Six-mark questions

Six-mark questions are extended open response questions. These require longer answers than the structured questions. It is wise to plan your answer rather than rushing straight into it, otherwise you may stray away from the key points.

Most questions on exam papers have mark schemes that give key points that are given marks. The six-mark questions are marked differently: they use a levels-based mark scheme. This type of mark scheme is used because these questions are more open-ended. To gain full marks, you need to:

  • support explanations using scientific knowledge and understanding
  • use appropriate scientific words and terms
  • write clearly and link ideas in a logical way
  • maintain a sustained line of reasoning, rather than getting lost or bogged down

Six-mark questions often use these command words:

  • Describe – you need to give an account but no reason
  • Explain – you must give reasons or explanations
  • Devise – you must plan or invent a procedure using your scientific knowledge and understanding
  • Evaluate – you must review information, including identifying strengths and weaknesses, and make a supported conclusion

Six-mark questions may be synoptic questions. These questions bring together ideas from two or more topics. For example, a question about fertilisers could include ideas about covalent substances, acids and alkalis, chemical calculations and effects on the environment.

The answers shown here give marking points as bullet points. You do not usually need to include all of them to gain six marks, but you do need to write in full sentences, linking them logically and clearly.

Answers are placed in three marking bands:

  • 1-2 marks for answers showing limited content and reasoning and with significant omissions.
  • 3-4 marks for answers that give some relevant points, with linking and reasoning and with fewer omissions.
  • 5-6 marks for answers that link most of the relevant points, with good links and reasoning. They will have few, if any, omissions.

Sample question 1 - Higher


Magnesium burns in air with a bright white flame to give a white powder called magnesium oxide.

Owain carried out an experiment to work out the formula of magnesium oxide.

He weighed a crucible, with its lid, then put a sample of magnesium ribbon into the crucible, put the lid on, and weighed it again.

He heated the crucible over a Bunsen burner for five minutes, and let it cool down. Then he measured the mass of the crucible and contents again.

The table shows Owain's data.

Mass of crucible and lid (g)19.80
Mass of crucible, lid and magnesium (g)20.28
Mass of crucible, lid and product after heating for 5 minutes (g)20.44

Owain expected the formula of magnesium oxide to be MgO.

Use the data to calculate the simplest formula for magnesium oxide and explain possible reasons for the unexpected results in his experiment.

You can assume that no product was spilt and that all weighings were carried out correctly. [6 marks]

Question courtesy of Eduqas.

Your answer should include the following:

Ar(Mg) = 24; Ar (O) = 16

  • calculation of mass of magnesium at the start
    • = 20.28 g - 19.80 g = 0.48 g
  • calculation of mass of oxygen that has combined with the magnesium
    • = 20.44 g - 20.28 g = 0.16 g
  • conversion of mass of magnesium to number of moles
    • = mass ÷ Ar = 0.48 g ÷ 24 = 0.02 moles
  • conversion of mass of oxygen to number of moles
    • = mass ÷ Ar = 0.16 g ÷ 16 = 0.01 moles
  • calculation of lowest ratio between Mg and O
    • = 0.02 : 0.01 = 2 : 1
  • conversion to empirical formula as Mg2O
  • consideration of possible errors, which should acknowledge that the amount of oxygen being combined with the magnesium is less than expected eg:
    • the magnesium used was already partly oxidised, so did not all react with oxygen
    • the magnesium was not heated for long enough for it all to react with oxygen
    • the lid was not lifted, so not enough oxygen was present to react with the magnesium
    • some magnesium reacted with nitrogen in the air, rather than with oxygen