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Hydrocarbon: GCSE Chemistry Definition

Alexandra Brennan

Written by: Alexandra Brennan

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2 minutes

Contents

  1. 1. What is a hydrocarbon?
  2. 2. Hydrocarbon Revision Resources to Ace Your Exams

What is a hydrocarbon?

In GCSE Chemistry, a hydrocarbon is an organic compound consisting of carbon and hydrogen atoms only. Fossil fuels including natural gas, crude oil and coal are made up of hydrocarbons. 

Two families of hydrocarbons are alkanes and alkenes. Alkanes are saturated hydrocarbons; they are hydrocarbons with only single bonds. The first five alkanes in the homologous series are shown below, along with their name and molecular formula. 

Displayed formula

Name

Molecular formula 

Diagram of methane molecule showing a carbon atom in the centre bonded to four hydrogen atoms in a tetrahedral structure, with labels H and C.

methane

CH4

Ethane molecular structure showing two carbon atoms bonded together, each with three hydrogen atoms. Structure depicted in a linear diagram.

ethane

C2H6

Chemical structure of propane, showing three carbon atoms bonded linearly with surrounding hydrogen atoms.

propane

C3H8

Structural formula of butane showing four carbon atoms in a chain with surrounding hydrogen atoms, depicting single covalent bonds.

butane

C4H10

Structural formula of pentane showing five carbon atoms in a chain with hydrogen atoms surrounding them. Copyright text is visible below.

pentane

C6H12

Alkenes are unsaturated hydrocarbons; they do not have only single bonds, they contain one double bond between carbon atoms. The first four alkenes in the homologous series are shown below, along with their name and molecular formula.

Displayed formula

Name

Molecular formula

Ethene molecule structure with two carbon atoms double-bonded and each carbon atom bonded to two hydrogen atoms, depicted with lines.

ethene

C2H4

Structural formula of propene with three carbon atoms. The first carbon is double-bonded to the second, with hydrogen atoms attached.

propene

C3H6

Structural formula of but-1-ene, displaying a chain of four carbon atoms with a double bond between the first two carbons and hydrogen atoms attached.

butene

C4H8

Skeletal formula of butene, showing four carbon atoms in a chain with a double bond between the first two carbons, and single bonds with hydrogen atoms.

pentene

C5H10

All hydrocarbons can undergo combustion. Alkanes undergo complete combustion to produce carbon dioxide and water. Alkanes usually undergo incomplete combustion to produce carbon monoxide and / or carbon and water. To distinguish between alkanes and alkenes, bromine water is used. Bromine water decolourises in alkenes but remains orange in alkanes.

Hydrocarbon Revision Resources to Ace Your Exams

Most exam boards require you to be able to draw, name and identify alkanes and alkenes. You can revise everything on this topic using our hydrocarbon revision notes. To make sure you ace this topic in your exams, you can also practice our hydrocarbon topic questions.

Explore Our GCSE Chemistry Revision Resources

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Alexandra Brennan

Author: Alexandra Brennan

Expertise: Chemistry

Alex studied Biochemistry at Newcastle University before embarking upon a career in teaching. With nearly 10 years of teaching experience, Alex has had several roles including Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s passion for creating engaging content that enables students to succeed in exams drove her to pursue a career outside of the classroom at SME.

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