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I.Critical Reading
Read this passage based on the text and answer the questions that follow.
Troposphere
The troposphere is the lowest layer of the atmosphere. It rises to only about 12 kilometers (7 miles)
above Earth’s surface. Even so, this layer holds 75 percent of all the gas molecules in the atmosphere.
Therefore, air is densest in this layer.
The temperature of the troposphere decreases as you go higher above Earth’s surface. The troposphere
gets some of its heat directly from the sun. Most, however, comes from Earth's surface. The surface is
heated by the sun and some of that heat re-radiates back into the troposphere. This makes the
temperature higher near the surface than at higher altitudes. Warm air is less dense than cool air, so it
rises higher in the troposphere. This starts a convection current. Convection mixes the air in the
troposphere. Rising air is also a main cause of weather.
Sometimes air doesn’t mix in the troposphere. This happens when air is cooler closer to the ground than
it is higher above the surface. The cooler air is denser than the warmer air, so it stays near the ground.
This is called a temperature inversion. A temperature inversion can trap air pollution near the surface.
Temperature inversions are more common in the winter.
Questions
Identify and describe the troposphere.
Explain how temperature changes in the troposphere.
Why do convection currents occur in the troposphere?
Why do temperature inversions occur? Why do you think they are more common in the winter?
How does a temperature inversion affect air quality?
II.Multiple Choice
Circle the word of the correct choice.
1.Earth’s atmosphere is divided into layers based on
density.
pressure.
composition.
temperature.
2.The shortest layer of the atmosphere is the
exosphere.
mesosphere.
troposphere.
thermosphere.
3.Which sentence about ozone is false?
The splitting of ozone molecules warms the mesosphere.
Ozone protects Earth’s surface from harmful radiation.
A molecule of ozone consists of three oxygen atoms.
Ozone molecules absorb ultraviolet light.
4.The coldest temperatures in the atmosphere occur in the
mesopause.
tropopause.
stratopause.
none of the above
5.The International Space Station orbits Earth in the
exosphere.
mesosphere.
stratosphere.
thermosphere.
Matching
III.Match each definition with the correct term.
Definitions
_____ 1. layer of the atmosphere above the troposphere
_____ 2. layer of the atmosphere above the mesosphere
_____ 3. boundary between the troposphere and stratosphere
_____ 4. layer of the atmosphere above the thermosphere
_____ 5. boundary between the stratosphere and mesosphere
_____ 6. lowest layer of the atmosphere
_____ 7. layer of the atmosphere above the stratosphere
Terms
a. exosphere
b. mesosphere
c. stratosphere
d. thermosphere
e. troposphere
f. tropopause
g. stratopause
Source: http://www.ck12.org/section/Layers-of-the-Atmosphere-::of::-MS-Earths-AtmosphereWorksheets-::of::-CK-12-Earth-Science-For-Middle-School-Workbook/