[ANSWER KEY ]
Review Chemistry Honors Unit 11: States of Matter
1.
size
attractions
List the main parts of Kinetic-Molecular Theory (KMT) relating to each characteristic of gas particles:
a) gas particles have no significant volume (are tiny) compared to the great distance between them
b) gas particles have no significant attractive forces because they are so far apart______________
motion
c) gas particles are in constant, random motion_________________________________________
collisions
d) all collisions between gas particles are perfectly elastic (transfer KE without loss)____________
energy
2.
e) the average kinetic energy of gas particles in a sample is directly proportional to temperature_
List the 3 states of water in order of decreasing kinetic energy. (highest to lowest)
1) Gas
2) Liquid
3) Solid
3.
What happens to the kinetic energy of a liquid as it is heated? increases
4.
Define temperature. measure of average kinetic energy of particles of a substance.
avg. KE of a substance is proportional to the temperature
5.
Which has particles that are moving at 0oC? (circle all that are correct)
A. solid iron
B. liquid iodine
C. ammonia vapor
D. hydrogen gas
Which has the greatest average kinetic energy?
A. nitrogen gas at –50 C
B. neon gas at 20 C
C. CH3CH2OH vapor at 25 C
D. H2O vapor at 100 C
Choice _D_ because the higher temperature is directly proportional to higher avg KE
of a gas regardless of the chemical formula of the gas.
6.
What is the temperature at which there is absolutely NO motion of particles?
It’s called
7.
absolute zero
at ___0__ K or –273 oC.
Why are gases compressible, but liquids and solids are not? b/c of the great amount of
space between the particles (they to be pushed closer together)__________
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8.
Consider the simple water cycle diagram below. Group the phase changes by heat energy
absorbed or released, by interparticle space, and by intermolecular attractions in the boxes.
condensation
absorbs energy
releases energy
melting
vaporization
sublimation
freezing
condensation
deposition
more space
between molecules
less space
between molecules
melting
vaporization
sublimation
freezing
condensation
deposition
less attraction
between molecules
more attraction
between molecules
melting
vaporization
sublimation
freezing
condensation
deposition
melting
evaporation
freezing
deposition
sublimation
9.
During each of the phase changes listed in #8, the temperature of the water will remain constant
because its potential energy is changing while its average kinetic energy is constant.
10. List the intermolecular attractions in decreasing order of strength from strongest to weakest:
hydrogen bonding < dipole-dipole forces < dispersion forces
Strongest
Weakest
11. Describe how dispersion forces occur between two atoms or molecules.
The random motion of electrons causes a temporary dipole which attracts a nearby molecule
12. Describe dipole-dipole forces between two molecules.
Permanently polar molecules (dipoles) attract each other.
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13. Which substance has hydrogen bonding as its main intermolecular force?
A. SO2
(dipole-dipole forces)
B. HCl
(dipole-dipole forces)
C. F2
(dispersion forces)
D. NH3
(hydrogen bonding)
How do you recognize a molecule that can form hydrogen bonds?
have H bonded to N, O, or F
H-bond
14. Describe how a hydrogen bond forms between two molecules.
An electron deficient H atom bonded to a very electronegative atom (N, O, or F) is
attracted to an N, O, or F atom on a nearby molecule.
15. The strong attractions between polar water molecules cause water to have which of the
following properties: (circle all that apply)
A.
B.
C.
D.
E.
F.
G.
greater surface tension
higher density liquid than solid (ice)
greater attraction to nonpolar molecules
higher boiling point
higher temperature
higher specific heat capacity
higher heat of fusion
H. higher heat of vaporization
S
H2S
H
H2O
H
16. Hydrogen sulfide (H2S) boils at –60oC. Even though water is a smaller molecule that
should become a gas more easily than H2S, water doesn’t boil until it reaches 100oC.
Why are water molecules so difficult to separate from liquid phase to form a gas?
The H-bonds between water molecules are stronger intermolecular attractions than the
dipole-dipole forces of H2S). The stronger attractions require more energy to be overcome.
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17. Stronger intermolecular attractions cause liquids to have _____________ boiling points and
cause solids to have ______________ melting points.
A.
B.
C.
D.
lower
lower
higher
higher
, lower
, higher
, lower
, higher
18. Identify which of the following changes involves the breaking of intramolecular bonds,
and which involve the breaking of intermolecular attractions? (circle one for each)
A. H2O(s)  H2O(l)
intramolecular bonds or intermolecular attractions
B. Fe2O3(s)  2 Fe(s) + 3 O2(g)
intramolecular bonds or intermolecular attractions
C. F2(g)  2 F(g)
intramolecular bonds or intermolecular attractions
D. NH3(l)  3 H2(g) + N2(g)
intramolecular bonds or intermolecular attractions
19. Warm water vapor from the air condenses onto a glass of cold ice water.
This happens when the water vapor __________ heat to/from the glass
causing the glass to become ___________.
A. releases/to , warmer
B.
releases/to , cooler
C. absorbs/from , warmer
D. absorbs/from , cooler
20.
Heat is energy that is transferred due to a difference in temperature
21.
Describe the direction of heat flow when a hot rock at 105 C is placed into cool water at 18 C.
o
o
Heat flows from the rock to the water making the
rock cooler and the water warmer.
22.
o
Describe the direction of heat flow when a piece of solid water (ice) at 0 C is held in
o
your hand at 37 C.
Heat flows from the hand to the water (ice) making
the hand cooler and water warmer.
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For #23-26, refer to the heating curve below for water as heat is added at a constant rate.
E
Temperature ( C)
D
o
C
B
A
Heat added
23. Circle which phase(s) of water exist(s) in each section of the heating curve.
section A.
solid liquid gas
section B.
solid liquid gas
section C.
solid
liquid gas
section D.
solid
liquid gas
section E.
solid
liquid gas
24. Circle which type of energy is increasing in the sample during each section as heat is being added.
section A.
kinetic
potential
section B.
kinetic
potential
section C.
kinetic
potential
section D.
kinetic
potential
section E.
kinetic
potential
25. If heat were removed instead of added, the process occurring in section D would be _____.
A.
B.
C.
D.
vaporization
freezing
condensation
NONE of the above
26. Section B is shorter than section D because water has a lower heat of fusion
than heat of vaporization so it takes more energy to vaporize a sample of water than it does to
melt the same sample of water.
5
o
27. A cup of water contains 55 g of water at a temperature of 21.4 C. How much heat must be
o
o
removed from the water to lower its temperature to 2.5 C? (the specific heat of water is 4.18 J/g C)
q = mcΔT
q = (55) (4.18) (2.5 – 21.4)
q = –4300 J
For #28-33, refer to the phase diagram below for water.
5
A
Label each
section on the
diagram
B
solid
1
liquid
2
(A, B, C)
with the
correct phase
(s, l, g)
4
C
3
gas
28. The phase change from A to C is called sublimation and from C to B is condensation.
29. The boiling point of the substance is shown at Point _2_ which is the point at which
liquid and gas phases coexist in equilibrium.
30. Point 4 represents the triple point, which is the point at which…
solid, liquid, and gas phases coexist in equilibrium
31. The critical point is shown at Point _5_ which represents the temperature above which a
liquid could not exist and the pressure above which a gas could not exist.
32. A sample of the substance is held constant at a temperature of 300 K while the
pressure is decreased from 10 atm to 0.01 atm. The phase change that occurs is vaporization.
33. A sample of the substance is held constant at a pressure of 1 atm while the temperature
is increased from 150 K atm to 250 K. The phase change that occurs is melting.
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