一、可归纳为两个知识点的相关知识1.组成(1)在组成中一定含有氧元素的两类物质是:氧化物、碱;一定含有氢元素的两类物质是:酸、碱;碱一定含有的元素是:氢、氧。(2)空气中的两种主要气体是:氮气(含量约为78%)、氧气(含量约为21%)。(3)空气中的两类污染物:有害气体、烟尘。(4)金属材料包括纯金属材料和合金两类;铁的两种合金是:生铁、钢,它们的相同点是都是铁的合金(或主要成分都是铁),不同点是含碳量不同。(5)溶液是由溶质和溶剂混合而成的。2.性质(1)合金与金属相比的两大主要优点是:硬度 First, the knowledge can be summarized into two knowledge points 1. Composition (1) The composition of the two types of substances that contain oxygen must be: oxides, alkalis; two types of substances that must contain hydrogen are: acids, bases; Alkali must contain the elements are: hydrogen, oxygen. (2) The two main gases in the air are nitrogen (about 78%) and oxygen (about 21%). (3) two types of pollutants in the air: harmful gases, dust. (4) Metallic materials include two types of pure metal materials and alloys; the two alloys of iron are: pig iron, steel, their common are all iron alloy (or the main component is iron), the difference is the carbon content different. (5) The solution is a mixture of solute and solvent. 2. Properties (1) The two main advantages of alloys compared to metals are: Hardness