初中物理义务教材第二册第 12页有这样一则实验 :如图 1,把一个装有空气的瓶子倒着放在装有密度较大的红棕色二氧化氮气体的瓶子上 ,使两瓶口相对 ,两瓶口之间原来用一块玻璃盖板隔开 ,当抽掉盖板后 ,可以看到 ,下面瓶子里的二氧化氮虽然密度比空气大 ,但仍然运动到上面的瓶子? There is an experiment on the 12th page of the second volume of the junior middle school physical education textbook. As shown in Figure 1, a bottle filled with air is placed on a bottle filled with dense red-brown nitrogen dioxide gas to make two bottles. Relatively speaking, the two bottles were separated by a glass cover. When the cover is removed, it can be seen that although the density of nitrogen dioxide in the lower bottle is greater than air, it still moves to the upper bottle.