初中物理课本第二册第五章第四节“改变物体热能的方法”一节教材,在说明气体对外做功消耗了热能时,设计了气体膨胀做功使气体热能减少的实验(图5—6)。我在教学过程中,觉得这个实验只说明了气体膨胀能够做功,而并不能说明做功过程中消耗了水蒸汽的热能。为了使学生能够看到气体膨胀做功时热能减少, In the second volume of the junior high school physics textbooks, Chapter 4, Section 4 “Methods for Changing the Thermal Energy of Objects,” a textbook that describes the use of gas as heat to dissipate heat from the external work, designs an experiment for gas expansion to reduce the heat of the gas (Figure 5— 6). In the course of teaching, I felt that this experiment only explained that gas expansion can do work, but it does not explain the heat energy that consumes water vapor during work. In order to enable students to see that the heat energy is reduced when the gas expands to do work,