Chapter 9, Problem 117QRT

The phase diagram for water over a relative narrow pressure and temperature range is given in Figure 9.19. A phase diagram over a considerably wider range of temperature and pressure (kbar) is given nearby. This phase diagram illustrates the polymorphism of ice, the existence of a solid in more than one form. In this case, Roman numerals are used to designate each polymorphic form. For example, Ice I, ordinary ice, is the form that exists under ordinary pressures. The other forms exist only at higher pressures, in some cases extremely high pressure such as Ice VII and Ice VIII.

1. (a) Using the phase diagram, give the approximate P and T conditions at the triple point for Ice III, Ice V, and liquid water.
2. (b) Determine the approximate temperature and pressure for the triple point for Ices VI, VII, and VIII.
3. (c) What is anomalously different about the fusion curves for Ice VI and Ice VII compared to that of Ice I?
4. (d) What phases exist at 8 kbar and 20 °C?
5. (e) At a constant temperature of −10 °C, start at 3 kbar and increase the pressure to 7 kbar. Identify all the phase changes that occur sequentially as these conditions change.
6. (f) Explain why there is no triple point for the combination of Ice VII, Ice VIII, and liquid water.