1. The Atmosphere & Weather

2. Bell Work What is the most abundant gas in the atmosphere?

3. Weather Condition of Earth’s atmosphere at a particular time and place Atmosphere The envelope of gases that surrounds the planet

4. Composition of Earth’s Atmosphere: 1. Nitrogen –most abundant; ¾ of the air we breathe 2. Oxygen – 2 nd most abundant, usually molecules have 2 oxygen atoms Ozone – form of oxygen with 3 oxygen atoms per molecule - forms when lightning interacts with oxygen in air (odor after thunderstorm) 3. Carbon Dioxide- increased when fuels (coal & gas) burn 4. Other Gases – “trace gases”  only small amounts present

5. Water Vapor Water in the form of a gas Invisible NOT the same as steam (tiny drops of liquid water Plays an important role in EARTH’s WEATHER Water Vapor condenses  clouds form  clouds contain tiny droplets of liquid water(rain) OR crystals of ice(snow/sleet) If the droplets/crystals become heavy enough they fall to the Earth.

6. Why is the Atmosphere Important? Makes conditions of Earth suitable for living. Contains oxygen living things need Traps energy from the sun Living things need warmth Keeps Earth’s surface warm enough for water to exist as a liquid Protects living things from the sun’s radiation Prevents Earth’s surface from being hit by most meteoroids

7. Air Pressure Does Air have Mass? If it has mass, it has to contain other properties! Properties of Air: 1. Density = Mass/Volume Air's density depends on: Its temperature Its pressure Amount of water vapor

8. Air Pressure Properties of Air: 2. Pressure – force pushing on an area or surface The ATMOSPHERE’s weight puts a force on surfaces Air Pressure – result of the weight of a column of air pushing down on an area Atmosphere is heavy, but doesn’t crush us because the molecules push in all directions On objects/People - Air pushing DOWN is balanced by air pushing UP Air pressure changes daily: Dense object  more mass per volume Dense air  exerts MORE pressure than less dense air

9. Measuring Air Pressure Barometer – an instrument used to measure air pressure Two types of Barometers: 1. Mercury Barometer Consists of a glass tube open at the bottom end and partially filled with mercury Space at top of tube is vacuum (very little air) Air pressure on the dish of mercury = pressure of weight of column of mercury in tube Air pressure increases  presses on mercury more  vacuum decreases

10. Measuring Air Pressure 2. Aneroid Barometer Air tight metal chamber that is sensitive to changes in air pressure Air pressure increases  walls are pushed in Air pressure decreases  walls bulge out As the shape changes the needle on the dial moves

11. Altitude & the Properties of Air Altitude – distance above sea level Altitude Affect Air Pressure Air pressure decreases as Altitude Increases Sea level(greatest) vs Mountain Top(Least) Why? Altitude Affects Density Density decreases as Altitude Increases Gas molecules in the atmosphere are father apart at HIGH altitudes than they are at sea level Is it harder to breathe at sea level or on top of a mountain? Why?

12. Layers of the Atmosphere Classified according to changes in temperature Four Main Layers 1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere

13. The Troposphere Lowest Layer/Layer we live in LAYER IN WHICH EARTH’s WEATHER OCCURS 16 km above equator & less than 9 km above poles Most of the mass of the atmosphere Altitude Increases  Temperature Decreases (opposite of stratosphere)

14. The Stratosphere From top of troposphere to about 50 km above Earth Second Layer of Atmosphere Contains the OZONE LAYER Protects Earth’s living things fro UV radiation from the sun Altitude Increases  Temperature Increases (opposite of Troposphere) Middle contains a layer of air with more ozone Ozone absorbs energy from the sun to create heat

15. The Mesosphere Above the stratosphere, marked by a drop in temperature “meso”- middle layer of atmsophere 50km above Earth – 80 km above Earth Protects Earth’s surface from being hit by most meteoroids

16. The Thermosphere Outermost layer of Earth’s Atmosphere Extends from 80 km above Earth and gradually blends into space Very thin, hot air sunlight strikes the thermosphere first 2 Layers 1. Ionosphere The lower layer 80 km above the surface and extends to about 400 km. Gas molecules here are electrically charged because of the sun's energy. Radio waves bounce back from the ionosphere to Earth’s surface Location of Auroras 2. Exosphere The outer layer