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Hydrogen is a colorless gas that is less dense than air and is highly flammable.
The "pop test" is used to identify hydrogen gas in the school laboratory. A test tube mixture of hydrogen and air will pop when ignited producing water as a by-product. The chemical reaction is
Hydrogen + oxygen ==> Water + Energy
2H2 + O2 ==> 2H2O + Energy
The Hindenburg was a German airship that was filled with hydrogen gas. On landing in the USA in 1937 after a transalantic flight the passenger airship caught fire. Thirty six people died.