Elements, compounds and mixtures - Six-mark questions
Six-mark questions are extended open response questions. These require longer answers than the structured questions with fewer marks. It is wise to plan your answer rather than rushing straight into it, otherwise you may stray away from the key points.
Six-mark questions are marked using a levels-based mark scheme because they are 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
You are likely to see command words such as:
- 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. This means they 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.
Remember that the topics covered in the first paper are assumed knowledge for the second paper, so questions in the second paper may need knowledge and understanding of those topics too.
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.
Writing six-mark answers with Dr Alex Lathbridge
Listen to the full series on 大象传媒 Sounds.
How to write six-mark answers in your science GCSE exams.
Sample question 1 - Foundation
Question
A student is separating a mixture of three solid substances (A, B and C).
Look at the table. It gives information about these substances.
| Substance | Colour | Is it magnetic? | Melting point (掳C) | Is it soluble in water? |
| A | grey | yes | 1535 | no |
| B | white | no | 801 | yes |
| C | yellow | no | 1427 | no |
| Substance | A |
|---|---|
| Colour | grey |
| Is it magnetic? | yes |
| Melting point (掳C) | 1535 |
| Is it soluble in water? | no |
| Substance | B |
|---|---|
| Colour | white |
| Is it magnetic? | no |
| Melting point (掳C) | 801 |
| Is it soluble in water? | yes |
| Substance | C |
|---|---|
| Colour | yellow |
| Is it magnetic? | no |
| Melting point (掳C) | 1427 |
| Is it soluble in water? | no |
Suggest how the student can separate the mixture to get pure, dry samples of substances A, B and C.
Explain why your methods work.
[6 marks]
OCR Gateway Science, GCE Chemistry, Paper J248, 2016.
The following are valid 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.
Separating A from B and C:
- use a magnet
- A is magnetic but B and C are not
- A sticks to a magnet/B and C do not stick to a magnet
Separating B from C:
- add water
- B dissolves but C does not
- filter the mixture of B, C and water
- solid C stays in filter paper
- C is insoluble in water
- wash C with water and allow to dry
- B passes through filter paper in solution
- B is soluble in water
- heat filtrate/solution B
- water evaporates to leave dry B
- melting point of B/C is higher than the boiling point of water
Sample question 2 - Foundation
Question
Describe how the arrangement of elements in the periodic table is related to the atomic structure of their atoms.
[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 following are valid 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.
- in the periodic table the elements are arranged in order of increasing atomic number/proton number
- the horizontal rows are called periods
- the atomic number of the elements increases steadily across a period
- elements in the same period have the same number of electron shells
- the vertical columns are groups
- elements in the same group have similar chemical properties
- atoms of elements in the same group have the same number of outer electrons
- the number of outer electrons is equal to the group number
- the number of occupied electron shells increases down a group
Sample question 3 - Higher
Question
Food colourings contain a mixture of water soluble dyes. Devise a method to separate the dyes in a sample of food colouring. Explain how this method works.
[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 following are valid 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.
- draw a horizontal line in pencil near the bottom of a piece of chromatography paper
- add a spot of food colouring on the line
- place the paper in a container with some water/solvent
- allow the water/solvent to travel through the paper
- remove the paper before the water/solvent reaches the top of the paper, and allow it to dry
- the spots on the paper will indicate the number and type of dyes present
- paper chromatography uses a mobile phase (the solvent/water)
- and a stationary phase (contained on the paper)
- forces of attraction between the dyes and these phases cause the dyes to move at different rate over the paper
- depends on solubility of the dyes in mobile and static phase
Sample question 4 - Higher
Question
The table shows the melting points of different substances.
| Substance | Melting point (掳C) |
| Sodium chloride | 801 |
| Water | 100 |
| Diamond | 3730 |
| Substance | Sodium chloride |
|---|---|
| Melting point (掳C) | 801 |
| Substance | Water |
|---|---|
| Melting point (掳C) | 100 |
| Substance | Diamond |
|---|---|
| Melting point (掳C) | 3730 |
Explain these results by referring to the structures of the substances.
[6 marks]
OCR Gateway Science, GCE Chemistry, Paper J248, 2016 - Higher.
The following are valid 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.
- sodium chloride contains ions in a regular lattice
- there are electrostatic forces of attraction between oppositely charged ions
- the forces/ionic bonds are strong
- a lot of energy is needed to overcome/break these forces/bonds
- water exists as simple molecules
- there are weak intermolecular forces between molecules
- less energy needed to overcome these forces
- diamond exists as a giant covalent structure
- there are covalent bonds between atoms
- many strong covalent bonds
- a very large amount of energy is needed to break bonds