Limestone and Building Materials

Transcription

1 Limestone and Building Materials Mark Scheme Level Subject Exam Board Unit Topic Difficulty Level Booklet GCSE Chemistry AQA C Limestone and Building Materials Bronze Level Mark Scheme Time Allowed: 23 minutes Score: /23 Percentage: /00 Grade Boundaries: A* A B C D E U >85% 75% 70% 60% 55% 50% <50% Page

2 M.(a) (i) any one from: destruction of habitats fewer plants / trees to absorb carbon dioxide dust / noise / air / visual (pollution) allow breathing problems more traffic any one from: provides employment local business make more profit new transport links ignore future use of quarry (rain water is) acidic (b) (i).2(g).4(g) allow ecf from (b)(i) any one from: temperature of the flame varied allow flame was too hot or not hot enough different purity of the limestone incorrect measurement of mass heated for different times Page 2

3 (c) (i) decomposition 2.2(g) limewater test must be correct to gain second mark turns cloudy allow turns milky or white (precipitate) [0] M2.(a) (i) magnesium oxide decomposition (b) (i) bar chart more limewater turns cloudy / milky Page 3

4 accept forms a white precipitate [6] M3. (a) ߦ one / (molecule of) methane (reacts with) two / 2 (molecules of) oxygen two / 2 (molecules of) water / steam / hydrogen oxide and one / (molecule of) carbon dioxide (are produced) if no other marks awarded all four names correct or correct number and name for two molecules or 4 correct numbers gains mark allow all four names correct and correct number of atoms in each substance for 2 marks (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also apply a best-fit approach to the marking. 0 marks No relevant content Level (-2 marks) There is a simple description of a positive and / or a negative impact caused by the plan to quarry limestone and / or make cement. Level 2 (3-4 marks) There is a clear description of both a positive and a negative impact caused by the plan to quarry limestone and / or make cement. Level 3 (5-6 marks) There is a detailed description of both positive impacts and negative impacts caused by the plan to quarry limestone and / or make cement. examples of the chemistry points made in the response Positive impacts: Limestone / cement is used for building Limestone needed for industrial processes Page 4

5 Company landscapes / provides recreation facilities in the quarry after use Provides employment Improves local economy Improved transport links Negative impacts: Destruction of habitats Fewer plants / trees to absorb carbon dioxide Example of visual pollution Example of noise pollution Example of atmospheric pollution More traffic 6 [8] M4. (a) (i) 2.5(kg) ignore units 40% (cement) and Test 3 ignore units because it is anomalous or because it is much lower than the other two readings accept value not used to calculate mean ignore outlier Page 5

6 as the percentage of cement increases the mass needed to break the sleeper increases allow strength for mass needed allow correct relationship using percentage of sand (iv) volume/percentage / amount of water accept temperature (b) any two from: availability (of the raw materials) cost of the raw materials purity (of the raw materials) 2 [7] M5.(a) (i) react allow neutralise allow bubbles / fizzes accept produces gas / CO 2F ignore rises stop reacting / producing stops on its own is insufficient allow stop working / bubbling / fizzing the (hydrochloric) acid / (calcium) carbonate is used up accept because the (calcium) carbonate has neutralised the (hydrochloric) acid Page 6

7 OR have been used up () the graph line becomes horizontal / levels out () OR stays the same / no change () ignore reference to graph line no further reaction () bubble the gas through limewater / calcium hydroxide solution allow (add) limewater test must be correct to gain result mark (the solution) goes cloudy allow milky (b) advantage > Quarrying limestone provides building materials, employment and new road links disadvantage > Quarrying limestone releases dust, and lorries release carbon dioxide from burning diesel fuel [7] M6. (a) / one 3 / three Page 7

8 (b) (i) air linked to nitrogen and oxygen quicklime linked to calcium oxide waste gases linked to nitrogen and carbon dioxide mixture burns / combusts accept methane reacts with air / oxygen accept as a fuel to provide energy / heat (c) as a building material to make cement [9] M7. (a) building (b) provides jobs Page 8

9 (c) any two from: ignore references to water noise allow sound pollution dust / visual pollution accept global dimming ignore smoke air / atmospheric exhaust gases accept acid rain / global warming / named gaseous pollutants (more) traffic accept more lorries 2 (d) O ignore any numbers 3 / three (e) calcium oxide accept quicklime do not accept calcium dioxide [7] M8. (a) causes dust pollution Page 9

10 increases traffic (b) (i) decomposition 44(g) (c) (calcium) hydroxide (calcium) carbonate substances must be in the order shown [6] M9. (a) (i) 3 nucleus electron (b) (i) methane / CH 4 accept natural gas ignore air do not allow other gases carbon dioxide Page 0

11 (c) (i) any two from: medical risks asthma cancer dirt causes global warming / global dimming / greenhouse effect / acid rain ignore death accept effect on health accept difficulty breathing/ lung disease allow smoke particles allow harmful for the environment 2 any two from: have a test done / scientific evidence independent (evidence) comparison of smoke particles / when different fuels used medical evidence or more / less asthma attacks or cancer or dirt on cars 2 [0] M0. (a) / one 3 / three (b) (i) (wear safety) glasses / masks / gloves accept do not handle hot objects / use tongs or accept other safety points Page

12 such as, tie hair back calcium oxide accept quicklime carbon dioxide / CO 2 is given off accept a gas is given off (d) (i) any two from: dust / atmospheric pollution noise eyesore destroys habitats (extra) traffic any other named pollution or description of pollution 2 any one from: employment increases local trade / makes money future development of quarry recreation / park / lake / reservoir do not accept cheaper houses / land / new roads [8] M. clay limestone Page 2

13 water [3] M2. (a) (i) limestone / chalk / marble breakdown / splits up with heat to burn / react with air / oxygen release energy / heat / exothermic / keeps temperature high (iv) calcium carbonate calcium oxide + carbon dioxide calcium oxide correct equation (b) (i) exothermic / slaking / hydration not hydrolysis calcium hydroxide / slaked line mortar / neutralise acidity in soil / neutralise acid lake water / soften hard water / to make cement not in agriculture not to make lime water Page 3

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