the behavior of gases
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The Behavior of Gases. Part 1. The Properties of Gases. Kinetic energy – The energy due to motion What does temperature measure? - PowerPoint PPT PresentationTRANSCRIPT
The Behavior of GasesThe Behavior of GasesPart 1Part 1
The Properties of GasesThe Properties of Gases
Kinetic energy –Kinetic energy – The energy due to motionThe energy due to motion
What does temperature measure?What does temperature measure? The average kinetic energy of the The average kinetic energy of the
particles within a sample of matter. particles within a sample of matter. In a gas, the temperature (in Kelvin) In a gas, the temperature (in Kelvin) is a way of indicating how fast the is a way of indicating how fast the particles are moving.particles are moving.
Kinetic Theory RevisitedKinetic Theory Revisited
Assumption #1: Physical Assumption #1: Physical Properties of Gas ParticlesProperties of Gas Particles Hard, spherical particlesHard, spherical particles Individual volumes are insignificantIndividual volumes are insignificant Lots of empty space between the Lots of empty space between the
particles (this is why gases are so particles (this is why gases are so compressible)compressible)
Kinetic Theory RevisitedKinetic Theory Revisited
Assumption #2: Intermolecular Assumption #2: Intermolecular forcesforces Gas particles are not attracted to Gas particles are not attracted to
each other – no intermolecular each other – no intermolecular forcesforces
Gases expand to the shape and Gases expand to the shape and volume of their containersvolume of their containers
Kinetic Theory RevisitedKinetic Theory Revisited
Assumption #3: Particle Assumption #3: Particle movementmovement Random walksRandom walks Perfectly elastic collisions, which Perfectly elastic collisions, which
means there is no average kinetic means there is no average kinetic energy loss over timeenergy loss over time
Variable Describing GasesVariable Describing Gases
VariableVariable SymbolSymbol UnitUnit
Variable Describing GasesVariable Describing Gases
VariableVariable SymbolSymbol UnitUnit
PressurePressure PP kPa or atmkPa or atm
Variable Describing GasesVariable Describing Gases
VariableVariable SymbolSymbol UnitUnit
PressurePressure PP kPa or atmkPa or atm
VolumeVolume VV LL
Variable Describing GasesVariable Describing Gases
VariableVariable SymbolSymbol UnitUnit
PressurePressure PP kPa or atmkPa or atm
VolumeVolume VV LL
Temperature Temperature TT K K (ALWAYS!)(ALWAYS!)
Variable Describing GasesVariable Describing Gases
VariableVariable SymbolSymbol UnitUnit
PressurePressure PP kPa or atmkPa or atm
VolumeVolume VV LL
Temperature Temperature TT KK
Number of molesNumber of moles nn molmol
The Gas LawsThe Gas Laws
Boyle’s Law:Boyle’s Law: For a fixed mass of gas at For a fixed mass of gas at
constant temperature, the volume constant temperature, the volume of the gas varies inversely with of the gas varies inversely with pressurepressure
2211 VPVP
The Gas LawsThe Gas Laws
Example: Example: The pressure on 2.50 L of The pressure on 2.50 L of anesthetic gas changes anesthetic gas changes from 105 kPa to 40.5 kPa. from 105 kPa to 40.5 kPa. What will be the new What will be the new volume if temperature volume if temperature remains constant?remains constant?
V1
P1 P2
The Gas LawsThe Gas Laws
.48L640.5kPa
2.50L105kPa
P
VPV
P
VP
P
VP
2
112
2
22
2
11
The Gas LawsThe Gas Laws
Charles’s Law:Charles’s Law: The volume of a The volume of a
fixed mass of gas is fixed mass of gas is directly proportional directly proportional to its Kelvin to its Kelvin temperature if the temperature if the pressure is kept pressure is kept constant.constant.
2
2
1
1
T
V
T
V
The Gas LawsThe Gas Laws
Example: Example: Exactly 5.00 L of air at -50Exactly 5.00 L of air at -50ooC C is warmed to 100is warmed to 100ooC. What C. What is the new volume if the is the new volume if the pressure remains constant?pressure remains constant?
V1 T1 = -50+273 = 223K
T2 = 100+273 = 373K
The Gas LawsThe Gas Laws
8.36L373K223K
5.00L
TT
VV
TT
VT
T
V
T
V
T
V
21
12
22
22
1
1
2
2
1
1
The Gas LawsThe Gas Laws
Gay-Lussac’s Law:Gay-Lussac’s Law: The pressure and The pressure and
Kelvin temperature Kelvin temperature of a fixed mass of a of a fixed mass of a gas are directly gas are directly proportional at proportional at constant volume.constant volume. 2
2
1
1
T
P
T
P
The Gas LawsThe Gas Laws
Example: Example: The pressure of an automobile The pressure of an automobile
tire is 198 kPa at 27tire is 198 kPa at 27ooC. At the C. At the end of a trip on a hot sunny end of a trip on a hot sunny day , the pressure has risen to day , the pressure has risen to 225 kPa. Assuming the volume 225 kPa. Assuming the volume is constant, what is the new is constant, what is the new temperature?temperature?
P1 T1 = 27+273 = 300K
P2
The Gas LawsThe Gas Laws
341K198kPa
300K225kPa
P
TPT
P
TP
P
TP
T
P
T
P
1
122
1
12
1
21
2
2
1
1
The Gas LawsThe Gas Laws
Combined Gas Law:Combined Gas Law: A relationship describing the A relationship describing the
behavior of gases that combines behavior of gases that combines Boyle’s law, Charles’s Law, and Boyle’s law, Charles’s Law, and Gay-Lussac’s law.Gay-Lussac’s law.
2
22
1
11
T
VP
T
VP
The Gas LawsThe Gas Laws
Example: Example: A gas at 155 kPa and 25A gas at 155 kPa and 25ooC C
occupies a container with initial occupies a container with initial volume of 1.00 L. By changing volume of 1.00 L. By changing the volume the pressure of the the volume the pressure of the gas increases to 605 kPa as the gas increases to 605 kPa as the temperature increases to temperature increases to 125125ooC. What is the new C. What is the new volume?volume?
The Gas LawsThe Gas Laws Example: Example:
A gas at 155 kPa and 25A gas at 155 kPa and 25ooC occupies C occupies a container with initial volume of a container with initial volume of 1.00 L. By changing the volume the 1.00 L. By changing the volume the pressure of the gas increases to 605 pressure of the gas increases to 605 kPa as the temperature increases to kPa as the temperature increases to 125125ooC. What is the new volume?C. What is the new volume?
VV11 = 1.00 L = 1.00 LTT11 = 25 = 25ooC +273 = 298 KC +273 = 298 KPP11 = 155 kPa = 155 kPa
The Gas LawsThe Gas Laws Example: Example:
A gas at 155 kPa and 25A gas at 155 kPa and 25ooC occupies C occupies a container with initial volume of a container with initial volume of 1.00 L. By changing the volume the 1.00 L. By changing the volume the pressure of the gas increases to 605 pressure of the gas increases to 605 kPa as the temperature increases to kPa as the temperature increases to 125125ooC. What is the new volume?C. What is the new volume?
VV11 = 1.00 L = 1.00 L VV22 = ? = ?TT11 = 298 K = 298 K TT22 = 398 K = 398 KPP11 = 155 kPa = 155 kPa PP22 = 605 kPa = 605 kPa
The Gas LawsThe Gas Laws
345L.0298K605kPa
398K1.00L155kPa
PT
TVPV
P
T
T
VP
P
T
T
VP
T
VP
T
VP
21
2112
2
2
2
22
2
2
1
11
2
22
1
11