At normal temperature and pressure, hydrogen is a highly flammable, colorless, transparent, odorless and tasteless gas, which is insoluble in water. Hydrogen is the least dense gas known in the world, and its density is only114 of that of air, that is, at 0℃.
At a standard atmospheric pressure, the density of hydrogen is 0.0899 g/L, so hydrogen can be used as the filling gas for airships and hydrogen balloons (airships are now filled with helium due to its flammability and low safety).
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The discovery of hydrogen
In the history of chemistry, the discovery of hydrogen and the discovery and proof that water is a hydroxide compound rather than an element are mainly attributed to the British chemist and physicist cavendish (H.1731-1810).
There is an interesting story about these papers in the history of chemistry. Cavendish did an experiment in 1785. He let an electric spark pass through the mixture of ordinary air and oxygen, trying to oxidize all the nitrogen in it, and the nitrogen dioxide produced was absorbed by caustic potash. The experiment was done for three weeks, and finally there was a small bubble that could not be oxidized, and the rest was hydrogen.
References:
Baidu encyclopedia-hydrogen