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课时1我们周围的空气重点难点热点1.空气的主要成分及作用(1)空气的主要成分是氮气(N_2)和氧气(O_2),其中氮气约占空气体积的78%.(2)探究空气中氧气含量的实验(如图1).选用红磷作燃料的原因是红磷在空气中能燃烧且只消耗氧气。生成物不是气体.测得的结果偏小的可能原因有红磷量不足,装置气密性不好,燃烧结束后没有冷却到室温就打开弹簧夹等.根据进入集气瓶的水量得出结论:氧气约占空气体积
Class hours 1 Air around us Highlights Difficulties 1. Main components and roles of air (1) The main components of air are nitrogen (N2) and oxygen (O2), of which nitrogen accounts for about 78% of the volume of air. (2) Oxygen in the experiment (Figure 1). The reason for using red phosphorus as fuel is that red phosphorus can burn in the air and only consume oxygen. The resulting product is not a gas.The measured results may be due to the small amount of red phosphorus, the device is not tight, the end of the combustion did not cool to room temperature to open the spring clip, etc. According to the amount of water into the gas collection bottle concluded Oxygen accounts for the volume of air