BACKGROUND:
Air weighs over 5 quadrillion
tons, but yet we can't see, smell, or feel it. Even so, air is a
powerful force on Earth. Most organisms cannot live without air.
Astronauts that go into space must take tanks of air with them. Divers
that go under the ocean, must take air with them. If we climb a mountain
that is too high, the air becomes less and less breathable. The downward
force exerted by overlying air causes greater pressure at the bottom of
atmosphere. Air molecules are actually “squeezed” by the weight of
the air above.
The atmosphere is layered between
the surface of the Earth and outer space. The layer we live on is
called the troposphere. The air moves up and down, the winds blow,
moisture builds up, and different types of weather are created. The
layer above the troposphere is called the stratosphere which is 32 kilometers
thick (20 miles). The upper part of the stratosphere contains
a higher percentage of ozone. This layer of ozone is a form of oxygen that
protects the surface of the Earth from the Sun's ultraviolet rays.
The next layer is called the mesosphere
which is much colder than the stratosphere. The thermosphere is the
next very thick layer which is divided into the ionosphere and exosphere.
Radio waves from Earth hit the ionosphere and bounce back to Earth
This makes it possible for you to hear a radio station. Beyond the
exosphere lies outer space.
Each of these layers acts as a unit
because they have similar characteristics including chemical composition,
temperature, and pressure.
PROCEDURE:
- Give students worksheet
and point out the information discussed in background. Show students
the wave machine and illustrate how the clear liquid (kerosene) does not
mix with the colored liquid (oil). This is similar to how the layers
of the atmosphere interact.
- If you want the students to prove
that air is everywhere but is invisible, have a student put a straw into
a glass of water and blow into it. They will see bubbles form, rise
to the surface and pop. The student has caused air to move in the
water.
Other demonstrations to show students:
- Bernoulli’s pipe
- Blow in one side and the ball will be suspended if the ball is placed
correctly over the stream of air. You can also be more dramatic by
using a ping pong ball with a hair dryer blowing air underneath it.
If placed in the correction position it will seem as the ball is suspended
in air.
- Tour of Bubbles - When you
turn the long cylinder upside down, a small bubble will form slowly and
rise, pushing the heavy liquid away from its path.
- Puddle Jumper - When you
twirl the base away from your body and let go, the design of the puddle
jumper acts like a helicopter and uses the air to move.
- You can also prove that air is
all around by using a balloon and just blow into it. The balloon
changes shape because of the air.
- Use the worksheet for the
students to color the different “spheres” of the atmosphere. The
troposphere ends around 17,600 meters, the stratosphere ends around 48,000
meters, the mesosphere ends around 88,000 meters, and the ionsphere goes
up to 200,000 meters. Notice that the exosphere does not fit into
the scale of this diagram.
- You may also tell students that
flying through the troposphere can be “bumpy” if the weather is active.
Modern jet airplanes avoid this problem by going into the stratosphere
where the air is calm.
