Liquid water density

Liquid Water— Density—Compressibility — Viscosity — Vapour Pressure — Capillary Water—Supercooled Water—Thermal Conductivity—Specific Heat—Surface Tcnsmu—Electrical Conductivity—Spectrum— Colour. 

Practice Problem 10.11 Calculate the volume of liquid water (density = 1.00 g/mL) produced by burning 48.4 g of propane gas, CsHg, and condensing the gaseous water produced. ... 

Pore volumes have been obtained from water adsorption considering two different water densities. The density of water in solid phase (0.92 g/cc) has been used to estimate the micropore volume from the amount of water adsorbed until relative pressure around 0.6. In the other hand, the liquid water density has been used to calculate the water volume adsorbed on the relative pressure range around 0.6-0.95. The pore volumes obtained from water adsorption data are quite similar to the corresponding micropore and mesojxrre volumes obtained by nitrogen adsorption, which seems to corroborate that water adsorbs in the microporosity as solid ice, while it adsorbs in the mesoporosity as liquid. 

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... 

Figure 5 Temperature dependence of the concentration C of the tetrahedrally ordered four-coordinated water molecules (upper panel) and of the liquid water density (lower panel) along the liquid-vapour coexistence curve. Vertical dashed line indicates the temperature of the liquid-liquid transition. Dotted lines indicate the densities and concentrations of the coexisting phases. Stars indicate percolation transition of the tetrahedrally ordered four-coordinated molecules.

The sap flows in wood through the vascular system produced by the cambium. This liquid, present in the cell cavities, is usually referred to as free water just because its properties are very close to those of liquid water density, viscosity, saturated vapor pressure, etc. 

Various experimental methods were used to study density depletion of a liquid water near hydrophobic surfaces. In some experimental studies (ellipsometry [223, 224] and neutron reflectivity [225]), density depletion was not found [225]. In many other studies (neutron reflectivity [145, 226-228], X-ray reflectivity [229-231], ellipsometry [232], thermal conductivity [233], liquid water intrusion in hydrophobic pores [234]), noticeable depletion of the hquid water density near various hydrophobic surfaces was detected. Density depletion was found sensitive to the presence of dissolved gases [227], but no such sensitivity was observed in other studies [230, 231]. The available experimental methods do not give exphcit profiles of a liquid water density but rather allow estimation of a density deficit near the surface. For simplicity, this deficit may be attributed to the homogeneous vapor film (the so-called slab approximation), whose thickness D can be used as a measure of a liquid density depletion. If the realistic liquid density profile is close to a sigmoid-like function, D approximately corresponds to a distance between the inflection point of this function and the surface. 

Unlike Western reactors that have negative feedback coefficients in all phases of operation, the RBMK reactors had a positive feedback coefficient under some circumstances. While the graphite provided the vast majority of neutron moderation, the cooling water also absorbed some neutrons. Under certain operating conditions, especially at lower power levels, an increase in power could turn some of the water in the core into steam. This increase in steam would then cause a reduction in neutron absorption because of the reduction in liquid water density. Thus, if power increased while at a low power state, the positive void feedback coefficient would drive the power higher, and potentially exacerbate an accident situation. 

A recent Monte Carlo study of structure of the dilute aqueous solution of methane from this Laboratory involves one methane molecule and 124 water molecules at 25°C at liquid water density. The configurational energy of the system is developed under the assumption of pairwise additivity using potential functions representative of initio quantum mechanical calculations for both the water-water and methane-water interactions. For the water-water interaction we have carried over the MCY-CI potential function used in our previous study of the structure of liquid water reviewed in the preceeding section. For the methane water interaction energy, we have recently reported an analytical potential function representative of quantum mechanical calculations based on SCF calculations and a 6-31G basis set, with correlation effects Included via second order Moller-Plesset (MP) corrections,52 This function was used for the methane-water con-... 

One important class of integral equation theories is based on the reference interaction site model (RISM) proposed by Chandler [77]. These RISM theories have been used to smdy the confonnation of small peptides in liquid water [78-80]. However, the approach is not appropriate for large molecular solutes such as proteins and nucleic acids. Because RISM is based on a reduction to site-site, solute-solvent radially symmetrical distribution functions, there is a loss of infonnation about the tliree-dimensional spatial organization of the solvent density around a macromolecular solute of irregular shape. To circumvent this limitation, extensions of RISM-like theories for tliree-dimensional space (3d-RISM) have been proposed [81,82],... 

Density — the mass per unit volume of any substance, including liquids. The density of a liquid determines whether a spilled material that is insoluble in or immiscible with water will sink or float on water. Knowledge of this behavior is essential in checking whether to use water to suppress a fire involving the material. 

The simulated free surface of liquid water is relatively stable for several nanoseconds [68-72] because of the strong hydrogen bonds formed by liquid water. The density decrease near the interface is smooth it is possible to describe it by a hyperbolic tangent function [70]. The width of the interface, measured by the distance between the positions where the density equals 90% and 10% of the bulk density, is about 5 A at room temperature [70,71]. The left side of Fig. 3 shows a typical density profile of the free interface for the TIP4P water model [73]. 

The major difference of the water structure between the liquid/solid and the liquid/liquid interface is due to the roughness of the liquid mercury surface. The features of the water density profiles at the liquid/liquid interface are washed out considerably relative to those at the liquid/solid interface [131,132]. The differences between the liquid/solid and the liquid/liquid interface can be accounted for almost quantitatively by convoluting the water density profile from the Uquid/solid simulation with the width of the surface layer of the mercury density distribution from the liquid/liquid simulation [66]. 

V = liquid viscosity, centistokes = Density water/Density liquid ... 

For solids and liquids, the density is a weak function of pressure and, therefore, the temperatures T and T, ., are usually stated. Also, the reference substance is commonly taken as water at 4°C at which p = 1.000 g/cm = 62.43 Ib/ft . If a single temperature is stated, it implies that both densities have been measured at that temperature. 

Molecules are much closer to one another in liquids and solids. In the gas state, particles are typically separated by ten molecular diameters or more in liquids or solids, they touch one another. This explains why liquids and solids have densities so much larger than those of gases. At 100°C and 1 atm, H20(/) has a density of 0.95 g/mL that of H20(g) under the same conditions is only 0.00059 g/mL For the same reason, liquids and solids are much less compressible than gases. When the pressure on liquid water is increased from 1 to 2 atm, the volume decreases by 0.0045% the same change in pressure reduces the volume of an ideal gas by 50%. 

E3.10 In the following table are presented a (coefficient of expansion), k (compressibility), and p (density) for liquid water and liquid CCI4. Use... 

FIGURE 5.20 Variation in the densities of water and tetrachloromethane with tem )erature. Note that ire is less dense than liquid water at its freezing point and that water has its maximum density at 4°C. 

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