-such as the tension of water molecules.

As the saying goes, "draw water with a sieve". In fact, if you look carefully, you will find that the bamboo basket draws water with nothing: there are countless water films at the bottom and around the bamboo basket. What is the reason? We must start with intermolecular forces.

As we know, all matter is made up of molecules, and the molecules that make up matter are not only moving endlessly and irregularly, but also have both interactive attraction and mutually repulsive force between molecules. Under normal circumstances, the attraction between molecules is equal to repulsion. If the distance d between molecules is the equilibrium distance at this time, then when the distance between molecules is slightly greater than the equilibrium distance, the intermolecular force will show as attraction (if it is greater than 10 times the molecular diameter, there is almost no interaction between molecules). When the distance between molecules is less than the equilibrium distance, the force between molecules shows repulsive attraction. When the bamboo basket is immersed in water, due to the attraction of bamboo stick molecules to water molecules, when the bamboo basket is lifted, the distance between water molecules in the gap becomes larger, and the force between molecules shows attraction, thus forming countless water films.

In fact, any water surface has a water film. This is because some fast-moving molecules on the water surface keep running into the air (that is, water evaporates), which makes the distance between water molecules larger, and the attraction between molecules is obviously greater than the repulsion, thus forming the so-called tension, which makes the water surface look like a thin and elastic "skin". This is one of the reasons why many light insects can walk freely on the water. To say that the surface tension here is really not small, enough to make some light plastic rice baskets float on the water without sinking.

But if a part of the water film is destroyed, other parts will move under the action of gravity. For example, use a wooden pencil to cut open the core to make a boat, insert wax oil into the small hole drilled behind the boat, put the boat on the water, and the boat will move forward. This is because the wax oil in contact with water destroys the tension of the water surface, which suddenly reduces the tension of this part of the water surface, so the ship moves in the direction of greater tension. In addition, due to diffusion, wax oil molecules shoot at water at a certain speed, because the forces are mutual, which also produces a force to push the ship forward.

You see, how wonderful the world is, drawing water with a sieve. It is really important to pay attention to physics everywhere. Let's enjoy this beautiful world with a scientific eye!