When you were a child, were you ever fascinated by beautiful soap bubbles? Do you know why soap water can make bubbles, while ordinary water can't? The key factor here is the surface tension of the liquid. The surface layer of the liquid is different from the inside. Its molecular distribution is sparser than that of the liquid inside, and the main interaction between molecules is gravity, which we call "surface tension". This force causes the surface layer of the liquid to contract, like an elastic membrane. In summer, some insects can crawl freely on the water's surface, as if walking on flat ground. The surface tension of water is one of the reasons for this. In addition, the contracting tendency of this "elastic membrane" will "pull" the surface area of the liquid to the smallest possible extent, so the dew is "pulled" into a spherical shape. Of course, this is also the reason why soap bubbles are spherical.
So, does soap water make bubbles because its surface tension is higher or lower than that of ordinary water? Take two identical cups and wash them clean. Pour soap water and pure water into them respectively, and add them drop by drop until the liquid level is just above the rim of the cup. At this time, you will find that the bulge formed by pure water at the mouth of the cup is higher than that formed by soap water. That is to say, the surface tension of soap water is lower than that of pure water. Because the surface tension of water is too high, the water sticks together tightly, making it difficult to blow out bubbles. When soap is dissolved in water, the surface tension of water is reduced, making it easier to blow out bubbles. Just like a balloon. If the elasticity of the material is too strong, it will be difficult to blow it up, but if the elasticity is appropriate, it will be easy to blow it into large bubbles.