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Changes in the Earth and its
Atmosphere
Mark Scheme
Level
Subject
Exam Board
Unit
Topic
Difficulty Level
Booklet
Time Allowed:
GCSE
Chemistry
AQA
C1
Changes in the Earth and its Atmosphere
Gold Level
Mark Scheme
138 minutes
Score:
/138
Percentage:
/100
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M1.(a)
(i)
Wegener / they could not explain how continents could move
allow not enough or no evidence or no proof (of movement)
ignore status / technology
1
(ii)
because the (Earth’s) crust
1
(is divided into tectonic) plates
1
the heat (released) from radioactive processes
1
causes convection currents
1
in the mantle (that move the tectonic plates)
1
(b)
(i)
forms a solid or freezes
accept would block pipes
1
(ii)
neon
1
(iii)
argon
1
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because the boiling points are almost the same or only 3 degrees
different
do not allow reference to melting points
1
[10]
M2.(a)
methane
1
because at the surface temperature of −179°C only methane has melted but
has not boiled
accept a correct explanation using the boiling points (and
melting points) of the gases or methane is a liquid and all
the others are gases
1
(b)
CH4 is a hydrocarbon or methane / carbon monoxide contains carbon or
carbon monoxide + hydrogen → hydrocarbon
1
nitrogen and hydrogen are present in Titan’s atmosphere or nitrogen +
hydrogen → ammonia
1
carbon monoxide contains oxygen or
carbon monoxide + hydrogen / methane → water
1
amino acids contain carbon, hydrogen, nitrogen + oxygen or amino acids can
be made from (methane), hydrogen, carbon monoxide and nitrogen
1
OR
lightning / ultraviolet / electrical discharge / high energy needed for reaction
[6]
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M3.(a)
any two from:
asks for cause therefore no marks for just describing the
change
must link reason to a correct change in a gas
carbon dioxide has decreased due to:
accept idea of ‘used’ to indicate a decrease
•
plants / microorganisms / bacteria / vegetation / trees
•
photosynthesis
ignore respiration
•
‘locked up’ in (sedimentary) rocks / carbonates / fossil fuels
•
dissolved in oceans
ignore volcanoes
oxygen has increased due to:
accept idea of ‘given out / produced’
•
plants / bacteria / microorganisms / vegetation / trees
•
photosynthesis
ignore respiration
nitrogen increased due to:
accept idea of ‘given out / produced’
•
ammonia reacted with oxygen
•
bacteria / micro organisms
ignore (increase in) use of fossil fuels / deforestation
2
(b)
(because methane’s) boiling point is greater than the average / surface
temperature or Titan’s (average / surface) temperature is below methane’s
boiling point
ignore references to nitrogen or water
1
any methane that evaporates will condense
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accept boils for evaporates
accept cooling and produce rain for condensing
1
(c)
CnH2n
1
[5]
M4.(a)
(i)
H2O
must be formula
1
CaO
must be formula
1
(ii)
carbon dioxide from the air / (Earth’s early) atmosphere
it = carbon (dioxide)
accept carbon dioxide from millions of years ago
1
formed (sedimentary) rocks or fossil fuels
ignore trapped / stored
1
(b)
(i)
decreases rapidly at first
it = carbon (dioxide)
1
then slowly or levels off
allow both marks if the description is correct using either
‘rapidly’ or ‘slowly’
allow correct use of figures for either marking point
if no other mark awarded, allow CO2 decreased for 1 mark
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1
(ii)
any two from:
it = carbon (dioxide)
accept photosynthesis
•
used by plants
•
dissolved in oceans
•
‘locked up’ in fossil fuels or formed fossil fuels
•
‘locked up’ in rocks or formed rocks
2
(c)
(yes)
it = percentage of carbon (dioxide)
ignore yes or no
because the percentage of carbon dioxide is increasing
1
which causes global warming (to increase)
allow (carbon dioxide) causes greenhouse effect/climate
change
1
or
(no)
because the percentage of carbon dioxide is low (1)
compared to millions of years ago (1)
allow global warming can be caused by other factors (e.g.
Sun / water vapour / methane)
[10]
M5.(a)
Earth consists of crust, mantle and core
1
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relative positions (of crust, mantle and core) correctly given
1
crust is thinner than the mantle and core
accept correct information from a labelled diagram
1
(b)
continents were joined together
accept there was a supercontinent / Pangaea
1
the continents then drifted apart or moved apart
ignore attempts at explanations for movement
1
[5]
M6.
(a)
because the nitrogen from dry air contained noble/Group 0 gases
ignore other gases
or
(because the nitrogen from dry air) contained argon / krypton / xenon
ignore helium and neon
1
and three / some of these gases, (argon, krypton, xenon) have a greater density
than nitrogen
ignore helium and neon
or
and argon / krypton / xenon has a greater density than nitrogen
1
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(b)
(i)
carbon dioxide would form / is a solid
accept carbon dioxide freezes or its freezing point is >
–200°C
ignore melting point
or
(solid) carbon dioxide would block pipes
1
(ii)
helium (and) neon
both needed for 1 mark
accept He and Ne
1
(iii)
argon (and) oxygen
accept Ar and O2
1
because there is only a difference of 3°C in their boiling points
accept because they have boiling points that are almost the
same
1
[6]
M7.
(a)
(i)
any one from:
•
insufficient evidence for any of the theories
accept no proof
•
mountain ranges formed millions of years ago
accept no scientist is certain of what the Earth was like
millions of years ago
•
scientists do not know what happens below the Earth’s crust
ignore different scientists have different theories
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•
scientists cannot test any theory
ignore references to other theories
1
(ii)
the Earth cooled (and formed a crust)
ignore references to other theories
1
the Earth contracted / shrank (causing wrinkles in the crust)
1
(b)
(i)
radioactive processes / decay
1
release energy / heat (inside the Earth)
1
forming convection currents in the mantle
1
(ii)
oceanic plate and the continental plate / two plates are moving towards
each other
accept oceanic plate and the continental plate / two plates
are colliding with each other
allow subduction
1
the continental plate / land is pushed up
accept sediments are pushed up
or seabed is pushed up
1
[8]
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M8.
(a)
no / insufficient evidence / proof / explanation
accept there were other theories such as a land bridge / solid
crust
1
(b)
(continental / tectonic) plates move
1
any one from:
•
(caused by) convection currents (in the mantle)
•
(driven by) heat (energy) released by radioactive processes / decay
•
sudden (movement) / vibrations
1
(c)
any one from:
•
do not know / see / able to detect / measure what is happening
below the Earth’s crust
ignore cannot measure movement of plates / unpredictable
•
build up of pressure between plates is randomly released
accept (movement) is random / no pattern
1
[4]
M9.
(a)
to remove solid / dust particles
1
(b)
because at –200 °C both (water and carbon dioxide) are solids
1
this would therefore block pipes / equipment
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1
(c)
oxygen
1
(d)
(i)
helium
1
(ii)
nitrogen > argon > oxygen
1
[6]
M10.
(a)
(Kent reported because) damage was caused or it was above 3 (on the
Richter scale)
accept description of damage
1
(others not reported because) no vibrations / not felt / not noticed
allow below 3 (on Richter scale)
ignore no damage
1
(b)
movement of (tectonic) plates
allow collision of plates or plates rubbing together
or plates pushing against each other
1
any two from:
•
vibration / (shock)waves (in the earth) or p and s waves
accept sudden jolts / slips
•
caused by convection currents (in the mantle)
•
heat / energy released from radioactive processes
2
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(c)
any two from:
scientists do not know:
•
what happens under the crust / mantle / under the surface
accept anything under the crust
•
where forces / pressures are building up
•
how to measure these forces / pressures
•
when these forces / pressures reach their limit
accept there is no pattern
ignore random / speed of movement
2
[7]
M11.
(a)
any two from:
asks for cause therefore no marks for just describing the
change
must link reason to a correct change in a gas
carbon dioxide has decreased due to:
accept idea of ‘used’ to indicate a decrease
•
plants / micro organisms / bacteria / vegetation / trees
•
photosynthesis
ignore respiration
•
‘locked up’ in (sedimentary) rocks / carbonates / fossil fuels
•
dissolved in oceans
ignore volcanoes
oxygen has increased due to:
accept idea of ‘given out / produced’
•
plants / bacteria / micro organisms / vegetation / trees
•
photosynthesis
ignore respiration
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nitrogen increased due to:
accept idea of ‘given out / produced’
•
ammonia reacted with oxygen
•
bacteria / micro organisms
ignore (increase in) use of fossil fuels / deforestation
2
(b)
(because methane’s) boiling point is greater than the average /
surface temperature or Titan’s (average / surface) temperature
is below methane’s boiling point
ignore references to nitrogen or water
1
any methane that evaporates will condense
accept boils for evaporates
accept cooling and produce rain for condensing
1
(c)
(i)
bonds must be displayed correctly
ignore bond angles
1
(ii)
poly(propene) / polypropene / polypropylene
do not allow polypropane
any two from:
•
double bonds open up / break / become single(*)
•
propene molecules / monomers / they join / undergo addition
polymerisation(*)
1
•
form chains / long molecules(*)
(*)correct chemical equation gains 2 marks
ignore large
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using monomer incorrectly max 2 marks
2
[8]
M12.
(a)
Quality of written communication
for any two ideas sensibly stated
1
any three from:
•
plants take in (CO2)
accept photosynthesis uses (CO )
•
converted to glucose / starch / carbohydrates
ignore carbon compounds by itself
•
CO2 locked up in fossil fuels
accept coal / oil / natural gas / methane for fossil fuels
•
CO2 reacts with / dissolves (sea)water
accept ocean removes CO2
•
producing hydrogencarbonates
accept carbonic acid
•
producing carbonates
accept named carbonates
•
marine animals use carbonates to make shells
do not accept bones
•
forms sedimentary rocks
accept limestone / chalk
accept marble
do not accept sediments alone
3
(b)
any two from:
•
burning of fossil fuels or cars /
industry / air travel / power stations
ignore increase in population
ignore more use of electricity
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•
natural processes cannot absorb all the extra CO2
•
deforestation
accept less photosynthesis
ignore volcanic activity
accept burn trees
2
[6]
•
M13.
heat released from (natural) radioactive decay
1
•
causes convection (currents) in the mantle / underneath the crust
do not accept in the magma
1
[2]
M14.
(a)
95% (1 mark for working)
2
(b)
Much less carbon dioxide
Much more nitrogen
2
(c)
Plants take up CO2
plants give out oxygen
when they die trap CO2 in rocks and fossil fuels
methane and ammonia reacted with oxygen
nitrogen gas produced
by reaction of oxygen and ammonia
and by denitryfying bacteria
formation of ozone layer
any 4 for 1 mark each
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4
[8]
M15.
(a)
(i)
convection currents
in the mantle (1)
driven by heat (1)
from radioactive processes (1)
3
(ii)
plates moving apart
magma rises to fill gap
forms new rock
each for 1 mark
3
(b)
Rock further from ridge is older
more time for sediment to settle
each for 1 mark
2
[8]
M16.
(a)
amount of CO2 (much) lower
amount of O2 (much) higher
amount of N2 (much) higher (owtte.)
less other gases/less NH3/less CH4
any 2 for 2 marks
2
(b)
4 points from:
plants (evolved)/photosynthesis/algae
take in CO2
give out O2
water vapour condensed
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ozone formed from oxygen
less CO2 is produced now from volcanic activity
CO2 from air trapped in sedimentary rocks or fossil fuels
nitrogen produced by bacteria/living organisms/microbes/decay of dead
organisms (not nitrifying bacteria, nitrogen fixing 4 bacteria)
nitrogen produced by reaction of NH3 with O2/decomposition of NH3
nitrogen builds up because it is unreactive
(Assume answer refers to today’s atmosphere)
any 4 for 1 mark each
4
[6]
M17.
(a)
(i)
burning / breathing / respiration / fuels / food
for 1 mark each
2
(ii)
1. rock is heated / subducted (owtte) / close to magma / melted
1. rock is decomposed / carbon dioxide released through volcanoes
for 1 mark each
2
(b)
carbon dioxide reacts / dissolves in sea-water / dissolves in rain water
insoluble carbonates / calcium carbonate are / is formed carbon dioxide turned into
shells / coral / limestone / chalk / sediments also soluble hydrogencarbonates
(calcium / magnesium) are formed photosynthesis by plants
any three for 1 mark each
3
(c)
(i)
sea unable to absorb all the extra carbon dioxide being produced
more trees being cut down / deforestation increased burning of fuels / more
cars / more industry (not more people)
any one for 1 mark
1
(ii)
global warming / greenhouse effect or effects such as melting ice caps /
rising sea levels / climatic change / more deserts
(not changes to ozone layer)
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for one mark
1
[9]
M18.
(a)
any two 1 mark each
burning / combustion
fossil fuels or (locked up) carbon
accept fuel / named fuel
oxygen used
2
(b)
any three from
produces (calcium) carbonate
which is insoluble
produces (calcium) hydrogencarbonate
which is soluble
photosynthesis
releases oxygen
3
[5]
##
(a)
either any two points (1) each from
* (surface) below 100 °C (the surface) below the boiling point
of water
* (allowed the) condensation (of water vapour)
accept (rate of) condensation greater than (the rate of)
evaporation
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* from the atmosphere
accept from the air
or condensed water (vapour) (1)
was pulled by gravity into depressions (1)
or idea of impervious sea bed
or from comets (which crashed on the Earth) (1)
ice (from these) melted (1)
2
(b)
any two processes (1) each from
* dissolving in (sea) water
* (taken in during) photosynthesis
accept taken in by algae or plants
•
formation of carbonate(s)
or calcium carbonate or chalk or
calcite
accept formation of shells or bones or corals
2
[4]
M20.
(a)
(i)
convection (currents)
accept (currents) which move the plates
1
(ii)
less dense (molten) rock / magma rises / moves up
or more dense (molten) rock / magma falls / moves down
1
heat (is transferred / conducted) to the mantle / crust
(resulting from natural) radioactive processes (in the core)
1
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or radioactivity
accept radiation provided there is no
contradiction as in, for example, radiation from the Sun
or fission
do not credit fusion
1
(b)
any two from
(formation of fold) mountains
or deformation(s)
hot springs
do not credit just springs
(oceanic) ridges
(oceanic) trench(es)
rift(s)
seismic waves
subduction
or recycling of rocks
tsunami(s)
do not credit tidal waves
volcano(es)
or volcanic activity / sill(s) dyke(s) lava flow(s)
2
[6]
M21.
(a)
nitrogen and oxygen
both required either order
1
(b)
(i)
any two from
(atmosphere) is now cooler water vapour has condensed
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to form sea(s) / ocean(s)
2
(ii)
any two from
has dissolved in / reacted with seawater has formed carbonates
(evolution of green) plants removed by photosynthesis
has formed fossil fuels
2
(c)
(i)
225
accept any date in the Triassic period
225 – 191 (mya)
do not credit 190 (mya)
1
(ii)
on different (tectonic) plates
or answer refers to African and South American plates
1
(movement) due to convection currents in the mantle
1
due to energy / heat from the core
or due to radioactivity
1
[9]
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