Phase Diagram Notes and Problems
Phase Changes
1. solid to liquid:
Melting
2. liquid to gas:
Evaporation
3. solid to gas:
5. gas to liquid:
Sublimation
4. liquid to solid:
Freezing
Condensation
6. gas to solid:
Deposition
Phase Diagram- A graph that tells you what state of matter a substance is in at a particular
temperature and pressure
Points on the Diagram
A = CRITICAL POINT – Highest temperature and pressure a substance can have and still be a
liquid
B = NORMAL MELTING/FREEZING PT – temperature at 1 atm
C = NORMAL BOILING POINT – temperature at 1 atm
D = TRIPLE POINT – Intersection of solid/liquid/gas phases
States of Matter of Specific Points
35⁰C and 1 atm:
 Solid/Liquid
50⁰C and 50 atm:
 Liquid
23⁰C and 0.67 atm:
 Solid/Liquid/Gas
50⁰C and 1 atm:
 Liquid/Gas
68⁰C and 51atm:
 Gas
-50⁰C and 0.75 atm:
 Solid
Phase Diagram Notes and Problems
Phase Diagram Problems
Part 1 – Water Diagram
1. Study the phase diagram of water. What two units are plotted against each other in a phase diagram graph?
Pressure (atm) and Temperature (celcius)
2. Give the state or states of matter present at each of the following conditions:
a. 100⁰C and 1 atm
b. 0⁰C and 1 atm
c. 100⁰C and 225 atm
d. 50⁰C and 1 atm
liquid and gas
solid and liquid
liquid and gas
liquid
f. 150⁰C and 225 atm g. 400⁰C and 240 atm h. 375⁰C and 230 atm
i. -50⁰C and 0.006 atm
liquid and gas
gas
gas
solid
e. 50⁰C and 0.0060 atm
gas
j. 0.01⁰C and 0.006 atm
solid, liquid, gas
3. After a substance passes a certain temperature (critical temperature), it cannot be liquefied. Regardless of the
amount of pressure applied, the substance will remain a gas. What is the critical temperature of water?
374⁰C
4. When a substance reaches its critical pressure, it can be liquefied if enough pressure is applied.
The pressure necessary to do this is called critical pressure. What is the critical pressure of water?
225 atm
5. Give the temperature and pressure for the triple point of water.
0.01⁰C and 0.006 atm
6. What unique condition occurs at the triple point?
All three phases are seen at once
Part 2 – Carbon Dioxide Diagram
7. Label the following on the phase diagram:
- critical temperature
- triple point
- critical pressure
- sublimation line
8. What are the critical temperature and critical pressure of carbon dioxide?
73 atm and 31.1⁰C
9. What is the triple point of carbon dioxide?
5.11 atm and -56.4⁰C
- freezing/melting point line
- boiling point line
Phase Diagram Notes and Problems
10. Can CO2 ever be a liquid at room temperature (25⁰)? Explain why or why not.
Yes if the pressure is high enough
11. When dry ice (solid carbon dioxide) is exposed to room temperature conditions, what process describes its phase
change? How does the phase diagram explain why CO2 does not "melt"?
Sublimation, which is the transition from solid to gas describes why CO2 doesn’t appear to melt when
exposed to room temperature and pressure conditions