The boiling point of water is not necessarily 100 degrees. Human body fluids can also boil. Do you believe it?

The freezing point of water is 0℃ and the boiling point is 100℃. Water has three states, solid, liquid and gas. That is, water is solid when it is below 0℃, liquid when it is between 0℃ and 100℃, and it will turn into gas when it is above 100 degrees Celsius.

This is just common sense about water.

This is also the only three states of matter that people knew in the early period. But this is only the state of water under specific conditions, that is, under an atmospheric pressure environment. Outside of this environment, the phase transition temperature of water is not the same.

At present, people know that there are seven states of matter, that is, in addition to the three states of gas, liquid and solid, there are four more states: plasma, Bose-Einstein condensate, fermion condensate, electron degenerate state and neutron degenerate state. These states of matter are not the topic of this article, so I will not elaborate on them here.

Now let's talk about the phase transition conditions of water. Under different air pressure environments, the phase transition temperature will change, and the common sense mentioned above is no longer common sense. Water will only freeze and become solid when it is below 0℃ under one atmospheric pressure; it will become liquid when it is above 0℃; and it will evaporate into water vapor when it reaches 100℃.

When out of an atmospheric pressure environment, the phase transition temperature will change.

As early as January 1, 1990, the International Committee for Weights and Measures promoted the adoption of the newly revised international temperature scale, stipulating that the thermodynamic temperature scale (Kelvin scale, symbol K) is the international unified temperature scale, and the Celsius temperature scale must correspond to the thermodynamic temperature scale, 0 K=-273.15℃, so that the previous Celsius temperature scale has some differences.

Strictly speaking, according to the new temperature scale, the boiling point of water at 1 standard atmosphere is 99.974℃. Of course, this difference from 100℃ can be ignored in our daily life. So, what is 1 standard atmosphere? It is 101325Pa (Pascals), which can also be called 101.325kPa (kilopascals) or 1013.25hPa (hPa).

In daily life, people often refer to 1 atmosphere of pressure as 1 kilogram of pressure, and so on.

As the air pressure changes, the boiling point of water also changes

The boiling point of water is different under different air pressures. Generally speaking, the higher the air pressure, the higher the boiling point, and the lower the air pressure, the lower the boiling point. Why do we say generally? This is because once the air pressure reaches an extremely high or extremely low state, the phase change of water is not a linear change, but will reach a supercritical state.

In our daily life, we often use high pressure to increase the boiling point. For example, when stewing bones in a pressure cooker, the pressure in the pot is kept increasing by sealing it, thereby raising the boiling point of water, making it easier and faster to stew the bones.

Household pressure cookers can generally withstand a maximum pressure of 2 kg, which is two atmospheres, or 101325Pa*2=202625Pa. Under such pressure, the boiling point of water can reach 134°C; and in order to ensure household safety, pressure cookers are generally kept below 1 atmosphere when in use. When the pressure in the pot reaches 1 atmosphere, the boiling point of water is about 120°C; household pressure cookers are generally used between 0.5 and 0.8 atmospheres, and the boiling point of water is about 112 to 117°C.

Industrial boilers can generally reach a pressure of 4 to 8 kilograms, and the boiling point of water can reach 150 to 170 degrees. Any gas leakage may injure people, so great attention should be paid to boiler safety.

It should be pointed out here that the reason why water boils is based on the principle of thermal expansion and contraction. When boiling water, some small bubbles appear at the bottom of the kettle, which are called vaporization nuclei. As the vaporization nuclei are heated, they will continue to rise, thus forming a boiling phenomenon. In some states where the kettle is not heated at the bottom, the water is relatively clean and it is difficult for vaporization nuclei to form in the water. Although the water temperature will continue to rise during the heating process, it will not boil when it exceeds 100℃.

If water is heated in a microwave oven, it will easily exceed the boiling point without a vaporization nucleus, and this water is called superheated water (liquid). If you add some small particles to this superheated water or stir it randomly, vaporization nuclei will suddenly appear, which will cause an instantaneous boiling phenomenon. Therefore, here is a special reminder that superheated water that has just been heated in a microwave oven should be left for a while before use to avoid personal injury.

Phase transition of water under extremely high pressure

If the water boiling container is repeatedly pressurized, will the water temperature increase linearly with the pressure increase, and will the boiling point also increase linearly? The answer is no, this is the unusual situation I mentioned earlier.

When the pressure increases again and again and reaches a critical point, the water under this pressure state will no longer boil; when the pressure rises to a certain level, the water will not only not boil, but also become solid. This is the phase change of water under pressure.

This critical point is: when the pressure rises to about 225 atmospheres, the boiling point of water reaches 374.3℃. If the pressure increases further, the water temperature will not rise and it will not boil. This is because the specific gravity of saturated steam and saturated water is the same at this time, and there is no difference between the two states. This water is called supercritical water.

When the pressure is greater than 10,000 to 100,000 atmospheres, that is, 10 million to 100 million tons of pressure per square meter of water surface, the water will no longer exist in liquid form, but in solid form. However, this solid state is no longer the common "ice" we see, but a special ice with a higher density.

As the pressure increases, when it reaches 10 million atmospheres, water will turn into a metallic state; if the pressure is higher, reaching 450 million atmospheres, the molecular structure of any substance will be destroyed, and the atoms will be flattened, including water, and will become electron-degenerate matter like a white dwarf; when the pressure reaches 10^28 atmospheres, that is, 1 trillion trillion atmospheres, any substance, including water, will become neutron-degenerate matter like a neutron star.

Of course, these are impossible to achieve under Earth conditions, but scientists have already used laser bombardment in the laboratory to achieve an atmospheric pressure equivalent to that of the Earth's core at a microscopic level, that is, 3 to 4 million atmospheres of pressure. In addition to natural ice, they have obtained 18 forms of ice. These are all phase change forms of water. Therefore, it can be said that there are as many as 21 forms of water.

Well, what we have said above is what happens to water when the pressure is increasing, especially the change in the boiling point of water. Now let's talk about the change in the boiling point of water under reduced pressure.

As the pressure decreases, the boiling point of water will become lower and lower

The boiling point of water decreases as the air pressure decreases, but it does not always show this linear relationship. When it reaches a threshold, the change stops abruptly. But this critical point is bounded by temperature. I will not elaborate on this today.

In aviation medicine, there is an Armstrong limit, which means that at an altitude of about 18,900 to 193,500 meters above the ground, when the atmospheric pressure drops to 6.3 kPa (about 0.062 standard atmospheric pressure), the boiling point of water is 37°C, which is about the same as human body temperature. Therefore, this altitude is a forbidden zone for humans. If there is no protection at this altitude, human body fluids will boil.

What does it feel like when your body fluids boil? It means that all the water in your body boils, including your tears, snot, saliva, sweat, blood, urine, etc., and the gas will expand even more. Therefore, experts warn people not to hold their breath in this environment, otherwise it will cause the alveoli to rupture.

In this state, all the gases in the body will rush out quickly. If the person is not unconscious, he or she will be able to hear the air holes above and below him or her exhaling, and the noise is much louder than a normal fart. The moisture in the tears, snot, sweat, and skin will sublime quickly. If the blood and urine boil, the person will burst and die.

Fortunately, most body fluids, such as blood, are wrapped and pressurized by the body's tissue cavity, so they will not boil all of a sudden. However, the body fluids in loose connective tissues such as the body surface and conjunctiva will still boil rapidly, resulting in horrible conditions such as protruding eyeballs, bleeding noses and mouths, and skin exudation, and the body will swell rapidly.

If people cannot escape from this environment as soon as possible, they will die quickly and quickly dehydrate into a mummy.

The lower the air pressure, the more serious this phenomenon is. Therefore, when astronauts are performing missions in space and are exposed to a vacuum environment without pressure protection, they will not suffocate to death, but will die from boiling and bursting of body fluids.

Several historical cases of vacuum exposure

The highest record for human high-altitude skydiving is 39,000 meters. This record was set by Austrian extreme athlete Felix Baumgartner on October 15, 2012 and has been maintained to this day. The record before him was set by American officer Joe Kittinger, who jumped from a helium balloon at an altitude of 31,300 meters in 1960.

Their parachuting heights were much higher than Armstrong's limit, so without protection, they would surely die. In order to cope with the boiling of body fluids and lack of oxygen caused by low air pressure, they all wore pressure-resistant oxygen supply suits similar to space suits before jumping. Their parachuting was successful, but Kittinger's jump had some problems, which almost put his life in danger.

The reason was that when he was falling, the right glove of Kittinger's pressure suit lost its seal and was instantly exposed to a near-vacuum environment. Kittinger felt a sharp pain in his right hand, which soon swelled to twice its normal size. Fortunately, the swollen hand blocked the air leak in the pressure suit. He fell freely at a speed close to the speed of sound and soon reached the troposphere. The air pressure gradually increased, and then he opened his parachute and landed safely soon. Soon, his swollen hand returned to normal.

In 1965, during a vacuum chamber experiment at NASA's space center, a subject named Subject suddenly had a leak in his space suit, exposing his entire body to extremely low pressure. After just 14 seconds, Subject lost consciousness. After the staff discovered the abnormality, they quickly inflated the vacuum chamber, and when the pressure reached an altitude of 5,000 meters, Subject regained consciousness. He said that the last thing he remembered was that the saliva on his tongue was boiling.

These were all incidents without any serious consequences, but what led to the irreversible tragedy was the space incident on June 30, 1971. On that day, three astronauts from the former Soviet Union who had completed their mission entered the atmosphere on the return capsule of the Soyuz 11 spacecraft. They had no idea that what awaited them was a quick death.

The three astronauts were: Commander Georgy Dobrovolsky, Experimental Engineer Viktor Patchayev and Flight Engineer Vladislav Volkov.

They stayed in the Salyut space station for 23 days and more than 18 hours, completed a series of observation and experimental tasks, and left the Salyut at 9 pm on June 29. But in the return capsule, the three did not wear space suits. They flew in orbit for more than 4 hours, communicating with the ground while waiting for the opportunity to leave the orbital module.

At 1:35 am on June 30, the spacecraft activated the braking rocket according to the program, lowered its orbit and re-entered the atmosphere. At this time, the return capsule and the orbital module needed to be separated according to the program, but the problem occurred here. The explosive bolts in the separation process should have been detonated one after another, but they detonated at the same time, which caused the return capsule's ventilation valve to be shaken open.

At this time, the return capsule was at an altitude of 168 kilometers and the cabin began to lose pressure. In just a few seconds, the cabin pressure dropped to a fatal level. They discovered this fatal problem, but the valve was located under Pachayev's seat. He quickly untied his straps and tried to plug the vacuum tube. The other two people watched helplessly because the space was too narrow but could not squeeze over to help. Therefore, there was no way to close the loophole within 30 seconds.

40 seconds later, the biological sensor device of the return capsule showed that these lives that were just alive had no signs of life, in just 40 seconds; 212 seconds later, the air pressure in the cabin dropped to zero.

The return procedure was still executed automatically, the parachutes opened as scheduled, and the return capsule landed safely, but what was sent back were the bodies of three astronauts, who died of boiling body fluids due to decompression. In addition to the mechanical failure, the lesson learned this time was that the astronauts did not wear space suits when returning, resulting in no protection after decompression and complete exposure.

The return capsule at that time was too small and the space suits were too bulky, so the former Soviet Union's space program stipulated that astronauts must take off their space suits before returning. This accident led to the dismissal of the general in charge of space flight and some regulations were changed. Since then, the world has strictly stipulated that astronauts must wear space suits when ascending and returning.

These stories tell us that exposure to low pressure is very dangerous. They also explain the properties and forms of water in various environments, and that the boiling point changes with the pressure environment. Welcome to discuss, thank you for reading.

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