the air
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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..