Hydrocarbons and carbon chains — Chemistry, 14–17 years
Carbon can join to itself in chains and rings, making an enormous family of substances. Chemistry, 14–17 years.
A carbon skeleton
Carbon atoms can link into straight chains, branches or rings, while hydrogen fills the remaining bonds. A molecule with only carbon and hydrogen is a hydrocarbon; methane, petrol molecules and the gas in a camping stove belong to this family.
Why structure matters
Chemists needed a way to organise thousands of carbon substances that seemed unrelated. Counting carbons and noticing single or multiple bonds gives clues about boiling point, reactivity and whether a molecule is saturated, without testing every substance from scratch.
Reading propane
Take propane, C₃H₈. First place three carbon atoms in a chain, giving two carbon–carbon bonds. Each end carbon then needs three hydrogen atoms, and the middle carbon needs two, so the total is 3 + 2 + 3 = 8: C₃H₈.
A formula is not a shape
A common mistake is to think that C₄H₁₀ describes only one molecule. The same formula can make straight-chain butane or branched methylpropane: the atoms are counted equally, but connected differently, so their properties are not identical.
Fuel and feedstock
Hydrocarbons are burned in petrol engines, boilers and camping stoves because their reactions release useful energy. They are also starting materials for plastics, paints and medicines. Their usefulness does not remove the costs of extraction, pollution or carbon dioxide emissions.
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