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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) www.pixl.org.uk The PiXL Club Ltd, Company number 07321607 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. 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 © Copyright The PiXL Club Ltd, 2016