1. 1
   A student is drawing the displayed structural formula of propene as part of a homework exercise on unsaturated hydrocarbons.

   (a)

   A student is asked to write the molecular formula of propene. Which formula is correct?

   [1 mark]

   • AC3H8
   • BC3H6
   • CC2H4
   • DC3H4

   (b)

   In a displayed structural formula, what does the symbol '=' between two carbon atoms represent?

   [1 mark]

   • AA single covalent bond
   • BNo bond at all
   • CAn ionic bond
   • DA double covalent bond

   (c)

   Describe the general feature that all alkene molecules, such as propene, have in common.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A teacher displays the structural formulae of ethene and ethane on the board and asks students to identify the difference between the two molecules.

   (a)

   A teacher shows displayed formulae for ethene and ethane side by side. Which feature distinguishes the ethene structure from the ethane structure?

   [1 mark]

   • AEthene has a double bond between the two carbon atoms; ethane has only a single bond
   • BEthene has more carbon atoms than ethane
   • CEthene contains a nitrogen atom; ethane does not
   • DEthane has a double bond between the two carbon atoms; ethene does not

   (b)

   Which molecular formula below fits the general formula for an alkene?

   [1 mark]

   • AC4H10
   • BC4H12
   • CC4H8
   • DC4H6

   (c)

   Explain how an alkene can be identified from its structural or displayed formula.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A chemist is given a list of molecular formulae for several hydrocarbons and must decide which of them represent alkenes rather than alkanes.

   (a)

   A chemist is given a list of molecular formulae and asked to identify which represent alkenes. Explain what makes a hydrocarbon molecule 'unsaturated', describing the type of bond involved and the general formula that applies.

   [3 marks]

   (b)

   Describe how propene, an alkene, can be represented using its molecular formula, its displayed formula and its structural formula.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A curriculum developer is writing revision materials to help students understand and represent unsaturated hydrocarbon molecules such as propene in different ways.

   (a)

   Explain what is meant by an 'unsaturated' hydrocarbon, and describe how alkene molecules can be represented using molecular, displayed and structural formulae, using propene as an example.

   [6 marks]

   (b)

   Compare how alkanes and alkenes are represented in structural and displayed formulae, and explain the significance of the double bond notation in distinguishing the two families of hydrocarbon.

   [6 marks]

   Total for question 4: 12 marks

End of questions