How can you tell that the air is around you?

Can you describe this

picture? A boy sleeping & covered

with a blanket

Do you that Earth has a

blanket too?

Really, How is that?

Yes, It is called

atmosphere

What is Atmosphere?

- It is a thin blanket of air that surrounds our planet Earth.

- - It is made up of many gases. “Oxygen – Carbon dioxide – ..etc”

It’s a mixture of gases

WeatherCan you tell the

weather in Christmas time in

USA?

The weather is so cold & snowy

What is the weather?

It’s the condition of atmosphere at a given time & place

Christmas timeUSA

- Weather changes depending on many conditions:

Does weather changes?

1 -Time of the day

Example: In the Desert

During the day During the night- The weather is very hot - The weather is cold

2 -Seasons

SpringIt’s rainy & warm

SummerIt’s hot & sunny

WinterIt’s cold & snowy

AutumnIt’s windy

3 -Place

- Measuring the weather depends on many factors:

How to measure weather?

1- Air Temperature2- Wind speed & direction3- Humidity4- Precipitation5- Air pressure

1 -Air temperature

-It describes how hot or cold the air is.Example: During Summer During Winter - Temperature is high - Temperature is low

-Air Temperature is measured using: Thermometer “ In Celsius / Fahrenheit”

2 -Wind

Can you

describe

these

pictures?

What’s the weather like in this picture?

There is a strong wind, the weather is windy

What’s the wind?It’s the moving air

“When the sun heats the surface of the Earth, the surface warms up the air, so the air moves up & the cold air gets down causing the wind”

- We measure the wind speed using: Anemometer- We measure the wind direction using: Wind vane

It points to the direction from which the wind blows

The faster the wind blows, the faster the cups spin

3 -Humidity

- Some times the air around us feels damp & sticky

like: In Alexandria - This is because of the “Humidity”

{Humidity: is the measure of how much moisture (water vapor)is in the air}

-The more the water vapor in the air, the more the humidity is in the air.-Examples: Desert Rain forest - Has low humidity - Has high humidity

- We measure the humidity in the air using: Hygrometer

4 -Precipitation

Any form of water that fall from the clouds is precipitation

Does this mean that

rain is precipitatio

n?

Yes, of course..

And snow too is a kind

of precipitatio

n

I wonder how many kinds of

precipitation are there?

Kinds of precipitation

Rain Snow Sleet Hail

“Flakes of snowmixed with water

drops”

“Chunks of snow”As the size of small

ballSnow fall as

crystals”

-We measure the amount of rain fall using: Rain gauge

5 -Air pressure

Can you tell

what are

these

people

measuring?

- They are measuring their weight “how heavy they are”

Really? How is

that?

Yes, it’s the air

pressure

Do you know that

air has weight too?

What’s air pressure?- It’s the weight of the air on a certain

area.OR-It’s the force of air pushing on a

certain area.

- Air pressure is around us, but we don’t feel it.- While, when we go diving or when we are in

an airplane, we fell that our ear is plugged, this is because of the air pressure change.

Examples

- Particles of the cool air are closer together than the particles of warm air.

- Particles of warm air are not packed together “have less density”.

- So, particles of cool air will weight more than particles of warm air.

So, Cool air has more pressure than warm air

-This why, As we heat air, it’s pressure decrease.

Which has more air pressure?“Cool air / Warm air”

Where to find high / low pressure ?- As air becomes hot, its particles moves away from each other & air becomes light, so it moves up & its pressure decrease.-While; cold air particles are close together, so air becomes heavy ,it goes down & its pressure increase.-This is why:

As we go up, pressure decrease “because this is where hot air is found”

(Places with low pressure)

Mountains – Top of buildings

Examples

(Places with high pressure)

Valleys– Submarines

- We use a barometer to measure air pressure.

Remember:Don’t get confused between the barometer &

the hygrometer..