Air is invisible, but it is all around us.
You feel it when a bag puffs up or a fan blows, and moving air is wind.
Warm air is light and rises, and cold air is heavy and sinks, which makes wind.
Move the slider to change the wind and watch the tree lean and the pinwheel spin.
What Happens When Wind Blows?
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Visualizing tree tilt and pinwheel rotation by wind strength
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🌬️ Feel the Wind!
①Move the slider — wind grows stronger
②Trees tilt, leaves fly
③Pinwheel spins around!
Air is Invisible but Real!
💨 Proof Air Exists
①Inflate a plastic bag — air is in it
②Turn on a fan → wind = air moving
③Balloon flies because air escapes
🎈 Air Has Weight Too!
①Inflated balloon weighs slightly more
②Lots of air = lots of force
③Typhoons are scary because air moves super fast
How Does Wind Form?
🌡️ Warm Air vs Cold Air
①Warm air is light → rises
②Cold air is heavy → sinks
③That motion is "wind"!
④Sea breeze works the same way!
Summary
🎯 Air & Wind Summary
①Air is invisible but real
②Wind = air movement
③Warm↑ + Cold↓ = wind
④Strength: breeze → light → strong → typhoon
⑤Without air we cannot breathe — so precious!
Examples and Unit Test
Example 1
What is wind? How do warm air and cold air move?
1
Wind is air moving.
2
Warm air is light and rises, while cold air is heavy and sinks.
▸ Wind = moving air / warm air rises · cold air sinks
As the air moves, the wind blows.
Example 2
Air is invisible. How can we tell that air is there?
1
When you puff up a plastic bag it gets full, because there is air inside it.
2
When you turn on a fan, wind comes, because that is air moving.
▸ A plastic bag puffs up and a fan makes wind, which shows that air is there
Air is invisible but it fills the space all around us.
Unit Test
What is the reason wind blows?
①Because air moves
②Because air disappears
③Because the ground shakes
④Because the Sun moves
⑤Because water flows
▸ ① Because air moves
1
Wind is air moving.
2
As warm air rises and cold air sinks, the air moves and the wind blows.