Techniques.
1. Don't be confused by the words "clean, mixed", clean things are not necessarily pure things, for example: clean air, clean mineral water is a mixture.
2. Don't be confused by the name of the substance, for example: carbon dioxide is the name of the substance, "oxygen" and "carbon" refer to the elements that make up the substance, not two substances, carbon dioxide is a pure substance, not a mixture.
3. Elemental substances and compounds are divided according to the type of element.
4. A substance composed of an element is not necessarily a monoprime (it may be a mixture), but a pure substance composed of an element is an elemental substance.
5. Oxides must contain oxygen elements, but oxygenated compounds are not necessarily oxides, such as KMNO4.
6. Substances composed of the same elements are not necessarily elemental, such as substances composed of oxygen and ozone belong to the mixture.
7. An acidic solution is not necessarily an acidic solution. The solution formed by ammonium chloride and copper sulfate is acidic, but they themselves belong to salt!
8. An alkaline solution is not necessarily a solution of alkali. For example, sodium carbonate solution and sodium bicarbonate solution are alkaline, but sodium carbonate and sodium bicarbonate belong to salt!
Tap. A substance composed of the same element must be pure. (×
Compounds containing oxygen are oxides. (×
A substance consisting of one element must be elemental. (×
Carbonaceous compounds must be organic. (×