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GCSE · Chemistry

C9b Climate Change and Atmospheric Pollutants

AQA 8464 · Calculator allowed · about 85 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

Figure 1: Global Carbon Dioxide and Temperature Data (illustrative)

Original data table written for Revision Library.

Year | Atmospheric CO2 concentration (ppm) | Global mean temperature anomaly (degC, relative to a 1850-1900 baseline)

1960 | 315 | +0.0

1990 | 355 | +0.5

2020 | 415 | +1.1

Note: these figures are simplified and illustrative for teaching purposes; they show the same overall trend reported in published international climate data.

This question is about greenhouse gases.

(a)Which of these gases is NOT considered a greenhouse gas linked to human-caused climate change?(1)

A) Carbon dioxide
B) Methane
C) Nitrogen
D) Nitrous oxide

(Total for Question 1 is 1 mark)

The Earth's surface is kept warm by the natural greenhouse effect, which has been enhanced by human activity since the industrial revolution.

(a)Explain how greenhouse gases in the atmosphere cause the Earth's surface to be warmer than it would otherwise be.(2)

(b)Name one greenhouse gas, other than carbon dioxide, that occurs naturally in the atmosphere.(1)

(Total for Question 2 is 3 marks)

Since the industrial revolution, human activities have increased the concentration of greenhouse gases in the atmosphere.

(a)Name the greenhouse gas released in the largest quantities by burning fossil fuels.(1)

(b)Name a human activity, other than burning fossil fuels, that releases significant amounts of methane into the atmosphere.(1)

(c)Explain why cutting down large areas of forest (deforestation) increases the concentration of carbon dioxide in the atmosphere.(2)

(Total for Question 3 is 4 marks)

Use the information in Figure 1 above to answer this question.

(a)Describe the trend in atmospheric CO2 concentration shown in Figure 1 between 1960 and 2020.(2)

(b)Calculate the percentage increase in atmospheric CO2 concentration between 1960 and 2020. Give your answer to 1 decimal place.(2)

(Total for Question 4 is 4 marks)

Scientists use several types of evidence, besides direct atmospheric measurements, to link global climate change to human activity.

(a)State two pieces of evidence that scientists use to link global climate change to human activity.(2)

(Total for Question 5 is 2 marks)

The Ahmed family are calculating the carbon footprint of a weekend trip.

(a)They drive 150 km to visit relatives. Their car produces 0.16 kg of CO2 equivalent (CO2e) per km. Calculate the CO2e produced by the car journey.(2)

(b)Two family members also take a return domestic flight, and each passenger's flight produces 105 kg of CO2e. Calculate the total carbon footprint of the whole trip (the car journey plus both flights).(2)

(Total for Question 6 is 4 marks)

Individuals, as well as governments, can take action to reduce greenhouse gas emissions.

(a)Define the term 'carbon footprint'.(1)

(b)State one way an individual could reduce their personal carbon footprint.(1)

(Total for Question 7 is 2 marks)

National governments can take action to reduce a country's total carbon footprint.

(a)Explain how carbon capture and storage (CCS) reduces the amount of carbon dioxide released into the atmosphere from power stations.(2)

(b)Explain how increasing the proportion of electricity generated from renewable sources, such as wind or solar power, reduces a country's carbon footprint.(2)

(Total for Question 8 is 4 marks)

Tomasz wanted to find out whether the gas produced when a hydrocarbon fuel burns is carbon dioxide.

Figure (to be drawn): A small sample of fuel is burned in a spirit burner; the gas produced is drawn through a delivery tube into a boiling tube containing about 2 cm depth of limewater.

(a)Describe a method, using limewater, that Tomasz could use to test whether the gas produced is carbon dioxide.(3)

(b)Suggest one variable that should be controlled when comparing the amount of carbon dioxide produced by burning different fuels, to make it a fair test.(1)

(c)Tomasz timed how long it took the limewater to turn cloudy for each fuel, and used this time to compare how much carbon dioxide each fuel produced. He noticed the limewater took longer to turn cloudy when a smaller sample of gas was collected. Explain why this is a problem for the reliability of his comparison.(2)

(d)State one safety precaution Tomasz should take when carrying out this experiment.(1)

(Total for Question 9 is 7 marks)

Aaliyah investigated whether rainwater collected near a busy road is more acidic than rainwater collected in a rural area, away from traffic. She used a calibrated pH probe to measure the pH of five rainwater samples from each location. Her results are shown in Table 1.
Table 1

Sample	Busy road pH	Rural area pH
1	5.1	6.2
2	5.3	6.1
3	3.9	6.3
4	5.2	6.0
5	5.0	6.2

Figure (to be drawn): A calibrated pH probe connected to a data logger is used to measure the pH of labelled rainwater samples collected in sealed sample tubes.

(a)State the independent variable in this investigation.(1)

(b)State one variable that should be controlled to make this a valid comparison between the two locations.(1)

(c)Identify the anomalous result in Table 1, and calculate the mean pH of the busy-road samples, excluding this anomaly. Give your answer to 2 decimal places.(3)

(d)Explain why Aaliyah took five repeat readings at each location.(2)

(e)The mean pH of the rural samples was higher than the mean pH of the busy-road samples. Explain why rainwater near a busy road is more acidic, referring to a pollutant gas released by vehicle engines.(2)

(Total for Question 10 is 9 marks)

Methane (CH4) is the main component of natural gas.

(a)Balance the equation for the complete combustion of methane: CH4 + O2 -> CO2 + H2O(1)

(b)16 g of methane undergoes complete combustion. Using the balanced equation and the relative formula masses (Mr: CH4 = 16, CO2 = 44), calculate the mass of carbon dioxide produced.(3)

(c)State and explain which type of combustion (complete or incomplete) produces carbon monoxide instead of carbon dioxide.(2)

(Total for Question 11 is 6 marks)

Carbon monoxide is a toxic pollutant produced when fuels burn in a limited supply of oxygen.

(a)Explain why carbon monoxide is produced when a fuel burns in a limited supply of oxygen.(2)

(b)Explain why carbon monoxide gas is dangerous to human health.(2)

(Total for Question 12 is 4 marks)

Particulates (soot) are solid particles released when fuels burn, especially during incomplete combustion.

(a)State one health problem that can be caused by breathing in particulates from burning fuels.(1)

(b)Explain what is meant by 'global dimming', and how particulates cause it.(2)

(Total for Question 13 is 3 marks)

Many fossil fuels, such as coal, contain small amounts of sulfur as an impurity.

(a)Explain how burning a fossil fuel that contains sulfur impurities produces sulfur dioxide.(2)

(b)Write a word equation for this reaction.(1)

(c)Explain how sulfur dioxide released into the atmosphere leads to acid rain.(2)

(d)State one problem caused by acid rain.(1)

(Total for Question 14 is 6 marks)

The high temperatures inside a car engine can cause a pollutant gas to form that is not present in significant amounts in unburnt fuel or clean air.

(a)Explain how oxides of nitrogen are formed inside a car engine when fuel is burned.(2)

(b)Write a balanced symbol equation for nitrogen reacting with oxygen to form nitrogen monoxide.(1)

(c)State one health problem associated with breathing air polluted with oxides of nitrogen.(1)

(d)Explain one environmental problem, other than acid rain, caused by oxides of nitrogen in the atmosphere.(2)

(Total for Question 15 is 6 marks)

Table 2 shows the mean concentration of oxides of nitrogen (NOx) measured at two monitoring stations over one year.
Table 2

Location	Mean NOx concentration (micrograms/m³)
Busy road	120
Rural area	30

(a)Calculate how many times greater the mean NOx concentration was at the busy road compared with the rural area.(2)

(b)Suggest one reason for the difference in NOx concentration between the two locations.(1)

(c)A newspaper claimed that this data proves traffic is the only cause of the higher NOx levels at the busy road. Evaluate this claim.(2)

(Total for Question 16 is 5 marks)

Global climate change is linked to rising sea levels and more frequent extreme weather events.

(a)Describe how rising global temperatures can lead to a rise in sea level.(2)

(b)State two effects that more frequent extreme weather events, caused by climate change, could have on the UK.(2)

(Total for Question 17 is 4 marks)

Rising global temperatures can affect where species live and how successfully crops can be grown.

(a)Explain how climate change could affect the distribution of species (living organisms) in the UK.(3)

(b)Explain one way climate change could affect agriculture (crop growing) in the UK.(2)

(Total for Question 18 is 5 marks)

Increasing concentrations of greenhouse gases in the atmosphere, caused by human activity, are linked to global climate change. You may refer to Figure 1 above where relevant.

Evaluate the methods that could be used, at a personal, national and international level, to reduce the negative effects of climate change caused by increased greenhouse gas emissions. In your answer, you should refer to the limitations of the evidence and methods you discuss.

(Total for Question 19 is 6 marks)

A coal-fired power station produces 500,000 tonnes of carbon dioxide per year. A carbon capture and storage (CCS) system is fitted, which captures 85% of the carbon dioxide produced before it can be released into the atmosphere.

(a)Calculate the mass of carbon dioxide captured by the CCS system per year.(2)

(b)Calculate the mass of carbon dioxide still released into the atmosphere per year.(2)

(Total for Question 20 is 4 marks)

A local council is deciding between two projects to help reduce the area's carbon footprint.
Project A: a tree-planting programme costing 2,000,000 pounds, saving 40,000 tonnes of CO2 per year.
Project B: an offshore wind farm costing 150,000,000 pounds, saving 2,500,000 tonnes of CO2 per year.

(a)Calculate the cost per tonne of CO2 saved per year for each project.(2)

(b)Using your answers to part (a) and one other factor, evaluate which project the council should choose.(2)

(Total for Question 21 is 4 marks)

Mark scheme · C9b Climate Change and Atmospheric Pollutants

Question 1

(a) B1 C (Nitrogen)
(a) Answer: C (Nitrogen makes up about 78% of the atmosphere but is not classed as a greenhouse gas linked to human-caused climate change)

Question 2

(a) B1 the Earth's surface absorbs (short-wavelength) radiation from the Sun and re-radiates it as longer-wavelength infrared radiation oe
(a) B1 greenhouse gases absorb this infrared radiation and re-radiate it in all directions, including back towards the surface, keeping the lower atmosphere warmer oe
(a) Answer: The Earth's surface absorbs radiation from the Sun and re-radiates it as infrared radiation; greenhouse gases absorb this infrared radiation and re-radiate it in all directions, including back to the surface, keeping it warmer
(b) B1 water vapour oe (accept methane)
(b) Answer: Water vapour (methane is also accepted)

Question 3

(a) B1 carbon dioxide cao
(a) Answer: Carbon dioxide
(b) B1 livestock farming/cattle rearing oe (accept rice growing/paddy fields, or landfill sites)
(b) Answer: Livestock farming (rice growing and landfill sites are also accepted)
(c) B1 fewer trees means less photosynthesis, so less carbon dioxide is removed from the atmosphere oe
(c) B1 cleared trees are often burned or left to decompose, releasing the carbon they had stored as carbon dioxide oe
(c) Answer: Fewer trees means less photosynthesis removing CO2 from the air, and cleared trees are often burned or decompose, releasing stored carbon as CO2

Question 4

(a) B1 the CO2 concentration increased/rose throughout the period oe
(a) B1 with a supporting figure, e.g. it rose by 100 ppm, from 315 ppm to 415 ppm oe
(a) Answer: It rose steadily throughout the period, increasing by 100 ppm from 315 ppm in 1960 to 415 ppm in 2020
(b) M1 (415 - 315) / 315 x 100 oe
(b) A1 31.7% cao (accept 31.6-31.8%)
(b) Answer: 31.7%

Question 5

(a) B1 any one from: ice core data showing historical CO2 and temperature levels; global temperature records rising alongside industrialisation; melting glaciers and polar ice caps; rising sea levels oe
(a) B1 any second, different point from the list above oe
(a) Answer: Any two of: ice core data; rising global temperature records; melting glaciers/ice caps; rising sea levels

Question 6

(a) M1 150 x 0.16 oe
(a) A1 24 kg CO2e cao
(a) Answer: 24 kg CO2e
(b) M1 2 x 105 (= 210) added to their answer to part (a) oe, ft
(b) A1 234 kg CO2e cao, ft from (a)
(b) Answer: 234 kg CO2e

Question 7

(a) B1 the total amount of greenhouse gases released, directly or indirectly, by an activity, product, individual or organisation, usually measured as CO2 equivalent, over a given period oe
(a) Answer: The total amount of greenhouse gases (measured as CO2 equivalent) released directly or indirectly by an activity, product, individual or organisation
(b) B1 any valid method, e.g. walk/cycle/use public transport instead of driving; take fewer flights; use energy-efficient appliances/insulate the home; eat less meat and dairy oe
(b) Answer: Any valid method, e.g. walking or cycling instead of driving, taking fewer flights, or improving home insulation

Question 8

(a) B1 carbon dioxide produced by burning fossil fuels is captured before it is released into the atmosphere oe
(a) B1 the captured CO2 is transported and stored, e.g. pumped into depleted oil and gas fields underground, so it cannot enter the atmosphere oe
(a) Answer: CO2 produced by burning fossil fuels is captured before release, then transported and stored underground (e.g. in depleted oil and gas fields) so it cannot enter the atmosphere
(b) B1 renewable sources do not burn fossil fuels, so they release little or no carbon dioxide when generating electricity oe
(b) B1 replacing fossil-fuel power stations with renewables therefore reduces the total CO2 released for the same amount of electricity generated oe
(b) Answer: Renewables do not burn fossil fuels, so they release little or no CO2 when generating electricity; replacing fossil-fuel power stations with renewables reduces total emissions

Question 9

(a) M1 collect the gas produced by the burning fuel, e.g. using a delivery tube leading into a test tube/boiling tube oe
(a) M1 bubble the collected gas through (or shake it with) limewater oe
(a) A1 if the gas is carbon dioxide, the limewater turns cloudy/milky cao
(a) Answer: Collect the gas produced using a delivery tube into a boiling tube, then bubble it through limewater; if the gas is CO2, the limewater turns cloudy/milky
(b) B1 any one sensible control variable, e.g. mass/volume of fuel burned; time the fuel is burned for; volume of limewater used; distance of the fuel from the apparatus oe
(b) Answer: Any one of: mass or volume of fuel burned, time the fuel burns for, or volume of limewater used
(c) B1 the time taken depends on how much gas is collected, not only on which fuel produced it, so results will only be comparable if the volume of gas collected is controlled/kept the same oe
(c) B1 a fuel could appear to produce less CO2 simply because less gas was collected, not because it actually produces less CO2 per unit of fuel, making the comparison unreliable oe
(c) Answer: The time taken depends on the volume of gas collected as well as the fuel used, so unless this is controlled a fuel could wrongly appear to produce less CO2 simply because less gas was collected
(d) B1 any valid precaution, e.g. wear eye protection; keep flammable materials away from the flame; ensure good ventilation; tie back long hair oe
(d) Answer: Any valid precaution, e.g. wearing eye protection or keeping flammable materials away from the flame

Question 10

(a) B1 the location where the rainwater sample was collected (busy road or rural area) oe
(a) Answer: The location where the rainwater sample was collected
(b) B1 any sensible control variable, e.g. same type of collection container; same collection time period; samples tested using the same calibrated pH probe; same volume of sample tested oe
(b) Answer: Any sensible control variable, e.g. using the same type of collection container and the same calibrated pH probe for every sample
(c) M1 sample 3 (pH 3.9) identified as the anomalous result oe
(c) M1 (5.1 + 5.3 + 5.2 + 5.0) / 4 oe
(c) A1 5.15 cao
(c) Answer: Anomaly: sample 3 (pH 3.9). Mean pH of remaining samples = 5.15
(d) B1 repeats allow anomalous results to be identified (and excluded) oe
(d) B1 they allow a mean to be calculated, which is more reliable than relying on a single reading oe
(d) Answer: Repeats allow anomalous results to be spotted and excluded, and allow a mean to be calculated, which is more reliable than a single reading
(e) B1 vehicle engines burn fuel and release oxides of nitrogen (accept sulfur dioxide from impurities in the fuel) oe
(e) B1 these gases dissolve in atmospheric water and react (with oxygen) to form dilute nitric acid (and/or sulfuric acid), lowering the pH of the rainwater oe
(e) Answer: Vehicle engines release oxides of nitrogen (and sulfur dioxide), which dissolve in atmospheric water and react to form dilute nitric acid (and/or sulfuric acid), lowering the pH of the rainwater

Question 11

(a) B1 CH4 + 2O2 -> CO2 + 2H2O cao
(a) Answer: CH4 + 2O2 -> CO2 + 2H2O
(b) M1 moles of CH4 = 16 / 16 = 1 (mol) oe
(b) M1 mole ratio of CH4 : CO2 is 1 : 1, so moles of CO2 = 1 (mol) oe
(b) A1 mass of CO2 = 1 x 44 = 44 g cao
(b) Answer: 44 g
(c) B1 incomplete combustion cao
(c) B1 because there is not enough oxygen available for all the carbon to be fully oxidised to carbon dioxide oe
(c) Answer: Incomplete combustion, because there is not enough oxygen for all the carbon to be fully oxidised to carbon dioxide

Question 12

(a) B1 there is not enough oxygen to fully oxidise all the carbon in the fuel oe
(a) B1 so some carbon is only partially oxidised, forming carbon monoxide instead of carbon dioxide oe
(a) Answer: There is not enough oxygen to fully oxidise all the carbon, so some carbon is only partially oxidised, forming carbon monoxide
(b) B1 carbon monoxide is a toxic gas with no colour, taste or smell, so it is not easily detected oe
(b) B1 it combines with haemoglobin in red blood cells (in place of oxygen), reducing the amount of oxygen the blood can carry around the body oe
(b) Answer: It is a colourless, odourless toxic gas that combines with haemoglobin in red blood cells, reducing the oxygen the blood can carry

Question 13

(a) B1 respiratory problems/damage to the lungs oe (accept named example, e.g. asthma, bronchitis)
(a) Answer: Respiratory problems/lung damage (e.g. asthma or bronchitis)
(b) B1 particulates released into the atmosphere reflect/absorb sunlight back into space oe
(b) B1 this reduces the amount of sunlight reaching the Earth's surface, an effect called global dimming oe
(b) Answer: Particulates in the atmosphere reflect sunlight back into space, reducing the amount reaching the Earth's surface; this effect is called global dimming

Question 14

(a) B1 the sulfur impurities in the fuel react with oxygen in the air during combustion oe
(a) B1 forming sulfur dioxide gas (SO2) oe
(a) Answer: Sulfur impurities in the fuel react with oxygen during combustion, forming sulfur dioxide gas
(b) B1 sulfur + oxygen -> sulfur dioxide cao
(b) Answer: sulfur + oxygen -> sulfur dioxide
(c) B1 sulfur dioxide dissolves in atmospheric water droplets (in clouds/rain) and reacts with oxygen oe
(c) B1 forming (dilute) sulfuric acid, which falls as acid rain oe
(c) Answer: Sulfur dioxide dissolves in atmospheric water and reacts with oxygen, forming dilute sulfuric acid, which falls as acid rain
(d) B1 any valid problem, e.g. damages/kills trees and plants; acidifies lakes and rivers, harming aquatic life; erodes limestone buildings and statues; corrodes metal structures oe
(d) Answer: Any valid problem, e.g. damage to trees and plants, or acidification of lakes and rivers

Question 15

(a) B1 the high temperature inside the engine (from burning fuel) causes nitrogen and oxygen from the air to react together oe
(a) B1 forming oxides of nitrogen, e.g. nitrogen monoxide (NO) oe
(a) Answer: The high temperature inside the engine causes nitrogen and oxygen from the air to react together, forming oxides of nitrogen such as nitrogen monoxide
(b) B1 N2 + O2 -> 2NO cao
(b) Answer: N2 + O2 -> 2NO
(c) B1 respiratory problems/irritation of the lungs and airways oe (accept worsens asthma)
(c) Answer: Respiratory problems/irritation of the lungs and airways (can worsen asthma)
(d) B1 oxides of nitrogen react with other pollutants/hydrocarbons in sunlight oe
(d) B1 forming photochemical smog, which reduces air quality oe (accept contributes to ground-level ozone formation)
(d) Answer: Oxides of nitrogen react with other pollutants in sunlight, forming photochemical smog, which reduces air quality

Question 16

(a) M1 120 / 30 oe
(a) A1 4 (times greater) cao
(a) Answer: 4 times greater
(b) B1 there is more traffic/more vehicles burning fuel at the busy road, releasing more oxides of nitrogen oe
(b) Answer: There is more traffic at the busy road, so more fuel is burned in vehicle engines, releasing more NOx
(c) B1 the data shows a correlation/association between traffic and higher NOx levels but does not, on its own, prove traffic is the (only) cause oe
(c) B1 other factors could contribute, e.g. nearby industry or weather conditions affecting how the gas disperses, so further evidence would be needed to establish a causal link oe
(c) Answer: The data shows a correlation but does not, on its own, prove traffic is the only cause; other factors (e.g. nearby industry, weather affecting dispersion) could contribute, so more evidence would be needed to prove causation

Question 17

(a) B1 higher temperatures cause polar ice caps and glaciers to melt, adding water to the oceans oe
(a) B1 higher temperatures also cause thermal expansion of sea water (water expands as it warms), both increasing sea level oe
(a) Answer: Melting ice caps and glaciers add water to the oceans, and thermal expansion of warming sea water also increases its volume; both raise sea level
(b) B1 any one effect, e.g. increased risk/frequency of flooding from heavier rainfall or storms oe
(b) B1 any second, different effect, e.g. damage to homes, infrastructure and agriculture, or increased risk of heatwaves/drought oe
(b) Answer: Any two of: increased flooding from heavier rainfall/storms; damage to homes, infrastructure and agriculture; increased risk of heatwaves or drought

Question 18

(a) B1 as temperatures rise, the climate further north/at higher latitudes becomes suitable for species that previously could only survive further south oe
(a) B1 so the range of some species, e.g. certain insects, birds or plants, shifts or expands northwards (or to higher altitudes) oe
(a) B1 species that cannot migrate or adapt quickly enough may decline in number or become locally extinct oe
(a) Answer: As temperatures rise, conditions further north become suitable for species previously limited to warmer areas, so their range shifts north; species that cannot migrate or adapt may decline or die out locally
(b) B1 changes in temperature and rainfall patterns affect which crops can be successfully grown in a given region oe
(b) B1 e.g. increased frequency of drought or flooding can reduce crop yields, or warmer temperatures could allow new crops to be grown that previously could not survive oe
(b) Answer: Changing temperature and rainfall patterns affect which crops grow well; for example, more frequent drought or flooding can reduce yields, though warmer conditions might allow new crops to be grown

Question 19

Level 3 (5-6): A detailed and coherent evaluation, referring to methods at more than one scale (personal/national/international) with clear explanation of how each reduces greenhouse gas emissions, together with a discussion of at least one limitation (e.g. cost, scientific uncertainty, need for international cooperation) and a reasoned conclusion. The answer is logically structured throughout.
Level 2 (3-4): Relevant methods are described at one or more scales with some explanation of how they reduce emissions. Some limitations may be mentioned but are not fully linked to a conclusion. The answer has some structure.
Level 1 (1-2): Basic or isolated statements about reducing climate change are given, with little or no explanation or evaluation, and limited use of scientific terminology.
Level 0 (0): No relevant content.
Indicative content:
- Personal: reduce car use by walking, cycling or using public transport; take fewer flights; improve home insulation and use energy-efficient appliances; eat less meat and dairy, which reduces methane from farming; reduce, reuse and recycle to lower personal carbon footprint.
- National: increase the proportion of electricity generated from renewable or low-carbon sources such as wind, solar or nuclear power; use carbon capture and storage at power stations and industrial sites; government taxation or incentives, e.g. taxing high emitters or subsidising renewables and electric vehicles; tree-planting and reforestation programmes to increase carbon sinks.
- International: international agreements or targets to limit greenhouse gas emissions; carbon trading or carbon pricing schemes between countries; sharing or funding low-carbon technology with developing countries.
- Limitations: many methods are expensive to implement, e.g. carbon capture and storage or renewable infrastructure; they require international cooperation and agreement, which can be difficult to achieve or enforce; scientific models used to predict the effects of climate change and of interventions have uncertainties, due to incomplete data and simplifying assumptions about complex systems; changes may take a long time to have an effect, e.g. trees take years to grow and behaviour change is slow; some methods have their own drawbacks, e.g. land use for wind farms or tree planting, or costs passed on to consumers.

Question 20

(a) M1 500,000 x 0.85 oe
(a) A1 425,000 tonnes cao
(a) Answer: 425,000 tonnes
(b) M1 500,000 - 425,000 (ft from a) oe, or 500,000 x 0.15
(b) A1 75,000 tonnes cao
(b) Answer: 75,000 tonnes

Question 21

(a) M1 Project A: 2,000,000 / 40,000 = 50 pounds per tonne oe
(a) A1 Project B: 150,000,000 / 2,500,000 = 60 pounds per tonne cao (both values correct)
(a) Answer: Project A: 50 pounds per tonne. Project B: 60 pounds per tonne
(b) B1 correct comparison based on part (a), e.g. Project A is more cost-effective per tonne of CO2 saved (lower cost per tonne), ft from (a), but Project B saves a far greater total mass of CO2 per year oe
(b) B1 valid reference to at least one additional factor, e.g. permanence (trees can be lost to disease, fire or felling, whereas a wind farm provides consistent generation for its lifetime), land use, or the timescale before benefits are realised (trees take years to mature) oe, with a justified conclusion
(b) Answer: Accept either project if justified: e.g. Project A is more cost-effective per tonne (50 pounds vs 60 pounds), but Project B saves a much greater total mass of CO2 and is more permanent/reliable than trees, which take years to mature and can be lost to disease or fire

Climate Change and Atmospheric Pollutants - Worksheets, Questions and Revision