Air PressureAir Pressure

Ch. 15Ch. 15

Air Pressure ReviewAir Pressure Review

Air has mass.Air has mass.

Air takes up space.Air takes up space.

Air has density.Air has density.

Air pressureAir pressure is the is the weight of a column of weight of a column of air pressing down on air pressing down on an area.an area.

Atmosphere/PressureAtmosphere/Pressure

Atmosphere held in place by gravityAtmosphere held in place by gravity

Pressure strongest at surface-more air Pressure strongest at surface-more air above youabove you

*as altitude increases, air pressure *as altitude increases, air pressure decreasesdecreases– Stack of booksStack of books– (Volleyball example)(Volleyball example)

Air PressureAir Pressure

As Air Pressure As Air Pressure decreases, so does decreases, so does density.density.

AtmosphereAtmosphere

Atmosphere: a mixture of gases that Atmosphere: a mixture of gases that surrounds Earth: acts like a blanketsurrounds Earth: acts like a blanket– Contains oxygenContains oxygen– Protects from sunProtects from sun

Layers of the AtmosphereLayers of the Atmosphere

Troposphere-we live here, weather Troposphere-we live here, weather happens herehappens here

Stratosphere: ozone layerStratosphere: ozone layer

Mesosphere: “middle layer”Mesosphere: “middle layer”

ThermosphereThermosphere

AtmosphereAtmosphere

Composition of TroposphereComposition of Troposphere

Nitrogen=78%Nitrogen=78%

Oxygen=21%Oxygen=21%

Other 1%=water vapor, CO2 and otherOther 1%=water vapor, CO2 and other

Weather FactorsWeather Factors

Sun’s energy travels to earth as Sun’s energy travels to earth as Electromagnetic waves.Electromagnetic waves.

Weather FactorsWeather Factors

Scattering: Reflections of light in all Scattering: Reflections of light in all directions.directions.

Why is the sky blue?Why is the sky blue?

RadiationRadiation

Sun on your face Sun on your face

standing by campfirestanding by campfire

direct transfer of energy by direct transfer of energy by electromagnetic waves through space.electromagnetic waves through space.

ConductionConduction

Bare feet burned by hot sandBare feet burned by hot sand

direct transfer of heat from one substance direct transfer of heat from one substance to another through direct contact.to another through direct contact.

ConvectionConvection

Basement colder than Basement colder than upstairsupstairstransfer of heat by the transfer of heat by the movement of fluid or air. movement of fluid or air. Hot air rises, cold air Hot air rises, cold air sinks.sinks.

ExamplesExamples

Cooking on the stove-pot on burnerCooking on the stove-pot on burner

Hot air balloon risingHot air balloon rising

Fireplace warming a roomFireplace warming a room

Curling iron on hairCurling iron on hair

Blow dryer on hairBlow dryer on hair

Air from furnace heating the houseAir from furnace heating the house

How is Earth heated?How is Earth heated?

Light/heat from the sun Light/heat from the sun RADIATESRADIATES through the atmosphere, hits the Earth through the atmosphere, hits the Earth where it is absorbed.where it is absorbed.This heats the air above it by This heats the air above it by CONDUCTIONCONDUCTION..This heat rises up to the greenhouse This heat rises up to the greenhouse gases where it is trapped, cools, sinks and gases where it is trapped, cools, sinks and heats at the surface again.-heats at the surface again.-CONVECTIONCONVECTION..

Weather FactorsWeather Factors

Greenhouse EffectGreenhouse Effect

These gases absorb These gases absorb the heat and act as a the heat and act as a “blanket” to keep “blanket” to keep Earth warm.Earth warm.

Some greenhouse Some greenhouse gases: water, gases: water, methane, carbon methane, carbon dioxide.dioxide.

Runaway Greenhouse EffectRunaway Greenhouse Effect

Runaway Greenhouse EffectRunaway Greenhouse Effect

http://www.epa.gov/climatechange/kids/http://www.epa.gov/climatechange/kids/global_warming_version2.htmlglobal_warming_version2.html

Define and DesignDefine and Design

Draw, color, label and explain your own Draw, color, label and explain your own picture of the Greenhouse Effect.picture of the Greenhouse Effect.

Egg in Egg in bottlebottle

Fire warmed up air inside, molecules escaped Fire warmed up air inside, molecules escaped before egg was put on top and when egg before egg was put on top and when egg wobbled.wobbled.

When fire went out, temperature cooled, When fire went out, temperature cooled, molecules condensed, changing air pressure.molecules condensed, changing air pressure.

Since the pressure outside bottle was higher, Since the pressure outside bottle was higher, the higher pressure tried to get in the bottle.the higher pressure tried to get in the bottle.

Since the egg is squeezable, it got pushed into Since the egg is squeezable, it got pushed into the bottle by the air.the bottle by the air.