Alkanes

ChemistryAQAGCSEUnit: Organic Chemistry
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The basics

The Simplest Carbon Family

⛓️ The Simplest Carbon Family

Carbon is special. It can bond to four other atoms at once, and it loves bonding to other carbon atoms. This lets it form chains — short chains, long chains, branched chains, rings...

The alkanes are the simplest family of carbon compounds. They're like the "basic" hydrocarbons — just carbon and hydrogen, with only single bonds. Methane (natural gas), propane (BBQ gas), and petrol are all alkanes!

🔗 The Chain Link Analogy

Alkanes are like a chain of people holding hands! Each carbon (person) can hold hands with 4 others. In a chain, they hold two carbons and fill the rest with hydrogens. The longer the chain, the stronger the forces between molecules — that's why longer alkanes have higher boiling points (they "stick together" more)!

Exam tip

Earn the mark scheme marks

🧠 Memory Aid: MEPB — The First Four Alkanes

Remember the first four alkanes using the phrase:

Many Elephants Play Badminton

  • Methane — CH₄ (1 carbon)
  • Ethane — C₂H₆ (2 carbons)
  • Propane — C₃H₈ (3 carbons)
  • Butane — C₄H₁₀ (4 carbons)

To use the general formula CₙH₂ₙ₊₂: double the number of carbons, then add 2. For propane (n=3): 2×3+2 = 8. Formula = C₃H₈. Check: 3 carbons and 8 hydrogens — correct!

Now try it yourself

Quiz · Question 1 of 20

What is the general formula for the alkane homologous series?

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