Chemistry · Ch 4 — Hydrogen
Physical Properties
4.5.2
Physical Properties
Water is a colourless, volatile liquid. Many of its familiar but, on reflection, unusual bulk properties in the liquid and solid states -- an unexpectedly high melting point and boiling point for so small a molecule, in particular -- trace back to a single cause: extensive intermolecular hydrogen bonding between water molecules (developed fully in Section 4.9). Table 4.2 collects the key physical parameters of water alongside the corresponding values for heavy water (D₂O) and super-heavy water (T …
Table 4.2Properties of water, heavy water and super heavy water
| Property | H₂O | D₂O | T₂O |
|---|---|---|---|
| Molecular weight | 18.015 | 20.0276 | 22.031 |
| Melting point (K) | 273.0 | 276.8 | 277.5 |
| Boiling point (K) | 373.0 | 374.4 | 374.5 |
| Temperature of maximum density (K) | 277.0 | 284.2 | 286.4 |
| Maximum density (g/cm³) | 1.000 | 1.106 | 1.215 |
| Density (g/cm³) | 0.997 | 1.104 | 1.214 |
| Vapour pressure (mm Hg) | 23.75 | 20.51 | 19.80 |
| Viscosity (cP) | 0.890 | 1.107 | --- |
| Dielectric constant | 78.39 | 78.06 | --- |
| Enthalpy of formation (kJ/mol) | −285.9 | −294.6 | --- |