Solids and Liquids Test Review Problems
Name _________________________
I. Intermolecular Forces (IMF)
1. List these intermolecular forces in terms of increasing strength: dipole-dipole forces, dispersion
forces, hydrogen bonding.
Weakest: dispersion aka London aka London dispersion forces
Dipole-dipole
Strongest: H – bond
2. Do gas molecules have the same kinds of intermolecular forces as solids? If so, explain why gas particles are
considered to be “independent” or not attracted to each other.
Yes, gas molecules have the same IMFs as solids and liquids, but the IMFs are effective, or noticeable, in solids
and liquids only. Gas molecules are considered independent of one another since the IMFs between them are not
noticeable. The IMFs are not noticeable because gas molecules possess larger amounts of kinetic energy (when
compared to liquids and solids). These large amounts of energy disrupt and break the IMFs. Also, gas molecules
are spaced very far apart, they move randomly and thus are not close enough to each other for the IMFs to be
noticeable.
3. Explain why H2O exhibits hydrogen bonding while H2S does not.
•
H-bonding occurs between molecules containing a hydrogen atom bonded to a small, highly
electronegative atom (H-N, H-O & H-F)
• The small electronegative atom must have at least one lone pair of electrons
Even though H2S has two lone pair of electrons on the central S atom, S is not a small highly electronegative
atom and both of the conditions given above must be met for H-bonding to occur.
4. List the type(s) of IMF present in samples of the following molecules:
a. carbon disulfide
This molecule is linear, S=C=S, and nonpolar. As a result only dispersion forces are present.
b. hydrochloric acid
H-Cl, polar molecule, dispersion, dipole-dipole
c. water
dispersion, dipole-dipole, H-bond
d. hexane
Remember: All C-H bonds are nonpolar. Thus this is a nonpolar molecule and only has dispersion forces
between the molecules.
II. Liquids
1. What is the relationship between temperature and viscosity?
Indirect/inverse relationship. As temperature increases, viscosity decreases and vice versa.
2. What is the relationship between IMF and viscosity?
Direct. As the strength of the IMFs increase, viscosity increases.
3. List two substances that will be highly viscous and two that will have low viscosity.
Highly viscous: honey, heavy syrup, gels.
Low viscosity: air, rubbing alcohol, acetone, water (when compared to the materials listed above)
4. What is surface tension and what factors of a molecule affect it.
Surface tension is defined as the imbalance of forces at the surface of a liquid.
The uneven forces at the surface of a liquid make the surface behave as if it has a tight film stretched
across it.
Factors that affect it are a molecule’s IMFs and since molecular size, molar mass, and distribution of
charge (i.e. how polar a molecule is) affects IMF, these factors also affect surface tension. The stronger
the intermolecular forces, the higher the surface tension.
5. Explain how surface tension of a liquid acts to support a small mass.
The uneven forces at the surface of a liquid make the surface behave as if it has a tight film stretched
across it. A small mass is unable to break these strong IMFs and thus can’t penetrate the tight film at the
surface of the liquid.
III. Solids
1. Identify the following as allotropes or alloys:
a. Bronze - alloy
b. Ozone - allotrope
c. carbon steel - alloy
d. white phosphorus - allotrope
e. diamond - allotrope
f. brass - alloy
g. stainless steel – allotrope
2. How is an amorphous solid different from other solids?
An amorphous solid is a solid whose particles lack a regular repeating pattern. The particles are arranges in a
disordered arrangement. One could describe this arrangement as that of a liquid that has been cooled to such a
low temperature that its viscosity becomes very high. Examples are glass, rubber, wax and tar. Amorphous solids
also get softer over a wide range of temperatures before melting.
Other solids have particles that exist in a highly ordered repeating pattern.
3. How does a crystal lattice differ from a unit cell?
A unit cell is the smallest pattern that repeats itself. A bunch of unit cells from the crystal lattice.
4. Classify the following as a specific type of solid:
a. Xe
molecular solid, crystalline
b. Sugar
molecular, crystalline
c. NaCl
ionic, crystalline
d. Quartz
covalent-network, crystalline
e. iron
metallic, crystalline
f. diamond
covalent-network, crystalline
g. glass
amorphous
h. Cu
metallic, crystalline
i. Sulfur
molecular solids, crystalline
j. Graphite
covalent-network, crystalline
5. Why does ice float in water when most other solids sink when placed in their liquids?
Ice is less dense than liquid water. In liquid water each molecule is hydrogen bonded to between 2.5 and 3.5 other
water molecules. In ice each molecule is hydrogen bonded to 4 other molecules. The presence of the additional
H-bonds causes an arrangement of water molecules so that the structure opens up or expands. The ice structure
takes up more volume than the liquid water molecules; hence ice is less dense than liquid water.
IV. Changes of State
1. Complete the following chart describing changes of state:
Solid
Liquid
Gas
2. What is the relationship between vapor pressure and IMF?
Stronger IMFs, lower vapor pressure. Weaker IMFs, higher vapor pressure.
3. What is the relationship between melting point and vapor pressure?
High melting point, low vapor pressure. Low melting point, high vapor pressure
Strong IMFs are associated with a high boiling point and a high melting point and low vapor pressure.
Weak IMFs are associated with low boiling point, low melting point, and high vapor pressure.
4. Using the table below, determine the boiling point of each of the following under the conditions listed:
PVapor (kPa)
0.2
1
2
5
891
979
1025
1085
BPLi (K)
1040
1145
1200
1275
a. Li at 80 kPa
between 1530 and 1620 K
b. Mg at 60 kPa
slightly greater than 1295 K
c. Mg at 30 kPa
d. Li at 70 kPa
(don’t worry about question # 4)
BPMg (K)
10
1140
1345
20
1205
1415
50
1295
1530
101.325
1366
1620
5. What is the triple point of a substance?
The temp and pressure when all three states exist at the same time
6. Label the figure 6 phase diagram to indicate a) solid state, b) liquid state, c) gas state, d) normal melting
point, e) normal boiling point, f) triple point, g) critical temperature, and h) critical pressure.
See slide with phase diagram, slide 66
Normal boiling and melting point corresponds to 1 atm
Figure 6
Figure 7
7. Use figure 7 to determine the state of matter that exists for hydrogen under the following conditions:
a. 20 K and 750 kPa b. 7 K and 255 kPa c. 16 K and 1250 kPa d. 15 K and 250 kPa e. STP
These values don’t fall on the figure…sorry about that. But basically you need to look for the pressure on the yaxis, temperature on the x-axis and find where your point lies.
8. Complete the following chart regarding changes of state:
Change
SL
GS
LG
SG
LS
GL
Name
Melting
Deposition
Vaporization
Sublimation
Freezing
Condensation
Endothermic or exothermic?
Endothermic
Exothermic
Endothermic
Endothermic
Exothermic
Exothermic
9. Does the following graph describe an endothermic or exothermic process? Exothermic
Which state of matter does this substance begin in? Gas
Which state is present at the end of the process? Solid
BP
MP
heat (J)
Hfusion= 334 J/g
Hvap = 2260 J/g
Cpice = 2.06 J/goC
Cpwater = 4.184 J/goC
Cpsteam = 2.02 J/goC
10. How much energy is needed to heat 152.65 g of water from 36.8 oC to 98.7 oC? endothermic or exothermic?
11. How much energy released when 798.2 g of water is cooled from 136.8 oC to 8.7 oC? endothermic or
exothermic?
12. How much energy is needed to heat 100.0 g of water from -36.8 oC to 18.7 oC? endothermic or exothermic?
13. How much energy released when 15.6 g of water condenses? endothermic or exothermic?
Don’t worry about 10 -13.
Good luck!
If you have any questions, you can email me at mgouws@kennesaw.edu or Ms. D.