1．在实验装置中，试管口为什么要略向下倾斜？若试管口向上倾斜，会发生以下两种情况：①H2和CuO反应生成的水及药品里的湿存水受热气化后，在试管口冷凝成水滴倒流到试管的加热部位，而使试管炸裂。②H2比空气轻，一方面不易把试管里的空气排尽，加热时可能引起爆炸；另一方 1. Why does the tube port tilt slightly downwards in the experimental setup? If the test tube port is tilted upwards, the following two conditions will occur: (1) After the H2 and CuO reaction water and the wet storage water in the medicine are heated and vaporized, they will condense at the test tube mouth and flow back to the heated part of the test tube, which will burst the test tube. 2H2 is lighter than air, on the one hand, it is not easy to exhaust the air in the test tube, and it may cause explosion when heated;