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