Physical Properties

Hydrogen gas (H₂) is colourless, odourless and tasteless. It is the lightest gas known and is highly flammable. As a diatomic molecule made of two identical atoms, it is non-polar. It can be liquefied, but only under a combination of low temperature and high pressure, since its very low mass means weak intermolecular (van der Waals) attractions. Chemically, hydrogen behaves as a good reducing agent -- a character that flows into its chemical reactions covered next. The detailed physical constants of the H₂ molecule (melting point, boiling point, critical temperature, bond …