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SCX Chemistry · Chapter 5: Fuels and combustion

Year 11 SCX · About 15 minutes with activities · Turn your sound on

Chapter 5 · Fuels and combustion
Air hole openblue flame, clean tile
Air hole closedyellow flame, sooty tile
Unburnt carbonlands on the tile as soot
Blue flameair hole open · no soot
Yellow flameair hole closed · sooty
Air hole (collar)turn it to let air in
Gas inthe fuel
White tileheld above to catch soot
Water vapourabundant, short stay
MethaneGWP about 25 × CO₂
Carbon dioxidelots, and stays for long
Carbon monoxideindirect: makes CO₂

Chapter 5 recap

  • Enough O₂ → complete combustion: CO₂ + H₂O, blue flame. Too little O₂ → incomplete: CO and C (soot) as well, yellow flame.
  • Balance C, then H, then O last: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.
  • H₂O, CH₄ and CO₂ trap heat (CO acts indirectly). Soot harms lungs and leaves, CO stops blood carrying O₂, CO₂ acidifies the ocean.
  • Next: Chapter 6 · Specific energy and comparing fuels

Why does a yellow flame leave soot but a blue flame doesn't?

Chapter 5 · About 15 minutes · sound on

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