How is the physical water formed in the second day of junior high school? Please answer in detail, thank you! (7 2:18:17)

There are still great differences on the understanding of the origin of water. At present, there are about 32 theories about the formation of water. Here are some main theories. One theory holds that there was a primitive nebula of H2O molecules in the initial matter before the formation of the earth, similar to the meteorite with an average water content of .5% at present, which fell to the earth after the formation of the earth, thus making the earth have water.

another theory holds that the original elements (hydrogen and oxygen) that formed water only after the formation of the earth. Hydrogen combines with oxygen under suitable conditions. Generate hydroxyl (OH). The hydroxyl group undergoes complex changes to form water (H2O).

Dutch astronomer Otto believes that the main source on the earth is the upper mantle of the lithosphere inside our planet. Half of the material in the lithosphere is composed of silicon, including silicate and water. These rocks are dehydrated at a certain temperature and under suitable conditions (such as volcanic eruption), thus forming the water of the earth. American scholar Kennedy and others think that when rocks are completely mixed in melting, they contain 75% silicate and 25% water. In the early days of the earth's formation, volcanoes erupted frequently, which accelerated the formation of water on the earth. Due to the high temperature inside the earth, the water on the earth is still increasing. In the study, some data show that the ocean surface has risen by 1.3m in the past 1 years. However, the rapid rise of ocean water level in recent decades may be mainly caused by global warming.

composition and experiment of water

composition of water has long been considered as a simple substance because it is difficult to decompose it by general heating methods. It was not until the end of the 18th century that scientists experimentally proved that water is a compound.

what element is water a compound? We can do research in the following two different ways.

in experiment 1, the glass tube of water electrolyzer was filled with water, and direct current was applied to observe the gas generated on the electrode and in the glass tube and its volume. After a while, check the gas in the two glass tubes with the lighted wooden strips respectively.

The experiment shows that when direct current is switched on, bubbles are generated on the electrode, and colorless gas is collected in the two glass tubes. Wherein, the gas generated at the end connected with the positive electrode is less than that generated at the end connected with the negative electrode, and their volume ratio is about 1: 2.

reaction chemical equation: 2H2O== electrify ==2H2↑+O2↑

Small gas can make the burning wood stick burn more vigorously, which proves that it is oxygen.

a gas with a large volume can burn, and this is hydrogen.

Hydrogen and oxygen are generated by water electrolysis, which shows that water is a compound composed of two elements: hydrogen and oxygen.

experiment 2 ignited the pure hydrogen generated from the hydrogen generator. Put the pointed nozzle pipe for igniting hydrogen into the dry gas cylinder filled with oxygen (Figure 4-5). Take a closer look at the inner wall of the gas container.

The inner wall of the dry gas cylinder is covered with a layer of water vapor, indicating that hydrogen reacts with oxygen to generate water. This reaction is shown as follows:

Both the electrolysis of water and the combustion of hydrogen in oxygen have proved that water is indeed a compound composed of hydrogen and oxygen. After a lot of experimental determination and scientific analysis, it is confirmed that a water molecule is composed of two hydrogen atoms and one oxygen atom. The molecular formula of water is H2O.

combination reaction and decomposition reaction. After careful analysis of the reactions in the above two experiments, we found that the forms of these two reactions are different. The reaction of electrolyzing water is that water reacts with one substance to produce two substances: hydrogen and oxygen.

chemically, the reaction in which one substance reacts to produce two or more other substances is called decomposition reaction. Potassium permanganate is heated to produce oxygen, potassium permanganate and manganese dioxide, which is also a decomposition reaction.

The experiment of hydrogen burning in oxygen to produce water is that hydrogen and oxygen react to produce water.

chemically, a reaction in which two or more substances react to form another substance is called a combination reaction. Magnesium burns in the air to produce magnesium oxide, which is also a chemical reaction.

decomposition reaction and combination reaction are two basic types of chemical reactions.