Reality → Matter → Molecule → Water
The structure of the simple yet delicate water molecule accounts for important anomalies of water. Two hydrogen atoms bond covalently with the central oxygen atom in a V-structure [1] that renders a polar molecule (charged negatively on the oxygen end and positively on the hydrogen end). In liquid state, each molecule bonds loosely via hydrogen bonds with four other molecules [2] . In solid (ice) state, the polar molecules firmly arrange themselves in a symmetrical pattern with increased distance between them [3] (in snowflakes, the underlying forces lead to a fantastic variation of forms). The lower density of the solid state is most unusual in nature: while water is densest at 4 centigrades above freezing point, almost all other substances are densest when frozen. Other remarkable properties of water that can be traced back to its molecular structure include: an extraordinary high specific heat capacity, sudden condensation at dew point, exceptional solvent action, and strong cohesion. These properties make water the essential medium for life [4] .
In the V-structure, the bond angle between the two hydrogen atoms is 104.5°. Due to repulsion from 4 unused oxygen valence electrons, the hydrogen configuration is slightly squeezed, or 'bent', from the normal tetrahedral bond angle of 109.5°.
Due to the thermal vibrations of the atoms and molecules, the hydrogen bonds in the liquid state are very weak, i.e., molecules constantly connect and disconnect in milliseconds (see video).
In solid state, the bond angle between the two hydrogen atoms changes to the normal tetrahedral angle of 109.5 ° and all atoms arrange themselves in a highly symmetrical, spatially hexagonal pattern with a distance between their centers that equals the sum of the (short) covalent distance and the (long) hydrogen bond distance.
The unusual heat capacity of water, along with high latent heat of vaporization and melting, softens climatic conditions and makes our planet livable. Water is one of the best solvents and is crucial for metabolic processes. The cohesion of water molecules provides surface tension and capillary action, without which plants and life on our planet would not exist.