Air Pressure

• I can compare and contrast high and low pressure systems.

• I can describe that high pressure systems result in fair weather due to air sinking, and low pressure systems may result in severe weather due to air rising.

Air Pressure Cornell NotesKey Words Notes

Summary:

Air Pressure Activities

A.Inverted Glass

B.Stop the Leak

C.Collapsing Can

In your notebook:

1. Diagram of set-up

2. Description of results

3. Explanation/principle involved

Air Pressure

Air Pressure• Air Pressure is

a measure of the force of the air pressing down on the earth’s surface

Air Pressure can vary at any can vary at any particular point on the Earth particular point on the Earth

depending on the density of the airdepending on the density of the air

Density = mass / volumeDensity = mass / volume

Challenge:

Results and Explanation:

1. Fill a cup with water. 2. Cover the cup with an index card.

3. Invert the cup. What happened?

Does the water spill out of the cup? Explain (using concepts on pressure)

Title: Activity 1. Inverted Cup Date: Feb. 2010

Summary:

Inverted CupInverted Cup

cardboard

Air Pressure

When cup is completely filled with water, no air is

left in cup, thus no air pressure. The inverted cup can therefore hold

water up because the air pressure is working

against the underside of the cup.

There is higher air pressure outside pushing There is higher air pressure outside pushing upward than the inside of cup pushing downward.upward than the inside of cup pushing downward.

Challenge:

Solution:

Results and Explanation:

How can you stop the leak in this soda can?

Title: Activity 2. Stop the Leak Date: Feb. 2010

Summary:

Challenge:

Solution:

Results and Explanation:

How can cause a can to collapse?

Title: Activity 3. Collapsing Can Date: Feb. 2010

Summary:

Explain the principle behind the collapsing can.

Collapsing CanCollapsing Can

Before heating, the can was filled with water and air.

By boiling the water, the liquid changed into water vapor

The water vapor or steam pushed the air that was inside, out of the can.

In closing off the can, air is prevented from going back to the can.

Cooling (water in basin) condenses water vapor back to water. All the

vapor which took up space inside the can turned into a few drops of

water, which take up less space.

Pressure inside can drops allowing outside air pressure to push on the can and

crush it.

Challenge:

Results and Explanation:

Who can drink the fastest?

Title: Activity 3. Straw drinking race Date: Feb. 2010

Summary:

Explain the principle behind straw drinking. When you drink liquid through a straw, is it accurate to say the liquid is sucked up the straw or pushed up the straw?

Regular straw Modified straw

Straw Drinking RaceStraw Drinking Race

Sucking creates a partial vacuum or a lower pressurelower pressure in straw above the

liquid that we drink

The higher pressure in outside air pushes the

liquid up the straw in our mouth

The student with the leaky straw cannot

create a vacuum above the liquid, so the liquid

is not pushed up.

Density of Air DensityDensity = Mass / Volume

Warm air is less dense than cool air. Warm air rises. Cool air sinks.

Air at high altitudes is less

dense than air at lower altitudes.

Factors that affect Air Factors that affect Air Pressure Pressure

TemperatureTemperature

Water Vapor

Elevation

TEMPERATURE AND AIR PRESSUREHeat= Heat= Molecules move faster=Molecules move faster= molecules move apart, become molecules move apart, become fewer, weight less=fewer, weight less= less, low air less, low air pressurepressure

HIGH (Hot) TEMPERATURE= LOW AIR PRESSURE

LOW (Cold) TEMPERATURE=HIGH AIR PRESSURE

AMOUNT OF WATER VAPOR

Consists of air and water molecules

Amount of Water VaporAmount of Water Vapor

More water vapor means less air molecules= Low Air Pressure

Dry air (less water vapor)= High Air Pressure

Measuring Measuring Air PressureAir Pressure

Air Pressure is measured by an instrument called A Barometer

Types of BarometerMercury BarometerAneroid

Air pressure increases, column of mercury rises

Air pressure decreases, column of mercury drops

Air Pressure & WeatherAir Pressure & Weather

High pressure generally means fair weather

Air mass in upper atmosphere is sinking (cold, dense air)

Layer of Air

Warm, moist air cannot rise

No clouds

Low pressure generally means cloudy, rainy weather

Air masses move apart

Warm air rises, clouds form

Weather Map SymbolsWeather Map Symbols

Factors Affecting Air PressureFactors Affecting Air PressureFACTOR Increase/Decrease Air Pressure

Density

Density

Temperature

Temperature

Water Vapor

Water Vapor

Altitude

Altitude

QUESTIONS – use your QUESTIONS – use your knowledge of air pressure to knowledge of air pressure to

explain the following situationsexplain the following situations A falling barometer is followed by A falling barometer is followed by

several days of rainy weather.several days of rainy weather. Some people find it hard to Some people find it hard to

breathe at high altitudes.breathe at high altitudes. A rising barometer indicates a A rising barometer indicates a

spell of cool dry weather.spell of cool dry weather.

Air Pressure: Pushing the WeatherAir Pressure: Pushing the Weather

HomeworkHomework

Fronts

•I can describe the causes and effects (weather conditions) of cold fronts, warm fronts, and stationary fronts.

Air Masses

•Air masses are huge chunks air that is the same temperature and density.

What are Fronts?• Fronts happen

when 2 different air masses meet BUT they do not mix together

•4 Different Types of Fronts:

• Cold Front• Warm Front• Occluded Front• Stationary FrontFronts: Mr Parr Rap Song

How do air masses move?• Cold air (more dense)

ALWAYS sinks under warm air (less dense).

• So what is the difference between the 4 types of fronts?– Which air mass takes

over the other! It’s a battleground.

– One air mass is pushing the other out of the way because it does not want to mix!

Video on Air Masses: http://www.youtube.com/watch?v=vPC5i6w3yDI&feature=related

Demos:

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es2002/es2002page01.cfm?chapter_no=visualization

• Lab Demos: – Hot/cold air (via water) demo

Hot and Cold Water Demo:http://www.youtube.com/watch?v=Ak9CBB1bTcc&feature=related

Cold Front Warm Front Stationary Front

What is happening?

(Write it)

What is happening?

(Draw it)

Weather forecast

Symbol

Cold FrontsWhat happens? A

fast moving cold air mass runs into a slow moving warm air mass, pushing the warm air up quickly to form clouds.

Weather forecast: heavy rains and thunderstorms

Cold Front: Weather map symbol

• A cold front symbol—The direction that the teeth point indicate the direction the front is moving.

Warm FrontsWhat happens? A fast moving warm air mass collides with a slowly moving cold air mass. Warm air slowly moves over the cold air.

Weather forecast: slow steady rain!

Warm front: Weather Map Symbol

• Warm Front symbol—The directions that the bumps face is the direction the front is moving.

What types of fronts can you find on the map? In which direction are they

moving?

Stationary FrontWhat happens: A cold air mass and warm air mass meet, but neither air mass has enough force to move the other air mass.

Can sometimes mix together OR will turn into a warm or cold front.

Weather forecast: clouds, rain for multiple days

Stationary Front: Weather Map Symbol

Not moving in any direction!

Occluded Front

• What happens:

An occluded front happens when a cold front overtakes the warm front in a low pressure storm system.

Weather forecast: Precipitation will diminish and the winds will lessen.

What types of fronts can you find on the map? In which direction are they

moving?

Summary of Front Symbols

Practice Reading Weather MapsWhich types of fronts can you find on this

map?

What types of fronts are on the map? In which direction are they moving?What type of weather would it produce?

What types of fronts are on the map? In which direction are they moving?What type of weather would it produce?

What types of fronts are on the map? In which direction are they moving?

What type of weather would it produce?

Analyze a Map

Front Classification• 1. When a warm air mass moves in on a cold air mass.• 2. When a warm and cold air mass meet, but neither one has

enough force to rise over the other.• 3. Brings gentle rains that may last for hours or days. • 4. Strong winds are formed followed by heavy rain, crashing

thunder, and flashing lightning. • 5. When the front passes, the temperature warms up and it

becomes humid. • 6. When the front passes, the weather turns cooler. • 7. Tornados could occur. • 8. Usually happens and is over with quickly. • 9. Stay in the same area for a long period of time. • 10. When a cold air mass moves in on a warm air mass. 11.

Causes warm air to move up slowly • 12. Causes warm air to move up quickly

Interpreting Weather Maps

• In groups, complete the interpreting weather maps activity

• When finished, work on the “Reading a Weather Map” Worksheet