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.

These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.

Sample question 1 - Foundation

Question

Methane is used as a fuel in most homes in the UK. It is burned in a boiler which is commonly located on an external wall in the kitchen. Air is drawn into the boiler from the outside through a tube called a flue, which is also used to get rid of the waste gases from the boiler.

Why is it essential that the flue is clear of any obstructions and what would be the consequences of a faulty or blocked flue? [6 marks]

The following are vaild points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.

  • A blocked flue would decrease the supply of air/oxygen to the boiler
  • This would lead to incomplete combustion
  • Incomplete combustion releases less energy
  • Incomplete combustion produces particulate carbon
  • …which is dirty and can cause breathing difficulties
  • Incomplete combustion produces carbon monoxide
  • …which is poisonous
  • …because it binds to haemoglobin the blood and prevents it from carrying oxygen
  • …but it is colourless and odourless, so not easy to detect
  • …so the people living in the house would be in danger of poisoning/death

Sample question 2 - Foundation

Question

Compare fractional distillation to cracking. In your answer, include, for each process:

  • A brief outline of the purpose of the process
  • The names of the types of changes involved
  • How the substances that are produced are useful

[6 marks]

The following are vaild points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.

  • Fractional distillation separates the hydrocarbons in crude oil into fractions but...
  • ...cracking breaks up big hydrocarbon molecules to smaller ones.
  • Fractional distillation involves changes of state/evaporation and condensation but...
  • ...cracking involves a chemical reaction.
  • Fractional distillation makes fuels but...
  • ....cracking makes fuels and alkenes for making polymers/other useful substances.

Sample question 3 - Higher

Question

This question is about propane, C3H8 and heptane, C7H16.

Predict how the properties of heptane compare to the properties of propane.

In your answer, include reasons for your predictions and balanced chemical equations. [6 marks]

The following are vaild points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.

  • Since the complete combustion of alkanes makes carbon dioxide and water, the complete combustion of both propane and heptane makes carbon dioxide and water
  • The equation for the complete combustion of propane is C3H8+ 5O2 → 3CO2 + 4H2O
  • The equation for the complete combustion of heptane is
  • C7H16+ 15O2 → 3CO2 + 4H2O
  • Since boiling point increases with molecular size, the boiling point of heptane is higher than the boiling point of propane
  • Since flammability decreases with molecular size, it is easier to ignite propane than it is to ignite butane
  • Since viscosity increases with molecular size, heptane is more viscous than propane

Sample question 4 - Higher

Question

In one cracking reaction, the alkane with the formula C10H22 makes three products.

The formulae of the products are propene, C3H6, and heptane, C7H16.

Write a balanced chemical equation for the cracking reaction, and predict the properties and uses of the two products. Give reasons for your predictions. [6 marks]

The following are vaild points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.

  • The equation for the complete combustion of propane is C10H22 → C7H16 + C3H6
  • Heptane burns to make carbon dioxide and water
  • Heptane is used as a fuel, since its combustion releases energy
  • Propene reacts with bromine water, making orange bromine water colourless
  • Propene is an alkene and heptane is an alkane, so propene is more reactive than heptane
  • Propene is used to make polymers and other chemicals