Gases
&
Atmospheric Chemistry
 Read 11.1 (p. 516 – 519)
 Draw 3 particle pictures of the different states of matter.
Include a container in your diagram.
 Add symbols to illustrate the motion of the particles.
 Volunteers?
 Vgas=Vcontainer
 Define: KE, T
 Explain pop can demo.
 Define: P
Introduction…
Demo 1: Water and Cue Card
Why does the water stay in the glass?
Demo 2: Pop Can
What is happening in terms of STATES of water?
Liquid  Gas  Liquid
What is happening in terms of VOLUME of water?
Small  EXTREMELY LARGE  Small
1 mol H2O(l)= 18 mL or 0.018L
1 mol of H2O(g)= 22.4 L
We are surrounded by gases!
 Air (or the Atmosphere) is made up
of:
 This air is colliding with us…this is
called PRESSURE
…Or specifically the pressure we feel
is “Atmospheric Pressure”
What would the pressure be like on
top of Mount Everest?
Pressure: force exerted on an object
per unit of surface area
Air pressure= 1 atmosphere= 1 atm
States of Matter
 How do intermolecular forces of attraction differ
between states?
 Generally, how is particle size related to states of
matter?
 CH4 vs. C5H12
 Larger molecules= higher boiling points= liquid
@ room temp
 Why???? The bigger the molecule the more
opportunities for temporary dipoles to
form…dispersion forces add up and this
increase the IMF of attraction
Are all states compressible?
 Only gases…what is condensation?
Types of Kinetic Energy
Every moving particle has energy=
kinetic energy
Kinetic=motion
Solid= vibrational motion
Liquid= rotational and vibrational
motion
Gas= Translational, rotational, and
vibrational motion
Kinetic Molecular
Theory of Gases
1. The volume of an individual gas molecule is negligible
compared to the volume of the container.*
2. No attractive or repulsive forces between gas molecules.*
3. Gas molecules move randomly in all directions, in straight
lines (translational, rotational, vibrational).
4. Perfect elastic collisions between gas molecules (i.e. no
loss of kinetic energy).
5. An increase in temperature will increase the motion of
molecules. This means there is an increase in the
average kinetic energy.
* Assumptions for an IDEAL GAS
What can affect kinetic energy?
TEMPERATURE! How?
 Temperature= 
Kinetic energy
How is pressure affected?
 Temperature= 
Kinetic energy =  Pressure
How is volume affected?
 Temperature= 
Gas*
Kinetic energy =  Pressure=  Volume of
*space that the gas take up BUT usually Vgas= Volumecontainer
* Temperature is
a measure of the
average kinetic
energy
Pressure
 The force exerted on an object
per unit of surface area
P= F = N = Pa
A m2
Pressure: kinetic motion and
collisions with surroundings
Atmospheric Pressure is what we
feel around us.
- Air molecules have a mass.
-They are pulled by gravity
(acceleration of objects on earth=
9.81 m/s2 or 32.2 ft/s2) to exert
pressure on Earth.
Units of Pressure
Pressure can be measured by:
 Atmospheres= 1 atm
 KiloPascals (SI Unit)= 101.3 kPa
 Millimeters of Mercury= 760 mmHg (1st
mercury barometer)
 Torricelli’s= 760 torr
 Pounds per square inch (Imperial)= 14.7
psi
1 atm= 101.3kPa= 760 mmHg= 760 torr=
14.7 psi
How many kPa are in 3.57 atm of pressure?
Discovering Pressure
Barometer= 1st instrument to measure air pressure
Torricelli’s Barometer”
Torricelli found that air pressure at 0° C
1 atm= 101.3kPa= 760 mmHg= 760 torr= 14.7 psi
Standard Temperature and Pressure (STP) 0°C 101.3kPa
Standard Ambient Temperature and Pressure (SATP)
25°C 100kPa
760mm ~
30 inch
K: No
negative
values!
Kelvin Scale
 Charles found that the xintercept would always be 273°C
 Kelvin (c.1800) inferred that
at -273°C VOLUME WOULD
BE ZERO (molecular motion
would cease, NO kinetic
energy)
 p. 549 #1,2
0 K= -273°C= “Absolute zero”
TK= °C + 273.15
Charles’ Law
Gay-Lussac (c.1800) referenced
Charles’ work, and it became
known as…
Charles’ Law: the volume of a
fixed mass of gas is
proportional to its
temperature (K) when the
pressure is kept constant
V1 = V2
T1 T2
T MUST be K!
Practice
Pg. 552 #2
Boyle’s Law
 Boyle’s Law (1662): the
volume of a given amount of
gas at constant temperature,
varies INVERSELY with the
applied pressure
 If we change the pressure by
a factor of x, then the volume
will change inversely by that
same factor
Mathematically: P1V1= P2V2
p. 559 #1,2
Gay-Lussac’s Law
Recall:
1. Temperature is a measure of average
kinetic energy
2. Vgas= Volume of container
Gay- Lussac’s Law: the pressure of
a fixed amount of gas, at constant
volume, is directly proportional to
its Kelvin temperature.
MUST use K!
Practice
Pg. 559 Q: 1-3
P1 = P2
T1 T2
p. 559 #3
Combined Gas Law
Recall:
STP 0°C/273K & 101.3kPa
SATP 25°C/298K & 100kPa
P1V1 = P2V2
T1
T2
p. 560 #1-3
Combine:
1. Bolye’s Law PiVi= PfVf
2. Charles Law Vi = Vf
Ti Tf
3. Gay-Lussac’s Law Pi = Pf
Ti Tf
Ex. A sample of gas has a volume of
150mL at 260K and 92.3kPa. What
will the new volume be at 376k and
123 kPa?
T MUST be K!
Dalton’s Law of Partial
Pressures
Ptotal= P1 + P2 + P3 + … +Pn
Imagine mixing 3 different gases
each having a different
pressure…
What would the final pressure
be?
Dalton’s Law of Partial
Pressures: the total pressure
of a mixture of gases is the
sum of the pressures of each
of the individual gases
Ex. What is the pressure of O2 in
the atmosphere?
Practice
Pg. 594 #1-4
Pg. 596 #1-3