The Atmosphere Essential Question: What is the significance of the atmosphere to the existence of life on earth? pp. 392-407

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 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 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

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 Air is invisible, so how does it have density? What significant role does the atmosphere have in providing us with water to drink? Air is invisible, so how does it have density? How does air pressure change as altitude increases? How does density change? Which layer of the atmosphere is the most important to you? Justify you reasons.

It is the layer of gases that surround the earth. What is the Atmosphere? It is the layer of gases that surround the earth.