Download DTT Final test Edexcel Core Therapy Topic 3 Evolution of the

SOLUTIONS
Final test: Edexcel Science – Evolution of the Atmosphere and rocks (15 marks)
1. What gas has increased in the air over the last 200 years? (circle the correct answer)
A.
B.
C.
D.
Nitrogen
Oxygen
Carbon dioxide
Argon
(1 mark)
2. Fill in the gaps using some of the words in the box.
Igneous rocks are formed by the solidification of molten rock, magma (inside the Earth) or lava (on the Earth’s
surface). They contain crystals whose size depends on the rate of cooling and an example of an igneous rock is
granite. Metamorphic rocks are formed when heat and pressure is applied to other rocks.
basalt
mantle
heating
igneous
granite
cooling
sedimentary
(3 mark)
3. Explain how sedimentary rocks are formed.



Eroded fragments of rock or sediments.
These form layers.
They are then compacted over millions of years.
(3 marks)
4.
What are extrusive and intrusive rocks?


Extrusive rock are rocks that cool quickly above ground.
Intrusive rocks cool slowly underground.
(2 marks)
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5. QWC: Compare the composition of the atmosphere today the atmosphere in phases 1,2 and 3. You need to
state the percentages of gases in the air today.
QWC Suggested marking guidance (Total 6 marks)
Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the
standard of the scientific response. Teachers should apply a ‘best-fit’ approach to the marking.
0 marks
No relevant
content.
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Level 1 (1-2 marks)
Level 2 (3-4 marks)
Level 3 (5-6 marks)
At least two gases named
and % correct or one
comparison made.
The spelling, punctuation
and grammar are very
weak.
At least two gases named and %
correct and one comparison made.
There is reasonable accuracy in
spelling, punctuation and grammar,
although there may still be some
errors
At least three gases named % correct
and a clear comparison made. The
answer shows almost faultless
spelling, punctuation and grammar.
Gas
Formula
%
Nitrogen
N2
78
Oxygen
O2
21
Carbon
dioxide
CO2
0.04
Argon
Ar
1
The early atmosphere was mainly carbon dioxide with water vapour (nitrogen, methane and
ammonia) whereas todays atmosphere is (see above). The earth cooled and water vapour
condensed to form the oceans.
In Phase 2 bacteria algae and green plants started to photosynthesise and the carbon dioxide
levels went down.
In phase 3 a build-up of oxygen caused some early lifeforms to die off.
This allowed more complex molecules to evolve.
As O2 levels increased O3 formed the ozone layer which protects against harmful rays.
(6 marks)
1
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