1. Nitrogen Composition of Air
78%
Carbon
Dioxide,
Water
Oxygen
Vapour and
21%
other Gases
1%

2. Oxygen
• makes up 21% of the air.
• it is essential to for most living
things.
• plants and animals take in oxygen
during the process of respiration.
• not only can it be found in air, it is
also found in water and soil.
• is needed for burning.

3. Respiration
The process when living things
take in oxygen in order to break
down digested food to produce
energy.
Oxygen
Digested Energy +
Food Carbon dioxide

4. Nitrogen
• makes up 78% of the air.
• is not used by most living things
except for –
• nitrogen-fixing bacteria in the soil
• the roots of some plants to use it
to form nitrates, e.g. peanuts
• absorbed by plant as nitrates to
make plant protein.

5. Carbon dioxide
• is essential to green plants for
the process of photosynthesis.
• is combined together with
water and the energy from the
sunlight, to make food or simple
sugars. Oxygen is produced in
the process.

6. Water Vapour
• plays an important part in the
water cycle.
• helps to form the clouds in the
sky.
• returns to the Earth in the form
of rain, snow, hale or sleet.

7. Rare Gases
• includes argon, helium,
neon, krypton and xenon.
• are inert, meaning they do
not take part in reactions
under normal circumstances.

8. A Healthy Balance
Carbon
Oxygen
dioxide
produced
used by
from plants
the plants