Water is called the "source of life" in our daily lives, it is a necessary condition for all life activities, and it is also an indispensable and important part of the human body.
The weight of water in the human body accounts for two-thirds of the total weight of the human body, the human body water content of adults is about 65%, and the water content in our blood is 97%.
Water is the most important substance for human bodily functions. First of all, metabolism cannot occur without water, and harmful substances accumulated inside the human body cannot be excluded.
Second, water can make up cells and maintain their functioning, and it can also transport nutrients to provide energy to the body. In addition, because of its high thermal conductivity, it can well help the human body to regulate body temperature. Therefore, a sufficient daily intake of water is very important for human health.
Water resources on Earth
As a beautiful "blue planet", the earth has been distributed with vast oceans since its birth, and the interior is also rich in water resources. The oceans on Earth are much larger than the land area, and the water on Earth does not seem to be "expired", but we put water in containers, and after a period of time, the water in it will always expire and deteriorate, especially in the hot summer. Is the water in the bottle "stagnant water"?
The water resources on the earth are broadly the total amount of all water bodies, but the water we say in our daily lives refers to the freshwater resources that can be used by us.
As the "indigenous people of the earth with a large population", water is very common in our daily lives, and the most exposed to us should be surface water and oceans. The ocean accounts for most of the earth's water, but because of the characteristics of seawater, it cannot be quoted by humans, and rivers and lakes, which account for 0.6% of the total freshwater of the earth, have become the main way for humans to obtain freshwater resources.
There are three main types of water on earth, natural precipitation (rain, snow, hail, etc.), surface water (river water, lake water, sea water, etc.), and the third is groundwater.
There is a saying in life that "water does not expire and has no shelf life", thanks to the earth's strong material circulation capacity, we can enjoy a steady stream of freshwater resources produced through the water cycle today.
Deep in the Earth's crust, the basic constituent elements of water, hydrogen and oxygen, are constantly merging, in other words, as long as the combination of hydrogen and oxygen can be achieved in a fixed physical environment, endless water resources will be created. The earth's water has been around for 4.4 billion years and continues to meet human water needs driven by the water cycle.
Water is actually the same age as Earth
It has been 4.6 billion years since the birth of the Earth, and liquid water has existed on the Earth for 4.4 billion years. In other words, for 4.4 billion years, there has been a distribution of water resources on the earth. In the history of our human existence, tens of thousands of years are not worth mentioning in front of the 4.4 billion years of water existence.
The Earth was not what it is when it was first born, because it was constantly hit by space meteorites, the rocks were melted by the high temperature, the earth's crust was very active, and the earth's uneven surface magma was everywhere, so the earth looked more like a red fireball.
Large areas of magma covered the Earth and melted the surface until about 140 million years after the high temperature state lasted, the Earth's temperature dropped and the large area of magma eventually cooled into rock. The cooling of surface magma causes water from the Earth's interior to begin to seep out continuously and pool at the surface, eventually forming oceans.
In addition, scientists have proposed the hypothesis of prolonged rainfall, which they believe has seen as a long rainy season on Earth. The water resources in the Earth's interior are continuously converted into water vapor through volcanic eruptions and stored in the atmosphere. After tens of thousands of years of water circulation, there was a continuous rainstorm around the world, and massive amounts of liquid water continued to pool to form the ocean.
As a result, the amount of water in the Earth's interior is unmatched by the water resources we see today, and these oceans, which existed for 4.4 billion years, still account for 71% of the region's area.
Why doesn't water on Earth expire?
Judging from the chemical composition of water, water itself is a very stable substance. Water is an inorganic substance composed of two elements, hydrogen and oxygen, which are very common in our daily lives. Among them, oxygen is an element that we are not unfamiliar with, as a necessity to maintain the operation of human life, it is widely present in nature.
Oxygen and hydrogen make up water molecules, due to the stability of their own structure, water molecules are not easy to be decomposed, chemical structure in nature is relatively stable, but will change their physical form.
There is an old Chinese saying that "flowing water does not rot, and the household center does not beetle." "That is to say, the flowing water does not emit a foul smell, and the door shaft that often rotates is not easily eroded." In other words, they effectively defend against the invasion of organisms in non-stop motion and maintain their own state of motion. This has been the case with water on Earth for 4.4 billion years, leaving itself out of the ordinary in a constant cycle of movement.
It is precisely because of the stability of the water molecules themselves that the water we drink now may also be water 4.4 billion years ago, but after a never-ending cycle of purification, it appears in front of our eyes in another physical form.
The water cycle is one of the forms of the material cycle, a process that has been going on earth for 4.4 billion years, and it is through this cycle that water has not expired until now.
The water cycle, as the name suggests, refers to the migration of water on Earth to another place by changing its form in different ways. The movement of the water body does not only refer to the flow of water, but also refers to the transformation of the form of the water body.
Water exists on Earth in gaseous, liquid and solid forms and is able to circulate continuously between land, oceans and atmospheres by absorbing the sun's energy.
Solar radiation and gravity are the two major reasons why the water cycle can produce physical morphological changes, they give kinetic energy to the water cycle, and the characteristics of the water molecules themselves that can be easily transformed in the three forms also determine the occurrence of the water cycle process.

The water cycle is a means to regulate the distribution of water resources in various regions and geographical environments around the world, which is divided into three ways: intercontinental circulation, intra-sea circulation and intracontinental circulation.
The water cycle ensures that water is dynamic, that water resources do not deteriorate in this context, and that the ability of water to purify itself ensures that the earth's water does not expire today, 4.4 billion years later.
When the water body is polluted, after the multiple effects of various substances in the water body, the pollution degree will be reduced, and this self-purification ability will basically restore the water body to normal water quality without serious interference. Its multiple functions are biological, physical and chemical.
From the perspective of biological action, the activity of various organisms in water bodies, especially microorganisms, can reduce the degree of water pollution. The oxidative decomposition effect of microorganisms on organic matter in water causes pollutants to be digested and diluted, and the purpose of purification is finally achieved, but the biological effect has a small impact on the three types of effects, accounting for a small proportion.
From the perspective of physical action, "dilution" is the core process of physical purification, and various pollutants in water resources settle and mix in the water body, and finally achieve the effect of dilution.
Chemical action is the core process of self-purification of water bodies. Water oxidizer in the process of water self-purification is an important indicator to measure the strength of self-purification ability, the higher the water oxidant, the faster the cycle speed of chemical substances, so that the water body will be more vibrant, it is difficult to expire.
The second is the oxidative decomposition process of organic infectious substances, which directly affects the quality of water.
In general, through the biological, physical and chemical is a triple action, the pollutants can be used in the water body after sedimentation, dilution, dispersion, oxidation, reduction and other processes to achieve self-purification effect.
Why does bottled water expire and spoil?
The deterioration of water is not a change in the chemical sense of water molecules, we often say that metamorphism refers to the appearance of chemicals harmful to the human body inside the object. For example, food spoilage may be because of the growth of bacteria that are not conducive to human health, and water is the same, which will breed bacteria after being put in the bottle, so the bottled drinking water we often drink will set a shelf life.
If water such as surface water or natural precipitation is packed in a sealed space such as a bottle, the water molecules stop flowing and cut off the process of water participating in natural circulation.
The liquid water in the bottle has no flow process, the hydrogen element and oxygen element have no exchange and renewal process, and the dissolved oxygen in the water is constantly self-consuming in the bottle, and eventually the water body loses its self-purification ability, that is, it is "stagnant water".
For the drinking water in the bottle, its deterioration is inevitable. In the biochemical community, sterile and confined spaces can ensure the stability of the molecular structure of water, but it is difficult for water to achieve such harsh conditions after being bottled.
Before being put into the bottle, the water will be sterilized and disinfected, and oxygen, hydrogen and other trace elements will produce a corresponding chemical reaction in the bottle, which will breed bacteria for a long time and cause the water in the bottle to deteriorate.
In addition, the material of the bottle containing the water will also affect the state of the water. In general, drinking water bottles are made from a polymer compound called polyester.
Polyester in long-term contact with water will release low molecular weight compounds that affect the movement of water molecules, which will greatly affect the dominant characteristics of water, such as color, taste or odor.
In addition, its molecular structure is far less stable than water molecules, under special conditions, the chemical state of polyester will be affected, resulting in water deterioration, soon expired, and even under extreme conditions to produce toxic chemicals, endangering human health.
Nowadays, although the production process of the bottle filled with water has been pure, because of the material factor, it is difficult to completely isolate the harmful substances, and once the air and the low molecules in the bottle enter the water body, the water quality will be destroyed and eventually expire.
Due to the existence of the natural law of the water cycle, water that appeared on the earth 4.4 billion years ago does not expire, but has been changing its physical form and reappearing on the earth. The correctness of "flowing water is not corrupt" has been verified again and again thanks to the self-purification ability of the water body, water in nature is an indispensable part of the ecosystem, because of the participation of water, the ecological cycle can play a role, at this time the earth is equivalent to a super power water purifier.
When the water is loaded into the bottle, it is equivalent to stripping it from the natural ecological environment, and it is a fantasy to carry out cyclic purification in the structure of the bottle. Bacteria come into contact with water to breed microorganisms, and when the sanitary conditions are not up to standard, they naturally expire.
epilogue
Water in nature does not expire and is free to use, but at the same time we must also realize that the freshwater resources we need for human beings are unevenly distributed, and we have to pay a price for carrying and handling water. As an extremely important strategic resource, we must also establish a sense of resource crisis, save water and cherish water resources while recognizing why it will not expire.