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初中学生在观察用排气集气法收集氧气、氢气时,由于待收集的气体是无色透明的,无法观察排气集气的过程,也无法直接观察是否集满。本实验以烟充人集气瓶进行排烟集气,可使学生直观地观察到排气集气的过程,并理解其原理。一、步骤 1.收集烟将燃烧着的纸塞至瓶口处,燃烧较旺时捂住瓶口使火熄灭,取出未燃烧的纸。如果天气冷,为避免瓶壁出现水雾影响观察效果,可在集气瓶里插入一漏斗(如图),在倒置的漏斗底点燃纸。其它操作同前。 2.排烟集气过程收集气体时,要求制取该气体的反应速度适中,同时视气体的密度不同可采用向下或向上排烟法,不要将毛玻璃片取下,留一导气管恰好插入的缝隙以防烟逸出集气瓶过快。二、效果 1.在收集气体的过程中能清楚地看到两层气体
When junior high school students observe the collection of oxygen and hydrogen by the exhaust gas collection method, since the gas to be collected is colorless and transparent, the process of exhaust gas collection cannot be observed, and it is impossible to directly observe whether the gas is full. In this experiment, the smoke collection and collection of gas cylinders for smoke collection and gas collection allows students to visually observe the process of exhaust gas gathering and understand its principle. First, the steps 1. Collect the cigarettes and put the burning paper into the mouth of the bottle. When it is burning, grab the bottle mouth to extinguish the fire and take out the unburned paper. If the weather is cold, in order to avoid the appearance of water mist on the bottle wall, you can insert a funnel (as shown in the figure) into the gas cylinder to ignite the paper at the bottom of the inverted funnel. Other operations are the same as before. 2. When the gas is collected during the gas gathering process, the reaction rate of the gas is required to be moderate. At the same time, depending on the density of the gas, the downward or upward fume extraction method may be adopted. Do not remove the glass wool piece and leave a gas pipe just inserted. The cracks prevent smoke from escaping the collection cylinder too quickly. Second, the effect 1. In the process of collecting gas can clearly see the two layers of gas