Year-11 Chemistry

1. Gases in the atmoshpere

2. Gases in the atmosphere
Gas
Percentage in dry
air
Nitrogen 78%
Oxygen 21%
Argon <1%
Carbon dioxide 0.04%
The atmosphere also contains
tiny amounts of a few other
gases and also varying
amounts of water vapour.

3. explain how experiments
involving the reactions of
elements such as copper, iron
and phosphorus with air can be
used to investigate the
percentage by volume of
oxygen in air

4. explain how experiments
involving the reactions of
elements such as copper, iron
and phosphorus with air can be
used to investigate the
percentage by volume of
oxygen in air

5. explain how experiments
involving the reactions of
elements such as copper, iron
and phosphorus with air can be
used to investigate the
percentage by volume of
oxygen in air
We can use the reaction between
hot copper and oxygen to
determine the percentage of
oxygen in the atmosphere:
Copper + Oxygen  Copper oxide
2Cu + O2  2CuO

6. Oxygen in the air
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/oil
s/changesrev5.shtml

7. explain how experiments
involving the reactions of
elements such as copper, iron
and phosphorus with air can be
used to investigate the
percentage by volume of
oxygen in air

8. Oxygen in the air
A measuring cylinder is
inverted into a beaker of
water. Previously, a piece of
iron wool had been placed
inside the measuring
cylinder. The apparatus is
left for a couple of days.

9. Oxygen in the air
As the iron wool rusts, it
absorbs oxygen from the air
inside the measuring
cylinder. When there is no
more change in the water
level, the height of water
inside the cylinder is
measured, and from this the
volume of oxygen in air can
be calculated.

10. explain how experiments
involving the reactions of
elements such as copper, iron
and phosphorus with air can be
used to investigate the
percentage by volume of
oxygen in air

11. Oxygen in the air
A bell jar is placed into a
trough of water. Coins are
placed for the bell jar to
rest on – this ensures that
water can move into the bell
jar. Water is poured in to
the bell jar to the zero level.
A piece of phosphorus is
placed on a watch glass
floating on the water
surface.
http://www.tutorvista.com/content/chemistry/chemistry-i/air-mixture/air-oxygen.php

12. Oxygen in the air
The phosphorus is lit using a
hot metal rod and the top is
placed on the bell jar
http://www.tutorvista.com/content/chemistry/chemistry-i/air-mixture/air-oxygen.php

13. Oxygen in the air
As the yellow phosphorus
starts to burn, the air space
inside the bell jar fills with
white fumes of phosphorus
oxide. This dissolves in the
water to form an acidic
solution.
http://www.tutorvista.com/content/chemistry/chemistry-i/air-mixture/air-oxygen.php

14. Oxygen in the air
As the phosphorus burns it
reacts with the oxygen in
the air in the bell jar, so the
water level rises as the
oxygen is used up. When the
reaction ends, the
percentage of oxygen in the
air can be calculated from
the change in the water
level.
http://www.tutorvista.com/content/chemistry/chemistry-i/air-mixture/air-oxygen.php

15. The preparation of oxygen
in the laboratory
Oxygen can be prepared in the laboratory
by the catalytic decomposition of
hydrogen peroxide solution:
2H2O2(aq) 2H2O(l) + O2(g)
Manganese oxide is the catalyst used in
this reaction
MnO2

16. The preparation of oxygen
in the laboratory
Hydrogen
peroxide
Manganese
oxide
Oxygen

17. End of Section 2 Lesson 2
In this lesson we have covered:
Group 7 elements – chlorine, bromine
and iodine.
Gases in the atmosphere
Oxygen in the air