Composition of the Atmosphere 3/2/15

15-1a pgs. 392-394

• IN: What is air made of?

TERMS TO LEARN & OBJECTIVESTERMS TO LEARN & OBJECTIVESTERMS:

ATMOSPHERE AIR PRESSURE ALTITUDE

OBJECTIVES:

Discuss the composition of the Earth’s atmosphere.

Explain why pressure changes with altitude.

Explain how temperature changes with altitude.

What is an atmosphere?What is an atmosphere?

Atmosphere – a mixture of gases that surrounds a planet, such as Earth.

Composition of the AtmosphereComposition of the Atmosphere

• Contains mostly Nitrogen and Oxygen.

• Besides gas the atmosphere also contains small amounts of solids and liquids.

Atmospheric PressureAtmospheric Pressure

• The Earth’s atmosphere is held around the planet by gravity.

• Gravity pulls that gas molecules in the atmosphere toward the Earth’s surface, giving them weight.

Atmospheric PressureAtmospheric Pressure

• As you move farther away from the Earth’s surface, air pressure decreases because fewer gas molecules are pushing on you.

• Like the bottom row of the human pyramid, the lower atmosphere experience greater pressure than the upper atmosphere.

Atmospheric PressureAtmospheric Pressure

• Altitude – the height of an object above the Earth’s surface.

Atmospheric PressureAtmospheric Pressure

• As altitude increases, air pressure decreases.

Air TemperatureAir Temperature

• Air temperature also changes as you increase altitude.

• As you pass through the atmosphere, air temperature changes between warmer and colder conditions.

Air Temperature

• The temperature differences result mainly from the way solar energy is absorbed as it moves downward through the atmosphere.

• Some parts of the atmosphere are warmer because they contain gases that absorb solar energy.

Air Temperature

• As altitude increases, air temperature varies from hot to cold.

Air TemperatureAir Temperature

Atmospheric Pressure and Atmospheric Pressure and TemperatureTemperature

• OUT: Explain why pressure decreases but temperature varies as altitude increases.