Essential Question: What is the significance of the atmosphere to the existence of life on earth?

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The Atmosphere

The Atmosphere

The atmosphere is the layer of gases and other particles that surround earth much like the peel of an apple covers it.

Benefits of atmosphere for humans include:

• provides gases like oxygen

• traps heat energy from sun which keeps us warm and water in a liquid state

• protects from UV rays & most meteoroids

Properties of Air in the Atmosphere

• Air in the atmosphere has density– Air has mass because

it is composed of atoms and molecules

– Air has volume because it takes up space

– density = mass/volume

• Air also has pressure– Air molecules push

on objects from all directions

– As altitude increases air pressure and density decrease because its molecules are spread farther apart

Composition of the Atmosphere • Nitrogen 78%

• Oxygen 21%

• All other gases 1%

• Tiny solid and liquid particles of:

–dust

–smoke

–salt

–chemicals

Structure of the Atmosphere

• Troposphere• Stratosphere• Mesosphere• Thermosphere

–Ionosphere–exosphere

Troposphere

• 0-12 km above Earth’s surface

• Temperature varies– For every 1km of altitude increase, temp decreases

approx 6.5oC – Constant -60oC in upper troposphere

• Where weather occurs and most clouds

• Where hot air balloons travel

Stratosphere

• 12-50 km above Earth’s surface

• Temp in lower stratosphere about -60oC– Warmer in upper stratosphere due to ozone

layer which absorbs ultraviolet radiation

• Where airplanes and weather balloons travel

Mesosphere

• 50-80 km above Earth’s surface

• Temp drops to -90oC in outer mesosphere

• Where most meteoroids burn up– Seen from Earth as shooting stars (meteors)

Thermosphere

• Everything 80km above Earth’s surface

• Temp up to 1,800oC

• Air very thin

• Includes the ionosphere and exosphere

More on the Thermosphere

Ionosphere• 80-550km above

Earth’s surface• Radio waves

reflected from ionosphere to Earth

• Aurora borealis (Northern Lights) occur in ionosphere

Exosphere• 550km - no limit

above Earth’s surface• Satellites orbit Earth

in the exosphere– Phone signals– Television signals

Review Questions

a. What significant role does the atmosphere have in providing us with water to drink?

b. Air is invisible, so how does it have density?

c. How does air pressure change as altitude increases? How does density change?

d. Which layer of the atmosphere is the most important to you? Justify you reasons.

What is the Atmosphere?

It is the layer of gases that surround the earth.