Ch. 13.4 - Liquids &
Solids
III. Changes of State
C. Johannesson
A. Phase Changes
C. Johannesson
A. Phase Changes
 Evaporation
• molecules at the surface gain enough
energy to overcome intermolecular
forces
 Volatility
• measure of evaporation rate
• depends on temp & intermolecular
forces
C. Johannesson
A. Phase Changes
Boltzmann Distribution
p. 477
temp
# of Particles
volatility
IMF
Kinetic Energy
C. Johannesson
volatility
A. Phase Changes
 Equilibrium
• trapped molecules reach a balance
between evaporation & condensation
C. Johannesson
A. Phase Changes
 Vapor
Pressure
• pressure of vapor above
a liquid at equilibrium
v.p.
p.478
• depends on temp & IMF
• directly related to volatility
temp
v.p.
IMF
C. Johannesson
temp
v.p.
A. Phase Changes
 Boiling
Point
• temp at which v.p. of liquid
equals external pressure
• depends on Patm & IMF
• Normal B.P. - b.p. at 1 atm
Patm
b.p.
IMF
C. Johannesson
b.p.
A. Phase Changes
 Melting
Point
• equal to freezing point
IMF
m.p.
 Which
has a higher m.p.?
• polar or nonpolar?
• covalent or ionic?
C. Johannesson
polar
ionic
A. Phase Changes
 Sublimation
• solid  gas
• v.p. of solid equals
external pressure
 EX:
dry ice, mothballs,
solid air fresheners
C. Johannesson
B. Heating Curves
Gas - KE 
Boiling - PE 
Liquid - KE 
Melting - PE 
Solid - KE 
C. Johannesson
B. Heating Curves
 Temperature
Change
• change in KE (molecular motion)
• depends on heat capacity
 Heat
Capacity
• energy required to raise the temp of 1
gram of a substance by 1°C
• Water has a high heat capacity
C. Johannesson
B. Heating Curves
 Phase
Change
• change in PE (molecular arrangemen
• temp remains constant
 Heat
of Fusion (Hfus)
• energy required to melt 1 gram of a
substance at its m.p.
C. Johannesson
B. Heating Curves
 Heat
of Vaporization (Hvap)
• energy required to boil 1 gram of a
substance at its b.p.
• usually larger than Hfus…why?
 EX:
sweating,
steam burns
C. Johannesson
C. Phase Diagrams
 Show
the phases of a substance at
different temps and pressures.
C. Johannesson
 Phase
diagram
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Ch. 14.1 - Gases
I. Physical
Properties
(p. 450-455)
C. Johannesson
A. Kinetic Molecular Theory
 Particles
in an ideal gas…
• have no volume.
• have elastic collisions.
• are in constant, random, straightline motion.
• don’t attract or repel each other.
• have an avg. KE directly related
to Kelvin temperature.
C. Johannesson
B. Real Gases
 Particles
in a REAL gas…
• have their own volume
• attract each other
 Gas
behavior is most ideal…
• at low pressures
• at high temperatures
• in nonpolar atoms/molecules
C. Johannesson
C. Characteristics of Gases
 Gases
expand to fill any container.
• random motion, no attraction
 Gases
are fluids (like liquids).
• no attraction
 Gases
have very low densities.
• no volume = lots of empty space
C. Johannesson
C. Characteristics of Gases
 Gases
can be compressed.
• no volume = lots of empty space
 Gases
undergo diffusion & effusion.
• random motion
C. Johannesson
D. Temperature
 Always
use absolute temperature
(Kelvin) when working with gases.
ºF
-459
ºC
-273
K
0
C  59 F  32
32
212
0
100
273
373
K = ºC + 273
C. Johannesson
E. Pressure
force
pressure 
area
Which shoes create the most pressure?
C. Johannesson
E. Pressure
 Barometer
• measures atmospheric pressure
Aneroid Barometer
C. Johannesson
Mercury Barometer
E. Pressure
 Manometer
• measures contained gas pressure
U-tube Manometer
C. Johannesson
Bourdon-tube gauge
E. Pressure
 KEY
UNITS AT SEA LEVEL
101.325 kPa (kilopascal)
1 atm
760 mm Hg
760 torr
N
kPa  2
m
14.7 psi
C. Johannesson
F. STP
STP
Standard Temperature & Pressure
0°C
273 K
-OR-
1 atm
101.325 kPa
C. Johannesson
Ch. 14.2 - Gases
II. The Gas
Laws
C. Johannesson
A. Boyle’s Law
Volume
(mL)
Pressure
(torr)
P·V
(mL·torr)
10.0
20.0
30.0
40.0
760.0
379.6
253.2
191.0
7.60 x 103
7.59 x 103
7.60 x 103
7.64 x 103
P1V1=P2V2
P
V
C. Johannesson
 Boyles
Law
C. Johannesson
A. Boyle’s Law
 The
pressure and volume
of a gas are inversely
related
• at constant mass & temp
P1V1=P2V2
P
V
C. Johannesson
Applying Boyles Law

Practice Problems
1.
2.
3.
What pressure will be needed to reduce the volume
of 77.4 L of helium at 98.0 kPa to a volume of 60.0
L?
A 250.0 mL sample of chlorine gas is collected when
the barometric pressure is 105.2 kPa. What is the
volume of the sample after the barometer drops to
100.3 kPa
A weather balloon contains 59.5 L of helium at sea
level, where the atmospheric pressure is 101.3 kPa.
The balloon is released from a 4000m mountaintop
where the pressure is 61.7 kPa. What is the volume
of the balloon when it is released?
Answers
1.
2.
3.
126 kPa
262.2 mL
97.7 L
C. Johannesson
B. Charles’ Law
Volume
(mL)
Temperature
(K)
V/T
(mL/K)
40.0
44.0
47.7
51.3
273.2
298.2
323.2
348.2
0.146
0.148
0.148
0.147
V1 V2

T1 T2
V
T
C. Johannesson
B. Charles’ Law
 The
volume and absolute
temperature (K) of a gas
are directly related
• at constant mass &
pressure
V1 V2

T1 T2
V
T
C. Johannesson
Example

Practice Problems
1.
2.
3.
A sample of SO2 gas has a volume of 1.16 L at a
temperature of 23°C. At what temperature will the
gas have a volume of 1.25 L?
A balloon is inflated with 6.22 L of helium at a
temperature of 36°C. What is the volume of the
balloon when the temperature is 22°C?
A student collects a 125.0 mL sample of hydrogen.
Later the sample is found to have a volume of
128.6 mL at a temperature of 26°C. At what
temperature was the sample collected?
Answers
1.
2.
3.
46°C (319K)
5.94 L
18°C (291K)
C. Gay-Lussac’s Law
Temperature
(K)
Pressure
(torr)
P/T
(torr/K)
248
273
298
373
691.6
760.0
828.4
1,041.2
2.79
2.78
2.78
2.79
P1 P2

T1 T2
P
T
C. Johannesson
C. Gay-Lussac’s Law
 The
pressure and absolute
temperature (K) of a gas
are directly related
• at constant mass &
volume
P1 P2

T1 T2
P
T
C. Johannesson
Combined Gas Law
 All
of the gas laws can be
combined into a single law
 You can find the value of any one
of the variables if you know the
other five
C. Johannesson
D. Combined Gas Law
P 1V 1
T1
=
P 2V 2
T2
P1V1T2 = P2V2T1
C. Johannesson
Applying the combined gas law

C. Johannesson
1.
2.
A sample of ammonia gas occupies a
volume of 1.58 L at 22° C and a pressure of
0.983 atm. What volume will the sample
occupy at 1.00 atm and 0° C?
A student collects 285 mL of O2 gas at a
temperature of 15° C and a pressure of 99.3
kPa. The next day, the same sample
occupies 292 mL at a temperature of 11° C.
What is the new pressure of the gas?
C. Johannesson
Answers
1.
2.
1.44 L
95.6 kPa
C. Johannesson
Avogadro’s principal
 One
mole of any gas occupies a
volume of 22.4 L
 Given that the mass of a mole of
gas is the molecular mass
expressed in grams
 Avogadro’s principal allows you to
interrelate mass, moles, pressure,
volume and temperature for any
sample of gas
C. Johannesson
Applying Avogadro’s principal

C. Johannesson
Applying Avogadro’s principal

C. Johannesson
Practice Problems
1.
2.
3.
How many moles of acetylene
(C2H2) gas occupy a volume of
3.25 moles at STP?
Determine the volume of 12.3 g
of formaldehyde gas (CH2O) at
STP
What is the volume of 1.000 kg of
helium gas at 36°C and a
pressure of 98.7 kPa
C. Johannesson
Answers
1.
2.
3.
0.145 mol
9.18 L
0.145 mol
C. Johannesson
The Ideal Gas Law

C. Johannesson
Applying the gas law 2

C. Johannesson
Practice Problems
1.
2.
3.
What is the pressure in atm of 10.5 mol of
acetylene in a 55.0 L cylinder at 37°C?
What volume does 0.056 mol of H2 gas
occupy at 25°C and 1.11atm of pressure
A sample of carbon monoxide has a
volume of 344 mL at 85°C and a pressure
of 88.4 kPa. Determine the amount in
moles of CO present.
C. Johannesson
Answers
1.
2.
3.
4.86 atm
5.45 x 10-4 mol
4.86 atm
C. Johannesson
Using Mass with the Ideal Gas Law

C. Johannesson
Determining the Molar Mass

C. Johannesson
Practice Problems
1.
2.
A 250.0 mL sample of a noble gas
collected at 88.1 kPa and 7°C has a mass
of 0.378 g. What is the molar mass of the
gas. Identify the sample
A sample of gas is known to be either H2S
or SO2. A 2.00 g sample of the gas
occupies a volume of 725 mL at a
temperature of 13°C and a pressure of
102.4 kPa. What are the molar mass and
the identity of the gas?
C. Johannesson
Answers
1.
2.
40.0 g Argon
64.1 g/mol Sulfur dioxide
C. Johannesson
Gas Stoichiometry

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
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