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第十五届天原杯赛第三大题(23、24、25题,见本期58、59面)为实验题,着重考查学生的实验能力,该大题用三道题目分别从原理分析、实验探究、实验对比三个层面对学生实验能力进行了考查。 23题是一道实验原理分析的题目,给出两套装置和检查气密性的方法,要求学生评价题中气密性检查的方法正确与否。A装置中,关闭弹簧夹a,从长颈漏斗向试管内注入一定量的水后,试管内压强增大,使长颈漏斗中形成水柱。水柱稳定,说明试管内压强稳定,即该装置不漏气。如果装置A漏气,则长颈漏斗中不会形成稳定的水柱或不能形成水柱。 B装置中,关闭弹簧夹a,如果装置不漏气,由于分液漏斗和烧瓶间用橡皮管相连,使分液漏斗中液面
The fiftieth title of the fifteenth Tianyuan Cup (23, 24, and 25 questions, see the 58th and 59th sides of the current issue) is an experimental question that focuses on students’ experimental abilities. The three questions are analyzed from the principles, Experimental investigations and experimental comparisons were conducted to examine students’ experimental abilities. 23 questions are the subject of an experimental principle analysis. Two sets of devices and methods for checking airtightness are given. Students are required to evaluate whether the airtightness test is correct or not. In the A device, when the spring clip a is closed and a certain amount of water is injected into the test tube from the long neck funnel, the pressure in the test tube is increased to form a water column in the long neck funnel. The water column is stable, indicating that the pressure inside the tube is stable, ie the device does not leak gas. If device A leaks, there will be no stable water column or no water column in the long neck funnel. In the B device, the spring clip a is closed. If the device does not leak gas, the liquid level in the separatory funnel is caused by connecting the separating funnel and the flask with a rubber tube.