BACKGROUND:
Pure air is colorless, odorless,
and tasteless. It is made up of nitrogen (78%), oxygen (21%) and argon
(0.09%). The remaining 0.1% is made up of carbon dioxide and a number
of other trace gases. The water vapor content (not included in these
figures) varies widely.
Air is found everywhere that first graders
are likely to venture. It is concentrated near the surface of the
Earth, but gets thinner at mountain tops. Air is not usually found
inside the earth's crust, unless it is trapped in caves. The higher
you get up in the atmosphere the less air you find, until there is
a point where there is no air.
If you go in an airplane you need to bring
a source of air, because the air is so thin and does not contain enough
oxygen. However, airplanes can still fly because the air flowing
over the top of the wing (which is curved) is going faster that the air
passing over the bottom of the wing (which is straight). When air
goes faster, the air pressure is less. Therefore, air is pushing
up on the bottom more than it is pushing down on the top, and the plane
rises. First graders can probably handle an explanation that simply
says that air going fast over the top of the wing lifts the wing.
This lab will try and prove that air is something
that you can capture and hold. Although air is all around us, young
children don’t quite understand that meaning.
PROCEDURE:
- The first experiment for
students is to prove that there is air. Catch some air in a plastic
grocery bag and close it. It will blow up. Ask the children
what is in the bag, and tell them that this is one way of knowing that
there is air in a particular place. Ask them if they can think of
places in the room where there is no air. Give each a bag and have
them check it out. Discuss what they found. Emphasize that
air is everywhere. We need air to live.
- The second part of this activity will have
students experiment with a pinwheel. They will observe that air can
make a pinwheel move without blowing on it. Ask the students to find
out which way they can move to make the air move the pinwheel the fastest.
Give them some clues. Tell them to move the pinwheels side by side,
up and down, twirl around, move it in a figure eight, ellipse, or any other
movement. (Twirling around tends to produce the fastest motion).
You may want to do some of this exercise outside and then inside without
wind.
