Unit 9
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Independent particles, moving in straight
lines
Change direction with collisions
Travel randomly
Assume shape of container and volume of
their container
Large amount of empty space
Compressible
No attractive forces between particles
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Fluidity – gas particles glide and flow past
each other
Expansion – fill any container
Compressibility – can decrease the volume
Diffusion – spontaneous mixing of two gases,
flow until evenly distributed. Flow from an
area of high concentration to an area of low
concentration.
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Dependent on the force of the collision and
the number of collisions that occur between
particles.
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Pressure = Force/Area
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Atmospheric or barometric pressure – results
from collisions of air molecules with objects
on earth.
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Manometer
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Barometer
 Developed by Evangelista Torricelli
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Pressure gauge
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SI unit = Pascal (Pa)
 A pascal is small so normally the kilopascal (kPa)
is used which is 1000 Pascal.
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Atmosphere (atm)
 1 atm is the atmospheric pressure at sea level.
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Pounds per square inch (psi)
Millimeters of mercury (mmHg)
Torr
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Named after Robert Boyle
It says that at a constant temperature
pressure and volume are inversely
proportionate.
As volume goes up the pressure goes down
and vice versa.
P1V1=P2V2
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Weather Balloon
 Helium vs. Air
 Equilibrium
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Airplanes
 Pressure as you climb
 Volume
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Bike Pump
The maximum volume of air that a weather balloon can hold
without rupturing is 22,000L. It is designed to reach an altitude
of 30 km. At this altitude, the atmospheric pressure is o.o125
atm. What maximum volume of helium gas should be used to
inflate the balloon before it is launched?
Two liters of air at atmospheric pressure are compressed into
the 0.45 L canister of a warning horn. If its temperature
remains constant, what is the pressure of the compressed air in
the horn?
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Named after Jacques Charles
States that at a constant pressure the volume of
a gas is directly proportional to its kelvin
temperature.
As temperature goes up volume goes up.
𝑉1 𝑉2
=
𝑇1 𝑇2
Temperature must be in Kelvin:
K=oC +273
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Lid in refrigerator
 Air hot
 Cools down and sinks
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Tires on the road
 Too inflated pops tire
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Balloon
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A balloon is filled with 3.0 L of helium at 22oC and 760
mmHg. It is then placed outdoors on a hot summer day
when the temperature is 31 oC. If the pressure remains
constant what will the volume of the balloon be?
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Named after Joseph Gay-Lussac
States that at a constant volume the pressure
and temperature of a gas are directly
proportional.
As temperature goes up pressure goes up.
𝑃1 𝑃2
=
𝑇1 𝑇2
Temperature must be in Kelvin:
K=oC +273
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Aerosol can in fire
 Pressurized can
 Increase temp= explosion
All three gas laws put together.
𝑃 1 𝑉1 𝑃 2 𝑉2
=
𝑇1
𝑇2
Temperature must be in Kelvin:
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K=oC +273
STP = Standard Temperature and Pressure
 Defined as 273K and 1 atm
A toy balloon has an internal pressure of 1.05 atm and a volume
of 5.0L. If the temperature where the balloon is released is
2ooC, what will happen to the volume when the balloon rises to
an altitude where the pressure is 0.65 atm and the temperature
is -15 0C?
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Hyper: above or excessive
Hyperbaric refers to pressure that is greater
than normal
Hyperbaric chambers uses:
 cure burns
 Decompression sickness
 Anemia
 Infections