Elements, compounds and mixtures - Structured questions
Simple recall questions are usually worth one mark. They are often have command words like 'Give...', 'State...', 'Name...' or 'Identify...'. Some questions may ask you to state two things, rather than just one, and will be worth two marks.
Structured questions, with command words such as 'Describe...' or 'Explain...', will be worth two or more marks:
- if you are asked to describe something, you need to give an account but no reason
- if you are asked to explain something, you must give reasons or explanations
More complex structured questions will be worth three to five marks. They include questions with complex descriptions and explanations, questions in which you need to compare and contrast two different things, or calculations with several stages.
The mark schemes given here may show answers as bullet points. This is to show clearly how a mark can be obtained. However, it is important that your answer is written in a logical, linked way.
Learn about command words with Dr Alex Lathbridge
Listen to the full series on 大象传媒 Sounds.
Understanding the different command words in your science GCSE exams.
Sample question 1 - Foundation
Question
Nanoparticles are used as catalysts.
Describe a property of nanoparticles that make them useful as catalysts.
[2 marks]
OCR Gateway Science, GCE Chemistry, Paper J248, 2016.
Large surface area [1 mark] to volume ratio [1 mark]
Sample question 2 - Foundation
Question
Diamond and graphite are two forms of carbon.
Diamond does not conduct electricity. Graphite is a good conductor of electricity.
Use ideas about structure and bonding in diamond and graphite to explain these observations.
[3 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.
- in diamond, each C atom is bonded to 4 other atoms but in graphite each C atom is bonded to 3 other atoms [1 mark]
- therefore there are delocalised electrons in graphite (but not in diamond) [1 mark]
- delocalised electrons in graphite can move [1 mark]
Sample question 3 - Higher
Question
Sodium chloride has a melting point of 801 掳C but water melts at just 0 掳C.
Explain why, in terms of structure and bonding.
[4 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.
- strong electrostatic forces of attraction between ions in sodium chloride [1 mark] must be broken to melt it [1 mark]
- weak intermolecular forces/weak forces between water molecules [1 mark] are easily overcome/broken [1 mark]