Download how much oxygen is produced? - 8

HOW MUCH OXYGEN IS PRODUCED?
LINKS
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Areas of interaction:
Environments, Health and social education
You would be aware of the necessity of trees, plants and grasses. They remove carbon dioxide (CO2 ) from the
air and produce oxygen which is vital for the survival of all animal species.
LEAF AREA
During daylight hours healthy trees produce oxygen in their leaves at an average hourly rate of about 1:2 mL per
cm2 of area.
mL of oxygen produced per hour = area of leaf (in cm2 ) £ 1:2
That is
For example: for a leaf of area 14 cm2 ,
oxygen produced per hour = 14 £ 1:2 mL = 16:8 mL.
So, a tree with 4000 leaves of area 14 cm2 on a day with 12 hours of sunlight would produce
4000 £ 12 £ 16:8 mL
= 806 400 mL
¼ 806 L of oxygen.
What to do:
1 Find the approximate area of each leaf drawn on the 1 cm by 1 cm grid by counting squares.
a
b
c
e
d
f
Reminder:
² a full square counts as 1,
² more than half a square counts as 1, and
² less than half counts as 0.
2 For each leaf in 1, calculate the oxygen produced in a day with 12 hours of sunlight.
3 Select any one of the leaf types in 1 and calculate the oxygen produced by a tree with 3500 leaves during a
full year, assuming an average of 12 hours of sunlight per day.
Y:\HAESE\IB_MYP3\IB_MYP3_LN\010IB_MYP3_LN.cdr Monday, 16 June 2008 9:21:17 AM PETER
How much oxygen is produced each hour?
2
PRACTICAL ACTIVITY:
1 Select a typical blade of grass from a lawn and, by using a suitable method, find a reasonably accurate
estimate of its area on one side.
2 Count the number of blades of grass in a typical square of lawn. (This could be a 4 cm by 4 cm square for
grass with large blades or a 1 cm by 1 cm square for blades which are small.)
3 From 2, estimate the number of blades in a square metre of lawn.
4 Now, estimate the volume of oxygen produced for the whole lawn and for a soccer pitch of the same grass.
5 Using the formula ‘litres of oxygen needed each hour by an average person = 0:63 L/kg £ mass (kg)’,
find the number of litres of oxygen needed by an average person of mass 78:5 kg each day.
6 Using 5, estimate the number of people for whom the soccer pitch could provide oxygen in one day.
7 Write a brief report on your findings.
RESEARCH:
² Use the internet to research the rate at which native forests are declining throughout the world.
² Research the number of trees of a particular species that could reasonably be planted on a vacant square
kilometre of land in a reaforestation project.
DISCUSSION:
² What are the advantages and disadvantages of using synthetic grass on sporting arenas?
² Has the knowledge you have obtained from this ‘link’ influenced the type of tree you would plant in your
school grounds or local park?
² Should we look to plant more evergreen trees than deciduous ones throughout the world?
POSSIBLE SURVEY:
Survey the tree types in the school grounds or a local park. Which types would produce more oxygen? Why?
What factors may cause an error in the way you have approached this problem? Are your findings consistent
with others in the class?
Y:\HAESE\IB_MYP3\IB_MYP3_LN\010IB_MYP3_LN.cdr Friday, 13 June 2008 11:09:52 AM PETER