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教师在课堂演示实验时应当注意以下几点: (一)直观性强,实验内容不应过於复杂。(二)要简而易行,不可占时间太长。(三)节省药品。根据这三个条件,我在做演示当中得到以下几点经检。(我所教课本是周芬王悦祖编的初中化学1953年北京版)。一、课本41页的图25和图26中,所画的烧杯内的水平面低於瓶内玻璃导管口的水平面;这样一来,瓶内的气压就要小於瓶外面的大气压力。因
When teachers demonstrate experiments in the classroom, they should pay attention to the following points: (1) Intuitive, experimental content should not be too complicated. (B) to be simple and easy, can not account for too long. (C) save drugs. According to these three conditions, I am doing the demonstration which received the following points by the prosecution. (I teach textbook Zhou Fen Wang Yuezu junior high school chemistry 1953 Beijing version). First, the text in Figure 25 on page 41 and Figure 26, the beaker painted in the water level lower than the level of glass in the mouth of the bottle; so that the pressure inside the bottle is less than the pressure outside the bottle of air. because