Gases PowerPoint notes

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Gases PowerPoint notes
Agenda
• Seating Plan
• Welcome back; tell me the most exciting
thing you did during the break and what
do you hope to achieve in Chemistry this
semester?
• Brief overview of this semester
• Review of class expectations, safety rules
• 7UP
**HOMEWORK: NONE!
Agenda
• Warm Up
• Kinetic Molecular Theory lesson
• KMT practice ws
**HOMEWORK: KMT practice ws due
tomorrow, Ch. 13 vocab p.509 (17 terms),
due on the day of the test TBA ~ likely the
30th. Remember, vocab pages can be found
on my website; mrsnasr.weebly.com
Warm Up
• In your notebook, write a 3-5 sentence
paragraph describing a few properties of
gases, and why gases are considered
“fluids”.
4 states of matter
•
•
•
•
Solid
Liquid
Gas
Plasma
– Main difference b/w the
4 types:
• the amount of Kinetic
Energy b/w the molecules
• The distance b/w the
molecules
Gases
• Gases:
– Have the most kinetic energy
– Have particles that are very far
apart
– Exhibit unique behaviors b/c of
the motion of their particles
•Explained by the Kinetic Molecular
Theory
Kinetic Molecular Theory of
Gases
The word “gas” comes from the
Greek word meaning “chaos.”
Numerous experiments have led
to the Kinetic Molecular Theory (KMT) of
Gases. The KMT explains the unique
behavior of gases.
The Kinetic Molecular
Theory
Remember, the word kinetic
means motion.
The KMT is composed of 5
assumptions…
KMT of Gases
Assumption #1
1. Gases are
made up
of tiny
particles
KMT of Gases
Assumption #2
2. These
particles have
negligible
volume
(i.e.insignificant,
very small).
KMT of Gases
Assumption #3
3. Gas particles
are far apart,
they do not
attract or
repel each
other.
KMT of Gases
Assumption #4
4. Gas particles are in constant motion
and move very fast (thousands of km
an hour!)
KMT of Gases
Assumption #4
• This constant motion can be called
the “random walk.” Gas particles
will move in a straight line until
they collide with
another particle and
then change direction.
Elastic!
KMT of Gases
Assumption #4
Gas pressure is caused by the
collisions of gas particles with each
other and the walls of their
container.
• As the number of collisions
increases, pressure will increase
• We will revisit pressure later….
KMT of Gases
Assumption #5
• The average kinetic energy of the
gas particles depends on the
temperature. As temperature
increases, the particles move faster.
• What does this mean for pressure?
Kinetic Theory of Gases
• Particles move independently of each
other, this is why gases expand to fill
their container.
– The word “diffuse” means to move
out.
• Gases have no definite volume.
Agenda
•
•
•
•
Warm Up
Pressure lesson
“Collapsing can”
Altitude Training reading (annotate) and
questions.
**HOMEWORK: complete the reading, annotation
and questions. Ch. 13 vocab due on the day of the
test (tentatively the 30th)
Warm Up
• You were told by a car mechanic that you must
let air out of your tires in the summer, and add
more air in the winter. In your notebook, write
2-3 sentences explaining why this suggestion
was made.
Gas Pressure
Recall, gas pressure is caused by
the simultaneous collisions of
gas particles.
• Pressure can measured in three
different units:
atm, kPa, mmHg (torr)
Gas Pressure
A region of space where no gas
pressure is exerted is called a
vacuum.
• Gas pressure is equal to zero, so
there are no collisions.
• Example: Peeps 
Gas Pressure
More collisions will result if…
• There are more particles in a
particular space.
• As temperature increases, pressure
will increase, because particles are
colliding with each other and the
walls of the container more
frequently.
Gas Pressure
Atmospheric pressure (atm) is the
pressure caused by the air in our
atmosphere.
• Depends on weather and altitude
conditions.
• As altitude increases, atmospheric
pressure decreases. Air gets thinner
as you go up!
Gas Pressure
To help us understand the relationship
between temperature and atmospheric
pressure we will use “the collapsing
can” demo.
Measuring Atmospheric Pressure
A barometer is a
device used to
measure
atmospheric
pressure.
Gas Pressure
Standard pressure is the average
pressure as measured at sea level.
• Standard pressure equals four
quantities.
• These four quantities all represent
the same thing just with different
units.
Standard Pressure Units
= 1 atm (atmosphere)
= 760 mmHg (millimeters of Hg)
= 760 torr
= 101.3 kPa (kilopascal)
Memorize these!
Agenda
• Warm Up
• Converting pressure and temperature units
lesson
• Review HW (KMT ws and reading answers)
• Conversion practice ws
**HOMEWORK: complete conversion practice ws.
Continue to work on vocab (p. 509 – 17 terms)
due tentatively on the 30th.
Warm Up
• In your notebook, write 2-3 sentences
describing why the pop can in yesterday’s
demo became crushed after inverting it
into an ice bath.
All pressure
conversions can be
done in one step.
Example
Example: The pressure inside a balloon is
4.17atm, how many kPa is this?
K: 4.17atm
What conversion factor are
U: ? kPa
you101.3kPa
using?
4.17atm x
= 422 kPa
1
atm
1 atm = 760 mmHg = 101.3kPa
Example
A gas is at a pressure of 1.50 atm.
Convert this pressure to mmHg.
1.50 atm x
760
mmHg
1
atm
= 1140 mmHg
= 1.14 x 103 mmHg
Example
The pressure at the top of Mt.
Everest is 33.7 kPa. What is that
measurement in mmHg?
33.7 kPa x
760
mmHg
101.3 kPa
= 253 mmHg
= 2.53 x 102 mmHg
KE Distribution for Gas Particles
Temperature is really a measure
of the amount of kinetic energy a
sample of matter has.
• But not all particles in the sample
have the same amount of KE.
• Most of the particles move with
an average amount of KE
• Some particles move slower than
average
• Some particles move faster than
average.
Kinetic Energy and Temperature
Average KE is directly proportional to
the Kelvin (K) temperature.
• The formula to calculate
temperatures in Kelvin is:
Kelvin = °C + 273
• Kelvin is never a negative number.
Example
Example: Room temperature is 25°C.
What is this in Kelvin?
25°C + 273 =
298 K
Kinetic Energy and Temperature
As temperature decreases, particles
move slower and slower.
• The particles would theoretically stop
at 0 Kelvin (absolute zero) but this
does not happen due to the kinetic
theory.
• This temperature has yet to be
reached!
Standard Temperature
•Recall, STP stands for
standard temperature
and pressure.
•Temperature Equals 0°C or
273K.
•Pressure equals 1 atm
Calculating the Factor by
which KE changes
Since KE is directly proportional to the Kelvin
temperature, the factor by which KE increases or
decreases can be easily calculated.
Example: If temperature goes from 200K  400K,
double
then the average KE will __________________.
Always put the final temperature 400/200 = _____
2
over the initial temperature.
Calculating the Factor by
which KE changes
Example: If temperature goes from 100K  300K,
triple
then the average KE will __________________.
3
300/100 = _____
Example: If temperature goes from 300K  100K,
be a third
then the average KE will __________________.
1/
3
100/300 = _____
Calculating the Factor by
which KE changes
WAIT! STOP! .
KE is proportional to
double
127°C, then the average KE will ______________.
the KELVIN
2
400 200 = _____
_____/_____
temperature!
NOT
-73°C + 273 = 200K
degrees
Celsius!
127°C
+ 273 = 400K
Example: If temperature goes from -73°C 
Agenda
•
•
•
•
•
•
Warm Up
Boyles and Charles Law lesson
Short balloon demo Charles Law
Peer grading intro to gas laws HW
Boyles and Charles Law practice ws
Per 4: Start Combined Gas Law
Homework
• Complete Boyles and Charles Law
practice
• VOCAB
• **I will be available for extra help
this Friday at lunch in C13**
Warm Up
• In your notebook, write 3-5
sentences fully describing why the
relationship between amount of gas
and pressure is a direct one; why the
relationship between volume and
pressure is an indirect one; and why
the relationship between
temperature and pressure is a direct
one.
Factors Affecting Gas Pressure
• Recall that 4 variables are used to
describe gases:
– Pressure
– Volume
– Temperature
– Amount (moles)
• Remember that a change in one of these
variables always affects the others.
Boyle’s Law: Pressure and Volume
Robert Boyle was the first
person to study the pressurevolume relationship of gases.
• In 1662 Boyle proposed a law
to describe this relationship.
Boyle’s Law: Pressure and Volume
We can simplify this relationship by the
formula:
P1 V1 = P2 V2
Where,
P1, P2 = pressure in any unit (atm, kPa,
mmHg), BUT they must match!
V1, V2 = volume in any unit (usually, L or
mL), BUT they must match!
Boyle’s Law: Example
A gas has a volume of 30.0L at 150 kPa. What is the
volume of the gas at 0.252 atm?
P1= 150 kPa x 1 atm
P1 V1=P2 V2
= 1.5 atm
101.3 kPa
V1= 30.0L
P2= 0.252 atm
V2= ?
(1.5 atm) (30.0L) = (0.252 atm) (V2)
V2 = 180L
Charles’s Law: Temperature
and Volume
Jacques Charles studied
the effect of
temperature on volume
of a gas at constant
pressure.
• In 1787 Charles
proposed a law to
describe his
observations.
Charles’s Law: Temperature
and Volume
We can simplify this relationship by the
formula:
V1 V2
=
T1 T2
Where,
V1, V2 = volume in any unit (L or mL), BUT
they must match!
T1, T2 = temperature is always in Kelvin!
(Recall, just add 273 + °C)
Charles’s Law: Example
A gas has a volume of 4.0L at 27°C. What is its
volume at 153°C?
V1= 4.0L
T1= 27°C +273= 300K
V2= ?
T2= 153°C+273= 426K
V1 V2
=
T1 T2
(4.0L)
(300K)
=
(V2)
(426K)
V2 = 5.7L
Agenda
• Warm Up
• Gay-Lussac, Avogadro and Combined
Gas Laws lesson
• Peer grading Boyles and Charles Law
• Combined Gas Law practice ws
• SCUBA diving article
Homework
• Complete Combined Gas Law
practice due Mon.
• SCUBA diving reading and questions
due Mon.
• VOCAB due 30th
• **I will be available for extra help
this Friday at lunch in C13**
Warm Up
• 15.35L of a gas is at a pressure of
198.0 kPa. At what pressure would
the gas have a volume of 13.78L?
• At what temperature would the
volume of a gas be equal to 0.796L if
the gas had a volume of 1180 mL at
144ºC?
Gay-Lussac’s Law: Pressure
and Temperature
Joseph Gay-Lussac
discovered the
relationship between
temperature and
pressure.
• His name is on the gas
law that describes
this relationship.
Gay-Lussac’s Law: Pressure
and Temperature
We can simplify this relationship by the
formula:
P1 P2
=
T1 T2
Where,
P1, P2 = pressure in any unit (atm, kPa, or
mmHg), BUT they must match!
T1, T2 = temperature is always in Kelvin!
(Recall, just add 273 + °C)
Gay-Lussac’s Law: Example
A gas has a pressure of 103kPa at 25°C. What will the
pressure be when the temperature reaches 928°C?
P1= 103kPa
P1 P2
=
T1= 25°C +273= 298K
T
T
1
2
P2= ?
T2= 928°C+273= 1201K
(P2)
(103kPa)
=
(1201K)
(298K)
P2 = 415kPa
The Combined Gas Law
The combined gas law is a
single expression that
combines Boyle’s, Charles’s,
and Gay-Lussac’s Laws.
•This gas law describes the
relationship between
temperature, pressure, and
volume of a gas.
•It allows you to do
calculations where only the
amount of gas is constant.
RB + JC +
JG-L = BFFs!
The Combined Gas Law
Helpful hint: You are able to
get which law you need by
For example, if there is no
IfIfthere
thereisisno
nomention
mention
of
ofpressure
volume in
in
covering
the
variable
that
mention of temperature in the
1
1
2
2
theisproblem,
cover
PV up
up
and
and
you
you
are
are
not
mentioned
in
the
problem!
problem, cover T up and you are
left There
with the
relationship
between
T 4
is
no
need
to
memorize
left with the relationship between
and
andP.V.(aka
(aka
Gay-Lussac’s
Charles’s 2
Law!)
Law!)
1
individual
just memorize
the
P and V. laws,
(aka Boyle’s
Law!)
Combined Gas Law and you can
derive all of the others!
PV PV
=
T
T
The Combined Gas Law
A gas occupies 3.78L at 529mmHg and 17.2°C. At what
pressure would the volume of the gas be 4.54L if the
temperature is increased to 34.8°C?
P1 V1 P2 V2
=
P1= 529mmHg
T
T
1
2
V1= 3.78L
T1= 17.2°C + 273= 290.2K
(P2)(4.54L)
(529mmHg)(3.78L)
P2= ?
=
(307.8K)
(290.2K)
V2= 4.54L
P2 = 467mmHg
T2= 34.8°C + 273= 307.8K
Avogadro’s Law: Volume and
Moles
Avogadro discovered
the relationship
between volume and
amount (i.e. moles).
• His name is on the gas
law that describes
this relationship.
The mole/volume relationship
• 1 mole of any gas occupies a volume of
22.4 L at STP
• “STP” stands for ‘standard temperature
and pressure’.
• Standard temperature = 0ºC
• Standard pressure = 1 atm (101.3 kPa)
Agenda
•
•
•
•
Warm Up
Per 4,5,6 –peer grade Boyles/Charles
Gas Variables POGIL
**HOMEWORK: POGIL due Mon.,
Vocab due 30th, Combined Law ws
and Scuba reading due Mon.
Warm Up
• What is the pressure of 1.27 L of a gas at
288oC, if the gas had a volume of 875 mL
at 145 kPa and 176oC?
Agenda
• Warm Up
• Ideal Gas Law lesson
• Review CGL and SCUBA HW
• Ideal Gas Law practice ws
**HOMEWORK: Ideal Gas Law practice
ws, VOCAB/NB check due Fri!
LAB on Wednesday, TEST on Friday,
tutoring Wednesday @ lunch C13
Warm Up
• A gas has a volume of 13.4L at 17ºC.
What is the volume of the gas at
standard temperature?
• What is the volume of a gas at 0.43atm, if
it had a volume of 720mL at a pressure of
698mmHg?
Ideal Gas Law
•When using the combined gas law, we
manipulated P, V and T, but kept amount
constant.
•The combined gas law can be modified
to include the amount of gas (in moles)
by including the variable, n.
• The modified law is called the Ideal
Gas Law
Ideal Gas Law
This gas law relates the
amount of gas (in moles) to
the volume it would occupy
at a particular temperature
and pressure.
Ideal Gas Law
STOP!
It
is
PV=nRT
Where,
often
called
P= pressure
(atm)
V= volume (L)
the “picky” law!
n= moles (mol)
The
units must be
R= 0.0821
L·atm/mol·K
T= temperature
(K) see here!
what you
R is called the Ideal Gas Constant
(it has multiple values, but for our
purposes we will only use this one).
Ideal Gas Law Example
At what pressure would 0.212 mol of a gas occupy
6.84L at 89°C?
PV=nRT
P= ?
(P)(6.84L)=(0.212mol)(0.0821)(362K)
V= 6.84L
P = 0.92atm
n= 0.212mol
R= 0.0821L·atm/mol·K
T= 89°C + 273= 362K
Ideal Gas Law Example
At what temperature would 52.3g of methane
(CH4) gas occupy 65.7L at 184kPa?
PV=nRT
P= 184kPa x 1 atm =1.82 atm
101.3kPa
V= 65.7L
1 mol CH4
52.3gCH
x
n=
= 3.26 mol CH4
4
16.05gCH4
R=0.0821L·atm/mol·K
(1.82atm)(65.7L)= (3.26mol)(0.0821) (T)
T= ?
T = 447K
Agenda
• Warm Up
• Short lesson on Dalton and Graham’s
Laws
• Review ideal gas HW
• Review POGIL
• Practice Dalton and Graham
**HOMEWORK: Dalton/Graham practice
ws, VOCAB/NB check due Fri!
LAB on Wednesday, TEST on Friday,
tutoring Wednesday @ lunch C13
Warm Up
• At what temperature would 0.46mol
of a gas occupy 13.3L if the pressure
is 734mmHg?
• What is the pressure of 62.76g of CO2
gas if it occupies a volume of 35L at
standard temperature? (C = 12g/mol,
O = 16g/mol)
Recall, gas pressure results from
collisions of gas particles.
•Gas pressure depends on the
amount of gas and the KE of its
particles.
•Since particles in a mixture of
gases at the same temperature
contain the same average KE, the
kind of particle is unimportant.
Example: Composition of Dry Air
Component Volume Partial Pressure
Nitrogen
78.08%
79.11 kPa
Oxygen
20.95%
21.22 kPa
Carbon dioxide
0.04%
0.04 kPa
MISC gases
0.93%
0.95 kPa
Total 100.00%
101.32 kPa
Dalton’s Law of Partial Pressures
Ptotal= P1 + P2 + P3…
Units of pressure must match!
“The total pressure
of a mixture of
gases is equal to
the sum of the
individual (partial)
pressures.”
Example: Dalton’s Law
What is the total pressure for a mixture of O2 and
CO2 if PO2= 0.719 atm and PCO2= 423mmHg.
760mmHg
PO2= 0.719atm x
= 546mmHg
1atm
PCO2= 423mmHg
Ptotal=546mmHg + 423mmHg
Ptotal=969mmHg
Thomas Graham (1846)
•Diffusion: Is the tendency of gas
particles to spontaneously spread out
until uniformly distributed. High 
Low concentration
•Effusion: The escape of a gas through
a tiny pinhole in a container of gas.
–Gases with lower molar masses
effuse more quickly.
Agenda
• Go over lab procedure
• LAB
• After collecting data, begin working
on calculations
**HOMEWORK: Lab due tomorrow!
VOCAB/NB check due Fri!
TEST on Friday, tutoring today @ lunch
C13
Agenda
• Turn your lab in to MY basket
• Warm Up
• Review Dalton/Graham HW
• Gas Laws Unit Review Packet
• Distribute KEY
**HW: Complete Unit Review, STUDY
for Test tomorrow, Vocab/NB check
tomorrow
Warm Up
• What is the pressure of a mixture of O2,
N2 and CO2 gases if the pressure of these
gases are PO2=254 mmHg, PN2=0.351atm
and PCO2=43.9kPa. Express your answer in
mmHg.
• A mixture of gases has a total pressure of
1465mmHg. The mixture is made up of
CO, CO2 and SO2. What is the pressure of
the SO2 if PCO=234mmHg and
PCO2=871mmHg. Express your answer in
atm.
Agenda
Take out a pencil, eraser and calculator
Notebook up front
Please hook your backpack on the side wall
On short answer questions, please BOX
your final answer!
• There is a Q3 short answer!
• Amendments: Q1 short answer, express
answer in L!!, Q17 m.c. should say
“number 16”
**HW: None! Enjoy your weekend!
•
•
•
•
Agenda
• Warm Up
• Intro to Gas Laws lesson
• Peer grading pressure conversion HW
• Intro to Gas Laws practice ws
**HOMEWORK: Intro to Gas Laws practice
ws, VOCAB tentatively due on the 30th (17
terms, p. 509)
Warm Up
• Convert 1.35 atm to mmHg
• Convert 100.4 kPa to atm
• What is STP? What does it stand for? What
are the numerical values?
Review: Kinetic Molecular Theory
KMT makes five major assumptions about
the particles in a gas:
1. Gas particles are tiny
2. Gas particles have negligible volume
3. Particles are in random motion. These
collisions cause pressure.
4. Particles have no attraction or repulsion
5. Higher the temp, higher the KE
Variables affecting gases
Four variables are generally used to
describe a gas.
1. Pressure (kPa, mmHg, atm)
2. Volume (L or mL)
3. Temperature (always in Kelvin!)
4. Amount (moles)
Factors Affecting Gas Pressure
Effect of adding or removing gas:
•When the amount of gas in a given volume
is increased, pressure increases.
•Example: Doubling amount of gas
= gas particle
2x Amount of gas,
2x Pressure
Factors Affecting Gas Pressure
•More particles means more
collisions, which means more
pressure!
•This is a direct relationship: If
the number of particles double,
pressure doubles.
Factors Affecting Gas Pressure
Effect of changing volume of container:
•When the volume is decreased (for a given
amount of gas) pressure increases.
•Example: Decreasing volume by half
= gas particle
½ Volume,
2x Pressure
Factors Affecting Gas Pressure
•Particles are closer together in a
container which means more
collisions which really means more
pressure!
•This is an indirect relationship: If
the volume is halved, pressure is
doubled and vice-versa.
Factors Affecting Gas Pressure
Effect of changing temperature of a gas:
•When the temperature of a gas increases the
particles have more KE, and pressure
increases.
•Example: Doubling temperature
= gas particle
298K
596K
2x Temperature,
2x Pressure
Factors Affecting Gas Pressure
•The particles move faster when
heated, and strike the walls of the
container with more force, so the
pressure builds.
•This is a direct relationship: If
the temperature is doubled,
pressure is doubled and viceversa.