Not
long
ago, in a chemistry
Mayso
the
FORCE/area
be with you
lab far far away…
1. List 5 properties of gases
2. Identify the various parts of the kinetic
molecular theory
3. Define pressure
4. Convert pressure into 3 different units
5. Define temperature
6. Convert a temperature to Kelvin
Airbags fill with N2 gas
in an accident.
 Gas is generated by
the decomposition of
sodium azide, NaN3.
 2 NaN3 --->
2 Na + 3 N2

There is a lot of “free” space
in a gas.
 Gases can be expanded
infinitely.
 Gases fill containers
uniformly and completely.
 Gases diffuse and mix
rapidly.

To Review
Gases expand to fill their containers
Gases are fluid – they flow
Gases have low density
1/1000 the density of the equivalent
liquid or solid
Gases are compressible
Gases effuse and diffuse
Gas properties can be
modeled using math. This
model depends on —
 V = volume of the gas (L)
 T = temperature (K)
› ALL temperatures in the
entire unit MUST be in
Kelvin!!! No Exceptions!
 n = amount (moles)
 P = pressure
(atmospheres)
Ideal Gases
Ideal gases are imaginary gases that perfectly
fit all of the assumptions of the kinetic
molecular theory.
 Gases consist of tiny particles that are
far apart relative to their size.
 Collisions between gas particles and
between particles and the walls of the
container are elastic collisions
 No kinetic energy is lost in elastic
collisions
Ideal Gases
(continued)
 Gas particles are in constant, rapid motion.
They therefore possess kinetic energy, the
energy of motion
 There are no forces of attraction between
gas particles
 The average kinetic energy of gas particles
depends on temperature, not on the identity
of the particle.
RULE 2
The world won't care about your self-esteem. The
world will expect you to accomplish something
BEFORE you feel good about yourself.
Pressure
Is caused by the collisions of molecules with the
walls of a container
Is equal to force/unit area
SI units = Newton/meter2 = 1 Pascal (Pa)
1 atmosphere = 101,325 Pa
1 atmosphere = 1 atm = 760 mm Hg = 760 torr
1 atm = 29.92 in Hg = 14.7 psi = 0.987 bar =
10 m column of water.
Measuring Pressure
The first device for
measuring atmospheric
pressure was developed
by Evangelista Torricelli
during the 17th century.
The device was called a
“barometer”
Baro = weight
Meter = measure
An Early Barometer
The normal
pressure due to
the atmosphere at
sea level can
support a column
of mercury that is
760 mm high.
Column height measures
Pressure of atmosphere
 1 standard atmosphere
(atm) *
= 760 mm Hg (or torr) *
= 29.92 inches Hg *
= 14.7 pounds/in2 (psi)
= 101.325 kPa
(SI unit is PASCAL)
= about 34 feet of water!
OK, so it’s really not THIS
kind of STP…
STP in chemistry stands for
Standard Temperature and
Pressure
Standard Pressure
= 1 atm (or an
equivalent)
Standard Temperature
= 0 deg C (273 K)
STP allows us to compare
amounts of gases between
different pressures and
temperatures
Let’s Review:
Standard Temperature and Pressure
“STP”
P = 1 atmosphere, 760 torr
T = 0C, 273 Kelvins
The molar volume of an ideal gas is
22.42 liters at STP
Hint #1. When you don't know what you are
doing, do it neatly.
A. What is 475 mm Hg expressed in atm?
475 mm Hg x
1 atm
760 mm Hg
= 0.625 atm
B. The pressure of a tire is measured as 29.4 psi.
What is this pressure in mm Hg?
29.4 psi x
760 mm Hg
14.7 psi
= 1.52 x 103 mm Hg
A. What is 2.00 atm expressed in torr?
2.00 atm x
760 torr
1 atm
= 1520 torr
B. The pressure of a tire is measured as 32.0 psi.
What is this pressure in kPa?
32.0 psi x
101.325 kPa
14.7 psi
= 221 kPa
Converting Celsius to Kelvin
Gas law problems involving temperature
require that the temperature be in
KELVINS!
Kelvins = C + 273
°C = Kelvins - 273
1. List 5 properties of gases
2. Identify the various parts of the kinetic
molecular theory
3. Define pressure
4. Convert any kind of pressure to atmospheres
5. Define temperature
6. Convert a temperature to Kelvin
Pass the
Clicker!!!
1.
2.
3.
4.
5.
2.533
25.33
142.5
1425
Not listed
1.
2.
3.
4.
5.
310
3100
240
2400
Not listed
1.
2.
3.
4.
5.
-130
533
0.95
-13
Not listed
The End!!!