15'1 The Air Around You

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15.1 The Air Around You

• What is the composition of Earths atmosphere?
• How is the atmosphere important to living things?

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Composition of the Atmosphere

• Earths atmosphere is made up of nitrogen,
  oxygen, carbon dioxide, water vapor, and many
  other gases, as well as particles of liquids and
  solids (other gases that make up less then 1 are
  argon, neon, helium, methane, krypton and
  hydrogen)
• Nitrogen is most abundant gas 78
• Nitrogen is found in pairs
• Oxygen is the second most abundant gas 21
• Most oxygen is found in pairs
• Ozone is a form of oxygen that has three oxygen
  atoms in each molecule instead of the usual two

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15.2 Air Pressure

• What are some of the properties of air?
• What instruments are used to measure air
  pressure?
• How does increasing altitude affect air pressure
  and density?

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Properties of Air Pressure

• Air has mass
• Therefore air has density and pressure
• Density is the amount of mass in a given volume
• DENSITY MASS/VOLUME (kg/L)
• MASS DENSITY X VOLUME (kg)
• VOLUME MASS/DENSITY (L)
• If there are more molecules in a given volume the
  density is greater. Less molecules in a given
  volume the density is less.

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If Spiderman is beating the Joker and exhales air
that has a mass of 90kg and has a volume of 30
liters, what is the airs density?

• Densitymass/volume
• Density90kg/30L
• Density3kg/L

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On the same day and same time on Mount Everest,
the air has a density of 75 kg/L in a volume of 5
liters. What is the mass of the air?

• MDV
• M(75kg/L)(5 L)
• M375 kg

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On the same day and same time in Miami, the air
has a density of 130kg/L in a volume of 5 liters.
What is the mass of the air?

• MDV
• M(130kg/L)(5 L)
• M 650 kg

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Bugs Bunnys brain has a mass of 28 kg and takes
up a volume of 7 liters, what is the density of
Bugs Bunnys brain?

• DM/V
• D 28 kg/7L
• D 4kg/L

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The density of Mrs. Razs 5th hour class is
12,500kg/L and the mass is 200,000kg. What is
the volume of the class?

• VM/D
• V200,000kg/12,500kg/L
• V16L

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Your table has a density of 750 kg/L and a mass
of 100kg. What is the volume of your table?

• VM/D
• V100kg/750kg/L
• V.13 L

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Pressure

• Pressure is the force pushing on an area or
  surface
• Weight of the atmosphere exerts a force on
  surface and air pressure is the result of the
  weight of air pushing down on an area
• The column of air extends through the entire
  atmosphere

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Pressure

• Molecules in air push in all directions therefore
  it does not crush us
• Air pressure can change from day to day
• Denser substances have more mass per unit volume
  than less dense substances so denser air exerts
  more pressure than less dense air

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Measuring Air Pressure

• Barometer
• Two kinds
• Mercury barometer consists of a glass tube open
  at the bottom end and partially filed with
  mercury
• Aneroid barometer has an airtight metal chamber
  and is most commonly used
• Figure 5 on page 518
• Units of air pressure are inches of mercury and
  millibars
• 30 inches of mercury is approximately equal to
  1,016 millibars

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Altitude and Properties of Air

• Air Pressure and Altitude
• Air pressure decreases as altitude increases.

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• Altitude and Density
• The density of air decreases as altitude
  increases. Air at sea level has more gas
  molecules in each cubic meter than air at the top
  of a mountain.

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15.3 The Layers of the Atmosphere

• What are the four main layers of the atmosphere?
• What are the characteristics of each layer?

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Layers of the Atmosphere

• Four main layers classified according to changes
  in temperatures
• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Includes the ionosphere and the exosphere
• KNOW FIGURE 9 ON PAGE 523

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Troposphere

• Lowest layer of the atmosphere
• Weather (the condition of earths atmosphere at a
  particular time) occurs
• Goes 9-16km from the surface of the earth
• Shallowest layer
• Contains almost all of the mass of the atmosphere
• As altitude increases the temperature decreases
• At the top the temp stays at about -60 degrees
  Celsius and water forms thin, feathery clouds of
  ice

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Stratosphere

• Extends from the top of the troposphere to about
  50km above earth's surface
• Contains the ozone layer
• The lower part is cold, about -60 degrees Celsius
  and the upper part is warmer because of the ozone
  layer
• Ozone layer gets heated from the sun

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Mesosphere

• Middle layer of the atmosphere
• Begins 50km above earths surface and ends at an
  altitude of 80km above earths surface
• Outer mesosphere it is about -90 degrees Celsius
• Protects earths surface from being hit by most
  meteoroids

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Thermosphere

• Outermost layer of earths atmosphere
• Extends 80km above earths surface and goes
  outward into space, no definite outer limit
• Extremely hot up to 1800 degrees Celsius
• Because sunlight strikes the thermosphere first
  and nitrogen and oxygen molecule convert suns
  energy into heat
• Would not feel hot because there are not very
  many molecules in this layer

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Thermosphere

• Divided into two layers
• Exosphere the outer layer
• Extend from about 400km outward thousands of
  kilometers
• Ionosphere the lower layer
• 80km above the surface and extends about 400km
• Energy from sun cause gas molecule to become
  electrically charged particle called ions
• Radio waves bounce off ions make brilliant light
  displays (Northern lights aka Aurora Borealis)

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15.4 Air Quality

• What are the major sources of air pollution?
• What cause smog and acid rain?
• What can be done to improve air quality?

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Sources of Pollution

• Some air pollution occurs naturally
• Forest fires, soil erosion, dust storms
• Human activities
• Burning fossil fuels
• Cars
• Factories
• Power plants that burn coal
• Burning of fossil fuels can cause smog and acid
  rain