Gas PropertiesGas Properties

GassesGasses

A state of matter characterized by:A state of matter characterized by:Filling the container it occupiesFilling the container it occupiesHaving a volume that is not fixedHaving a volume that is not fixedParticles that have little or no intermolecular Particles that have little or no intermolecular

forces acting on themforces acting on themParticles have freedom of motionParticles have freedom of motion

PressurePressure PressurePressure – Force – Force

per Areaper Area

Atmospheric Atmospheric pressure is 14.7 pressure is 14.7 lbs/inlbs/in22

Pressure is Pressure is caused by the caused by the force of force of molecules striking molecules striking a surfacea surface

PressurePressure

Typical Units IncludeTypical Units Include Atmospheres (atm)Atmospheres (atm) Kilopascals (kPa)Kilopascals (kPa) Millimeters of mercury (mmHg)Millimeters of mercury (mmHg) Torr (torr)Torr (torr)

1atm = 101.325 kPa = 1atm = 101.325 kPa = 760 mmHg = 760 torr760 mmHg = 760 torr

TemperatureTemperature

Relative measure ofRelative measure of Translational energyTranslational energy

Movement in a particular Movement in a particular directiondirection

Vibrational EnergyVibrational Energy Rotational EnergyRotational Energy

If two substances are at If two substances are at the same temperature, no the same temperature, no NET energy is transferred NET energy is transferred between them.between them.

Temperature ScalesTemperature Scales

Temperature ConversionsTemperature Conversions

Convert 25°C to KelvinConvert 25°C to KelvinConvert 345K to CelsiusConvert 345K to CelsiusConvert -45°C to KelvinConvert -45°C to KelvinConvert 288K to CelsiusConvert 288K to Celsius

Properties of GasesProperties of Gases The properties of gases are interdependent.The properties of gases are interdependent.

Pressure (P)Pressure (P) VolumeVolume (V)(V) Temperature (T)Temperature (T) Amount (moles, n)Amount (moles, n)

Changing one can affect the othersChanging one can affect the others Exception - The amount of gas affects the other Exception - The amount of gas affects the other

variables but the other variables do not affect the variables but the other variables do not affect the amountamount

Gas LawsGas Laws

Animated Gas LabAnimated Gas Lab http://www.grc.nasa.gov/WWW/k-12/airplane/Ani

mation/frglab2.html Hold two variables constantHold two variables constant

VolumeVolume Amount of gasAmount of gas

What is the relationship between pressure and What is the relationship between pressure and temperature?temperature? As temperature increases, pressure increasesAs temperature increases, pressure increases Direct RelationshipDirect Relationship

With NumbersWith Numbers A stoppered flask in a hot water bath is allowed A stoppered flask in a hot water bath is allowed

to cool along with the bath.to cool along with the bath.P

ress

ure

(atm

)

Temperature (°C)

Pressure vs. TemperaturePressure vs. Temperature

Calculate the x-interceptCalculate the x-intercept When P = 0… When P = 0…

That’s very close to -273 °CThat’s very close to -273 °C

atmTP Catm 6745.0002366.0

Pressure vs. TemperaturePressure vs. Temperature To avoid having the x-intercept not at the origin…To avoid having the x-intercept not at the origin…

We define We define absolute temperatureabsolute temperature – Kelvin – Kelvin

K = K = °C + 273°C + 273

This defines an absolute zeroThis defines an absolute zero Absolute zero Absolute zero - (0K) - the temperature where a - (0K) - the temperature where a

substance is in its lowest possible energy state.substance is in its lowest possible energy state.

Always use Kelvin in Gas Law ProblemsAlways use Kelvin in Gas Law Problems

Pressure vs. TemperaturePressure vs. Temperature

P = (constant) x T

Racquet ballRacquet ball

Liquid_Nitrogen_-_Racquet_Ball.aviThink of the ball as a container of gas – Think of the ball as a container of gas –

balls bounce because they have a pocket balls bounce because they have a pocket of gas insideof gas inside

Use liquid nitrogen to cool a racquet ballUse liquid nitrogen to cool a racquet ballWhat changes?What changes?

Plunger FunPlunger Fun Monitor the pressure in a container while the Monitor the pressure in a container while the

plunger is moved in and out.plunger is moved in and out. http://www.grc.nasa.gov/WWW/k-12/airplane/Ani

mation/frglab2.html What is held constant?What is held constant?

Pressure?Pressure? Volume?Volume? Temperature?Temperature? Amount of gas?Amount of gas?

What is the relationship between pressure and What is the relationship between pressure and volume?volume? As the volume increases, pressure decreasesAs the volume increases, pressure decreases Inverse RelationshipInverse Relationship

Pressure vs. VolumePressure vs. Volume

VP

constant

Balloon and Vacuum PumpBalloon and Vacuum Pump

Injecting Air Into a Sealed Injecting Air Into a Sealed ContainerContainer

What is held constant?What is held constant? Pressure?Pressure? Volume?Volume? Temperature?Temperature? Amount of gas?Amount of gas?

What is the relationship between pressure and What is the relationship between pressure and amount of gas?amount of gas? As the amount of gas increases, pressure increasesAs the amount of gas increases, pressure increases Direct RelationshipDirect Relationship

Pressure vs. Moles (n)Pressure vs. Moles (n)

P = (constant) x nP = (constant) x n

Can ActivityCan Activity

Put water in the soda can to cover the Put water in the soda can to cover the bottom surface.bottom surface.

Heat the can on the hot plate until you Heat the can on the hot plate until you can see steam.can see steam.

With the tongs, QUICKLY turn the can With the tongs, QUICKLY turn the can upside down and immerse it in the cold-upside down and immerse it in the cold-water bath.water bath.

Record your observations.Record your observations.

Can ActivityCan Activity Explain your results in terms of P, V, n, and T.Explain your results in terms of P, V, n, and T. Where did all the water in the can come from?Where did all the water in the can come from? What do you think would happen if you did this What do you think would happen if you did this

experiment with a glass jar instead of a can?experiment with a glass jar instead of a can? What do you think would happen if you did this What do you think would happen if you did this

experiment with an empty can?experiment with an empty can? What do you think would happen if you did this What do you think would happen if you did this

experiment with twice as much water?experiment with twice as much water?

Cold BalloonsCold Balloons Submerge an inflated balloon in liquid nitrogen Submerge an inflated balloon in liquid nitrogen

(-196(-196°C) °C) MIT_Physics_Demo_--_Balloons_in_Liquid_Nitrogen.avi

What is held constant?What is held constant? Pressure?Pressure? Volume?Volume? Temperature?Temperature? Amount of gas?Amount of gas?

What is the relationship between temperature What is the relationship between temperature and volume?and volume? As the temperature decreases, volume decreasesAs the temperature decreases, volume decreases Direct RelationshipDirect Relationship

Volume vs. TemperatureVolume vs. Temperature

Two Equations to Rule Them AllTwo Equations to Rule Them All

P = (constant) TP = (constant) Tat a constant V and nat a constant V and n

P = (constant) nP = (constant) nat a constant V and Tat a constant V and T

P = (constant) / VP = (constant) / Vat a constant n and Tat a constant n and T

V

nTP )constant(

Ideal Gas LawIdeal Gas Law

nRTPVV

nRTP

RV

nTP

constant

)constant(

R = Universal Gas ConstantR = Universal Gas Constant

K mol torrL

K molmmHg L

K molkPa L

K molatm L

4.624.62

314.80821.0

Combined Gas LawCombined Gas Law

If we have a sealed containerIf we have a sealed container The number of moles is constantThe number of moles is constant

2

22

1

11

constant

(constant)

T

VP

T

VPT

PV

TPV

Practice ProblemsPractice Problems

What is the pressure in kilopascals inside What is the pressure in kilopascals inside a 20.0L container filled with 8.92mol of a 20.0L container filled with 8.92mol of hydrogen gas at 25°C? hydrogen gas at 25°C?

Practice ProblemsPractice Problems

A 50.0L cylinder of argon gas at 19.8 atm has a A 50.0L cylinder of argon gas at 19.8 atm has a temperature of 19.0°C. What volume of air could temperature of 19.0°C. What volume of air could it displace in a room at 0.974atm pressure at the it displace in a room at 0.974atm pressure at the same temperature? same temperature?

Practice ProblemsPractice Problems A 550mL balloon is placed in a Bell jar attached A 550mL balloon is placed in a Bell jar attached

to a vacuum pump. The vacuum pump is to a vacuum pump. The vacuum pump is accidentally reversed so that the pressure accidentally reversed so that the pressure increases inside the Bell jar from 0.987atm to increases inside the Bell jar from 0.987atm to 3.50atm before the Bell jar explodes. What is 3.50atm before the Bell jar explodes. What is the volume of the balloon in the Bell jar before the volume of the balloon in the Bell jar before the jar explodes?the jar explodes?

Practice ProblemsPractice Problems A certain car tire has a volume of 29.0L. The A certain car tire has a volume of 29.0L. The

maximum rated operating pressure is 80.0psi. maximum rated operating pressure is 80.0psi. The temperature of a hot tire can reach as high The temperature of a hot tire can reach as high as 105as 105°C on a race track. What is the maximum °C on a race track. What is the maximum amount of gas that should be pumped into the amount of gas that should be pumped into the cold tire to ensure it doesn’t burst in the middle cold tire to ensure it doesn’t burst in the middle of a race? (1atm = 14.7 lbs/inof a race? (1atm = 14.7 lbs/in22))

Practice ProblemsPractice Problems

What mass of nitrogen is in a cylinder with What mass of nitrogen is in a cylinder with a volume of 3.25L and a pressure of a volume of 3.25L and a pressure of 15500 mmHg at 25°C?15500 mmHg at 25°C?

Methanol/air fires can burn at temperatures as Methanol/air fires can burn at temperatures as high as 1900high as 1900°C. After shooting an 18.9L °C. After shooting an 18.9L methanol rocket down the hall, it is quickly methanol rocket down the hall, it is quickly stoppered to seal the remaining gas in the stoppered to seal the remaining gas in the container. What is the pressure inside the container. What is the pressure inside the container once it cools back down to room container once it cools back down to room temperature? Assume that atmospheric temperature? Assume that atmospheric pressure is 1.00atm.pressure is 1.00atm.

The typical pressure in Boone is around 670 The typical pressure in Boone is around 670 torr. Opening shampoo after driving from torr. Opening shampoo after driving from Winston-Salem (where the typical pressure is Winston-Salem (where the typical pressure is around 740torr) to Boone is occasionally a around 740torr) to Boone is occasionally a slightly hazardous experience. If you have a slightly hazardous experience. If you have a bottle with a 150mL of head space in Winston-bottle with a 150mL of head space in Winston-Salem, what volume should it occupy in Boone?Salem, what volume should it occupy in Boone?

Methanol/air fires can burn at temperatures as high as Methanol/air fires can burn at temperatures as high as 19001900°C. After shooting an 18.9L methanol rocket down °C. After shooting an 18.9L methanol rocket down the hall, it is quickly stoppered to seal the remaining gas the hall, it is quickly stoppered to seal the remaining gas in the container. What is the pressure inside the in the container. What is the pressure inside the container once it cools back down to room temperature container once it cools back down to room temperature (25.0°C)? Assume that atmospheric pressure is (25.0°C)? Assume that atmospheric pressure is 1.00atm.1.00atm.

What mass of nitrogen is in a cylinder with a volume of What mass of nitrogen is in a cylinder with a volume of 3.25L and a pressure of 15500 mmHg at 25.0°C? 3.25L and a pressure of 15500 mmHg at 25.0°C?

The typical pressure in Boone is around 670 torr. The typical pressure in Boone is around 670 torr. Opening shampoo after driving from Winston-Salem Opening shampoo after driving from Winston-Salem (where the typical pressure is around 740torr) to Boone (where the typical pressure is around 740torr) to Boone is occasionally a slightly hazardous experience. If you is occasionally a slightly hazardous experience. If you have a bottle with a 150mL of head space in Winston-have a bottle with a 150mL of head space in Winston-Salem, what volume should it occupy in Boone?Salem, what volume should it occupy in Boone?

A certain car tire has a volume of 29.0L. The maximum A certain car tire has a volume of 29.0L. The maximum rated operating pressure is 80.0psi. The temperature of rated operating pressure is 80.0psi. The temperature of a hot tire can reach as high as 105a hot tire can reach as high as 105°C on a race track. °C on a race track. What is the maximum amount of gas that should be What is the maximum amount of gas that should be pumped into the cold tire to ensure it doesn’t burst in the pumped into the cold tire to ensure it doesn’t burst in the middle of a race? (1atm = 14.7 lbs/inmiddle of a race? (1atm = 14.7 lbs/in22))

Collecting a Gas Over WaterCollecting a Gas Over Water

Mixtures of GassesMixtures of Gasses

How do we deal with them?How do we deal with them?The total pressure is the sum of the The total pressure is the sum of the

pressure of each component.pressure of each component.Pressures are additivePressures are additive

PPtotaltotal = P = P11 + P + P22 + P + P33 + P + P44 + … + …PP11 = Pressure of Component 1 = Pressure of Component 1

= Partial Pressure of 1 = Partial Pressure of 1Dalton’s Law of Partial PressuresDalton’s Law of Partial Pressures

PracticePractice The atmosphere is made up of many gasses. The atmosphere is made up of many gasses.

The three largest components are nitrogen, The three largest components are nitrogen, oxygen, and argon gasses with partial pressures oxygen, and argon gasses with partial pressures of 0.78084atm, 0.20946atm, and 0.00934atm of 0.78084atm, 0.20946atm, and 0.00934atm respectively. What is the partial pressure of all respectively. What is the partial pressure of all of the minor components of air combined?of the minor components of air combined?

Collecting a Gas Over WaterCollecting a Gas Over Water

OHOtotal PPP22

•Vapor Pressure of Water – the partial pressure of water in an air sample that is saturated with water vapor.

•Temperature Dependent

PracticePractice How many moles of oxygen gas were produced by the How many moles of oxygen gas were produced by the

decomposition of potassium chlorate with a manganese(IV) decomposition of potassium chlorate with a manganese(IV) oxide catalyst if 250mL of oxygen was collected over water at oxide catalyst if 250mL of oxygen was collected over water at 740mmHg and 22.0740mmHg and 22.0°C? The vapor pressure of water at °C? The vapor pressure of water at 22.022.0°C °C is 19.83mmHg.is 19.83mmHg.

How many grams of potassium chlorate were decomposed?

Kinetic Molecular Theory Kinetic Molecular Theory for Ideal Gassesfor Ideal Gasses

A rather simple but powerful systemA rather simple but powerful systemCan derive the ideal gas law from itCan derive the ideal gas law from itDescribes gases pretty well under certain Describes gases pretty well under certain

conditionsconditionsNot perfect and has limitationsNot perfect and has limitations

Kinetic Molecular Theory Kinetic Molecular Theory for Ideal Gasesfor Ideal Gases

1.1. Gases consist of large numbers of particles (atoms Gases consist of large numbers of particles (atoms or molecules) that are in continuous random or molecules) that are in continuous random motion.motion.

2.2. The combined volume of all the molecules of the The combined volume of all the molecules of the gas is negligible compared to the total volume in gas is negligible compared to the total volume in which the gas is contained.which the gas is contained.

3.3. Attractive and repulsive forces between gas Attractive and repulsive forces between gas molecules are negligible.molecules are negligible.

4.4. Energy is transferred between particles during Energy is transferred between particles during collisions. These collisions are completely elastic collisions. These collisions are completely elastic (there is no loss in kinetic energy.)(there is no loss in kinetic energy.)

5.5. The average kinetic energy of the particles is The average kinetic energy of the particles is proportional to the absolute temperature. At a proportional to the absolute temperature. At a given temperature, all different gases have the given temperature, all different gases have the same average kinetic energy.same average kinetic energy.