U3L2 - The Atmosphere

Unit 3 Lesson 2 The Atmosphere
Copyright © Houghton Mifflin Harcourt Publishing Company

Indiana Standards
• 8.2.1 Recognize and demonstrate how the sun’s
energy drives convection in the atmosphere and in
bodies of water, which results in ocean currents
and weather patterns.
• 8.2.4 Describe the physical and chemical
composition of the atmosphere at different
elevations.

Up and Away!
What is Earth’s atmosphere?
• The atmosphere is the mixture of gases that
surrounds Earth.
• The functions of the atmosphere include
protection from the sun, maintaining temperature,
and supplying gases necessary for breathing.

• The atmosphere is made of 78 percent nitrogen
gas, 21 percent oxygen gas, and 1 percent other
gases.
• The atmosphere also contains small particles of
dust, volcanic ash, sea salt, smoke, skin, bacteria,
and pollen.

• In the atmosphere, water is found in the clouds as
liquid droplets and solid water in the form of snow
and ice crystals.
• Most water in the air is in the form of water vapor.
Water vapor is an invisible gas.

How do pressure and temperature
change in the atmosphere?
• Gravity pulls gas molecules in the atmosphere
toward Earth, causing pressure.
• Air pressure is the measure of the force with
which air molecules push on a surface.

How do pressure and temperature
change in the atmosphere?
• As altitude, or distance from Earth’s surface,
increases, air pressure decreases.
• As altitude increases, temperatures change.
• Some parts of the atmosphere are warmer
because of gases that absorb solar energy.

Look Way Up
What are the layers of the atmosphere?
• The atmosphere is divided into four layers based
on temperature and other properties.
• The thermosphere is the uppermost layer with
temperatures that increase as altitude increases.
• The thermosphere feels cold because particles are
so far apart.

• The mesosphere is between the thermosphere
and stratosphere.
• Temperatures decrease as altitude increases.
• Meteoroids begin to burn up in the mesosphere.

• The stratosphere is between the mesosphere
and troposphere.
• Temperatures generally increase as altitude
increases.
• Ozone in the stratosphere absorbs ultraviolet
radiation from the sun, which warms the air.

• The troposphere is the lowest layer of the
atmosphere.
• Temperature generally decreases as altitude
increases. Temperatures near the surface vary
greatly.
• The troposphere contains 80 percent of the
atmosphere’s total mass.

How do
temperatures
differ with altitude
in the
atmosphere?

Here Comes the Sun …
How does the atmosphere protect life
on Earth?
• Earth’s atmosphere reflects or absorbs most of the
radiation from the sun.
• The ozone layer is in the stratosphere and
contains a high concentration of ozone. It absorbs
most of the solar radiation.

on Earth?
• Ozone-layer thickness changes by season and
location.
• Scientists have discovered a steady decrease in
the overall volume of ozone over time.
• Ozone can also be destroyed by certain chemicals
in the air.

on Earth?
• The greenhouse effect is the process by which
gases in the atmosphere absorb and radiate
energy as heat back to Earth.
• Shortwave radiation from the sun reaches Earth’s
surface and reradiates back into the atmosphere,
where it is trapped by greenhouse gases.

on Earth?
• How is the heat inside of a closed car in the
summer similar to the greenhouse effect?

U3L2 - The Atmosphere

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