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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.
Today’s experiment will demonstrate just how strong air pressure is.
What You Need:
Take a straw and try to push it into an apple. Hard isn’t it? The straw bends. Now put your thumb over one end of the straw while you try to push the other end into the apple. Now what happens?
When you try to push the straw into the apple the air molecules in the straw are squished closer together. If your thumb is not over the opposite end of the straw the air molecules just spill out the end. However, if your thumb IS over the opposite end of the straw the air molecules are trapped. All those packed together molecules make the straw stay stiff so that it can push into the apple. The straw seems empty, but it isn’t, it is full of air molecules.
Here are some websites and books that will help you undertand air pressure:
- CloudsRUs: Air Pressure
- NASA: It’s a Breeze How Air Pressure Affects You
- National Weather Service: Air Pressure
- Physical Geography: Introduction to the Atmosphere
- Science Experiments That Surprise and Delight Straw Through an Apple (page 12-13)
- Naked Eggs and Flying Potatoes Straw Through a Potato (page 15-17)
- Super Simple Things To Do With Pressure: Potato Plunger (pages 14-15)
Words to Know:
Air Pressure – The force exerted by the weight of air. Air pressure is the weight of the earth’s atmosphere as it sits on the earth’s surface.Print This Post