欧洲久久,久久精品视频一区,欧美日韩一区二区在线视频播放,久久精品观看,h片网,国产成人一区二区三区,奇米影视9999

At normal temperature and pressure, hydrogen is a gas that is extremely flammable, colorless, transparent, odorless, odorless, and difficult to dissolve in water. Hydrogen is the smallest known Density gas in the world. The Density of hydrogen is only 1/14 of that of air. That is, at 0 ° C, at a standard atmospheric pressure, the Density of hydrogen is 0.089g / L. Therefore, hydrogen can be used as a filling gas for airships and hydrogen balloons (because hydrogen is flammable and not very safe, airships are now filled with helium). Hydrogen is the substance with the smallest molecular weight and is mainly used as a reducing agent