Notes Gases 10.1 Properties of Gases

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Notes Gases 10.1 Properties of Gases
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Properties of Gases
• Expand to fill the volume of the
container they occupy
Gases 10.1
es
• Form homogeneous mixtures
Pressure
Kinetic Molecular Theory
Boyle’s Law
Charles’ Law
The Combined Gas Law
N
ot
• Low density
• Highly compressible
ts
'L
ec
tu
re
• Exert a pressure
Gases Exert Pressures in all
Directions
Pressure
N
Force
Pressure =
Area
m2
1 atm
1 atm
1 atm
1 atm
1 atm
ud
Gases exert pressure by bouncing off surfaces
en
Pa
1 atm
1 atm
• Gas particles are evenly distributed in a container.
1 atm
1 atm
1 atm
St
• The same number smash off every cm2 per unit of
time.
- Each collision exerts a force.
1 atm
1 atm
1 atm
1 atm
of
1 atm
C
op
y
• The pressure is constant at constant temperatures.
m
pl
e
Sucking gas particles out of a can
Atmospheric
Pressure (1 atm)
Vacuum
pump on
Open
ended
tube
1 atm = 760 mm Hg
Vacuum
(0 atm)
Atmospheric Pressure (1 atm)
Pinside = Poutside
Pinside < Poutside
760 mm
Sa
Vacuum
pump off
Barometers Measure Gas Pressure
Mercury - Hg(l)
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Kinetic Energy of Gas Molecules
Notes on Kinetic Molecular Theory
fast
• Rotational Energy
slow
• Vibrational Energy
N
ot
KEinitial =
es
• Collisions experienced by gas particles are
elastic.
- Kinetic Energy is conserved.
• Translational Energy
– gas molecules move through space in
straight lines.
KEfinal
ΣKEinitial = ΣKEfinal
slow
Most of a gas particle’s KE is related to its
translational velocity
ts
'L
ec
tu
re
fast
Boyle’s Law
Pressure – Volume Relationship
en
St
ud
Twice the Pressure
V1P1 = V2P2
Pressure
Relationship between
Pressure and Volume
of
Volume is inversely proportional to pressure.
Half the Volume
C
op
y
Volume
Sa
Relationship between
Temperature and Volume
V1
T1
=
V2
T2
Volume is proportional to temperature.
You must use absolute temperature (K)!
Relating Volume and Temperature
50
Volume (cm3)
m
pl
e
Charles’ Law
0
0
573
Temperature (K)
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Temperature – Volume Relationship
The Combined Gas Law
500 K
P1V1
T1
250 K
N
ot
Average KE = ½ x
P2V2
T2
=
es
Average KE = x
You must use absolute temperature (K)!
re
Half the Volume
ts
'L
ec
tu
Volume
Ex1) Combined Gas Law (cont.)
PV
PV
1 1
= 2 2
T1
T2
C
op
y
of
St
ud
Ex1) A cylinder of gas is kept at a constant
volume, as the temperature increases
from 24.1oC to 326.4oC.
If the initial pressure was 1.10 atm, what
is the final pressure in mm Hg?
en
Ex1) Combined Gas Law
m
pl
e
Ex2) Combined Gas Law
Sa
Ex2) A cylinder of gas is kept at a constant
pressure, as the volume decreases from
1.150 L to 0.860 L.
If the initial temperature was 21.8oC,
what is the final temperature?
Ex2) Combined Gas Law (cont.)
PV
PV
1 1
= 2 2
T1
T2
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