CDA #6 (KMT and Thermo) Review
Phase Changes: Be familiar with phase change graphs and when kinetic and potential energy change. Know
the parts of a phase diagram, including the 3 phases of matter, triple point, and critical point.
Thermodynamics: Know the 3 laws of thermodynamics and how to calculate energy and specific heat.
Calorimetry: Know how heat is transferred in a closed system and how to calculate specific heat of an
unknown object.
Phase Diagram Practice:
1. Consult the two phase diagrams below to answer the following questions. (Note: the graphs are not
drawn to scale.)
218
Pressure (atm)
73
Solid
Liquid
Solid
Liquid
5.1
1 atm
Gas
0.006
Gas
-78 -57
31
Temperature (C)
Carbon Dioxide (CO2)
0
100
374
0.001
Water (H2O)
a. At 1 atm of pressure and 55C, what phase is CO2 in? ________________________ And water?
_________________________
b. What is the value of the triple point for CO2? _________C, _________ atm. And for water?
_________C, _________ atm.
c. What is the value of the critical point for CO2? _________C, _________ atm. And for water?
_________C, _________ atm.
d. What is the value of the melting point for water? _________C. And the boiling point? _________C.
e. If the pressure on a block of ice is increased, the melting point of ice (increases, decreases, or stays the
same).
f. Pressure must be (increased / decreased) in order to liquefy water at 140ºC.
g. What is the name of the process when CO2 is cooled at 1atm from 25ºC to -100ºC?
h. Increased pressure will (lower / raise) the melting point of water.
i. Solid water was heated to its critical temperature at a pressure of 1.00 atm. List the phases and phase
changes in order as they occur.
j. A sample of solid water is held at a constant pressure of 1.00 atm and is heated to 200 oC. List the
phases and phase changes in order as they occur.
k. A sample of CO2 is held at a constant temperature of 0C. The pressure is increased form 0.006 atm to
73 atm. List the phases and phase changes in order as they occur.
l. List the phase change(s) for CO2 as temperature increases from -70ºC to 25 ºC at 1atm.
Thermodynamics Problems:
2. How much heat is required to rasise the temperature of 19.68g of calcium from 18.00°C to 82.40°C?
The specific heat for calcium is 0.647 J/g°C.
3. 150.0 J of heat are applied to a 35.73g sample of an unknown element. The sample’s temperature
increases from 20.00°C to 49.99°C. What is the specific heat of the element?
4. 1000.0J of heat are applied to a 140.0g sample of water. If the sample’s temperature was originally
15.00°C, what will its final temperature be? The specific heat of water is 4.184 J/g°C.
5. A 4.5 g sample of a unknown metal at 100 °C is placed in 50g of water at 20 °C. The final temperature
of the water and metal together is 23 °C. What is the specific heat of the unknown metal?
6. A 2.5 gram sample of an unknown metal at 11C is placed in 70 g of water at 62C. The final
temperature of the water and metal together is 58C. What is the specific heat of the unknown metal?
7. A sample of nickel at 100C is placed in 50 g of water at 22C. The final temperature of the water and
metal together is 26C. What was the mass of the piece of nickel? The specific heat of nickel is 0.540
J/g °C.
Review Questions:
8. Draw a phase change graph for water (temperature vs. heat). Show where solid, liquid and gas exist as
well as the relevant phase changes. Show where the kinetic and potential energy are increasing.
9. There are three laws concerning energy-explain and give an example of each.
10. What is entropy? Reactions always naturally occur to (increase / decrease) entropy.
11. Endo/Exothermic: define and give examples. What is the difference between them?
12. What is the difference between temperature and heat?