What is air?
What are its components? Elicit as much information as possible
from the children.
Air is made
up of a mixture of gases:
21% Oxygen (O2)
0.3%Carbon Dioxide (CO2)
We live at
the bottom of an ocean of gases-the atmosphere. These gases make
up the air we breathe. We can only survive near the surface of the
earth because we need oxygen. As you travel further away from the
earth's surface, the atmosphere changes.
Layers of gases surround the earth. These are called the troposphere,
stratosphere, mesosphere, thermosphere, and exosphere.
1. The lowest
layer is the troposphere, where we live. Most clouds are here. The
movement of air here is responsible for our weather. This layer
extends to 13 km above the earth's surface.
2. The next
layer is the stratosphere. It extends from 13 to 50 km above the
earth. Aircraft usually fly here, so they are above weather disturbances.
The ozone layer is found here. The temperature in the lower stratosphere
is about -55 degrees Celsius, the upper stratosphere -2 degrees.
3. The mesophere
is the next layer. It extends from 50 km to 80 km. above the earth.
If meteors fall into this area, they burn up and become 'shooting
4. The thermosphere
is a very thin layer. Space satellites fly in the lower part.
5. The exosphere
-This is the upper layer and there is hardly any air here. Outer
space lies beyond the exosphere.
children a few minutes in groups to compose a mnemonic devise to
remember the layes of the atmosphere (e.g. The Scary Monster Threw
Emily Out.) Children themselves vote anonymously for their favourite.
a diagram on the blackboard of the layers of the atmosphere. Children
suggest pictures to go with each layer (e.g. Stratosphere-aeroplane;
are given paper and pencils and asked to draw the layers.