Princeton 2012/Barron 4th ed.
AP Practice Problems
Unit 7 – States of Matter
Multiple Choice (no calculator)
For questions 1-4 refer to the phase
diagram below.
5. When a substance undergoes a phase
change from liquid to solid, which of
the following will occur? (P7.5)
a. Energy will be released by
the substance because
intermolecular forces are
being weakened.
b. Energy will be released by
the substance because
intermolecular forces are
being strengthened.
c. Energy will be absorbed by
the substance because
intermolecular forces are
being weakened.
d. Energy will be absorbed by
the substance because
intermolecular forces are
being strengthened.
e. The energy of the substance
will not be changed.
1. At this point, the substance
represented by the phase diagram
will be solely in the solid phase at
equilibrium. (P7.1)
2. This point represents a boiling point
of the substance. (P7.2)
3. At this point, the substance
represented by the phase diagram
will be undergoing sublimation.
(P7.3)
4. At this point, the substance
represented by the phase diagram
will be solely in the liquid phase at
equilibrium. (P7.4)
6. During which of the following phase
changes must heat be added to
overcome intermolecular forces?
(P7.6)
I.
II.
III.
Vaporization
Sublimation
Deposition
a.
b.
c.
d.
e.
I only
II only
I and II only
I and III only
III only
Princeton 2012/Barron 4th ed.
Use the following phase diagram to answer
questions 7-10.
9. Which of the following lists the three
phases of the substance shown in the
diagram in order of increasing
density at -5°C? (P7.9)
a.
b.
c.
d.
e.
7. As pressure on the substance
depicted in the diagram is increased
at constant temperature, which of the
following phase changes CANNOT
occur? (P7.7)
I.
II.
III.
10. When the temperature of the
substance depicted in the diagram is
decreased from 10°C to -10°C at a
constant pressure of 0.3 atmospheres,
which phase change will occur?
(P7.10)
a.
b.
c.
d.
e.
Condensation
Melting
Freezing
a.
b.
c.
d.
e.
I only
II only
III only
I and II only
I and III only
8. At a temperature of 50°C and a
pressure of 0.2 atmospheres, the
substance depicted in the diagram is
(P7.8)
a.
b.
c.
d.
e.
in the gas phase
in the liquid phase
in the solid phase
at its triple point
at its critical point
Solid, gas, liquid
Solid, liquid, gas
Gas, liquid, solid
Gas, solid, liquid
Liquid, solid, gas
Gas to liquid
Liquid to solid
Gas to solid
Liquid to gas
Solid to liquid
11. Which of the following processes
can occur when the temperature of a
substance is increased at constant
pressure? (P7.11)
I.
II.
III.
Sublimation
Melting
Boiling
a.
b.
c.
d.
e.
I only
II only
I and II only
II and III only
I, II, and III
Princeton 2012/Barron 4th ed.
12. The temperature above which gas
molecules become too energetic to
form a true liquid, no matter what the
pressure, is called the (P7.12)
a.
b.
c.
d.
e.
melting point
critical point
boiling point
triple point
freezing point
Questions 13-15 are based on the
information given below.
In an experiment, a solid 1 molar sample of
Substance A was gradually heated by a
source of constant energy for several hours
and the temperature was measured
periodically. At the end of the heating
period, Substance A had been converted to
the gas phase. The heating curve produced
by this experiment is shown below.
13. During the course of the experiment,
there was a period of time when the
solid phase of Substance A was in
equilibrium with the liquid phase.
At what temperature did this occur?
(P7.13)
a.
b.
c.
d.
e.
Between 100K and 150K
At 150K
Between 150K and 250K
At 250K
Between 250K and 350K
14. Based on the data given in the
heating curve, which of the
following statements is NOT true
regarding Substance A? (P7.14)
a. The boiling point of
Substance A is 250K.
b. The freezing point of
Substance A is 150K.
c. The heat of vaporization of
Substance A is greater than
the heat of fusion.
d. Substance A is a liquid at
room temperature.
e. The intermolecular forces
exhibited by Substance A are
weaker than those of water.
15. During the course of the experiment,
Substance A was gradually heated
from 100K to 350K. When the
temperature reached 250K, the
energy absorbed by Substance A
(P7.15)
a. was used to change from
liquid to gas phase.
b. was used to change from gas
to liquid phase.
c. was used to change from
solid to liquid phase.
d. was used to change from
liquid to solid phase.
e. was reduced to zero.
Princeton 2012/Barron 4th ed.
16. In which of the following are the
intermolecular forces listed from the
weakest to strongest? (B8.1)
a. Dipole-dipole > London >
hydrogen bonds
b. London < dipole-dipole <
hydrogen bonds
c. Hydrogen bonds < dipoledipole < London
d. London < hydrogen bonds <
dipole-dipole
e. London < hydrogen bonds <
dipole-dipole
17. Which of the following consistently
have the highest melting points?
(B8.2)
a.
b.
c.
d.
e.
Metals
Salts
Molecular crystals
Alkanes
Hydrogen-bonded
compounds
18. Carbon dioxide sublimes. Which
physical transition occurs in
sublimation? (B8.3)
a.
b.
c.
d.
e.
Gas to liquid
Gas to solid
Solid to liquid to gas
Solid to gas
Solid to liquid
19. Which of the following compounds
will NOT hydrogen bond? (B8.5)
a.
b.
c.
d.
e.
f.
CF4
CH3OH
H2NCH2CH2CH3
CH3CH2CH2CH2COOH
HOCH2CH2OH
HClO
20. When the following compounds are
kept at the same temperature, the
compound expected to evaporate
most quickly is (B8.6)
a.
b.
c.
d.
e.
C8H18
C8H17OH
C8H17NH2
C6H14
C7H15COOH
21. Which of the following will have the
greatest change in its boiling point if
the pressure at which it is boiled is
changed from 1.00 atm to 0.900 atm?
(The numbers in parentheses are the
heats of vaporization in kilojoules
per mole.) (B8.7)
a.
b.
c.
d.
e.
Water (43.9)
Ammonia (21.7)
Methane (8.2)
Bromine (15.0)
Fluorine (5.9)
22. Which of the following statements is
NOT consistent with the crystal
properties of the substance? (B8.8)
a. SiC is used to grind metal
parts to shape.
b. Tungsten is drawn into thin
wires.
c. Aluminum is used to cut
glass.
d. Graphite is used to lubricate
locks.
e. MgF2 shatters when dropped.
Princeton 2012/Barron 4th ed.
23. C30H62 is a nonpolar compound that
is a solid at room temperature and
water is highly hydrogen bonded but
is a liquid because (B8.9)
a. water molecules are very
light.
b. water molecules ionize
easily.
c. the 62 hydrogen atoms in
C30H62 allow for many
instantaneous dipoles that
exceed the attractive force of
a hydrogen bond.
d. C30H62 is so large that it
cannot melt.
e. C30H62 has a lower melting
point if dissolved in nonpolar
hexane.
24. On the basis of this heating curve,
which of the following statements is
true? (B8.11)
Use the phase diagram below for questions
25-28.
25. Determine, from the phase diagram,
the maximum temperature at which
this compound will sublime. (B8.13)
a.
b.
c.
d.
e.
100°C
230°C
115°C
95°C
It cannot sublime
26. What is the normal boiling point of
this compound? (B8.14)
a.
b.
c.
d.
e.
a. The heat of fusion and heat of
vaporization are about equal.
b. The heat capacities of the
solid, liquid, and gas are
approximately equal.
c. The heat capacity of the gas
is greater than that of the
liquid.
d. The heat capacity of the gas
is greater than the heat of
fusion.
e. The heat of vaporization is
less than the heat of fusion.
95°C
100°C
50°C
180°C
150°C
27. At 125°C and 1.50 atm of pressure
this substance will be (B8.15)
a.
b.
c.
d.
a liquid
a solid
a gas
a solid and liquid in
equilibrium
e. a gas and liquid in
equilibrium
Princeton 2012/Barron 4th ed.
28. Which pair of temperatures and
pressures will produce a supercritical
fluid? (B8.16)
a.
b.
c.
d.
e.
150°C and 2.00 atm
95°C and 1.00 atm
145°C and 2.30 atm
10°C and 0.15 atm
250°C and 2.00 atm
29. A student observed that a small
amount of acetone sprayed on the
back of the hand felt very cool
compared to a similar amount of
water. You explanation of this
phenomena should be that (B8.17)
a. all organic compounds do
this
b. acetone has a lower viscosity
and transfers heat quanta
better
c. water has a higher heat
capacity than acetone,
therefore, retaining more heat
d. the higher vapor pressure of
acetone results in more rapid
evaporation and heat loss
e. The observed effect is not
real and is only imagined
30. When a pot of water boils on the
stove, small bubbles form at the
bottom of the pan and rise to the
surface. What is inside these
bubbles? (B8.18)
a.
b.
c.
d.
e.
Steam
Hydrogen gas
Oxygen gas
A vacuum
Air
31. Diamond is classified as (B8.19)
a.
b.
c.
d.
e.
A covalent crystal
An ionic crystal
An amorphous solid
A metallic crystal
A molecular crystal
32. A liquid substance that exhibits low
intermolecular attractions is expected
to have (B8.20)
a. Low viscosity, low boiling
point, and low heat of
vaporization
b. High viscosity, low boiling
point, and low heat of
vaporization
c. Low viscosity, high boiling
point, and low heat of
vaporization
d. Low viscosity, low boiling
point, and high heat of
vaporization
e. High viscosity, high boiling
point, and high heat of
vaporization
Princeton 2012/Barron 4th ed.
Essays
1. The phase diagram for a substance is shown below. Use the diagram and your
knowledge of phase changes to answer the following questions.
a. When the substance is at a pressure of 0.8 atmospheres and a temperature of 50K,
what is its phase?
b. Describe the change in phase that the substance undergoes when the pressure is
decreased from 1.2 atmospheres to 0.6 atmospheres at a constant temperature of
110K.
c. A constant source of heat was applied to the substance at a constant pressure of 0.8
atmospheres. The substance was initially at a temperature of 50K. The temperature
of the substance increased at a constant rate until 70K was reached. At this point, the
temperature remained constant for a period of time, then continued to climb at a
constant rate. Explain what has happened.
d. What is the normal boiling point for this substance?
2. The phase diagram for a substance is shown below. Use the diagram and your
knowledge of phase changes to answer the following questions.
Princeton 2012/Barron 4th ed.
a. Describe the phase change that the substance undergoes as the temperature is
increased from points B to C to D at constant pressure.
b. Which of the phases are in equilibrium at point F? Give a name for one of the phase
changes between these two phases.
c. Could this phase diagram represent water? Explain why or why not.
d. What is the name given to point A, and what is the situation particular to this point?
Princeton 2012/Barron 4th ed.
Answer Key Unit 7 – States of Matter
Multiple Choice
1. B
2. D
3. A
4. C
5. B
6. C
7. C
8. A
9. D
10. B
11. E
12. B
13. B
14. D
15. A
16. B
17. B
18. D
19. A
20. D
21. A
22. C
23. C
24. A
25. D
26. D
27. A
28. E
29. D
30. A
31. A
32. A
Essays
1. a. solid
b. vaporization (liquid to gas)
c. At 70K, the substance melted. While the substance was melting, the heat from the
constant source went toward overcoming the strong intermolecular forces of the solid
instead of increasing the temperature. The heat that must be put into a solid to melt it is
called the heat of fusion. When the heat of fusion was overcome and the substance was
entirely in the liquid phase, the temperature of the liquid began to increase at a constant
rate.
d. 115K (boiling point at a pressure of 1 atm)
2. a. At point B, the substance is a solid. At point C, the substance is in equilibrium
between solid and liquid phase; it is melting. At point D, the substance is entirely in the
liquid phase.
b. At point F, the substance is in equilibrium between the gas and the solid phases. When
a substance changes from solid to gas phase, it is called sublimation. When a substance
changes from gas to solid phase, it is called deposition.
c. The diagram cannot represent water. For water, the slope of the solid-liquid
equilibrium line must be negative, indicating that the liquid phase of water is denser than
the solid phase.
d. Point A is called the triple point. At the triple point, all three phases can exist in
equilibrium.