War(warm?)air is frequently lighter as the molecules bump around, excited by the heat.

暖空气经常更轻一些，因为分子受到热量的激励而四处碰撞。

youdao

War(warm?)air is frequently lighter as the molecules bump around, excited by the heat.

暖空气经常更轻一些，因为分子受到热量的激励而四处碰撞。

youdao