Gases Chapter 11 (and 10)

Warm up 1.  What is a gas? 2.  What is pressure? 3.  What units are used to measure pressure?

Properties of Gas

� Expansion: indefinite shape and volume �  Fluidity: particle move pass each other � Low density: often floats � Compressibility: can press particle closer

together � Diffusion and effusion: ◦ Diffusion: mixing of gas by random motion ◦  Effusion: gas particles passing through tiny opening

Properties of Liquids: fluid � Relatively higher density � Relative incompressibility � Ability to diffuse: constant random movement of

particles causes them to mix slower than gas �  Surface tension � Evaporate and boil

Properties of water: �  Forms hydrogen bonds � high heat of vaporization: must be hot to

evaporate � Low melting point: stays as a liquid � Less dense as a solid

Properties of Solids � Definite shape and volume � Highest density �  Incompressibility � Low rate of diffusion

Can you rate solid, liquid and gas from low to high for each property? •  Density •  Compressibility •  Diffusion •  Boiling point •  Melting point

Ch 10 pg 347

Phase Diagram: shows critical points in the change of states of mater: temperature and pressure both affect the state of matter

Kinetic Molecular Theory of Gas

1.  Made of tiny particles that are relatively far apart

2.  Collisions between the particles does not lose energy

3.  Particles are in continuous rapid random motion

4.  There is no attraction between particles 5.  Temperature of gas depends on average

kinetic energy of particles

Ch 10 pg 329-330 Parameters for an ideal gas

Kinetic molecular theory only applies to “ideal” gases. Most gases are only nearly ideal if pressure is not too high and temperature is not to low

Pressure: force/unit area

�  Caused by the collisions of molecules with the walls of the container

�  SI units = Newton/meter2 = 1 Pascal (Pa) �  1 standard atmosphere = 101.3 kPa �  1 atm = 760 mmHg = 760 torr �  So…

◦ 1 atm = 760 mmHg = 101.3 kPa � 1 mmHg = 1 torr

barometer is a device used to measure atmospheric pressure

Pascal is the SI unit of pressure

1 atm = 760 mmHg = 101.3 kPa 1 mmHg = 1 torr

Continuing Ch 11 Gases notes

Given: atmospheric pressure = 0.830 atm Unknown: a. pressure in mm Hg

b. pressure in kPa a.

b. × =101.325 kPa0.830 atm

at84.1

m kPa

Pressure Conversions

× =760 mm Hg0.830 atm

a631

tmmm Hg

1 atm = 760 mmHg = 101.3 kPa

Factors that affect gases

1.  Kinetic theory 2.  Pressure 3.  Volume 4.  Temperature

*affect pressure

Factors that affect gases 1. Kinetic Theory—As collisions increases, pressure will increase. �  particles travel in straight line paths until they

collide with other particles or wall of the container. ◦  Pressure is measured �  Unit = kilopascal �  Standard pressure is

101kPa

2. Pressure (amount of gas) � As # of gas particles increases (without

increasing volume), pressure increases and collisions increases ◦  Filling a tire with air

� Gas naturally flows from high to low pressure Ex: Aerosol cans—pressure inside can is higher than pressure outside

Factors that affect gases

Relationship Between Pressure, Force, and Area

3. Volume �  As volume decreases, collisions ◦  increase and so pressure… ◦  increases

�  Volume is measured in liters

Factors that affect gas

4. Temperature �  As temperature increases, energy ◦  Increases so collisions… ◦  Increase causing pressure of a gas to ◦  Increase

�  Temp is measured in Kelvin ◦  K = oC + 273 ◦  Standard temp = 0oC ◦  Kelvin is used because 0 in an equation is problematic

Factors that affect gas

Absolute zero: not heat/energy: 0 oK https://www.youtube.com/watch?v=f1eAOygDP5s

STP: Standard Temperature and Pressure

� P = 1 atmosphere, 760 torr, 101.3 kPa � T = 0ºC, 273 Kelvins (K) ◦  convert to Kelvin: ºK = ºC + 273

� The molar volume of an ideal gas is 22.4L at STP

Dalton’s law of partial pressure �  total pressure of a mixture of gases is the

sum of their partial pressures � Ptotal= P1 + P2 + P3… Ex B: pg 367 Oxygen gas from decomposition of KClO3 was collected by water displacement. The barometric pressure was 731.0 torr and the pressure of the water vapor was 17.5 torr, find the partial pressure of oxygen.

Patm = Po2 + PH2O 731torr =Po2 + 17.5 torr 731 – 17.5 torr = 713.5 torr

HW

Ch 10 Section review � Pg 332 # 1-2, 5-6 � Pg 351# 1-5

Ex C pg 370 A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant? Given: V1 of O2 = 150.0 mL, P1 of O2 = 0.947 atm, P2 of O2 = 0.987 atm Unknown: V2 of O2 in mL

P1V1 = P2V2

Boyle’s Law: volume of the gas varies inversely with pressure

�  P1 (V1) = P2 (V2) �  Boyle’s Law defines the relationship

between pressure and volume �  Pressure of a gas increases as the volume ◦  decreases…when temp. is constant

= 1 12

2

PVVP

0.947 atm x 150.0mL = 144mL O2 0.987

� Boyle's Law clip � Cartesian diver demo �  Fish bubbles � Breathing ◦  Boyle's Law and

breathing ◦  https://

www.youtube.com/watch?v=NB1aCBId6qA

Sample Boyle’s Law Problem

�  A hot air balloon contains 30.0 L of He gas at 103 kPa. What is the volume of the balloon when it decreases in pressure to 25.0 kPa due to its rise in altitude? Assume the temp remains constant. ◦  What do we know? ◦  What are we trying to find? ◦  What law applies? ◦  Solve ◦  Does your answer make sense? (124 L)

P1 (V1) = P2 (V2)

More problems to practice… �  N2O is used as an anesthetic. The pressure of

gas changes from 105 kPa to 40.5 kPa. The ending volume is 6.48 L. What was the original volume due to this change in pressure if temp. is held constant. (2.50 L)

�  A gas with a volume of 4.00L is at a pressure of 1.30 atm. The gas is allowed to expand to 12.0 L. What is the new pressure in the container if the temp. is held constant? (0.433 atm)

Charles’ Law: Volume is directly proportional to temperature. �  V1 / T1 = V2 / T2

�  As the temperature of the enclosed gas increases, the volume ◦  Increases…when pressure is held constant. ◦  Don’t forget! K = ºC + 273, (temp can’t be zero)

V1T1

=V2T2

Ex D pg 372 A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?

Given: V1 of Ne = 752 mL, T1 of Ne = 25°C + 273 = 298 K, T2 of Ne = 50°C + 273 = 323 K Unknown: V2 of Ne in mL

1 2

1 2

V VT T⎛ ⎞

=⎜ ⎟⎝ ⎠

1 22

1

VTVT

=752mL x 323K = 815mL Ne 298 K

◦  Charles' Law clip ◦  Microwave popcorn ◦  Warming/cooling balloon over flask ◦  Demos ◦  https://www.youtube.com/watch?v=GcCmalmLTiU ◦  https://www.youtube.com/watch?v=7JKVtbe-hV8 ◦  https://www.youtube.com/watch?v=Uy-SN5j1ogk

Sample Charles’ Law Problem �  A balloon inflated in a room at 24°C has a volume

of 4.00 L. The balloon is then heated to a temperature of 50°C. What is the new volume of the balloon if the pressure of the room remains constant throughout the experiment? (4.35 L)

�  Exactly 5.00 L of air at -50.0°C is warmed. If the new volume of the balloon is 8.36 L, to what temperature in °C was it heated? Assume pressure is constant. (99.9°C)

�  If a sample of gas occupies a volume of 6.80 L at 325 °C, what will its volume be at 25.0°C if the pressure does not change? (3.39 L)

V1T1

=V2T2

Whose law?

� Balloon test ◦  ttps://www.youtube.com/watch?

v=JZSajBakGK4

�  Imploding drum ◦  https://www.youtube.com/watch?v=Uy-

SN5j1ogk

� Marshmallows in a vacuum

Gay-Lussac’s Law: The pressure of a gas is directly proportional to Kelvin temperature

�  P1/T1 = P2/T2

�  As the temperature of an enclosed gas increases, the pressure ◦  increases, if the volume is constant.

1 2

1 2

P PT T

=

Ex E pg 373 The gas in a container is at a pressure of 3.00 atm at 25°C. Directions on the container warn the user not to keep it in a place where the temperature exceeds 52°C. What would the gas pressure in the container be at 52°C? Given: P1 of gas = 3.00 atm, T1 of gas = 25°C + 273 = 298 K, T2 of gas = 52°C + 273 = 325 K Unknown: P2 of gas in atm

1 2

1 2

P PT T⎛ ⎞

=⎜ ⎟⎝ ⎠

1 22

1

PTPT

=3.00atm x 325K = 3.27 atm 298 K

Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C #1

Pg 372 sample D #1,2 Pg 374 sample E #1,2,3 Pg 375 sample F #1-2

11.3: Pg 385 sample I #1-2 More Practice: (do not do now…) Try pg 375 section review # 2-4 and pg 385 section review #3,5,6

Sample Gay-Lussac’s Law Problems �  The pressure in an empty aerosol can is 103 kPa. If the

can is thrown into a fire and increased in temp. from 25.0°C to 928°C what will the resulting pressure be. Volume is kept constant since the size of the can does not change. (415 kPa)

�  Think about the tires on your car. Why do you suppose that tire manufacturers recommend checking the air pressure in your ties before driving more than a mile?

�  The pressure in a car tire is 198 kPa at 27°C. After a long drive the pressure in the tire has increased to 225 kPa. What is the temp of the air in the tire? Assume tire volume is constant. (341 K)

Another problem.. �  A sample of nitrogen gas has a pressure of 0.58

atm at 539K. If the volume is kept constant and the temp. decreases to 211K, what is the new pressure? (0.23 atm)

Warm up: Who’s law is demonstrated in each? 1. Bag of chips pop when brought from a higher to lower

altitude. 2. Burning gun powder increases the pressure until a

cannon explodes. 3. Car tires become slightly smaller in the snow. 4. Pumping up a bike tire by adding air. 5. Heating corn kernels until they pop. https://www.youtube.com/watch?v=0m-Lr4Z2drc

Summary �  Boyle’s Law: P1 (V1) = P2 (V2) ◦  Indirectly related

�  Charles’ Law: V1 / T1 = V2 / T2 ◦  Directly related

�  Gay-Lussac’s Law: P1/T1 = P2/T2 ◦  directly related

https://www.youtube.com/watch?v=JZSajBakGK4 https://www.youtube.com/watch?v=Uy-SN5j1ogk

Combined Gas Law:

Boyle’s Law: P1 (V1) = P2 (V2)

Charles’s Law:

Gay-Lussac’s Law:

�  Gas law only works when the amount of gas is constant.

1 1 2 2

1 2

PV PVT T

=

Combined Gas Law Example F pg 375 A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.0°C? Given: V1 of He = 50.0 L

T1 of He = 25°C + 273 = 298 K T2 of He = 10°C + 273 = 283 K P1 of He = 1.08 atm P2 of He = 0.855 atm

Unknown: V2 of He in L

1 1 2 2

1 2

PV PVT T

=

1 1 22

2 1

PVTVPT

=1.08atm x 50.0LHe x 283K 0.855atm x 298 = 60.0L He

Sample Combined Gas Law Problems �  A volume of gas is 30.0L at 313K and 153 kPa.

What will the new volume be at standard temp. and pressure (STP)? (39.5 L)

�  A 5.00L air sample has a pressure of 1.07 atm at a temp of -50.0°C. If the temp is raised to 102°C and the volume expands to 7.00L, what will the new pressure be? (1.29 atm)

Ideal Gas Law: PV = nRT �  Combined gas law only works when amount of

gas is constant. �  You can’t use the combined gas law to compute

how many moles you have of a gas at a fixed volume and a known temperature and pressure, so to calculate that the Ideal Gas Law is used

�  It is expressed by the following equation: PV = nRT

Solve for R when PVT and n= standard values.

Ideal Gas Law: PV = nRT P = Pressure (kPa or atm) V = Volume (L) n = amount of gas in moles (mol) R = ideal gas constant (determined from STP values)

•  8.31 L kPa/K mol •  0.0821 L atm/K mol

T = Temperature (K) Ex I pg 385

What is the pressure in atmospheres exerted by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K?

Ex I pg 385 What is the pressure in atmospheres exerted by a 0.500 mol sample of nitrogen gas in a 10.0 L container at 298 K? Given: V of N2 = 10.0 L

n of N2 = 0.500 mol T of N2 = 298 K

Unknown: P of N2 in atm

nRTPV nRT PV

= → =

(0.500 mol)(0.0821 L atm)(298 K)10

1.0 L

.22 atmP •= =

Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C practice #1

Pg 372 sample D practice #1,2 Pg 374 sample E practice#1,2,3 Pg 375 sample F practice#1-2

11.3: Pg 385 sample I practice#1-2

Homework: Pg 375 section review # 1-6

Problems to practice… �  A child’s lungs can hold 2.20 L of air. How many

moles of air do her lungs hold at a pressure of 102 kPa and a body temp. of 37°C? (0.0871 mol)

◦  Use a value of 29.0 g/mol for the molar mass of air

and calculate the amount of GRAMS of air. (2.53 g)

1.  A volume of gas is 30.0L at 313K and 1.5 kPa. What will the new volume be at standard temp. and pressure (STP)?

2.  A child’s lungs can hold 2.20 L of air. How many moles of air do her lungs hold at a pressure of 102 kPa and a body temp. of 37°C?

Warm up: which law/equation do you use, then solve

39.5L

0.0871 mol

Summary so far….. �  Boyle’s Law:

�  P1 (V1) = P2 (V2) �  Charles’ Law: ◦  V1 / T1 = V2 / T2

�  Gay-Lussac’s Law: ◦  P1/T1 = P2/T2

� Combined Gas Law: �  Ideal Gas Law: ◦  PV = nRT ◦ What does each variable stand for?

Ch 11 notes

P = Pressure (kPa or atm) V = Volume (L) n = amount of gas in moles (mol) R = ideal gas constant (determined from STP values)

•  8.31 L kPa/K mol •  0.0821 L atm/K mol

T = Temperature (K)

Review of Ch 11 notes from last class

What law should you use to solve? � A gas has a volume of 800.0 mL at minus 23.00

°C and 300.0 torr. What would the volume of the gas be at 227.0 °C and 600.0 torr of pressure?

� At what temperature will 0.654 moles of neon gas occupy 12.30 liters at 1.95 atmospheres?

� What is the pressure of a gas at 200.0 K if its original pressure was 0.250 atm and 400.0 K.

� A sample of argon gas at STP occupies 56.2 liters. Determine the number of moles of argon and the mass in the sample.

�  2.00 L of a gas is collected at 25.0 °C and 745.0 mmHg. What is the volume at STP?

Combined Ideal Combined Ideal Combined

� Why is this lady’s explanation not really correct?

� https://www.youtube.com/watch?v=HhTm4k_TLFI

1.  A volume of gas is 30.0L at 313K and 1.5 kPa. What will the new volume be at standard temp. and pressure (STP)?

2.  A child’s lungs can hold 2.20 L of air. How many moles of air do her lungs hold at a pressure of 102 kPa and a body temp. of 37°C?

Warm up: which law/equation do you use, then solve

.395L

0.0871 mol

Real vs. Ideal Gases �  Ideal gases must follow all the gas laws at

all conditions of pressure and temp. ◦  have no volume and there is not attraction

between particles in the gas…no such gas exists

� Real gases have volume and there is often attraction between particles.

� Real gases act most like ideal gases at STP

Avogadro's law � Equal volumes of gas at the same temp.

and pressure contain equal # of particles � At STP: standard molar volume ◦  1mole = 22.4 liters

Ex G page 381 a.  What volume does 0.0695 mole of gas

occupy at STP?

b.  What quantity of gas, in moles in 2.21L at STP

1.53 L

0.0987 mol

Ex: 2 Ideal Gas Law and molar volume a.  A deep underground cavern contains 2.24 x 106 L of

CH4 (methane gas) at a pressure of 1500 kPa and a temp of 315 K. How many moles of CH4 are in the cavern? �  (1.27 x 106 mol)

b.  How many GRAMS in the cavern?

c.  How many LITERS are in the cavern at STP? �  Recall that moles can be converted to liters or grams using

the molar road map when the number of moles are known.

STP and not STP

Ex 3: A 30.6 g sample of gas occupies 44.8 L at STP. What is the molar mass of this gas? Ex 4: 96.0 g. of a gas occupies 48.0 L at 700.0 mm Hg and 20.0 °C. What is its molecular weight?

15.3 g/mol

700mmHg (1atm/760mmHg) = .921atm PV=nRT (.921)(48)=n(.0821)(293) n = 1.838 mol 96.0 g / 1.8388 mol = 52.2 g/mol

Diffusion and Effusion

� Diffusion: mixing of gas by random motion � Effusion: gas particles passing through tiny

opening

Ch 11.3 section review - put in classwork section of notebook � Ch 11.3, answer pg 385 section review

#1, 2, and 5

Ch 11 Practice Problems 11.1: pg 367 section review #1,2,4,6 11.2: Pg 370 sample C practice #1

Pg 372 sample D practice #1,2 Pg 374 sample E practice#1,2,3 Pg 375 sample F practice#1-2

11.3: Pg 385 sample I practice#1-2

Ch 11.3 section review pg 385 section review #1, 2, and 5

classwork

4/2/15

Goals: 1.  Finish classwork CH 11 practice problems 2.  Ch 11.4 section reviw 3.  Ch 11 study guide

Explain this…Whose law??

� Pack Mate—watch until 1:10 � Liquid nitrogen balloons � How do you fix a dented ping pong ball? ◦  start at 0:45 sec—stop at 1:54

� You give ME a practical application of one of the gas laws…

https://www.youtube.com/watch?v=JZSajBakGK4 https://www.youtube.com/watch?v=Uy-SN5j1ogk https://www.youtube.com/watch?v=0m-Lr4Z2drc

Ch 11.3 Answers

1.  Equal volumes of gas at the same temperature and pressure will contain equal numbers of particles. Volume and # of molecules vary directly with STP, 1mole=22.4 liters

2.  78mL 5. 2.63 atm or 265.5 pKa

(oxygen is diatomic, if not diatomic, 5.24atm)

Whose Law?

Gay Lussac Law

Whose law?

BOYLE

Whose Law?

Charles’ Law

Name the law…

Combined Gas Law

Name the law…

Boyle’s Law

Allows for respiration!

Common  Core  Standards  Physical  Science  

� HS-PS1-3. Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.

CA State Standards

Common  Core  Standards  Physical  Science  

� HS-­‐PS1-­‐6.  Refine  the  design  of  a  chemical  system  by  specifying  a  change  in  condi<ons  that  would  produce  increased  amounts  of  products  at  equilibrium.*    

� HS-PS2-6. Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.*

� HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

After Test

�  Science Fair Project: revise background research or work on procedures (pg5-6 in packet)

or � Read Ch12.1-12.2 pg 400-416. Take notes

(be sure to include all vocabulary) ◦ Title the notes “Ch 12 Solutions” ◦  Put in notes section of notebook (if you can)

or write on binder paper