新编初中物理教材第一册P38[实验与思考]有一个实验装置图,如附图-(a)所示。图的说明是:“在试管A未放入容器B中时,用温度计测出B中水温,再将A放入B中,让沸腾时产生的水蒸气通入试管A中,水蒸气至试管中遇冷将会怎样?过一段时间再测量容器B中水温,比较一下,温度是升高了还是降低了?这个实验说明了什么?” The new book of junior high school physics textbooks first book P38 [experiment and thinking] has an experimental device diagram, as shown in Figure - (a). The illustration is: "When the test tube A is not placed in the container B, the temperature of the water in the B is measured with a thermometer, and then A is put in the B, so that the water vapor generated during the boiling passes into the test tube A, and the water vapor reaches the test tube. What happens in cold water? After a period of time, measure the water temperature in container B. In comparison, does the temperature increase or decrease? What does this experiment illustrate?”