Does the weather where you live change often?Weather: the condition of Earth’s

atmosphere at a particular time and placeAtmosphere: the envelope of gases that

surrounds the planetImagine Earth as the size of an appleIf you breathe on the apple, a thin layer of

water droplets forms on the surfaceEarth’s atmosphere is like the water on the

appleA thin layer of gases on Earth’s surface

Composition of the AtmosphereMade 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

- The Air Around You

Composition of the AtmosphereEarth’s atmosphere is made up of nitrogen,

oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids.

NitrogenMost common gas in

the atmosphereMakes up more than

¾ of air we breatheEach nitrogen

molecule contains 2 nitrogen atoms

Nitrogen moves in a cycle from air to the soil, into living things, then back to the air

Oxygen2nd most abundant gas in atmosphereMakes up less than ¼ of the total volumePlants and other organisms use light to convert water

and carbon dioxide into oxygen and produce foodAny fuel uses oxygen to burn

Examples: Gasoline & candles Without oxygen a fire would go outBurning uses oxygen rapidlyOther reactions use oxygen slowly

Rust occurs when oxygen slowly reacts with steel Most oxygen molecules have two oxygen atomsOzone is a form of oxygen that has 3 oxygen atoms

instead of 2

Carbon DioxideOne atom of carbon and two atoms of oxygenEssential to lifePlants take in carbon dioxide from the air to

make foodWhen 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

Other GasesOxygen 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

Water VaporAir is not dry because it contains water vapor Water vapor: water in the form of invisible gasIt is not the same as steam which is liquid drops of

waterWater molecules contain 1 oxygen atom and 2

hydrogen atomsAmount of water vapor in the air varies from time to

time and from place to placeWater 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

ParticlesPure air contains only

gases Pure air only exists in

laboratoriesThe 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

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 sunThe warmth keeps water

in liquid form

Importance of The AtmosphereProtects 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

Air QualityBreathing brings air into your lungsThe oxygen you need is taken into your lungsNot everything you breathe in is healthfulYou may breathe in tiny particles or small

amounts of gasesNear the city you can see brown hazy clouds

and even far from the city harmful pollutants may be in the airPollutant: harmful substance in the air, soil, or

waterAir pollution can affect health of all living things

Sources of PollutionSome 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 pollenErupting volcanoes spew out clouds of ash and

poisonous gasesMost air pollution is from burning fossil fuels like

coal, oil, gasoline, and diesel fuelAlmost ½ of the pollution comes from cars and

factories Pollutants like carbon monoxide, nitrogen oxides

and sulfur oxides are released

Smog and Acid RainHigh levels of air pollution

decrease the quality of airBurning fossil fuels can

create smog and acid rain100 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

Smog and Acid RainSmog from coal is no longer commonToday we have air pollution called

photochemical smogPhoto- is the prefix meaning lightThe 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

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

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 pollutionPower 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