I. Physical
Properties
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. 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. Characteristics of Gases
 Gases
can be compressed.
• no volume = lots of empty space
 Gases
undergo diffusion & effusion.
• random motion
D. Temperature
 Always
use absolute temperature
(Kelvin) when working with gases.
ºF
-459
ºC
-273
K
0
C  F  32
5
9
32
212
0
100
273
373
K = ºC + 273
E. Pressure
force
pressure 
area
Which shoes create the most pressure?
E. Pressure
 Barometer
• measures atmospheric pressure
Aneroid Barometer
Mercury Barometer
E. Pressure
 Manometer
• measures contained gas pressure
U-tube Manometer
Bourdon-tube gauge
E. Pressure
 KEY
UNITS AT SEA LEVEL
101.325 kPa (kilopascal)
1 atm
760 mm Hg
760 torr
14.7 psi
N
kPa  2
m
F. STP
STP
Standard Temperature & Pressure
0°C
273 K
-OR-
1 atm
101.325 kPa
II. The Gas
Laws
BOYLES
CHARLES
GAYLUSSAC
A. Boyle’s Law
P
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
PV = k
V
A. Boyle’s Law
 The
pressure and volume
of a gas are inversely
related
• at constant mass & temp
P
PV = k
V
B. Charles’ Law
V
T
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
V
k
T
B. Charles’ Law
 The
volume and absolute
temperature (K) of a gas
are directly related
• at constant mass &
pressure
V
T
V
k
T
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
P
k
T
P
T
C. Gay-Lussac’s Law
 The
pressure and absolute
temperature (K) of a gas
are directly related
• at constant mass &
volume
P
k
T
P
T
D. Combined Gas Law
P
V
PV
PV = k
T
P 1V 1 P 2V 2
=
T1
T2
P 1 V 1T 2 = P 2V 2 T 1
E. Gas Law Problems
gas occupies 473 cm3 at 36°C.
Find its volume at 94°C.
A
CHARLES’ LAW
GIVEN: T V
V1 = 473 cm3
T1 = 36°C = 309K
V2 = ?
T2 = 94°C = 367K
WORK:
P1V1T2 = P2V2T1
(473 cm3)(367 K)=V2(309 K)
V2 = 562 cm3
E. Gas Law Problems
A
gas occupies 100. mL at 150.
kPa. Find its volume at 200. kPa.
BOYLE’S LAW
GIVEN: P V
V1 = 100. mL
P1 = 150. kPa
V2 = ?
P2 = 200. kPa
WORK:
P1V1T2 = P2V2T1
(150.kPa)(100.mL)=(200.kPa)V2
V2 = 75.0 mL
E. Gas Law Problems
gas occupies 7.84 cm3 at 71.8 kPa &
25°C. Find its volume at STP.
A
COMBINED GAS LAW
GIVEN: P T V WORK:
V1 = 7.84 cm3
P1V1T2 = P2V2T1
P1 = 71.8 kPa
(71.8 kPa)(7.84 cm3)(273 K)
T1 = 25°C = 298 K
=(101.325 kPa) V2 (298 K)
V2 = ?
P2 = 101.325 kPa V2 = 5.09 cm3
T2 = 273 K