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Science — Third Preparatory

Science — Third Preparatory

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Science — Third Preparatory 2026/2027

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Unit 1 - Force, Motion, Acceleration and Physical Quantities

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Text lesson

Unit 1 — Chemical Reactions and Their Environmental Impacts

Science — Third Preparatory

Unit 1 — Chemical Reactions and Their Environmental Impacts

2.8 Properties of the combustion products

2.8 Properties of the combustion products

Product Formed when Properties Effect
Carbon dioxide, CO₂ Complete combustion of carbon-containing fuel
  • Colourless
  • odourless
  • does not burn or support burning
  • denser than air
  • dissolves in water to form carbonic acid
  • H₂CO₃
 Greenhouse gas; contributes to global warming
Carbon monoxide, CO Incomplete combustion (lack of oxygen) Colourless, odourless, toxic Poisoning; binds haemoglobin
Water vapour, H₂O Burning hydrogen or hydrocarbons Condenses to droplets when cooled Harmless in small amounts
Carbon (soot), C Incomplete combustion of hydrocarbons Fine black solid Blackens surfaces, harms lungs
Sulphur dioxide, SO₂ Burning fuel with sulphur impurities
  • Colourless
  • choking odour
  • dissolves in water to give sulphurous acid (H₂SO₃)
 Acid rain, respiratory irritation
Nitrogen oxides, NOₓ
  • Burning fuels containing nitrogen compounds
  • and engine heat
  • NO is colourless and reacts with oxygen to form NO₂ (reddish-brown
  • pungent
  • choking)
  • NO₂ dissolves in water giving nitrous and nitric acids
 Acid rain, smog, lung irritation
Equations→S + O₂ → SO₂; 2NO + O₂ → 2NO₂.
  • Cross-cutting concept stability and change. In every combustion the substances change but the total mass of products equals the total mass of the reactants (conservation of matter).
  • Yet the products can change the environment and human health over time.
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