Year 9 Science Study Notes – Hydrocarbons

Organic compounds

Compounds that contain carbon bonded to hydrogen (C–H). Examples include CH₄, C₂H₆, C₃H₈.

Inorganic compounds

Compounds that do not contain carbon bonded to hydrogen. Examples include H₂O, NaCl, CO₂.

Memory rule for organic compounds

Carbon + Hydrogen = Organic.

Alkane formula

The general formula for alkanes is CₙH₂ₙ₊₂.

Complete combustion

The reaction of a hydrocarbon with oxygen, producing carbon dioxide and water.

Incomplete combustion

The reaction of a hydrocarbon with limited oxygen, producing carbon monoxide or carbon, and water.

Memory trick for complete combustion

Complete combustion produces CO₂, H₂O, and more energy.

Purpose of fractional distillation

To separate crude oil into different hydrocarbons.

Steps in fractional distillation

1. Heat crude oil 2. Hydrocarbons evaporate 3. Vapours rise into the fractionating column 4. Vapours cool 5. Different hydrocarbons condense at different temperatures 6. Fractions are collected.

Why fractional distillation works

Because different hydrocarbons have different boiling points.

Uses of hydrocarbons

1. Transport (petrol, diesel, vehicle fuel) 2. Materials (polymers, industrial chemicals, cosmetics) 3. Energy (electricity generation, heating, fuel for homes).

TME acronym

Transport • Materials • Energy.

Products of incomplete combustion

Carbon monoxide or carbon, and water.

Reason crude oil can be separated by fractional distillation

Different hydrocarbons have different boiling points.

Hexane formula

C₆H₁₄.