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IGCSE · Cambridge (CIE) · 0620

Reducing climate change and acid-rain emissions

Match each required strategy with the emission or removal process it addresses.

Chemistry of the environment · 10.3

Core and Extended · Chemistry 0620, 2026–2028. The detailed greenhouse mechanism, catalytic-converter equation and photosynthesis symbol equation are taught in separate Extended lessons.

Before you begin

  • Recall pollutant sources and effects.
  • Distinguish an acidic oxide from a basic oxide.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

Which required pollutant is directly reduced by lowering fuel sulfur?

What you will learn

  • State and explain the required climate-change strategies.
  • Connect catalytic converters, low-sulfur fuels and calcium oxide treatment with acid-rain emission reduction.

Explain the climate strategy through the carbon or methane link

Planting trees increases the potential for carbon dioxide uptake through photosynthesis as trees grow. Reducing livestock farming can reduce methane emissions associated with animals' digestion and their waste. Decreasing fossil-fuel use reduces the carbon-containing fuel combustion contribution to CO₂ emissions. Each explanation connects a named strategy with a source or removal process rather than claiming an immediate reversal of all warming.

Increasing use of hydrogen and renewable energy such as wind and solar can reduce reliance on fossil-fuel combustion. Hydrogen contains no carbon, so the hydrogen reaction itself does not produce CO₂; how the hydrogen and energy are produced still matters for a full impact comparison. Wind and solar electricity likewise avoid fuel combustion during generation, without proving every manufacturing or system impact absent. The required benefits are reductions in the specified emissions.

Choose an acid-rain strategy for its pollutant

Catalytic converters in vehicles reduce suitable harmful exhaust components, including oxides of nitrogen; the Extended lesson explains their formation and the required example equation. Low-sulfur fuels reduce the sulfur available to produce SO₂. Flue-gas desulfurisation uses calcium oxide to remove sulfur dioxide from exhaust gases in the school comparison: the basic oxide reacts with the acidic oxide.

Low sulfur does not mean no carbon dioxide from a carbon-containing fuel, and a catalytic converter does not make an engine carbon-free. A basic-oxide treatment intended for SO₂ should not be described as simply filtering every gas out of air. State the target pollutant and explain the relevant chemical or source change; an emissions table can show an improvement for one pollutant without proving every environmental issue solved.

Pause and explain

Which tree-planting explanation matches the required climate link?

Put the idea to work

Worked example

Explain how low-sulfur fuel and calcium oxide flue-gas treatment address SO₂, then identify a different strategy aimed at CO₂.

Show the worked solution
  1. Lower fuel sulfur reduces the source of SO₂ on combustion.
  2. Calcium oxide removes SO₂ through reaction of basic and acidic oxides in the treatment model.
  3. Decreasing fossil-fuel use reduces combustion-related CO₂; planting trees can increase CO₂ uptake as they grow.

Answer Low-sulfur fuel reduces formation; CaO treatment removes SO₂; lower fossil-fuel use or tree growth addresses the CO₂ link.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Explain planting trees, reducing livestock farming and decreasing fossil-fuel use as climate strategies.

Give me a hint

Attach each strategy to CO₂ uptake, methane sources or CO₂ production.

Compare my reasoning
  1. Growing trees can increase CO₂ uptake through photosynthesis.
  2. Less livestock farming can reduce the associated methane emissions.
  3. Less fossil-fuel combustion reduces its CO₂ emission contribution.

Trees: CO₂ uptake; reduced livestock: methane reduction; less fossil fuel: lower combustion-related CO₂.

Look for these in your work

  • All three required strategies are present.
  • Each explanation uses the appropriate gas/process.
2 · Independent

Explain increasing hydrogen, wind and solar use, then give the three required acid-rain emission strategies.

Give me a hint

Separate changes in energy supply from treatment of specific exhaust pollutants.

Compare my reasoning
  1. Hydrogen contains no carbon in its reaction; wind/solar generation avoids burning fossil fuel at that stage.
  2. Vehicle catalytic converters reduce suitable nitrogen-oxide exhaust; low-sulfur fuel lowers SO₂ formation.
  3. CaO flue-gas desulfurisation removes SO₂ by reaction; production and system impacts still need evidence for broader claims.

Hydrogen and wind/solar can reduce fossil-fuel dependence; catalytic converters, low-sulfur fuels and CaO treatment address specified acid-rain emissions.

Look for these in your work

  • The energy and exhaust strategies are separated.
  • Each acid-rain strategy has its target explained.
3 · Transfer

In hypothetical comparable exhaust data, SO₂ falls from 80 to 20 arbitrary units after treatment while CO₂ is unchanged. Find the percentage SO₂ reduction and assess the claim that climate change is now solved.

Give me a hint

Compute the decrease relative to the original SO₂ value, then inspect the separate gas.

Compare my reasoning
  1. SO₂ decrease is 80−20=60 units.
  2. Relative decrease is 60/80×100=75%.
  3. CO₂ is unchanged, and one SO₂ result does not establish every climate process resolved.

75% SO₂ reduction; the separate unchanged CO₂ result does not support the claim that climate change is solved.

Look for these in your work

  • The original value is the percentage denominator.
  • A pollutant-specific improvement is not made universal.

Common mistakes

  • Claiming low-sulfur fuel removes all carbon from the fuel.
  • Describing calcium oxide solely as a physical sieve for every gas.
  • Calling hydrogen a carbon-containing fuel.
  • Promising that one named strategy immediately eliminates all climate change.
Recall without your notes

What can you explain now?

Explain why calcium oxide is used in the stated flue-gas desulfurisation model.

Compare with the explanation

The basic oxide reacts with acidic sulfur dioxide, removing it from the flue gas.

This chemical removal targets SO₂ rather than every exhaust gas equally.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Match every required climate and acid-rain strategy with its process, then evaluate a pollutant-specific improvement without claiming universal success.

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Chemistry

Course scope and assessment

143 sequenced lessons cover all twelve syllabus areas with 429 guided, independent and application problems. 49 of the 49 syllabus sections have linked teaching and practice. This measures availability of mapped content, not full programme completion or guaranteed exam readiness. Three earlier starter lessons remain available. Extend your formula notebook as new reagents and ions appear; the starter notebook is not a universal formula reference. Paper-based method exercises support laboratory learning but do not demonstrate practical competence or complete either practical-assessment route. Written practice is self-checked.

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