C.7 EARTH AND ITS ATMOSPHERE MarkScheme M. (a) (i) it = water vapour condensed accept temperature went below 00 C / boiling point of water allow cooled to fm liquid / water / rain do not accept evapated fmed the oceans / seas igne rain accept (water vapour) cooled and fmed the ocean / sea f marks igne oxygen / nitrogen increased igne reference to volcanoes / respiration used by (green) plants / algae accept photosynthesis / plants give out oxygen changed into oxygen dissolved in oceans / seas accept (locked up) in shells / skeletons (of animals) (locked up) in carbonates / sedimentary rocks (locked up) in fossil fuels / named fossil fuel (b) (i) cannot get to / reach / drill to / see the ce accept the ce is (too) far down (into the Earth) / do not know what happens under the crust / Earth s surface accept it is (too) hot / radioactive igne lack of evidence unqualified any three from: heat / energy released from radioactive decay / processes accept radioactivity / nuclear reactions (causing) convection currents in the mantle 3 [8] Page
M.(a) (i) H O must be fmula CaO must be fmula carbon dioxide from the air / (Earth s early) atmosphere accept carbon dioxide from millions of years ago fmed (sedimentary) rocks fossil fuels igne trapped / sted (b) (i) decreases rapidly at first then slowly levels off allow both marks if the description is crect using either rapidly slowly allow crect use of figures f either marking point if no other mark awarded, allow CO decreased f mark accept photosynthesis used by plants dissolved in oceans locked up in fossil fuels fmed fossil fuels locked up in rocks fmed rocks (c) (yes) it = percentage of carbon (dioxide) igne yes no because the percentage of carbon dioxide is increasing which causes global warming (to increase) allow (carbon dioxide) causes greenhouse effect/climate change (no) Page
because the percentage of carbon dioxide is low () compared to millions of years ago () allow global warming can be caused by other facts (e.g. Sun / water vapour / methane) [0] M3.(a) (i) (Iceland is) on a boundary between (tectonic) plates allow where tectonic plates move apart / meet / collide any one from: igne trems (small earthquakes) are random / have no pattern igne difficult to predict / no evidence / no proof not all trems (small earthquakes) indicate that the volcano will erupt allow these trems (small earthquakes) may be false alarms scientists cannot monit what is happening below the Earth s crust in the Earth s mantle (b) water vapour / steam released by volcanic activity condensed to fm the oceans allow a description of condensing do not accept other gases condensing (c) earthquakes are caused by the sudden movement of the Earth's (tectonic) plates igne collision (of tectonic plates) caused by convection currents in the Earth's mantle caused (by the heat released) by radioactive processes (within the Earth) [7] Page 3
M4.(a) (i) Wegener / they could not explain how continents could move allow not enough no evidence no proof (of movement) igne status / technology because the (Earth s) crust (is divided into tectonic) plates the heat (released) from radioactive processes causes convection currents in the mantle (that move the tectonic plates) (b) (i) fms a solid freezes accept would block pipes (iii) neon argon because the boiling points are almost the same only 3 degrees different do not allow reference to melting points [0] M5. (a) carbon dioxide dissolves in water/oceans marine ganisms use (dissolved) carbon dioxide to fm their shells/skeletons limestone was fmed from the shells/skeleton of marine ganisms accept carbon dioxide became locked up in sedimentary rocks/carbonates/limestone precipitation fmation of insoluble carbonates plants / algae photosynthesise/ absb/use carbon dioxide accept remains of plants/algae/ marine ganisms contain locked up carbon dioxide/carbon in the fm of fossil fuels do not accept plants use carbon dioxide f respiration (b) (i) because these gases/molecules contain the elements / atoms in amino acids the gases / they contain carbon, hydrogen and nitrogen igne oxygen Page 4
igne small-scale / timescale igne references to water/oceans other theies nobody knows what was in the Earth s early atmosphere accept these gases / hydrogen / methane / ammonia may not have been in the Earth s early atmosphere accept carbon dioxide / nitrogen may have been in the Earth s early atmosphere accept reference to Venus present atmosphere igne concentration of gases there may not have been (continuous) lightning Miller and Urey selected only the gases needed to produce amino acids [5] Page 5