Year 9 Science Study Notes – Hydrocarbons
Based on the Materials Assignment test topics.
Organic vs Inorganic
Organic compounds
Contain carbon bonded to hydrogen (C–H)
Examples: CH₄, C₂H₆, C₃H₈
Inorganic compounds
Do not contain carbon bonded to hydrogen
Examples: H₂O, NaCl, CO₂
Memory rule: Carbon + Hydrogen = Organic
Alkanes (C1–C8)
Name | Formula |
|---|---|
Methane | CH₄ |
Ethane | C₂H₆ |
Propane | C₃H₈ |
Butane | C₄H₁₀ |
Pentane | C₅H₁₂ |
Hexane | C₆H₁₄ |
Heptane | C₇H₁₆ |
Octane | C₈H₁₈ |
Pattern: CₙH₂ₙ₊₂
Complete vs Incomplete Combustion
Complete | Incomplete |
|---|---|
Enough oxygen | Not enough oxygen |
CO₂ + H₂O | CO/Carbon + H₂O |
More energy | Less energy |
Cleaner flame | Smoky flame |
Word Equations
Complete combustion
Hydrocarbon + Oxygen → Carbon dioxide + Water
Incomplete combustion
Hydrocarbon + Limited oxygen → Carbon monoxide/Carbon + Water
Memory trick: Complete = CO₂ + H₂O + More energy
Fractional Distillation
Purpose: Separate crude oil into different hydrocarbons.
Steps
Heat crude oil
Hydrocarbons evaporate
Vapours rise into the fractionating column
Vapours cool
Different hydrocarbons condense at different temperatures
Fractions are collected
Why does it work? Different hydrocarbons have different boiling points.
Uses of Hydrocarbons
Transport
Petrol
Diesel
Vehicle fuel
Materials
Polymers (plastics)
Industrial chemicals
Cosmetics
Energy
Electricity generation
Heating
Fuel for homes
Memory: TME = Transport • Materials • Energy
5-Mark Quick Revision
Organic = Carbon + Hydrogen
Alkane formula = CₙH₂ₙ₊₂
Complete combustion = CO₂ + H₂O + More energy
Incomplete combustion = CO/Carbon + H₂O + Less energy
Fractional distillation = Heat → Evaporate → Rise → Cool → Condense → Collect
Practice Questions
What is the formula of hexane?
What condition is needed for complete combustion?
Name the products of incomplete combustion.
Why can crude oil be separated by fractional distillation?
List the three main uses of hydrocarbons.