Lesson No. 1 ｜ Hello classmates!Please understand these common sense

Today is the first day of school

The classmates finally returned to school

Tastest and busy studying life begins

Water is the source of life

It is closely related to our lives

Do you know water?

Where does the water come from?

Why save water?

Let's walk into the water together

Know the water knowledge you know and don't know

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What is water?

Water is one of the most common, contact and use of the most frequent substances around us. It is a kind of inorganic matter composed of two elements of hydrogen and oxygen (chemical formula H2O). It is one of the composition of the original atmosphere. It is a transparent liquid that is colorless and tasteless at normal temperature. The important resource of survival is also the most important part of the organism. Water is the source of life, and all life activities originate from water. Without water, animals and plants will not be able to survive, and human production and living activities cannot be carried out. Wherever there is water, there is life.

What are the main characteristics of water?

The characteristics of water include physical and chemical characteristics.

The main physical characteristics are: the form of water is solid, liquid and gaseous. Under normal pressure, the solidification point (freezing point) of water is 0 ° C, and the boiling point is 100 ° C; at 4 ° C, the mass of 1 cubic centimeter of water is 1 gram, and the density of the water is the largest at this time. After the water is made of ice, the volume is 1.09 times; the volume will increase by more than 1600 times. Water has strong dissolving ability to many substances. For example, water contains the dissolved air, and the creatures in the water are survived by the oxygen dissolved in the water.

The main chemical characteristics are: the stability of water is very strong, and it is not easy to break down under high temperature conditions. At normal temperature, the pH value of water is 7 (pH = 7 is neutral), which can react with lively metals such as sodium; at high temperature conditions, water energy can react with carbon and iron. Water can generate corresponding acids or alkali reactions with certain acid oxides or alkaline oxides, or it can be combined with certain substances as hydrations.

Where does the water come from?

There are divergent opinions on the sources of water on the earth, but it can be classified as two categories: one is native, and the other is foreign.

Native to say that the dust of the universe is condensed into the earth. As the earth rotates rapidly, the water contained in the raw material in a melting state moves to the ground and eventually releases. The gaseous water condensed into rain and landed to the ground. It is also said that a large amount of water erupted by volcanoes.

There are two views on foreign countries. One believes that a large amount of ice meteorite landed to the surface of the earth, thus continuously bringing the water of the universe to the earth; ——Sonin, it is combined with the electronics of the earth into a hydrogen atom, and then synthesized with oxygenization of hydrolysis. At present, most scientists believe that the water on the earth is formed by itself in the long historical process, that is, self -evidence. There are some facts based on the interpretation of the source of the water on the earth, but they all have one -sidedness. Where did the water from the earth come from? With the development of science and technology, I believe that scientific answers will be found.

How is the water on the earth distributed?

The water distribution on the earth is widely distributed. It is distributed in the form of solid, liquid, and gaseous in the ocean, land and atmosphere, forming various water bodies, and jointly forms a water ring. Among them, the ocean is the main body of the water ring, with an area of ​​about 361 million square kilometers, covering about 71%of the surface of the earth. Landwater includes surface water (such as river water, lake water, swamp water, etc.) and groundwater. The proportion of biological water and atmospheric water is small. In the "big water tank" provided by the earth for humans, there is only one tablespoon of water that can be consumed. Most of the water on the earth is salted water, accounting for about 97.2%, and freshwater accounts for only about 2.8%of the total amount of global water. Snow. What humans can really use are part of rivers and lakes and underground water.

How much fresh water can be used by humans?

The total amount of water on the earth reached 1385,984.61 trillion cubic meters, of which only groundwater and lakes, and the freshwater in the river can be used by humans. That is to say, the amount of fresh water available for human use only accounts for about 0.64%of the total water, which is 88.7.03 trillion cubic meters. Overall, there is no shortage of water in the world. However, the distribution of freshwater resources in the world is extremely uneven. About 65%of water resources are concentrated in less than 10 countries, while 80 countries and regions, which account for about 40%of the world's total population. The unreasonable way of human use of water resources and pollution have even more intensive water resources.

What is water circulation?

Various forms of water on the surface of the earth are constantly transforming. The process of water, liquid, and solid in the form of gaseous, liquid, and solid is circulating between land, ocean and atmosphere is water circulation.

The internal cause of water circulation is the characteristics of water, liquid, and solid state of water under normal environmental conditions. The external cause is the effect of solar radiation and gravity, which provides the physical state change and motion energy for water circulation. Water circulation is divided into sea and land cycling (large cycle) and internal circulation of land and internal circulation (small cycle) at sea.

The main role of water circulation is in three aspects: first, water is the medium of all nutrients, and the circulation of nutrients is inseparable from the water circulation; the other is that water is the solvent of substances, which plays energy transmission and utilization in the ecosystem in the ecosystem. The role of water; the third is that water is one of the causes of geological changes. The loss and deposition of mineral elements are often completed by water circulation. Water Knowledge Class

Do you want to know the origin of Han Jiang's name?

Do you want to know the principle of the operation of water conservancy engineering?

Can you find the difference between the faucet of the water?

First day of school

Guangdong Province Water Resources Department is prepared for everyone

A master of water love for a unique place

Look together ~~~

The total amount of water available to human beings is limited

The shortage of water resources seriously restricts the sustainable development of economic and society

Fully know water and understand water

In order to promote water management

conserve water

Protect water resources

Everyone is responsible

Text source: "You know and don't know water"

Video source: Guangdong Water Conservancy Department

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