在高一教材“化学反应中能量的变化”一节中，有两个演示实验，第一个利用温度计示数的变化来证明铝与盐酸反应放热，但较远处学生观察不到；第二个实验利用水被冷却结冰来证明氢氧化钡晶体与氯化铵晶体反应吸热，但此实验药品用量大，两种晶体必须研细，且搅拌要迅速，操作要? In the “Changes in Energy in Chemical Reactions” section of the first grade textbook, there are two demonstration experiments. The first one uses the changes in the number of thermometers to prove that the reaction between aluminum and hydrochloric acid is exothermic, but it is not observed by students far away; In the two experiments, water was cooled and frozen to prove that the cesium hydroxide crystal reacts with the ammonium chloride crystal to absorb heat. However, the amount of the experimental drug is large. The two crystals must be finely ground and the stirring must be rapid.