AQA GCSE Combined Science: Trilogy · 5.9

Chemistry of the atmosphere

Revision questions with answers for 5.9 Chemistry of the atmosphere in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All questions and answers

Question 1 · Spec 5.9.1.1
What are the approximate proportions of nitrogen and oxygen in today's atmosphere?
Answer:
About 80% nitrogen and 20% oxygen; more precise values are approximately 78% and 21%.
Question 2 · Spec 5.9.1.1
Which other gases occur in small proportions in the atmosphere?
Answer:
Noble gases, carbon dioxide and variable amounts of water vapour.
Question 3 · Spec 5.9.1.1
Using 20% oxygen, estimate its volume in 250 cm³ of air.
Answer:
Oxygen volume = 0.20 × 250 = 50 cm³.
Question 4 · Spec 5.9.1.2
Why is evidence about Earth's earliest atmosphere limited?
Answer:
It formed billions of years ago, and much direct evidence has been altered or destroyed.
Question 5 · Spec 5.9.1.2
What is one theory for the origin of the early atmosphere?
Answer:
Intense volcanic activity released gases that accumulated around the Earth.
Question 6 · Spec 5.9.1.2
Which gases may have been present in the early atmosphere?
Answer:
Mainly carbon dioxide, with water vapour and nitrogen; smaller amounts of methane and ammonia may have been present.
Question 7 · Spec 5.9.1.2
How did early atmospheric oxygen compare with today?
Answer:
There was little or no free oxygen gas, unlike the substantial proportion present today.
Question 8 · Spec 5.9.1.2
How did the first oceans form in this model?
Answer:
As Earth cooled, atmospheric water vapour condensed to form liquid water.
Question 9 · Spec 5.9.1.2
How did ocean formation reduce atmospheric carbon dioxide?
Answer:
Carbon dioxide dissolved in ocean water.
Question 10 · Spec 5.9.1.2
How did carbonate sediment formation affect carbon dioxide?
Answer:
Carbon became stored in carbonate sediments and rocks, reducing the amount in the atmosphere.
Question 11 · Spec 5.9.1.2
How did nitrogen become a major atmospheric component?
Answer:
Volcanoes released nitrogen, which gradually accumulated as the atmosphere developed.
Question 12 · Spec 5.9.1.3
Which organisms first increased atmospheric oxygen through photosynthesis?
Answer:
Photosynthetic algae, followed later by plants.
Question 13 · Spec 5.9.1.3
State the word equation linking photosynthesis to atmospheric change.
Answer:
Carbon dioxide + water → glucose + oxygen, using light energy.
Question 14 · Spec 5.9.1.3
Why was rising oxygen important for the evolution of many animals?
Answer:
It enabled widespread aerobic respiration, which transfers more energy per glucose molecule than anaerobic respiration.
Question 15 · Spec 5.9.1.4
How did plant and algal growth reduce atmospheric carbon dioxide?
Answer:
Photosynthesis converted carbon dioxide into carbon-containing organic molecules in biomass.
Question 16 · Spec 5.9.1.4
How is carbon stored in limestone?
Answer:
Carbonate-rich sediments, including remains of shelled organisms, become limestone, storing carbon in calcium carbonate.
Question 17 · Spec 5.9.1.4
How did coal deposits form?
Answer:
Plant remains accumulated, were buried and changed under geological conditions, storing carbon in coal.
Question 18 · Spec 5.9.1.4
How did crude oil and natural gas deposits form?
Answer:
Ancient biomass, mainly marine organisms, was buried and changed over geological time, storing carbon in fossil fuels.
Question 19 · Spec 5.9.1.4
How does burning fossil fuels reverse part of historical atmospheric carbon removal?
Answer:
Combustion returns carbon stored underground to the atmosphere as carbon dioxide.
Question 20 · Spec 5.9.2.1
Name three greenhouse gases in the specification.
Answer:
Water vapour, carbon dioxide and methane.
Question 21 · Spec 5.9.2.1
Why is the natural greenhouse effect necessary for life?
Answer:
It keeps Earth's surface warmer than it would otherwise be, allowing temperatures suitable for life.
Question 22 · Spec 5.9.2.1
What happens to much of the incoming short-wavelength solar radiation?
Answer:
It passes through the atmosphere and is absorbed by Earth's surface, warming it.
Question 23 · Spec 5.9.2.1
What radiation does the warmed Earth emit?
Answer:
Longer-wavelength infrared radiation.
Question 24 · Spec 5.9.2.1
How do greenhouse gases affect outgoing radiation?
Answer:
They absorb and re-emit some outgoing infrared radiation, reducing net energy loss from Earth's surface.
Question 25 · Spec 5.9.2.2
Give two human activities that increase atmospheric carbon dioxide.
Answer:
Burning fossil fuels and deforestation, including burning cleared vegetation.
Question 26 · Spec 5.9.2.2
Give two human activities that increase methane emissions.
Answer:
Livestock farming and disposal of biodegradable waste in landfill.
Question 27 · Spec 5.9.2.2
Why can deforestation increase carbon dioxide even without burning the trees?
Answer:
It removes photosynthetic organisms, reducing carbon dioxide uptake; decomposition can also release carbon dioxide.
Question 28 · Spec 5.9.2.3
What is the difference between weather and climate?
Answer:
Weather describes short-term atmospheric conditions; climate describes long-term patterns and averages.
Question 29 · Spec 5.9.2.3
Name four possible effects of global climate change.
Answer:
Rising sea levels, altered rainfall, more frequent or intense extreme weather, and changes in species distributions.
Question 30 · Spec 5.9.2.3
Why can warming raise sea level?
Answer:
Seawater expands as it warms, and melting land ice adds water to oceans.
Question 31 · Spec 5.9.2.3
How can climate change affect risks from extreme weather?
Answer:
It can change the frequency or intensity of events such as heatwaves, storms and heavy rainfall.
Question 32 · Spec 5.9.2.3
How can changed rainfall affect people and ecosystems?
Answer:
It can increase drought or flooding, changing water availability, agriculture and habitat suitability.
Question 33 · Spec 5.9.2.3
Why might species distributions change as climate warms?
Answer:
Conditions may become unsuitable in existing habitats and suitable in other regions, shifting survival and reproduction patterns.
Question 34 · Spec 5.9.2.2
Why do climate models contain uncertainty?
Answer:
Climate involves many interacting variables, and future emissions and some feedback effects are uncertain.
Question 35 · Spec 5.9.2.2
What makes a climate report's evidence more trustworthy?
Answer:
Clear methods, relevant long-term data, acknowledged uncertainty and consistency with multiple independent studies.
Question 36 · Spec 5.9.2.2
Why is peer review important in climate science?
Answer:
Other scientists scrutinise methods and conclusions, helping identify weaknesses before and after publication.
Question 37 · Spec 5.9.2.2
Why does one cold week not disprove global warming?
Answer:
A local short-term event does not establish a trend in long-term global average temperature.
Question 38 · Spec 5.9.2.4
Define carbon footprint.
Answer:
The total greenhouse gas emissions over the full life cycle of a product, service or event.
Question 39 · Spec 5.9.2.4
Why must a product's carbon footprint include manufacture and disposal?
Answer:
Emissions occur throughout its life cycle, not only while the consumer uses it.
Question 40 · Spec 5.9.2.4
Give three ways to reduce carbon dioxide emissions.
Answer:
Use less energy, improve energy efficiency and replace fossil fuel use with lower-carbon energy sources.
Question 41 · Spec 5.9.2.4
How can methane emissions from waste be reduced?
Answer:
Reduce biodegradable landfill waste or collect the methane produced, preventing its direct release to the atmosphere.
Question 42 · Spec 5.9.2.4
Why can reducing a carbon footprint be difficult?
Answer:
Costs, available technology, infrastructure, consumer choices and international coordination can limit action.
Question 43 · Spec 5.9.3.1
Name four pollutants that may be released when fuels burn.
Answer:
Carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates; carbon dioxide and water vapour may also be released.
Question 44 · Spec 5.9.3.1
How is carbon monoxide formed during combustion?
Answer:
Incomplete combustion of carbon-containing fuels when oxygen supply is insufficient.
Question 45 · Spec 5.9.3.1
How can soot form when a hydrocarbon burns?
Answer:
Incomplete combustion produces solid carbon particles that can enter the air as particulates.
Question 46 · Spec 5.9.3.1
Why can burning a sulfur-containing fuel produce sulfur dioxide?
Answer:
Sulfur impurities react with oxygen during combustion.
Question 47 · Spec 5.9.3.1
How do oxides of nitrogen form in engines?
Answer:
High temperatures allow nitrogen and oxygen from the air to react.
Question 48 · Spec 5.9.3.2
Why is carbon monoxide especially difficult to detect without equipment?
Answer:
It is a toxic, colourless and odourless gas.
Question 49 · Spec 5.9.3.2
What problems do sulfur dioxide and oxides of nitrogen cause?
Answer:
Respiratory problems and acid rain, which can damage organisms, habitats and buildings.
Question 50 · Spec 5.9.3.2
What problems can atmospheric particulates cause?
Answer:
They can harm human health and reduce sunlight reaching the surface, producing global dimming.

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