Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
127
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 12
Phase diagrams Temperature and pressure control the phase of a
substance. A phase diagram is a graph of pressure versus temperature that shows in which phase a substance exists under different
conditions of temperature and pressure. A phase diagram typically
has three regions, each representing a different phase and three
curves that separate each phase. The points on the curves indicate
conditions under which two phases coexist. The phase diagram for
each substance is different because the normal boiling and freezing
points of substances are different.
The triple point is the point on a phase diagram that represents
the temperature and pressure at which three phases of a substance
can coexist. All six phase changes can occur at the triple point:
freezing and melting, evaporation and condensation, sublimation
and deposition. The critical point indicates the critical pressure and
the critical temperature above which a substance cannot exist as a
liquid.
Practice Problems
12. Answer the following questions about the phase diagram for
water in Figure 13-28a on page 409 of your textbook.
a. List the phase changes a sample of ice would go through if
heated to its critical temperature at 1 atm pressure.
b. At what range of pressure will water be a liquid at temperatures above its normal boiling point?
c. In what phase does water exist at its triple point?
13. Answer the following questions about the phase diagram for
carbon dioxide in Figure 13-28b on page 409 of your textbook.
a. What happens to solid carbon dioxide at room temperature
at 1 atm pressure?
b. The triple point for carbon dioxide is 5 atm and Ϫ57°C. List
the phase changes a sample of dry ice would go through if
heated from Ϫ100°C to 10°C at 6 atm pressure.
▲
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
127
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 12
Phase diagrams Temperature and pressure control the phase of a
substance. A phase diagram is a graph of pressure versus temperature that shows in which phase a substance exists under different
conditions of temperature and pressure. A phase diagram typically
has three regions, each representing a different phase and three
curves that separate each phase. The points on the curves indicate
conditions under which two phases coexist. The phase diagram for
each substance is different because the normal boiling and freezing
points of substances are different.
The triple point is the point on a phase diagram that represents
the temperature and pressure at which three phases of a substance
can coexist. All six phase changes can occur at the triple point:
freezing and melting, evaporation and condensation, sublimation
and deposition. The critical point indicates the critical pressure and
the critical temperature above which a substance cannot exist as a
liquid.
Practice Problems
12. Answer the following questions about the phase diagram for
water in Figure 13-28a on page 409 of your textbook.
a. List the phase changes a sample of ice would go through if
heated to its critical temperature at 1 atm pressure.
b. At what range of pressure will water be a liquid at temperatures above its normal boiling point?
c. In what phase does water exist at its triple point?
13. Answer the following questions about the phase diagram for
carbon dioxide in Figure 13-28b on page 409 of your textbook.
a. What happens to solid carbon dioxide at room temperature
at 1 atm pressure?
b. The triple point for carbon dioxide is 5 atm and Ϫ57°C. List
the phase changes a sample of dry ice would go through if
heated from Ϫ100°C to 10°C at 6 atm pressure.
▲