Most inorganic substances can be divided into four categories: oxides, acids, bases and salts. Inorganic substances in organisms mainly include water and some inorganic salts, such as Na+, K+, Ca2+, Mg2+, Cl-, SO42- and so on. Human tissue contains almost all kinds of elements existing in nature. Except that carbon, hydrogen, oxygen and nitrogen mainly exist in the form of organic compounds, the rest are collectively referred to as inorganic substances (minerals or ash). Therefore, inorganic substances are mainly composed of water and inorganic salts, in which water can be divided into bound water and free water. Bound water is an important part of cell structure, and free water is a good solvent, transports substances and participates in chemical reactions. Inorganic salts can be divided into ionic salts and compound salts. Ions maintain the normal life activities of cells, and compounds are an important part of intracellular compounds.
oxide
It consists of two elements, one of which is a compound of oxygen. Substances that can react with oxygen are called oxides. According to different chemical properties, oxides can be divided into two categories: acidic oxides and basic oxides. Acid oxide: an oxide that can react with water to form an acid or with alkali to form a salt. Such as sulfur trioxide, phosphorus pentoxide, carbon dioxide, etc. Most nonmetallic oxides are acidic oxides.
Basic oxide: an oxide that can react with acid to form salt and water. Basic oxides include oxides of active metals and suboxides of other metals, such as calcium oxide, barium oxide, chromium monoxide and manganese oxide.
ferment
A general term for a class of compounds that can ionize in aqueous solution to produce hydrogen ions, as opposed to bases. When hydrochloric acid, sulfuric acid and nitric acid are ionized in aqueous solution, they produce different anions (called acid radical ions), but the same cations (namely hydrogen ions), so their properties are similar, such as sour taste; Can dissolve various metals; Can make blue litmus test paper turn red, etc. Narrow definition: All cations ionized in aqueous solution are hydrogen ion compounds (such as sulfuric acid). Most of these substances are soluble in water, and a few, such as silicic acid, are insoluble in water. The aqueous solution of acid is generally conductive, and some acids exist in the form of molecules in water, but they are not conductive; Some acids dissociate into positive and negative ions in water and can conduct electricity.
alkali
Bitter substances (such as litmus turning blue and phenolphthalein turning red). ) Its solution can discolor a specific indicator with PH greater than 7. All anions ionized in aqueous solution are hydroxyl ions, which react with acids to form salts and water. Typical alkalis are ammonium hydroxide (ammonia water), caustic soda (sodium hydroxide), hydrated lime (calcium hydroxide) and so on. The broad concept of alkali refers to the substance that provides electrons or accepts protons.
salt
The product of acid-base neutralization consists of metal ions (or ammonium ions) and acid ions. There are three types of salt in chemistry: normal salt: composed of metal ions (including ammonium ions) and non-metal ions; Acid salt: composed of metal ions (including ammonium ions), hydrogen ions and nonmetallic ions; Basic salt: It consists of metal ions (including ammonium ions), hydroxide ions and nonmetallic ions. Salt is an important source of chemical industry, which can be made into chlorine, sodium metal, soda ash (sodium carbonate), baking soda (sodium bicarbonate, baking soda), caustic soda (caustic soda, sodium hydroxide) and hydrochloric acid.
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