1. Constructing a Model of ppbv of Surface Ozone
GLOBE Ozone Protocol
Learning Activity
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2. Earth’s Atmosphere
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3. "The Rest" of Earth's Atmosphere
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4. Look at the Numbers Composition of Earth’s Dry Atmosphere (1976 Standard Atmosphere*)
Gas
Percentage
Running % N2
78.084 O2
20.948
99.032 Ar
0.934
99.966
CO2
0.0314*
He,Ne,Kr,Xe
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5. Expressing concentration of a gas
parts per billion volume
number density
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6. Let’s look at volume of ozone in this classroom
Example:
Ozone (trace gas) is probably ~ 20 ppbv in this room.
This means that ~ 20 billionths of the volume of gas in this room is ozone.
Suppose this room is 6 m wide by 9 m long by 3 m high
V = 6 m x 9 m x 3 m
V = 162 m3 = 162,000,000 cm3 = 162 x 106 cm3
So what is the volume of ozone in this room?
(20 billionths)(162 million cm3) = (20 x 10-9)(162 x 106 cm3)
= cm3
~ 3 cm3 ozone in this room
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7. How many molecules of gas in 1 cm3?
From ideal gas law, in 1 cm3 of air at 25°C and 1 atm, there are 2.5 x 1019 molecules
“25 billion billion” molecules in 1 cm3
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8. Let’s look at number density for ozone
Example:
Ozone (trace gas) is probably ~ 20 ppbv in this room
What is number density of ozone (2.5 x 1019 molecules/cm3)(20 x 10-9)
=50 x 1010 molecules ozone/cm3
=500 x 109 molecules ozone/cm3
or 500 billion molecules ozone/cm3
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