STATES OF MATTER AND

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```					KINETIC MOLECULAR
THEORY

GAS PRESSURE AND
VOLUME
Section 11.1
Section 11.2
SECTION
11.1
STATES OF MATTER: REVIEW
SOLIDS
•   Tightly packed particles
•   Crystal lattice
•   Definite shape and volume
•   Limited to NO movement
•   Affected by gravity
LIQUIDS
• More loosely packed particles
(than solids)
• Take the shape of container
or vessel
• Move with vibrational and
rotational energy
• Affected by gravity
GASES
• Particles move independently
of one another
• High degree of disorder
(bumping into each other)
• Vibrational, rotational AND
translational energy
• Flow in all directions
– Not affected by gravity
• Expand to fill the volume
of a container
THE KINETIC MOLECULAR
THEORY OF GASES
The theory makes these assumptions:
• Gas particles have virtually no volume (mostly
empty space in a container of gas)
• Gas particles have no attraction/ repulsion to
each other
• Gas particles have rotational, vibrational and
translational movement
• Their kinetic energy is DIRECTLY related to
temperature (higher temp = higher Kin energy)
• This is the description an “IDEAL GAS”
IDEAL GASES

“An ideal gas takes up
hardly any space and the
particles do NOT attract
each other”
- In reality, no gas is really ideal
SECTION 11.2
CLOSED SYSTEM
• How do gases behave in a closed
system?
• A CLOSED SYSTEM contains constant
moles of a substance
• It is not open to the atmosphere
• Examples:
– CO2 in a fire extinguisher
– O2 in a oxygen tank
FACTORS THAT AFFECT
GASES
• Temperature (T)
• Pressure (P)
• Volume (V)
PRESSURE (P)‫‏‬
• Force exerted per unit of surface area

f
• Common Units:          P
– Pascals (Pa)‫‏‬
– Kilopascals (kPa)‫‏‬
A
– atmosphere (atm)‫‏‬
– Torr (Torr)
– mm Hg
PRESSURE OF A GAS
• Not measurable like pressure of a solid
or liquid
• Pressure of gas is determined by
kinetic motion of molecules
• Ex:
– when filling a basketball with air, more
molecules collide with inside of basketball
– The total number of collisions and the
strength of the force = total gas pressure
PRESSURE OF A GAS
continued…
• As gas molecules
collide with sides
of a container
they exert a
force.
• These exert a net
force or pressure
on the container.
Standard Atmospheric pressure
• The column of air above one square meter at sea
level and 0°C is 101.3 kPa
– See pg 425, Fig 11.9
• Equivalent to:
– 760 mmHg
– 760 Torr
– 1 atm
• Or, 101.3 kPa = 760 mmHg= 760 Torr= 1 atm
• To convert between each: (use ratios!  )
– Ex: Convert 100kPa to torr
100.0 kPa x 760.0 torr = 750.2 torr
101.3 kPa
BOYLE’S LAW:
• Explains the relationship between pressure
and volume
• "The volume of a given gas is inversely
proportional to pressure"
• Temperature must remain constant for this
to occur

V 1P1  V 2 P2
(1 = initial,   2   = final)
BOYLE’S LAW
EX: BOYLE’S LAW
Ex: A balloon has a volume of 4.50 L at
room temperature but when the
pressure is increased to 110.2 kPa. What
will its final volume become?

•   P1 = 101.3 kPa
•   V1 = 4.50 L
•   P2= 110.2 kPa
•   V 2= ?
BOYLE'S LAW problem
continued…
V 1P1  V 2 P2
(4.50L) (101.3 kPa) = V2 (110.2 kPa)
V2 = 4.137 L

To Check:
• the unit for answer is in L (volume)
• when units cancel out only L should remain
• the volume of the balloon has decreased due to
increase in pressure
HOMEWORK

• Page 423 # 1,2,4,5,6,7
• Page 435 # 1,3,4,5

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