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关于俯视或仰视引起实验误差的题目,中学化学中比较常见。由于一些同学在分析这类题目时抓不住问题的关键,常常难以得到正确答案。在中学常见的化学仪器中,有五种量器:量筒、容量瓶、移液管、酸式滴定管、碱式滴定管。其中,容量瓶和移液管只有一个刻度线,酸(碱)式滴定管零刻度在上,量筒虽有刻度,但无零刻度。这五种量器在使用时会因为俯视或仰视引起误差。在分析这类误差时,关键问题是要搞清楚使用这种仪器时眼睛首先注视的是仪器的刻
The topics that cause experimental errors when looking down or looking up are common in middle school chemistry. Since some students cannot grasp the key to the problem when analyzing such topics, it is often difficult to get the correct answer. Among the common chemical instruments in middle schools, there are five kinds of measuring devices: measuring cylinders, volumetric flasks, pipettes, acid burettes, and basic burettes. Among them, there is only one scale line for the volumetric flask and the pipette, and the zero scale of the acid (alkali) titration tube is on the top. Although the graduated cylinder has a scale, it has no zero scale. These five gauges cause errors due to overhead or looking up when used. When analyzing such errors, the key issue is to make it clear that when the instrument is used, the eyes first look at the moment of the instrument.