Hydrocarbons

Question 1

Explain the properties of long hydrocarbons.

Answer 1

• They contain a high number of carbon and hydrogen atoms
• They have high boiling points as they have many intermolecular forces to overcome
• They are much harder to ignite since they have high boiling points, usually liquids at room temp
• They have a high viscosity, and the liquid is difficult to flow due to strong forces between hydrocarbon molecules

Question 2

Describe what is meant by a ‘homologous series’.

Answer 2

A family of molecules which have the same general formula and share similar chemical properties

Question 3

Describe the characteristics of compounds within a homologous series.

Answer 3

They:

• have the same general formula
• differ by CH₂ in molecular formulae from neighbouring compounds
• show a gradual variation in physical properties, as exemplified by their boiling points
• have similar chemical properties

Question 4

Describe the process of complete combustion.

Answer 4

• Reactions that happen when hydrocarbons are burned in oxygen, giving out lots of energy
• The only products are carbon dioxide and water