传统的初三化学教材(如人教版)都是用如图1所示的实验装置测定空气里氧气的含量。该装置存在着以下缺点:一是钟罩容积大,消耗红磷较多,产生大量的白烟,放出大量的热,使钟罩内气体压强过大,温度过高,难以冷却至室温,导致水面上升过慢。二是水槽中盛放的是无色的水,与钟罩颜色不能分开,当水沿着钟罩上升时,大部分学生观察不到液面上升的过程。三是所用钟罩不是规则图形,很难5等份。随着课程改革的进行,一 Traditional third-year chemistry textbooks (such as PEP) are used in the experimental apparatus shown in Figure 1 to determine the oxygen content in the air. The device has the following disadvantages: firstly, the volume of the bell jar is large, the red phosphorus is consumed more, a large amount of white smoke is generated, a large amount of heat is emitted, the gas pressure inside the bell jar is too large, the temperature is too high, it is hard to cool to room temperature, The water rises slowly. Second, the tank is filled with colorless water, and the bell can not be separated from the color, when the water rises along the bell, most students do not observe the rising liquid level. Third, the bell is not a regular pattern used, it is difficult to 5 equal parts. With the progress of the curriculum reform, one