1. Describe the composition of the Earths Atmosphere, and state how it makes life possible.
79% nitrogen
20% oxygen
1,5% water vapour
1 % argon and other gases
0,03% carbon dioxide

The mixture of gases is called AIR.

2. Describe the layered atmosphere, and state how these layers relate to altitudes of differing change in temperature.
The temperature of the Earth's atmosphere varies with altitude
(arranged from highest to lowest altitude, similar to the actual layers of atmosphere)
Exosphere
Thermosphere (including Ionosphere)
Mesosphere
Stratosphere
Troposphere

Exosphere:
from 500 – 1000 km up to 10,000 km, free-moving particles that may migrate into and out of the magnetosphere or the solar wind.

Ionosphere:
part of the thermosphere
(a) It is an area on the thermosphere where the atmosphere is ionized by solar radiation
(b) It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere.
(c) It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It makes long distance radio communication possible.
(d) It is located in the thermosphere and is responsible for auroras.
(e) It is very thin.
it has a temperature that increases with height because it is warmed by the ionization process

Thermosphere:
from 80 – 85 km to 640+ km
temperature increasing with height.

Mesosphere:
Middle layer.
The mesosphere extends from about 50 km to the range of 80 to 85 km
Temperature decreasing with height.
This is also where most meteors burn up when entering the atmosphere.

Stratosphere:
The stratosphere extends from the troposphere's 7 to 17 km range to about 50 km.
Temperature increases with height.
The stratosphere contains the ozone layer.
Ozone is mainly located in the lower portion of the stratosphere from approximately 15 to 35 km above Earth's surface.

Troposphere:
The troposphere is the lowest layer of the atmosphere.
It begins at the surface and extends to between 7 km at the poles and 17 km at the equator.
The troposphere contains roughly 80% of the total mass of the atmosphere.
Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km of the troposphere.

3. How is water trapped beneath the stratosphere and what is the significance of this?
Water is trapped beneath the stratosphere by the tropopause. Temperature decreases.
(tropopause is is the boundry between the troposphere and stratosphere)

4. Describe the interaction of nitrogen, oxygen and ozone molecules with high energy solar radiation in the mesosphere.
Ozone (trioxygen) O₃ is a triatomic molecule.
It consists of three oxygen atoms.
It is less stable than the diatomic O₂.

Ozone in the upper atmosphere (stratosphere) filters harmful ultraviolet radiation from reaching the Earth's surface.
The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer between about 10 km and 50 km above the surface.

5. Explain the role of CFC’s in the depletion of ozone and comment on why this is of concern.
CFCs in the atmosphere:
They were used:
:: in air conditioning units
:: as aerosol spray propellants
:: etc.

When such CFC’s reach the stratosphere, react with ultraviolet light to release chlorine atoms.
The chlorine atoms then act as catalysts, and break down of ozone molecules.

Consequences of ozone layer depletion.
The ozone layer absorbs harmful ultraviolet light from the Sun.
If the ozone layer is depleted,then this would allow for harmful UV radiation to reach the surface of the Earth.
This would be harmful to life.

The "ozone hole" is a hole in the ozone layer.
All of the ozone in the lower stratosphere is destroyed, creating a hole.
The ozone hole does not go all the way through the layer.
It is not a uniform 'thinning' of the layer either.
It is similar to a "hole in the ground".