"Don't pee on boiling water!" Everyone here must keep this sentence in mind, because if you are not careful, the boiling water may go upstream, and it may directly destroy the "tool for committing crimes".
Alas? Don't believe it, this is the famous Maragoni phenomenon in physics.
This phenomenon is in stark contrast to the ancient Chinese saying that "it is difficult to recover the water", which can not only be recovered, but also obediently come back by itself.
So what is the principle of this physical phenomenon that subverts everyone's common sense?
What is the Maragoni Effect?
The Maragoni effect refers to the fact that the liquid film of the liquid is disturbed by the external environment, which will make its liquid film locally thinner, and then it will form a Maragoni flow under the gradient of surface tension, so that the liquid can flow back to the thin liquid surface along the optimal route, so as to achieve the purpose of "repair".
Understanding the Maragoni effect by definition alone obviously does not give everyone an intuitive understanding of it, so let's explain it from its principle.
In fact, there is no other cause for the Maragoni effect, but it is the result of liquid tension. The greater the surface tension of the liquid, the stronger the pulling force on the smaller the surface.
Therefore, when there is a surface tension gradient in the liquid, the liquid with low surface tension will move along the gradient to the high surface gradient tension, forming the Maragoni flow.
For example, even if it is the same water, when boiling water with a high temperature is poured into the water at a low temperature, the surface of the boiling water will create a pull force and suck up the water at a lower temperature, making it look as if the water is flowing upstream.
Therefore, from the principle of the Maragoni effect, it is based on the change and gradient of the surface tension of the liquid, which leads to the flow of the liquid.
How was the Maragoni Effect discovered?
After explaining the principle of the Maragoni effect, let's take a look at how it was discovered.
One day in 2008, an Argentine physics student, after finishing his studies, planned to make himself a cup of strong tea to relieve his fatigue, who knew that something magical happened.
When the student was making tea, he was surprised to find that when he was heating water into the tea leaves, some of the powder in the tea leaves actually flowed back into the kettle with the water.
A spectacle of water flowing backwards opened up in front of this physics student.
And this student, who happens to be a good student who likes to break the casserole and ask the end, also told his mentor directly after discovering this phenomenon, and the two of them conducted research with great interest.
At first, the student's teacher thought that it was just a special capillary effect.
Here, it is necessary to explain what is called capillary action.
The so-called capillary effect refers to the attraction of the surface of the liquid to the surface of the solid. When the capillary is inserted to infiltrate the liquid, the liquid level in the tube rises to a higher level than the liquid outside the tube; The capillary is inserted into the non-wetting liquid, and the liquid inside the tube drops below the liquid level outside the tube. Such a phenomenon is called capillary phenomenon.
However, after studying for a period of time, the teachers and students found that this particular phenomenon is not a capillary phenomenon at all, but another phenomenon, that is, the Maragoni effect.
In this way, the Maragoni Effect was revealed to the world, and its discovery could not have been achieved without the observant student or the inquisitive spirit of his mentor, otherwise the Maragoni Effect might have been discovered some time later.
Application of the Maragoni effect
So are there any other examples of the Maragoni effect in life? The answer is yes, and there are many more.
First of all, one of the most common examples is the tears of wine, also known as the legs of wine. It is so called because after shaking the glass, the wine forms a thin film along the wall of the glass, and the alcohol in the wine is very volatile, after volatilization, the tension on the surface is out of control, and the wine spun and falls off the glass like a broken pearl.
This phenomenon is called "the tears of wine" by the romantic French.
In fact, this phenomenon is explained by unromantic physics, which is the perfect embodiment of the Maragoni effect. After the alcohol has evaporated, the concentration of alcohol on the walls of the glass decreases, leaving behind a liquid with a higher surface tension because the wine has more water and less alcohol.
In this way, a certain surface tension gradient is created between the wine on the wall of the glass and the wine in the glass. Since the area with a lower alcohol concentration pulls more on the surrounding fluid than the area with a higher alcohol concentration, the liquid is pulled up until its own weight exceeds the force, and eventually due to the imbalance between the gravity of the water and the surface tension, the water droplets fall and form wine tears.
Secondly, there is another cold knowledge in life that can reflect the Maragoni effect, that is, as mentioned at the beginning of the article, you can't pee in boiling water.
The temperature of human urine is generally more than 30 degrees, but the temperature of boiling water is generally more than 90 degrees.
Under the effect of the tension difference, the boiling water will cause some of the urine to flow back, so that the refluxed urine will bring back some of the boiled water. If you are not careful, you will directly confiscate the tools of the crime.
Therefore, from the point of view of physics, it can be explained why the older generation of people would advise children to "don't pee in boiling water" because it is too dangerous.
It can be seen that it is always right to learn more knowledge, which can help us avoid many dangers in our daily life.
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