Atmosphere Flashcards
(2) Iron reacts with oxygen to form iron oxide.
Iron wool was placed in the bottom of a wet test tube.
Explain why the water level in the test tube rose during the experiment.
the iron {reacts/combines}
with the oxygen (in the air)
/iron oxide formed(1)
• oxygen removed (from air)
(1)
• volume of gas decreases /
water rises to fill space (1)(2) The volume of air in the test tube at the start of the reaction was 10 cm3
.
Calculate the volume of gas that should be present in the test tube at the end of
the reaction.
% oxygen in air = 21 / % air remaining = 79 (1) volume of air remaining = 10 x 79 (1) 100 = 7.9 (cm3 )
(1) Iron reacts with oxygen to form iron oxide.
Iron wool was placed in the bottom of a wet test tube.
Most of the gas remaining in the test tube at the end of the experiment would be
nitrogen
(2) Explain how the use of fossil fuels affects the composition of the atmosphere.
burning/combustion (1)
• removes oxygen (1)
• adds carbon dioxide (1)
• adds water vapour (1)
(1) Some time after the early atmosphere had been formed, oceans appeared on
the Earth’s surface.
State how these oceans were formed.
{water vapour / steam}
condensed/ changed to liquid
(1) The amount of carbon dioxide in today’s atmosphere is much lower than that
in the early atmosphere.
State how the formation of the oceans caused this reduction
(carbon dioxide) dissolved/
absorbed / trapped
(2) The amount of oxygen in todays atmosphere is much higher that the early atmosphere
Describe the process that caused this decrease
(primitive) plants (produce
oxygen) (1)
• (by) photosynthesis (1)
(1) At the end of the experiment the apparatus was allowed to cool before the
final reading on the syringe was recorded.
This is because
the gas must be at room temperature when its volume is measured
(1) The percentage of oxygen in air at room temperature is 21%.
John thought the answer to part (iii) was the percentage of oxygen in air and
was surprised that the value was too high.
John confirmed that he had not made an error when doing his experiment.
Suggest why the answer calculated in part (iii) is higher than John expected.
oxygen in air in test tube also reacted /more than 32 cm3 of air because of air in test tube / air in test tube will react but is not measured
(2) John’s results were
initial volume of gas in syringe = 32 cm3
final volume of gas in syringe = 24 cm3
Calculate the percentage decrease in the volume of gas originally in the
syringe.
volume gas used = 32-24 (1) = 8 (cm3 ) percentage = 32-24/32 x 100 (1) = 25 (%)
(2) Explain why it is difficult to be precise about the composition of the Earth’s early
atmosphere.
nobody was there / OWTTE (1)
• there are no (written) records /
measurements (1)
• {different / conflicting} sources of
information (1)(1) As the Earth cooled, oceans formed.
How did this affect the composition of the atmosphere?
lowered the amount of {water vapour /
carbon dioxide} / oceans absorbed
carbon dioxide
(2) The first plants appeared about 400 million years ago.
Explain how the growth of these plants affected the composition of the
atmosphere.
photosynthesis (in plants) (1)
• {decreased / absorbed} carbon
dioxide (1)
• {increased / released} oxygen (1)
(1) What is the current approximate percentage of carbon dioxide in the Earth’s
atmosphere?
0.04
(1) State another cause of increasing amounts of carbon dioxide in the atmosphere.
deforestation (1)
• volcanic activity (1)
• respiration (1)
• increase in temperature (1)
(1) Which of these shows the relative amounts of carbon dioxide and oxygen in the
Earth’s early atmosphere?
large amount of carbon
dioxide and small amount of
oxygen
(2) Explain how carbon dioxide is removed from the atmosphere
plants (1)
photosynthesis / take in carbon
dioxide and release oxygen (1)
(2) Explain how carbon dioxide is released into the atmosphere
burning/ (complete) combustion(1) (fossil) fuels/wood/rubbish/plastic etc (1) or plants/animals/organisms (1) respiration / gas exhaled / breathing / decaying (1)
(2) Describe the test to show that a gas is carbon dioxide.
limewater (1)
turns milky/cloudy/white
ecipitate (1)
(3) Explain whether or not these graphs provide evidence that human activity is
causing the Earth’s temperature to rise.
concentration of carbon dioxide
increases (steadily) (1)
but the temperature
{fluctuates/increases and
decreases} (1)
dependent on at least 1
comment from a graph
any 1 from:
not all carbon dioxide is produced
by human activity (1)
none of the graphs refer to
human activity (1)
there is no proof that human
activity
causes the temperature to rise
(1)
other factors could cause the rise
in temperature (1)(1) The percentage of carbon dioxide in the Earth’s atmosphere today is
less than 0.5%
(2) Explain what has caused the percentage of carbon dioxide to decrease.
dissolves /is absorbed (1) • in the oceans (1) • incorporated into marine organisms (1) • formed carbonate rocks (1) • increase in (green) plants/plants start growing • photosynthesis /plants remove carbon dioxide
(1) Carbon dioxide and other gases in the atmosphere help to keep the Earth
warm.
State how these gases keep the Earth warm
traps heat
(2) Describe the test to show that a gas is oxygen.
glowing splint (1) M1 • relights (1) M2
(2) When the magnesium flame went out, there was some magnesium left in the
basin.
When the apparatus had cooled, the water in the bell jar had risen.
Explain why the water level had risen
volume of gas in bell jar decreases/water rises to fill the space (1) • oxygen is removed from the air (1)
(2) At the start of the experiment, the volume of the air in the bell jar was
1000 cm3
.
Assume that 21% of the air by volume is oxygen.
Calculate the volume of gas that was present in the bell jar at the end of the
experiment.
(amount of gases remaining) 79% (1)
(volume remaining) = 1000 x 79 (1)
100
= 790 (cm3
)
