OCR GCSE Chemistry A, Higher tier Active Recall Guide (J248)
OCR · GCSE
OCR GCSE Chemistry A, Higher tier Active Recall Guide
Every topic of specification J248 written as exam-style questions with the answers printed after them. 1,265 questions across 6 topics and 82 subtopics, at Higher tier, covering Paper 3 and Paper 4.
- OCR
- GCSE
- Specification J248
- 1,265 questions
Guide overview All topics Sample questions Papers and weighting Look inside Questions and answers
What the exam asks of you
OCR GCSE Chemistry A (Gateway Science, specification J248) is one of the three separate sciences and is examined by two written papers of 1 hour 45 minutes and 90 marks each, worth 50% apiece. Paper 3 covers the first half of the topics and Paper 4 the second, with the first half assumed. This is the Higher tier: it carries everything on the Foundation papers plus the higher-tier content, and grades 4 to 9 are available, with an allowed grade 3 for a student who just misses grade 4.
Chemistry at GCSE is a large number of small, precise things: a definition, a test, an equation, a named process. Almost none of it can be worked out in the hall from first principles, which makes recall the whole problem and a question list the instrument that matches it.
| Paper | Covers | Length | Marks | Weighting |
|---|---|---|---|---|
|
Paper 3 Chemistry A Paper 3 |
Chemical Reactions Elements, Compounds and Mixtures Particles |
1 hour 45 minutes | 90 marks | 50% |
|
Paper 4 Chemistry A Paper 4 |
Global Challenges Monitoring and Controlling Chemical Reactions Predicting and Identifying Reactions |
1 hour 45 minutes | 90 marks | 50% |
What is in the guide
All topics
Every topic has its own page with its subtopics, what it covers and sample questions.
Sample questions
Taken from the guide. Answer each one closed book first, then open the answer.
-
Writing formulae of elements and compounds
Sodium chloride is written NaCl even though it has no molecules. What does this formula represent?
Show the answer
The simplest whole-number ratio of the ions in the giant lattice, one sodium ion to one chloride ion. -
Purity, and melting point data
A sample contains nothing but copper atoms. Is it an element, a compound or a mixture, and is it pure?
Show the answer
It is an element, and it is pure because only one kind of atom is present. -
Extracting metals by reduction and by electrolysis
Give a word equation for the reduction of iron(III) oxide by carbon.
Show the answer
Iron(III) oxide + carbon → iron + carbon dioxide. -
Concentration in mol/dm³, and titration
Calculate the mass of sodium hydroxide, relative formula mass 40, in 100 cm³ of a solution of concentration 2.00 mol/dm³.
Show the answer
2.00 × 0.100 = 0.200 mol, and 0.200 × 40 = 8.00 g, given to 3 significant figures. -
The particle model and changes of state
Name the change of state in which a liquid becomes a gas, and the reverse change.
Show the answer
A liquid becoming a gas is boiling or evaporating, and a gas becoming a liquid is condensing. -
Groups 1, 7 and 0, and why they behave as they do
In what form do the elements of Group 7 exist?
Show the answer
As diatomic molecules of two atoms sharing a pair of electrons, such as Cl₂ and Br₂.
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
-
Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
-
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
-
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Look inside
Questions for a subtopic print together and the answers for that section print after them.
- Chemical Reactions276
- Elements, Compounds and Mixtures253
- Global Challenges353
- Monitoring and Controlling Chemical Reactions202
- Particles68
- Predicting and Identifying Reactions113
- In science, what does it mean to say that a substance is pure?
- What does the word 'pure' usually mean when it is used about food or drink in everyday language?
- Why would a carton labelled 'pure orange juice' not count as pure to a chemist?
- Is bottled spring water a pure substance in the scientific sense?
- Can a mixture of two elements ever be described as pure in the scientific sense?
- A sample contains nothing but copper atoms. Is it an element, a compound or a mixture, and is it pure?
- Give an example of a substance that is chemically pure but that many people would not call pure in everyday speech.
- Why do chemists need a stricter definition of purity than the everyday one?
- How does a pure substance behave when it is heated up to its melting point?
- A pure substance is a single element or a single compound, with nothing else mixed into it.
- In everyday use it means nothing has been added, so the product is natural or unadulterated.
- Because orange juice is a mixture of water, sugars, acids and many other compounds rather than one single compound.
- No, because it is a mixture of water with dissolved minerals and gases.
- No, because a pure substance contains only one element or only one compound.
- It is an element, and it is pure because only one kind of atom is present.
- Distilled water containing nothing but H₂O, which some people would describe as processed rather than pure.
- Because properties such as melting point and boiling point only take fixed, predictable values when a single element or compound is present.
- It melts sharply at one fixed temperature.
questions
Scroll sideways to turn through the pages.
Questions students ask first
Gateway or Twenty First Century? Which am I on?
OCR runs two GCSE science suites. Gateway Science is Chemistry A, J248, which is this guide. Twenty First Century Science is Chemistry B, J258 and is organised completely differently.
The code is on your exam timetable. Gateway chemistry topics are numbered C1 to C6.
Higher or Foundation. Which do I need?
This is the Higher tier guide, offering grades 9 to 4, with an allowed 3.
At OCR the tier also changes the paper number. Foundation sits Papers 1 and 2 and Higher sits Papers 3 and 4. You are sitting Paper 3 and Paper 4.
Higher carries everything on the Foundation papers plus the higher-tier content, so a student later moved to Foundation has lost nothing.
I do Combined Science, not separate sciences.
Then you need a different guide. Combined Science A is J250, a double award worth two GCSEs, and it examines less chemistry than the separate Chemistry A. Working from this guide would mean learning content your papers will not ask for.
The one you want is OCR GCSE Combined Science Chemistry, Higher.
Which topics are on which paper?
Paper 3 covers Chemical Reactions, Elements, Compounds and Mixtures, Particles. Paper 4 covers Global Challenges, Monitoring and Controlling Chemical Reactions, Predicting and Identifying Reactions.
The second paper assumes the content of the first, so nothing from the first half is ever safely dropped. The full breakdown is here.
OCR GCSE Chemistry A, Higher tier Active Recall Guide
Every question paired with its answer, grouped by topic and subtopic, ready to work in three passes.