1. 1
   A student is given a series of hydrocarbon samples, including methane, ethane and propane, and asked to identify their type and structure.

   (a)

   Which general formula correctly represents the alkanes?

   [1 mark]

   • ACnH2n
   • BCnH2n+2
   • CCnH2n-2
   • DCnHn

   (b)

   What type of bond joins the carbon atoms together in a saturated hydrocarbon such as an alkane?

   [1 mark]

   • AA single covalent bond only
   • BA double covalent bond
   • CAn ionic bond
   • DA triple covalent bond

   (c)

   Explain what is meant by the term 'saturated hydrocarbon', giving the names of the first three members of this homologous series.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A laboratory technician compares samples of methane, ethane and propane to investigate how their properties change as the number of carbon atoms increases.

   (a)

   A technician is given the molecular formula C3H8. Which alkane does this represent?

   [1 mark]

   • AMethane
   • BEthane
   • CPropane
   • DButane

   (b)

   As the chain length of alkanes increases, how does viscosity generally change?

   [1 mark]

   • AViscosity decreases
   • BViscosity becomes negative
   • CViscosity stays exactly the same
   • DViscosity increases

   (c)

   Describe how the boiling point of alkanes changes as the length of the carbon chain increases.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A fuel company is testing four alkane samples of increasing chain length to decide which fractions are most suitable for use as fuels.

   (a)

   A fuel company compares four alkane samples with increasing numbers of carbon atoms. Describe the general trend in flammability as molecular size increases.

   [3 marks]

   (b)

   Describe, with reference to molecular size, how boiling point, viscosity and flammability of alkanes are related.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A textbook author is writing a chapter to help students distinguish alkanes from other hydrocarbons using different types of chemical formula, and to understand how their properties change with size.

   (a)

   Explain what makes a hydrocarbon 'saturated', and describe how alkanes can be recognised from molecular, displayed and structural formulae, naming the first three members of the series.

   [6 marks]

   (b)

   Explain the trends in boiling point, viscosity and flammability of alkanes as molecular size increases, and explain why these trends matter when choosing an alkane for use as a fuel.

   [6 marks]

   Total for question 4: 12 marks

End of questions