Text | S.H.I.E.L.D.
When we were playing with fire as children, we always liked to be the fire-fighting heroes and then pee on the flames.
If adults see it, they will come over and scold you, and warn you not to pee in the fire or boiling water.
What is the principle of this?
1. Why can’t you pee in boiling water?
If I told you that boiling water would flow upstream and harm your family heirlooms, would you believe it?
Although it sounds unrealistic, the phenomenon of solution backflow does exist, and this phenomenon is very common.
One day in 2008, a physics student in Argentina wanted to make himself a cup of strong tea to relieve his fatigue in his spare time.
But when he was making tea, he accidentally discovered that a small amount of tea leaves in the teacup had flowed upstream and into the hot water kettle, which puzzled him.
I thought it was an accidental phenomenon, but after several experiments, I discovered that water can flow backwards.
So he recorded this phenomenon and reported it to the teacher.
After hearing this, the teacher was dubious and did another experiment himself. But when he saw the water flowing back with his own eyes, he was even more excited than the students.
So the two immediately started researching this.
At first, the teacher thought this was a special capillary action.
So what is capillary action?
In layman's terms, the liquid in the container will climb up to a certain height along the inner wall of the container.
For example, when we insert a thin glass tube into a larger container, we will find that the liquid level in the glass tube is higher than the liquid level in the container.
In addition, when we do experiments, we will find that the solution in test tube always presents a concave shape.
This is all caused by capillary action.
But after two people's research, they found that this was not capillary action at all, but a more special Maragoni effect.
2. Do you know what the Maragoni effect is? This magical effect can make water flow backwards. What exactly does it work on?
The teacher and the student studied the teapot for a long time before finally figuring out its principle.
It turns out that this is the surface tension of the liquid at work.
In official terms, any liquid has a special tension. When the liquid is stationary, a film will appear on the surface, which is called a liquid film.
This film is very special and has a certain self-protection function. It is mainly manifested in that if an external force pulls the liquid film and causes the local liquid film to become thinner, it will generate a tension to restore itself to its original shape.
This tension will form a Maragoni flow, allowing the liquid to flow back to the thin liquid surface along the optimal route for repair, so the solution backflow phenomenon occurs.
The type and temperature of the liquid are different, and the tension is also different.
This tension difference is called the Maragoni effect. It doesn't matter if
doesn't understand it. In layman's terms, when two liquids with different tensions come into contact with each other, the liquid with stronger tension will pull the liquid with weaker tension over.
When we dilute a liquid, we take advantage of this effect.
If the concentrations of the two liquids are different, the solution with higher concentration will penetrate into the solution with lower concentration, ultimately achieving the effect of dilution.
The reason why the tea leaves go upstream into the teapot is because under the influence of tension, some of the liquid that has been poured out is sucked back by it, and eventually there is a phenomenon of tea leaves in the kettle.
Of course, this backflow will be limited by height. If the tension is less than gravity, the water will not flow back anyway.
So this phenomenon will only occur when making tea at a close distance.
Similarly, this situation will also occur in the upper and lower reaches of the river.
Due to the Maragoni effect, water sources will also suffer from backflow pollution.
So don’t think that creating pollution downstream of the river will not affect the upper reaches.
Speaking of this, everyone suddenly felt that we had always misunderstood the wolf living upstream when we were young.
It insists that the sheep living downstream pollute the water source, which makes sense.
Maybe he is a wolf with a PhD degree.
In addition, the inability to pee in boiling water is also related to the Maragoni effect.
3. Why can’t people pee into boiling water? For the sake of happiness in the second half of your life, never blindly try
At first, when we heard this sentence from the older generation, we thought it was another feudal superstition.
After understanding the Maragoni Effect, did you suddenly feel that your life was really lucky when you were a child?
If you pee in boiling water, the temperature of the urine will be much lower than the temperature of the boiling water.
In this case, the tension difference between the two will become larger, and the boiling water will cause a small part of the urine to reflux, and the urine in the reflux will be mixed with a small amount of boiling water.
If you are careless, the consequences will naturally be needless to say.
Of course, this is only a situation that occurs with a certain probability, but you must not try it easily. Once it leaves a psychological shadow on yourself, it will be very worthless.
In addition, the Maragoni effect is also reflected in other aspects, the most famous of which is the tears of wine.
When you pour a glass of wine into a wine glass, you will find that the wine flows upward along the wall of the glass.
And a circle of transparent liquid will appear on the inner wall of the wine glass, which looks like human tears, so it is called wine tears.
In fact, this is mainly because under the influence of capillary action, alcohol will climb up and then evaporate, which results in the alcohol content of the upper solution being lower than that of the lower layer.
This tension difference will cause the lower liquid to be continuously sucked upward, and a small amount of it will be hung on the inner wall of the wine glass.
Then under the influence of gravity, it will flow into the inside of the wine glass again.
repeats this cycle, forming tears.
This is why the saying that good wine hangs on the wall comes from this.
In fact, this sentence does not make sense. Hanging on the wall only proves that the concentration of the wine is high, and has little to do with the quality of the wine.
In addition, do you know any other phenomena that have the Maragoni effect?
