Six-mark questions

Six-mark questions are extended open response questions. These require longer answers than the structured questions that have fewer marks. It is wise to plan your answer first by making some notes. This will help you to include all the key points.

To gain full marks, you need to:

  • support explanations using scientific knowledge and understanding
  • use appropriate scientific words
  • write clearly and link ideas in a logical way
  • maintain a sustained line of reasoning

Six-mark questions often use these command words:

  • Describe means you should recall facts, events or processes accurately. You might need to give an account of what something looked like, or what happened.
  • Explain means you need to make something clear, or state the reasons for something happening.
  • Compare means you need to describe similarities and differences between things. If you are asked to compare X and Y, write down something about X and something about Y, and give a comparison. Do not just write about X only or Y only.
  • Evaluate means you must use information supplied, or your own knowledge, to consider the evidence for and against or to identify strengths and weaknesses. You must then complete your answer with a conclusion, stating which is better and why, for example.

Six-mark questions may be synoptic questions, which 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 sentences, linking them logically and clearly.

Sample question 1 - Foundation

Question

A student investigated the rate of reaction between magnesium and dilute hydrochloric acid. The student used the apparatus shown in the diagram to collect the gas produced.

Gas syringe into conical flask of dilute hydrochloric acid and magnesium

Outline a plan to investigate how the rate of this reaction changed when the concentration of the hydrochloric acid was changed.

  • Describe how you would do the investigation and the measurements you would take.
  • Describe how you would make it a fair test.
  • You do not need to write about safety precautions.

[6 marks]

This question is AQA material which is reproduced by permission of AQA.

  • remove bung and add magnesium
  • start stopclock/timer
  • measure volume of gas at fixed time intervals
  • repeat with different concentrations of acid
  • control volume of acid
  • control initial temperature of acid
  • control amount/mass/length/particle size of magnesium

[6]

Sample question 2 - Foundation

Question

A pair of students are investigating rates of reaction using the reaction between calcium carbonate and dilute sulfuric acid. In the first experiment, they change the size of the calcium carbonate particles, using large lumps, small lumps and powder.

In the second experiment, they change the concentration of the acid. Predict their conclusions from both experiments, and explain your predictions using ideas about collisions between particles. [6 marks]

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

First experiment:

  • powder will give the fastest reaction
  • large lumps will give the slowest reaction
  • powders have a larger surface area
  • therefore collisions with the acid will be more frequent

Second experiment:

  • the highest concentration will give the fastest reaction
  • increasing the concentration of the acid means that the acid particles are more crowded
  • therefore collisions are more frequent

[6]

Sample question 3 - Higher

Question

A student investigated the reaction between 0.12 g of magnesium ribbon and excess hydrochloric acid at room temperature. She calculated the initial rate of reaction was 0.02 cm3/s and the total volume of gas produced was 120 cm3. Predict and explain the effect of using 0.24 g of magnesium powder at a temperature of 50°C. [6 marks]

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

The effect of doubling the mass of the limiting reactant:

  • twice as many moles of the limiting reactant
  • therefore there will be twice the volume of gas produced (240 cm3)

The effect of using powder:

  • higher surface area
  • therefore collisions will be more frequent
  • therefore rate of reaction will be faster (greater than 0.02 cm3/s)

The effect of using a higher temperature:

  • particles have more energy
  • therefore collisions are more frequent
  • and a greater proportion of collisions will be successful
  • therefore the rate of reaction will be faster (greater than 0.02 cm3/s)

[6]

Sample question 4 - Higher

Question

Methanol (CH3OH) is a useful chemical feedstock which is made in a reversible reaction.

CO(g) + 2H2(g) ⇌ CH3OH(g)

The forward reaction is exothermic. Use le Chatelier's principle to predict the conditions that would produce the highest yield of methanol. Explain why these conditions may not actually be chosen in industry. [6 marks]

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

The effect of pressure:

  • increasing pressure will favour the side with the fewest moles of gas
  • increasing the pressure increases the yield of methanol
  • but a high yield is more expensive
  • a compromise pressure is chosen

The effect of temperature:

  • increasing temperature will favour the endothermic direction
  • increasing the temperature will decrease the yield of methanol
  • a low temperature will maximise the yield of methanol
  • however, a low temperature will give a slow reaction rate
  • a compromise temperature is chosen

[6]