Water's unexplained properties
Density and specific volume of a liquid versus change in pressure and temperature. The density of water versus temperature and pressure is indicated below. Fluid pressure calculator solving for change in volume given bulk modulus, initial volume and pressure. Gas molecules inside a volume (e.g. a balloon) are constantly moving around freely. . If water were used instead of mercury, the height of the column equivalent to relationships linking the three variables temperature, pressure and density.
This relationship is shown below P' is the scaled pressure, that is, the left side of the above expression as the dashed lines, with the colored lines being the experimental data.
The best fit is thus around the compressibility minimum at The extrapolated density at zero T and P is 1. Densities of water tend towards a 6th power law dependent on temperature and pressure As this power law does not obey the rule of thumb that candidate power laws should exhibit an approximately linear relationship on a log-log plot over at least two orders of magnitude in both the x-axes and y-axes [ ], it seems likely that this relationship is purely empirical.
I am again grateful to Frank Grimer for pointing me at this relationship.
- Pressure, temperature, and volume relation in liquids
- Water's Unexpected Properties
Volume change increases as the square-root 3 power of the temperature The square-root 3 term is related to the Vesica Piscesbeing the ratio of the long to short diameter of intersecting expanded icosahedral water clusters the short diameter being the distance between the centers of neighboring dodecahedra and the long diameter associated with a plane of water molecules between the two pentameric boxes Figure 3h joining them.
I am again grateful to Frank Grimer for showing me this relationship.
Log10 T-T0 vs log viscosity data In the graph above, H2O values are shown by the green squares red lineand D2O values are indicated by the blue diamonds blue line. As this power law does not quite obey the rule of thumb that candidate power laws should exhibit an approximately linear relationship on a log-log plot over at least two orders of magnitude in both the x-axes and y-axes [ ], it seems possible that this relationship is curious but purely empirical.
Pressure, temperature, and volume relation in liquids | Physics Forums
This power law has recently been investigated using new viscosity data [ ]. The shape of this profile-curve is called a negative exponential decrease compare Figures 1.
The density profile behaves in a similar way. The pressure generated by an overlying column of fluid is thus termed the hydrostatic pressure. The upper boundary of the air column that gives rise to atmospheric pressure is the vacuum of space. Being rather light, the mass of a column of air with a 1 cm2 cross section is almost exactly 1 kg.Pressure vs. Volume and Boyle's Law
If a much heavier liquid substance is used to balance this air column, only a relatively small length would be needed. In addition, because the density of liquids does not change with height most liquids are incompressiblesuch an equivalent liquid column has a well defined upper boundary below a vacuumOne of the heaviest liquids at room temperature is mercury Hg and the height of the Hg-column that is equivalent to normal pressure mb is only mm long For this reason, columns of mercury, "hanging" in an inverted vacuum tube, can be used as practical instruments to measure atmospheric pressure see FigureLutgens and Tarbuck, If water were used instead of mercury, the height of the column equivalent to normal pressure would be The Gas Laws The example of the gas-filled balloon can also be used to explore the basic gas laws see also Appendix D, p.