AQA GCSE FOUNDATION Chemistry: Introduction to Hydrocarbons

AQA GCSE Foundation Chemistry: Introduction to Hydrocarbons

What are Hydrocarbons?

Hydrocarbons are compounds made up of only carbon and hydrogen atoms. They are the building blocks of many important fuels and materials.

Alkanes

• General Formula: CnH2n+2
• Saturated: They have only single bonds between carbon atoms.
• Properties:
  • They are relatively unreactive.
  • They are good fuels, burning readily in air to produce carbon dioxide and water.
  • Their boiling point increases with the number of carbon atoms.
• Examples:
  • Methane (CH4) - The simplest alkane, found in natural gas.
  • Ethane (C2H6) - A component of natural gas.
  • Propane (C3H8) - Used as a fuel for cooking and heating.
  • Butane (C4H10) - Found in lighters and camping gas.

Alkenes

• General Formula: CnH2n
• Unsaturated: They have at least one double bond between carbon atoms.
• Properties:
  • More reactive than alkanes due to the double bond.
  • They can undergo addition reactions where the double bond breaks and new atoms are added.
  • They are used to make polymers, such as plastics.
• Examples:
  • Ethene (C2H4) - The simplest alkene, used to make plastics.
  • Propene (C3H6) - Used to make polypropylene.
  • Butene (C4H8) - Used in the production of synthetic rubber.

Key Differences between Alkanes and Alkenes

How to Identify Alkanes and Alkenes

• Look at the formula: Alkanes have a general formula of CnH2n+2, while alkenes have a general formula of CnH2n.
• Look for double bonds: Alkenes have at least one double bond between carbon atoms.

Example

Compound: C4H8

• General Formula: Matches the general formula for alkenes (CnH2n).
• Double Bond: It has a double bond between two carbon atoms.

Conclusion: The compound is an alkene.