初中化学中气体的收集方法主要有：排水法和排空气法，排空气法又包括向上排空气法和向下排空气法。究竟选择哪一种收集方法由气体的性质即气体的密度和气体的溶解性来决定。凡是不易溶于水或难溶于水或微溶于水且不和水反应的气体都可用排水法来收集，如收集O2、H2。收集装置 Gas collection methods for junior high school chemistry include: drainage method and exhaust air method. Exhaust air method includes upward exhaust air method and downward exhaust air method. Which collection method is chosen is determined by the nature of the gas, namely the density of the gas and the solubility of the gas. Any gas that is not easily soluble in water or insoluble in water or slightly soluble in water and does not react with water may be collected by drainage, such as collecting O2, H2. Collecting device