| And we thought air was weightless... | | | | around us is equal on all sides. Once this air pressure |
| Although we think that air is weightless, air does have | | | | changes on any side, an object will begin to move. |
| weight. This air constantly exerts a force on our skin. | | | | Sounds mystical, doesn't it? This very phenomenon |
| We can't feel this weight because there is air on all | | | | causes winds. When there is a big difference between |
| sides, and therefore equal weight is exerted on our | | | | the pressures at two places, tornadoes are caused. |
| skin from all sides. The force air exerts on an object is | | | | Kites move higher due to this pressure. Airplanes are |
| called air pressure. This pressure can be demonstrated | | | | lifted off the runway by putting air pressure to use. |
| by simple homeschool science experiments. Air exerts | | | | Difference in pressure makes things move, and this |
| a pressure of 14.7 psi (pounds per square inch) on an | | | | can be demonstrated by our second homeschool |
| object, including our skin. This is the air pressure that a | | | | science experiment below. |
| huge 1inch x 1 inch vertical column of air in the earth's | | | | Bottle Fountain: Fill a plastic soda water bottle half with |
| atmosphere puts on you and me, or any object at sea | | | | water. Now insert a stiff plastic straw in the water and |
| level. This is called atmospheric pressure. I will | | | | seal the mouth of the bottle with clay. Blow hard |
| demonstrate the fact that air has weight by our first | | | | through the straw into the bottle and move your face |
| homeschool science experiment below. | | | | away from the bottle. What happens? Water rushes |
| Inverted Water Glass Trick: Fill one-third of a drinking | | | | out of the straw like a fountain. How did this happen? |
| glass with water. Place a piece of cardboard over the | | | | When you blew air through the straw, you increased |
| mouth of the glass. Keeping the cardboard piece in | | | | the pressure of the air inside the bottle. As the |
| place with your left hand, invert the glass. Now remove | | | | pressure inside the bottle increases it exerts this |
| your left hand while holding the inverted glass with your | | | | pressure on the water, pushing it out through the |
| right hand. What happens? Amazingly, the cardboard | | | | straw. |
| piece (and the water) stays in place. How did this | | | | The water moves due to the difference in air |
| happen? This is because the atmospheric air pressure | | | | pressure. Once the pressure becomes equal with the |
| of 14.7 psi (remember?) that is pushing the cardboard | | | | atmospheric pressure, the water stops spouting. |
| upward is greater than the combined weight of the | | | | Imagine doing some air pressure magic at your next |
| water and the air inside the glass that is pushing the | | | | science fair? Check out the free "Homeschool |
| cardboard downward. This is proof that the air that fills | | | | Parent's Guide to Teaching Science", for great science |
| our atmosphere does have weight. | | | | experiments and activities, click the link below. |
| Why do things move? As I said earlier, this pressure | | | | |