Introduction to Organic Chemistry
Year 9 🌿 Materials & Environment Describe hydrocarbons; crude oil fractions; fractional distillation.
⛽ Hydrocarbons & Crude Oil
Hydrocarbons contain only carbon and hydrogen. Crude oil is a mixture of hydrocarbons separated by fractional distillation.
Fractions (short to long chain): Refinery gases (1-4C) → Petrol (5-12C) → Kerosene (12-16C) → Diesel (14-20C) → Fuel oil (20-50C) → Bitumen (50+C).
Short-chain hydrocarbons: lower boiling point, less viscous, more flammable, more volatile.
🔗 Alkanes
Alkanes are saturated hydrocarbons (all C-C single bonds). General formula: CₙH₂ₙ₊₂.
| n | Name | Formula | State at RT |
|---|---|---|---|
| 1 | Methane | CH₄ | Gas |
| 2 | Ethane | C₂H₆ | Gas |
| 3 | Propane | C₃H₈ | Gas |
| 4 | Butane | C₄H₁₀ | Gas |
| 5 | Pentane | C₅H₁₂ | Liquid |
🔥 Cracking
Cracking breaks long-chain hydrocarbons into shorter, more useful alkanes and alkenes (using heat + catalyst).
Example of Cracking
$$\text{C}_{10}\text{H}_{22} \xrightarrow{\text{heat + catalyst}} \text{C}_8\text{H}_{18} + \text{C}_2\text{H}_4 \text{ (ethene)}$$ Alkenes (C=C double bond) are more reactive than alkanes. Test: decolourise bromine water (orange → colourless).
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Interactive Demonstration — Introduction to Organic Chemistry
Explore the first four alkanes and their structural formulas.
⛽ Hydrocarbon Formula Calculator
Find molecular formula and Mr for alkanes (CₙH₂ₙ₊₂).