我们在演示实验教学之前,虽经反复演示,力求一次成功,可是,无论教学经验多么丰富的教坛宿老,都不可避免地会出现一些意料之外的“反常”实验现象。学生分组实验时,无论课前怎样充分预习,也无论重点中学的学生整体素质有多好,也总难免有这样那样的“反常”实验现象发生,使实验未 Before demonstrating experimental teaching, we tried to make it successful once and for all. However, no matter how rich the teaching experience is, we will inevitably have some unexpected “abnormal” experimental phenomena. When students are grouped in experiments, no matter how well they prepare for pre-class study, and regardless of the overall quality of students in key middle schools, it is always difficult to avoid such “abnormal” experimental phenomena, so that the experiment does not occur.