Phase diagram of water

Phase diagram of water (not to scale). The curves and line represent the temperatures and pressures at which phases are in equilibrium. The triple point is at 0.0rC, 4.56 mm Hg the critical point is at 374°C. 

Figure 1.4 Phase diagram of water around the supercritical region.

Fig. 1.12. Phase diagram of water - glycerine. On the left hand side the dependence of the phase transition time from the ice temperature is shown At -140 °C, amorphous ice transforms into cubic ice in approx. 10 min (Fig. 8 from [1.98]).

Freeze drying is mostly done with water as solvent. Fig. 1.1 sows the phase diagram of water and the area in which this transfer from solid to vapor is possible. This step is difficult, even for pure water. If the product contains two or more components in true solutions or suspensions, the situation can become so complicated that simplified model substances have to be used. Such complex systems occur ubiquitously in biological substances. 

We now look at the phase diagram of water in Figure 5.6, which will help us follow the modem method of removing the water from coffee to yield anhydrous granules. A low temperature is desirable to avoid charring the coffee. Water vapour can be removed from the coffee solution at any temperature, because liquids are always surrounded by their respective vapour. The pressure of the vapour is the saturated vapour pressure, s.v.p. The water is removed faster when the applied pressure decreases. Again, a higher temperature increases the rate at which the vapour is removed. The fastest possible rate occurs when the solution boils at a temperature we call T oii). 

Figure 5.10 Phase diagram of water. Inset applying a high pressure from p (here p ) to pi causes the melting temperature of the ice to decrease from temperature T (here 0 °C) to 7i...

A summary of our results on the phase diagram of water is shown in Figure 8. We find that the molecular to non-molecular transition in water occurs in the neighborhood of the estimated ZND state of HMX. This transition shows that the detonation of typical energetic materials occurs in the neighborhood of the molecular to non-molecular transition. 

Figure 2.30. Typical one-component systems (a) Room temperature, room pressure region of the well-known PIT phase diagram of water (notice the logarithmic scale of pressure), (b) P-T phase diagram of elemental Fe. The fields of existence of the different forms of Fe are shown a (body-centred cubic Fe), (face-centred cubic), 6 (body-centred cubic, high-temperature form isostructural with a), e (hexagonal close packed), L (liquid Fe). The gas phase field, owing to the pressure scale and the not very high temperatures considered, should be represented by a very narrow region close to the T axis.

Recently, new ordered mesoporous silicas have also been synthesized by using self-organization of amphiphilic molecules, surfactants and polymers either in acidic or basic condition. A schematic phase diagram of water-surfactant is shown in the figure. 

Figure 4.34 Phase diagram of water (a) P versus V (b) V versus T...

Figure 3 The phase diagram of water. Critical temperature and pressure of light water, H2O, are 374 C and 22.1 MPa.

Draw a phase diagram of water. What is called a phase, component, and degree of freedom How many phases and degrees of freedom are there at different points of the phase diagram of water What is known as the freezing (boiling) point of pure substances ... 

Figure 7.1 Schematic phase diagram of water (not to scale), showing phase boundaries (heavy solid lines), triple point (triangle), critical point (circle-x), and a representative point (circle, dotted lines) at 25°C on the liquid-vapor coexistence curve.

A vacuum pump is attached to a flask of water at 0°C and 2 atm and the pressure on the liquid is decreased to 5 Torr. (a) Explain what would be observed, by using the phase diagram of water in Fig. 

Freeze-dried foods are prepared by freezing the food and removing water by subliming the ice at low pressure. Look at the phase diagram of water in Figure 10.28, and tell the maximum pressure (in mm Hg) at which ice and water vapor are in equilibrium. 

Phase diagrams of water, hydrocarbon, and nonionic surfactants (polyoxyethylene alkyl ethers) are presented, and their general features are related to the PIT value or HLB temperature. The pronounced solubilization changes in the isotropic liquid phases which have been observed in the HLB temperature range were limited to the association of the surfactant into micelles. The solubility of water in a liquid surfactant and the regions of liquid crystals obtained from water-surfactant interaction varied only slightly in the HLB temperature range. 

As a last example, we consider the binary phase diagram of water and 1-butanol (Figs. 6.16 and 6.17). There is a negative heat of mixing, HE, but a positive excess Gibbs energy of mixing, GE. The infinite dilution activity coefficient of 1-butanol in water is very... 

Fig. 1.11. Phase diagram of water. L = liquid water Ih = hexagonal ice lc = cubic ice 111—IX crystal configurations of ice (Figure 1 from [1.7])...

A substance that can exist in more than one crystalline form is said to exhibit allotropy, and the different forms are called allotropes. Figure 9 is the high-pressure part of the phase diagram of water and shows that water has a number of allotropes. The crystalline forms of water in the allotropes that melt are... 

C. Vega et al., Can simple models describe the phase diagram of water J. Phys. Condens. Matter 17, S3283-S3288 (2005)... 

Figure 7. Phase diagram of water s stable crystal polymorphs. Metastable polymorphs such as ice IV or ice XII do not show up. Adapted from Ref. [147].

Figure 13. Schematic phase diagram of water s metastable states. Line (1) indicates the upstroke transition LDA —>HDA —>VHDA discussed in Refs. [173, 174], Line (2) indicates the standard preparation procedure of VHDA (annealing of uHDA to 160 K at 1.1 GPa) as discussed in Ref. [152]. Line (3) indicates the reverse downstroke transition VHDA—>HDA LDA as discussed in Ref. [155]. The thick gray line marked Tx represents the crystallization temperature above which rapid crystallization is observed (adapted from Mishima [153]). The metastability fields for LDA and HDA are delineated by a sharp line, which is the possible extension of a first-order liquid-liquid transition ending in a hypothesized second critical point. The metastability fields for HDA and VHDA are delineated by a broad area, which may either become broader (according to the singularity free scenario [202, 203]) or alternatively become more narrow (in case the transition is limited by kinetics) as the temperature is increased. The question marks indicate that the extrapolation of the abrupt LDA<- HDA and the smeared HDA <-> VHDA transitions at 140 K to higher temperatures are speculative. For simplicity, we average out the hysteresis effect observed during upstroke and downstroke transitions as previously done by Mishima [153], which results in a HDA <-> VHDA transition at T=140K and P 0.70 GPa, which is 0.25 GPa broad and a LDA <-> HDA transition at T = 140 K and P 0.20 GPa, which is at most 0.01 GPa broad (i.e., discontinuous) within the experimental resolution.

The ideas underlying elemental structures models are to establish microstructures experimentally, to compute free energies and chemical potentials from models based on these structures, and to use the chemical potentials to construct phase diagrams. Jonsson and Wennerstrom have used this approach to predict the phase diagrams of water, hydrocarbon, and ionic surfactant mixtures [18]. In their model, they assume the surfactant resides in sheetlike structures with heads on one side and tails on the other side of the sheet. They consider five structures spheres, inverted (reversed) spheres, cylinders, inverted cylinders, and layers (lamellar). These structures are indicated in Fig. 12. Nonpolar regions (tails and oil) are cross-hatched. For these elemental structures, Jonsson and Wennerstrom include in the free energy contributions from the electrical double layer on the water... 

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