hydrocarbons imp.

• What type of reaction occurs when hydrocarbons are burnt in oxygen?

  Exothermic reaction
• What are the products of complete combustion of hydrocarbons?

  Carbon dioxide and water
• What is incomplete combustion?

  Burning hydrocarbons with insufficient oxygen
• What is a homologous series?

  A family of molecules with the same formula
• How do the molecular formulas of neighboring compounds in a homologous series differ?

  By a $CH_2$ unit
• What happens to the boiling point as the size of a hydrocarbon increases?

  The boiling point increases
• What determines the fraction of a hydrocarbon?

  The size of the hydrocarbon
• What influences the physical properties of hydrocarbons?

  The strength of intermolecular forces
• How does the boiling point relate to the size of hydrocarbons in fractions?

  Larger molecules have higher boiling points
• Why are shorter hydrocarbon fractions easier to ignite?

  They have lower boiling points
• What happens to some hydrocarbon molecules at room temperature?

  They mix with oxygen to form gas
• What is viscosity?

  How easily a substance flows
• How do intermolecular forces affect viscosity?

  Stronger forces make it harder to flow
• What is the viscosity of fractions containing longer hydrocarbons?

  They have high viscosity
• What is the viscosity of fractions with shorter hydrocarbons?

  They have lower viscosity