一、填空题1 .请你分别用两种物理方法,两种化学方法鉴别氢气和二氧化碳:　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　。2 .李芳在1 0 0℃时配制半烧杯硝酸钾饱和溶液,并在液面上放置一小木块,当溶液温度降到2 0℃时,观察到的现象有　　　　　　 First, fill in the blank questions 1. Please separate the two physical methods, two chemical methods to identify hydrogen and carbon dioxide :. 2.Fang Fang at 100 ℃ preparation of semi-beaker of potassium nitrate saturated solution, and the surface of the liquid placed a small piece of wood, when the solution temperature dropped to 20 ° C, the observed phenomenon