在知识点“沸腾”一节教学中,“观察水的沸腾”实验是一出重头戏,它决定着这节课的课堂教学质量.因为这个实验既是建立沸腾概念的基础,又是培养学生观察实验能力和训练学生非智力因素(如兴趣、科学态度)的重要手段.然而大多数学校按课本(华东版)上的实验装置做学生实验,效果均不尽如人意,可以毫不夸张地说,这些学校的绝大多数学生没能在实验中观察到清晰而真实的水的沸腾图景.因为用酒精灯作热源做实验,水温一般只能达到95℃—98℃之间,刚开始有少量气泡在上升过程中体积由小变大的现象出现,并未形成大量气泡上升、变大,到水面破裂开来,里面的水蒸气散发到空气中.这时的水温不再升高是因为供热不足造成的假象,并未达到水的沸点,充其量只能称之为“前沸腾”状态.是不是实验原理和实验装置有何不妥?不是,造成各种实验效果不佳的原因主要在实验器材的选择和实验方案的设计上. In the lesson of “Boiling” in the Knowledge Point, the experiment of “observing the boiling of water” is an important task, which determines the quality of classroom teaching in this class. This experiment is not only the foundation for establishing the concept of boiling, but also training students to observe the experiment. Ability and ability to train students in non-intellectual factors (such as interests, scientific attitudes) are important means. However, most schools do experiments based on experimental devices on textbooks (East China Edition). The results are not satisfactory and can be said without exaggeration. The overwhelming majority of students in these schools failed to observe a clear and realistic picture of the boiling water in the experiment. Because experiments were done using alcohol lamps as a heat source, the water temperature generally only reached 95°C-98°C, and there were a few bubbles at the beginning. In the process of ascent, the volume increases from small to large. It does not form a large number of bubbles that rise and become large, and it breaks open to the surface of the water. The water vapor inside is released into the air. The water temperature is no longer raised because of the heat supply. Insufficient illusion does not reach the boiling point of water, and at best, it can only be called the “pre-boiling” state. Is it wrong with the experimental principle and the experimental device? Is it not the cause of various experimental results? Mainly in the choice of experimental equipment and experimental design.