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The Concept of Single Substance, Pure Substance, Compound and Mixture
Posted Date:2020/11/18
1. Single substance: a pure substance composed of the same element, which can be divided into metal element and non-metal element,
(1) Metal element: such as Fe, Al, Cu, etc.
(2) Non-metal element: such as Cl2, O2, S, C, etc.
2. Pure substance: a substance composed of a single substance
Note: The substance composed of isotopic atoms is pure, for example, H2O and D2O are still pure after mixing.
3. Compound: a pure substance composed of different kinds of elements. It can be seen from different angles that compounds are divided into ionic compounds, covalent compounds, electrolytes and non-electrolytes, organic compounds and material compounds, acid-base salts and oxides.
4. Mixture: A substance made by mixing two or more substances. There is no chemical reaction between the various components that make up the mixture, and they retain their original properties.
The mixture has no fixed composition and generally has no fixed boiling point.
Common mixtures with special names: ammonia, chlorine, aqua regia, natural water, hard water, soft water, hydrochloric acid, concentrated sulfuric acid, formalin, water glass, explosive gas, water gas, natural gas, coke oven gas, blast furnace gas, petroleum Various fractions of gas, pyrolysis gas, air, alloy, superphosphate, bleaching powder, black powder, thermite, cement, iron catalyst, glass, coal, petroleum, and petroleum.
Note: Substances composed of allotropes are mixtures , Such as red phosphorus and white phosphorus.
GHS defines the mixture as:
Mixture refers to a mixture or solution composed of two or more substances but not reacting;
In the third part of the composition information in the SDS, it is necessary to determine whether the product is a single substance or a mixture. For example, carbon black is composed of one element C, and only one CAS No. is 1333-86-4, the content is close to 100%, then this product is a single substance. For example, the product is ammonia water, in which the content of ammonia (CAS: 1336-21-6) is 25% to 28%, and the rest is water (CAS: 7732-18-5). The product contains two essentially different chemical substances, ammonia and Water, then the substance is a mixture.