AQA GCSE Chemistry 8462: Chemistry of the atmosphere – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Topic 9, Chemistry of the atmosphere (sections 4.9.1 to 4.9.3), of the AQA GCSE Chemistry (8462) specification, for teaching from September 2016 with GCSE exams from June 2018 (version 1.1). The topic is examined on Paper 2 at both Foundation and Higher tier. No statement in this topic is Higher tier only, so every question suits both tiers.

Learn the content first in the study guide and the revision notes. The course hub is AQA GCSE Chemistry and the printable checklist lists every statement.

Questions

1. This question is about the air today.

(a) Give the approximate percentage of nitrogen and of oxygen in the atmosphere. [2] (b) A gas syringe holds 150 cm³ of dry air. The air is passed over hot copper until all the oxygen has reacted. Estimate the final volume of gas. [2]

2. Describe how the Earth’s early atmosphere and oceans formed, according to the theory in the specification. [4]

3. Oxygen now makes up a large part of the atmosphere.

(a) Write a balanced symbol equation for photosynthesis. [2] (b) Explain how the percentage of oxygen in the atmosphere increased over time. [3]

4. Limestone and coal both contain carbon. Describe how each formed, and explain how their formation changed the atmosphere. [5]

5. Explain how carbon dioxide in the atmosphere keeps the Earth’s surface warmer than it would otherwise be. Refer to wavelength in your answer. [4]

6. Human activities increase the amounts of some greenhouse gases.

(a) Give two human activities that increase the amount of carbon dioxide in the atmosphere. [2] (b) Give two human activities that increase the amount of methane in the atmosphere. [2]

7. A report gives these carbon dioxide levels (illustrative values): 280 parts per million (ppm) before industry grew, and 420 ppm today.

(a) Calculate the percentage increase. [2] (b) A headline says: “These figures prove that humans caused all recent warming.” Give two reasons why a scientist might say this claim goes beyond the evidence. [2] (c) Explain why it matters that the data in the report were peer reviewed. [1]

8. A town council wants to respond to global climate change.

(a) Describe four potential effects of global climate change. [4] (b) Suggest two actions the council could take to reduce its carbon footprint. For each, give one reason why the action may be limited. [4]

9. Diesel fuel contains carbon, hydrogen and a small amount of sulfur. It burns inside a hot engine where the oxygen supply is sometimes limited.

(a) Explain how carbon monoxide and soot are produced. [2] (b) Diesel contains no nitrogen. Explain why oxides of nitrogen are still released. [2] (c) Natural gas is treated to remove sulfur compounds before use. Suggest why burning it releases very little sulfur dioxide. [1]

10. This question is about combustion equations and a pollution calculation.

(a) Balance the equation for the complete combustion of propane: C₃H₈ + O₂ → CO₂ + H₂O [2] (b) Write a balanced symbol equation for the incomplete combustion of methane, CH₄, forming carbon monoxide and water. [2] (c) A power station burns 500 tonnes of coal containing 2.0% sulfur by mass. Every 32 g of sulfur forms 64 g of sulfur dioxide. Calculate the mass of sulfur dioxide formed, in tonnes. [3]

11. A city has high levels of carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates in its air. Describe and explain the problems these pollutants cause. [6]

12. A student reads about two theories of the early atmosphere.

• Theory A: mainly carbon dioxide and water vapour, with little or no oxygen.
• Theory B: mainly methane, ammonia and hydrogen, with little or no oxygen.

Evidence given:

1. Gases from volcanoes today are mostly water vapour and carbon dioxide, with some nitrogen.
2. The atmospheres of Mars and Venus are mostly carbon dioxide.
3. Some very old rocks contain iron compounds that form only when little or no oxygen is present.
4. In a laboratory, sparks passed through methane, ammonia, hydrogen and water produced amino acids.

Evaluate which theory is better supported by this evidence. [5]

Answers

1. (a) Nitrogen about 80% (four-fifths) [1]; oxygen about 20% (one-fifth) [1]. (b) Oxygen removed ≈ 1/5 × 150 = 30 cm³ [1]; final volume ≈ 120 cm³ [1]. Examiner insight: Allow 78% for nitrogen or 21% for oxygen in (a); in (b) show the 30 cm³ of oxygen removed, because an answer of 30 cm³ as the final volume scores only the first mark.

2. Intense volcanic activity in the first billion years [1]. Volcanoes released gases, mainly carbon dioxide, with little or no oxygen [1]. Water vapour released by volcanoes condensed to form the oceans [1]. Nitrogen was also released and gradually built up [1]. Examiner insight: Each mark is a separate idea; “volcanoes made the atmosphere” on its own scores one mark at most, so name the gases.

3. (a) Correct formulae: CO₂, H₂O, C₆H₁₂O₆, O₂ [1]; balanced: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ [1]. (b) Algae began to produce oxygen by photosynthesis, about 2.7 billion years ago [1]. Over the next billion years plants evolved and also photosynthesised [1]. Oxygen gradually increased to a level that allowed animals to evolve [1]. Examiner insight: The balancing mark depends on correct formulae; an equation with the wrong glucose formula cannot earn it.

4. Limestone: shells and skeletons of marine organisms, made of calcium carbonate [1], settled on the sea bed and were compressed into rock [1]. Coal: plant material was buried before fully decaying [1], then compressed and heated over millions of years [1]. The carbon came from carbon dioxide, so locking it in rock reduced the carbon dioxide in the atmosphere [1]. Examiner insight: Coal from “dead animals” loses the mark – the source organisms must match the deposit.

5. The Sun emits short wavelength radiation that passes through the atmosphere [1]. The Earth’s surface absorbs it and emits long wavelength (infrared) radiation [1]. Carbon dioxide absorbs some of this long wavelength radiation [1] and re-emits it, some towards the Earth, so less energy escapes to space [1]. Examiner insight: Answers about the ozone layer, or heat “bouncing off” carbon dioxide, are not credited; you need the idea of absorption of long wavelength radiation.

6. (a) Any two of: burning fossil fuels [1]; deforestation [1]; burning wood or other fuels. (b) Any two of: cattle or livestock farming [1]; rice paddy fields [1]; decay of waste in landfill. Examiner insight: Vague answers such as “pollution” or “factories” are not credited; name a specific activity for each mark.

7. (a) Increase = 420 − 280 = 140 ppm [1]; 140 ÷ 280 × 100 = 50% [1]. (b) Any two of: correlation does not prove cause on its own [1]; natural factors also affect climate [1]; past levels are measured indirectly, so they carry uncertainty; climate models are simplified. (c) Other scientists have checked the methods and conclusions, so the data are more likely to be valid [1]. Examiner insight: Dividing by 420 (giving 33%) loses the accuracy mark, but the method mark is still available if you show the subtraction.

8. (a) Any four of: sea level rise, causing flooding or coastal erosion [1]; more frequent or severe storms [1]; changes in rainfall, causing drought or floods [1]; temperature and water stress for people and wildlife [1]; changes in food production; changes in species distribution. (b) Action, e.g. install solar panels or use renewable electricity [1]; limited by cost or weather-dependent supply [1]. Action, e.g. insulate council buildings or run electric buses [1]; limited by up-front cost or people being unwilling to change habits [1]. Examiner insight: In (b) each limitation must match its own action; one general “it costs money” cannot score twice.

9. (a) When oxygen is limited, carbon in the fuel undergoes incomplete combustion [1], forming carbon monoxide, and with even less oxygen, carbon particles (soot) [1]. (b) The engine is very hot [1], so nitrogen and oxygen from the air react together [1]. (c) The fuel contains (almost) no sulfur, so there is nothing to form sulfur dioxide [1]. Examiner insight: In (b), both the high temperature and the air as the nitrogen source are needed for two marks.

10. (a) C and H balanced: 3CO₂ + 4H₂O [1]; C₃H₈ + 5O₂ → 3CO₂ + 4H₂O [1]. (b) Correct formulae CH₄ + O₂ → CO + H₂O [1]; 2CH₄ + 3O₂ → 2CO + 4H₂O [1]. (c) Mass of sulfur = 2.0/100 × 500 = 10 tonnes [1]; ratio 64/32 = 2 [1]; mass of sulfur dioxide = 20 tonnes [1]. Examiner insight: Allow error carried forward in (c): a wrong sulfur mass correctly doubled still earns the last two marks.

11. Carbon monoxide is toxic [1]; it is colourless and odourless, so people do not notice it [1]. Sulfur dioxide and oxides of nitrogen cause respiratory problems [1] and dissolve in rain to form acid rain [1], which damages buildings, trees and lake life. Particulates cause global dimming, so less sunlight reaches the ground [1], and cause health problems when breathed in [1]. Examiner insight: A six-mark answer needs every pollutant covered; linking a pollutant to the wrong effect (carbon monoxide causing acid rain) is not credited.

12. Evidence 1 supports Theory A: volcanoes release the gases A describes [1]. Evidence 2 supports A: Mars and Venus may resemble the early Earth [1]. Evidence 3 fits both theories, since both have little or no oxygen, so it cannot separate them [1]. Evidence 4 shows only that B’s gases could make amino acids, not that the atmosphere contained them [1]. Judgement: Theory A is better supported, though evidence is limited because of the 4.6 billion year time scale [1]. Examiner insight: “Evaluate” needs a judgement at the end; listing evidence with no conclusion is capped below full marks.

Where marks are usually lost

• Saying the early atmosphere was mainly nitrogen or oxygen.
• Explaining the greenhouse effect with no reference to long wavelength radiation.
• Mixing up the greenhouse effect, ozone depletion and acid rain.
• Naming “pollution” or “factories” as the source of methane.
• Unbalanced combustion equations, especially the oxygen count.
• Dividing by the final value when calculating a percentage increase.
• Saying nitrogen oxides come from nitrogen in the fuel.
• Giving one limitation for two different actions.
• Ending an “evaluate” answer with no judgement.

Next steps

• Chemistry of the atmosphere revision notes
• Chemistry of the atmosphere study guide
• Using resources practice questions
• AQA GCSE Chemistry course hub
• Printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

AQA GCSE Chemistry (8462) specification, for teaching from September 2016, GCSE exams June 2018 onwards, version 1.1, published by AQA – section 4.9 Chemistry of the atmosphere.