The document discusses the composition and importance of Earth's atmosphere. It is made up primarily of nitrogen, oxygen, and trace amounts of other gases like carbon dioxide and water vapor. The atmosphere protects living things from ultraviolet radiation, regulates temperature, and enables the water cycle. However, human activities like burning fossil fuels contribute to air pollution problems like smog and acid rain, which can harm health and the environment. Government agencies work to reduce pollution by regulating emissions but improving air quality remains an ongoing challenge.

1. Does the weather where you live
change often?
 Weather: the condition of Earth’s atmosphere at a
particular time and place
 Atmosphere: the envelope of gases that
surrounds the planet
 Imagine Earth as the size of an apple
 If you breathe on the apple, a thin layer of water
droplets forms on the surface
 Earth’s atmosphere is like the water on the apple
 A thin layer of gases on Earth’s surface

2. Composition of the Atmosphere
 Made up of a mixture
of atoms and
molecules of different
kinds
 Atom: the smallest
unit of a chemical
element that can exist
by itself
 Molecules are made
up of 2 or more atoms

3. - The Air Around You
Composition of the Atmosphere
 Earth’s atmosphere is made up of nitrogen, oxygen,
carbon dioxide, water vapor, and many other gases, as
well as particles of liquids and solids.

4. Nitrogen
 Most common gas in
the atmosphere
 Makes up more than
¾ of air we breathe
 Each nitrogen
molecule contains 2
nitrogen atoms
 Nitrogen moves in a
cycle from air to the
soil, into living things,
then back to the air

5. Oxygen
 2nd most abundant gas in atmosphere
 Makes up less than ¼ of the total volume
 Plants and other organisms use light to convert water and
carbon dioxide into oxygen and produce food
 Any fuel uses oxygen to burn
 Examples: Gasoline & candles
 Without oxygen a fire would go out
 Burning uses oxygen rapidly
 Other reactions use oxygen slowly
 Rust occurs when oxygen slowly reacts with steel
 Most oxygen molecules have two oxygen atoms
 Ozone is a form of oxygen that has 3 oxygen atoms instead
of 2

6. Carbon Dioxide
 One atom of carbon and two atoms of oxygen
 Essential to life
 Plants take in carbon dioxide from the air to make
food
 When plant and animal cells break down food to
produce energy, they give off carbon dioxide as a
waste product
 When fuels are burned they release carbon
dioxide
 Burning fuel increases the amount of carbon
dioxide in the atmosphere

7. Other Gases
 Oxygen and nitrogen
together make up 99%
of dry air
 Argon and Carbon
Dioxide make up most
of the other 1%
 Remaining gases are
called trace gases
because there are only
small amounts

8. Water Vapor
 Air is not dry because it contains water vapor
 Water vapor: water in the form of invisible gas
 It is not the same as steam which is liquid drops of water
 Water molecules contain 1 oxygen atom and 2 hydrogen
atoms
 Amount of water vapor in the air varies from time to time
and from place to place
 Water vapor is important to weather
 Clouds form where water vapor condenses into tiny drops of
liquid water or crystals of ice
 When particles become heavy enough they fall as
precipitation

9. Particles
 Pure air contains only
gases
 Pure air only exists in
laboratories
 The air we breathe
contains tiny solid and
liquid particles of dust,
smoke, salt, and other
chemicals
 You can see some of
the particles in the air
but most are too small
to see

10. Importance of the Atmosphere
 Earth’s atmosphere
makes conditions on
Earth suitable for living
things
 Living things need oxygen
and other gases in the
atmosphere to survive
 They also need liquid
water and warmth
 The atmosphere keeps
most of Earth’s surface
warm by trapping energy
from the sun
 The warmth keeps water
in liquid form

11. Importance of The Atmosphere
 Protects living things from
ultraviolet radiation from
the sun
 Protects from meteoroids
 Constantly changing with
gases moving in and out
of living things, the land
and the water
 In this way, air can be
considered a renewable
resource

12. Air Quality
 Breathing brings air into your lungs
 The oxygen you need is taken into your lungs
 Not everything you breathe in is healthful
 You may breathe in tiny particles or small amounts of
gases
 Near the city you can see brown hazy clouds and
even far from the city harmful pollutants may be in the
air
 Pollutant: harmful substance in the air, soil, or water
 Air pollution can affect health of all living things

13. Sources of Pollution
 Some occurs naturally
 Example: forest fires, soil erosion, and dust storms release a
lot of smoke and dust into the air
 The wind carries particles of molds and pollen
 Erupting volcanoes spew out clouds of ash and poisonous
gases
 Most air pollution is from burning fossil fuels like coal, oil,
gasoline, and diesel fuel
 Almost ½ of the pollution comes from cars and factories
 Pollutants like carbon monoxide, nitrogen oxides and sulfur
oxides are released

14. Smog and Acid Rain
 High levels of air pollution
decrease the quality of air
 Burning fossil fuels can
create smog and acid rain
 100 years ago London,
England was dark and dirty
from burning coal in houses
and factories
 The air was full of smoke
and fog
 In 1905 the words smoke
and fog were combined to
form smog which became to
new term to describe the air
pollution

15. Smog and Acid Rain
 Smog from coal is no longer common
 Today we have air pollution called photochemical
smog
 Photo- is the prefix meaning light
 The smog is created by the action of sunlight on
pollutants like hydrocarbons and nitrogen oxides
 The chemicals react to form a brown mixture of ozone
and other pollutants
 The mixture irritates eyes, throat and lungs and is
harmful to plants

16. Smog and Acid Rain
 Acid rain is a type of air pollution
 It contains more acid than normal
 The burning of coal that contains a lot of sulfur, produces sulfur
oxides (sulfur and oxygen)
 Acid rain forms when nitrogen oxides and sulfur oxides combine
with water in the air to for nitric acid and sulfuric acid
 Acid rain can damage the surface of buildings and statues
 It can harm lakes and ponds
 It can make water so acidic that plants and animals can no
longer live with it

17. Improving Air Quality
 Federal and state governments have passed a number of laws and
regulations to reduce air pollution
 EPA: (Environmental Protection Agency) monitors air pollutants in
the US
 Amounts of major pollutants have decreased
 New cars cause less pollution
 Power plants are less polluting
 Now there are more cars on the road and more power plants burning
fuels than in the past
 The air in many cities is still polluted
 People think stricter regulations are needed to control air pollution
 Some argue that reducing air pollution can be expensive and may
not be worth the cost