The properties of water and ions

Freezing and boiling temperature of dihydride molecules of elements in column VI of the periodic table as a function of their molecular mass. The actual values for H2O are connected by a solid line. Extrapolated melting and boiling points for water are indicated by the dashed line. Modified from Libes (1992). 

The cumulative heat energy needed to heat water from —50 to +150 C. Modified from Libes (1992). 

The specific structure of hquid water is poorly defined, but can be thought of as a slush of ice-like clumps floating in a pool of relatively unassociated H2O molecules. This t5q e of mixture helps explain many of the maxima and minima in such physical properties as density and viscosity that are often observed when liquid water is cooled or pressurized. The best known of these trends is the maximum in liquid water density near 4°C (Fig. 3.5). This phenomenon 

The structure of Ice-1, the predominant form of ice at one atmosphere pressure. Shaded spheres indicate oxygen atoms and open spheres hydrogen atoms. The darker shading represents four closest neighbor water molecules. 

The density of liquid water as a function of temperature. The relative proportions of free molecules (unconnected circles) and ordered molecules (circles connected by lines) are illustrated for selected temperatures (°C) in the schematic illustration. Modified from Libes (1992). 

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