Hydrogen - ₁H: physical properties

Under ambient conditions, hydrogen is a colourless highly flammable diatomic gas with the molecular formula H₂. Hydrogen gas has no small or taste. It is possible to make liquid hydrogen at atmospheric pressure by cooling it to below 20.28 K (-252.87 °C). Liquid hydrogen can be stored in insulated containers under pressure. Solid hydrogen may be made by cooling below the melting point of 14.01 K (-259.14 °C) and has a low density 88 kg m^-3 (0.088 g cm^-3). Hydrogen is not an electrical conductor. It may be that a liquid metallic hydrogen is present in the highly compressed interiors of Jupiter and Saturn where pressures are in the millions of atmospheres.

Density properties

• Density of solid: 88 kg m^‑3
• Molar volume: 11.42 cm³

Elastic properties

• Young's modulus: (no data) GPa
• Rigidity modulus: (no data) GPa
• Bulk modulus: (no data) GPa
• Poisson's ratio: (no data) (no units)

Hardnesses

• Mineral hardness: (no data) (no units)
• Brinell hardness: (no data) MN m^-2
• Vickers hardness: (no data) MN m^-2

Electrical properties

• Electrical resistivity: (no data) × 10^‑8 Ω m; or mΩ cm

Heat and conduction

• Thermal conductivity: 0.1805 W m^‑1 K^‑1
• Coefficient of linear thermal expansion: (no data) × 10^‑6 K^‑1

Optical properties

• Reflectivity: (no data) %
• Refractive index: 1.000132 (gas; liquid 1.12) (no units)

Acoustic properties

• Velocity of sound: 1270 m s^‑1