Properties of Hydrocarbons and Molecular Size

Key Concepts

• The properties of hydrocarbons are significantly influenced by the size of their molecules.
• Understanding these properties is crucial for exams.

Alkanes

• Family of hydrocarbons.
• First four alkanes:
  • Methane
  • Ethane
  • Propane
  • Butane
• Be able to draw these molecules for exams.

Key Properties of Hydrocarbons

1. Viscosity

• Definition: Thickness of a fluid; high viscosity means the fluid flows slowly (e.g., honey).
• Size Influence:
  • Larger hydrocarbon molecules have higher viscosity.
  • Long chain hydrocarbons are extremely viscous and flow slowly.

2. Flammability

• Definition: Ease with which a hydrocarbon combusts (burns).
• Size Influence:
  • Short chain hydrocarbons are very flammable (e.g., methane used in gas burners).
  • Larger hydrocarbon molecules are less flammable; long chain hydrocarbons are difficult to burn.

3. Boiling Point

• Definition: Temperature at which a liquid turns to gas.
• Size Influence:
  • Short chain hydrocarbons have low boiling points and are gases at room temperature.
  • As molecular size increases, boiling point also increases.
  • Very long chain hydrocarbons have high boiling points.

Additional Resources

• For further practice, refer to the questions on hydrocarbon properties in the vision workbook.