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Even though air seems like nothing, it really is something. Gases like air, even though they are not visible to our eyes, are made up of molecules just like solid objects. These molecules are pulled toward the earth by gravity.
Earth is surrounded by a layer of air that is heavy. That layer of air exerts pressure on the surface of the earth, a lot of pressure. Our bodies are used to it so it doesn’t bother us. In fact, we are so used to it that what bothers us is when the air pressure is gone.
The higher you go in the atmosphere, the less air pressure there is because the “thickness” of the air is less the higher you go. That’s why airplanes have “pressurized” cabins. We can’t survive in too little air pressure.
What You Need:
- Empty Water Bottle
- Thumb Tack
As the bottle is filled with water the water pushes any air left in the bottle out. When you put the lid on no air can get in the bottle either. Air on the outside of the bottle is pushing on it as well as the lid. The small holes in the bottle aren’t big enough for air to sneak in and increase the air pressure on the water…but when you open the cap more air can get in and press down on the water making it leak out the holes.
Here are some websites and books that will help you understand air pressure:
- National Weather Service: Air Pressure
- Physical Geography: Introduction to the Atmosphere
- Science Experiments That Surprise and Delight: Bottle Surprise (pages 14-15)
- Naked Eggs and Flying Potatoes: Do Not Open Bottle (pages 22-25)
- Super Simple Things to Do With Water: Bottled Up (pages 8-9)
Words to Know:
Air Pressure – The force that air exerts due to it’s weight. Even though air seems like nothing, it really is something. Gases like air, even though they are not visible to our eyes, are made up of molecules just like solid objects.Print This Post