Stop 12 of 12 · The path
Carbon & everyday chemistry
Carbon chains with itself — fuels, plastics, food, soap. It uses every earlier stop at once, which is why it sits last.
Bench tool
Burn a fuel, balance it
Pick a hydrocarbon — full combustion in plenty of air gives CO₂ + H₂O:
Bigger fuel, more energy per litre — and more CO₂ too.
How it works
- Chains and rings. C–C single, C=C double, C≡C triple. Longer chain, higher boil.
- Small group, big change. –OH makes alcohols mix with water; –COOH makes acids.
- Polymers repeat. One small unit, thousands joined. Properties come from length and cross-links.
Worked examples
Methane to octane. Bigger fuel molecule, more energy per litre, more CO₂ too.
Bread browns. Sugars + protein → hundreds of new flavour molecules (Maillard).
Soap lifts grease. Hydrophobic tail in grease, hydrophilic head in water — rinse carries both off.
Where it goes wrong
Natural ≠ safe, man-made ≠ harmful. Ask dose and structure, not origin. Botulinum is natural; aspirin is made.
Try it at home: breath test
Catch your CO₂. Blow through a straw into limewater (ask a pharmacy) and watch it turn milky — or fog a cold mirror and compare with still air. Your breath carries extra CO₂ and water from fuel-burning in your body.
For teachers
Learners think natural means safe and burning always gives the same products — probe with a yellow sooty flame. Quickest check: name the products of clean vs sooty fuel burning.