open and form bubbles. When the soap is dissolved in water, the surface tension is reduced. Like a balloon, if the elasticity of the material is too strong, it will be difficult to blow, and if the tightness is appropriate, it is easy to blow into large bubbles.
"Pearl" on lotus leaf
The surface of the lotus leaf has a layer of very fine pilose hair, which makes the falling water droplets not easy to disperse. In fact, when the lotus leaf is observed under the microscope, it can be found that the surface of the lotus leaf is not smooth, with many mastoid structures and a layer of wax. These two characteristics act at the same time, so that the lotus leaf surface has strong hydrophobicity. The water sprinkled on the leaf surface will automatically gather into water droplets. The rolling of water droplets will also absorb the dust and sludge falling on the leaf surface and roll out of the leaf surface to keep the leaf surface clean all the time. This is the famous "lotus leaf self-cleaning effect". When scientists further study the microstructure of lotus leaves, they found that in addition to waxy components on the surface of lotus leaves, the generation of "lotus leaf effect" is related to two structures of lotus leaves, one is micron scale bulge and the other is nano scale hairy structure. These two structures are the main causes of the "lotus leaf effect".
Why are most insects afraid of being caught in the rain
The surface tension of water has different effects on animals of different sizes. After a buffalo or elephant takes a bath in the river, due to the surface tension of the water, they will be covered with a layer of nearly 0.5mm thick water. For them, the weight of the water is nothing. But for a mosquito, this thin layer of water is heavier than itself! So once those little insects get wet in the rain, they can't fly!