Hum dum dee
Oh the wind is lashing lustily
And the trees are thrashing thrustily
And the leaves are rustling gustily
So it's rather safe to say
That it seems that it may turn out to be
feels that it will undoubtedly
looks like a rather blustery day, today
It seems that it may turn out to be
Feels that it will undoubtedly
Looks like a rather blustery day
Oh I know today is Windsday
And this is how I know
It is always on a Windsday
That the winds begin to blow
--Winnie the Pooh--
Why does the wind blow?
It is easy to feel the wind and to see the effects of it on the objects around us. It is not quite as easy to describe wind and explain how it works. Think for a moment about the wind. Why does the wind blow? Winnie the Pooh seems to think that every Windsday the wind comes around. However, if you have more brain in your head than fluff, you will know that his explanation is not quite right.
The weight of the atmosphere -
AIR Temperature and pressure
What does the pressure of our atmosphere have to do with wind? Everything! Well, half of everything. Air pressure and air temperature are two closely linked circumstances that create wind. Here’s the short explanation. As air temperature changes, its pressure (or the weight of the air) also changes. When patches of air change pressure, they move around . . . and wind is the result!
As air warms, it rises because its pressure (weight) decreases. Cool air is heavy, so when the warm air head up, cold air moves down and takes the place of the warm air. This creates wind! As warm air hangs out higher up in the atmosphere it doesn’t stay warm forever. Up, up in the atmosphere, this warm air cools down. As it cools down, all of its molecules huddle up together becoming compact and heavy. As it gets colder and heavier, it sinks back down . . . creating more wind! Wind, therefore, is movement of air in the atmosphere as a result of changes in its temperature and pressure.
Balloon in a Bottle
Watching Air Pressure Experiment
Based on what we just learned about temperature and air pressure, your job is to determine how the air in the bottle will react when it is heated or cooled. You will observe changes in the air by watching a balloon that will be attached to the neck of the bottle.
2. Take your balloon and put it inside the neck of your bottle. Stretch the neck of the balloon around the outer lip of the bottle.
- Pour your boiling water into your first bowl. Fill the bowl 2/3 to ¾ full. Place your bottle into the water, so that it is standing upright as much as possible.
- Observe the balloon. What happens to it? How does the balloon’s movement explain what is happening to the air inside the bottle as it heats up?
- Dump a tray of ice cubes into your second bowl. Then fill the bowl to 2/3 to ¾ full with the coldest possible tap water. Place your bottle directly from the hot bowl into the cold bowl, so that it is now standing in the cold water.
- Observe the balloon again. What happens to it? How does the balloons movement explain what is happening to the air inside the bottle as it cools down?
5. You can continue moving the bottle back and forth between the water baths as long as the hot water remains hot. As the waters return to room temperature, the balloon’s reaction will slow down. If you like, take a kitchen timer and a kitchen thermometer and record the temperature of each water bath and the time it takes for the balloon to react at each temperature.
WARM AIR. When the air heats up, all of its molecules like to spread out. This is why hot air rises. When placed into hot water, the air inside the bottle heated up. The air molecules in the bottle began to move around and expand the space they filled. They even filled the balloon so that it POPPED right out of the bottle and stood upright outside of it! This is an example of low pressure.