Good Chemistry revision starts from evidence of what you get wrong, not from the list of topics. You attempt, mark, sort your errors by cause, and retest with a fresh question. This page shows the method with a worked log entry and a weekly cycle.
Chemistry has a particular trap. A topic can feel familiar because you have read it, while the skill of using it in a new question is still missing.
What should you check before you start revising?
Confirm your scope first. Open the Cambridge Chemistry 0620 page, find the syllabus for your exam year and check the content for your route.
Then check each resource you plan to use. If a workbook, video series or set of notes was written for an earlier or different syllabus, compare its contents with the current list. The syllabus and exam-year navigator helps you keep a record of what you confirmed.
Your school or exam centre decides your route, and Cambridge holds the official details.
How do you sort a mistake?
Every lost mark belongs to one of five causes. The repair differs for each.
| Cause | What it looks like | What repairs it |
|---|---|---|
| Missing fact | You cannot recall a test result or a reactivity order | Retrieval practice, with a reason attached |
| Particle idea missing | You describe a trend but not what the particles do | Rebuild the explanation chain |
| Equation or formula error | Wrong formula or unbalanced equation | Atom table, see balancing without changing subscripts |
| Calculation error | Wrong ratio, unit or conversion | Labelled ratio line, see the mole ratio help page |
| Answer does not fit the question | A correct fact that does not answer what was asked | Underline the command word and the quantity asked for |
The mistake log and retest queue lets you record these privately in your browser, group them by cause and queue a fresh question for later.
A worked example of one log entry
Task. “Explain why the rate of reaction increases when the concentration of hydrochloric acid is increased.”
Student answer. “The particles have more energy, so they react faster.”
What is wrong. Concentration changes the number of particles in a given volume, not the energy each one has. Energy would be the right answer for a temperature change. The student used a correct idea for the wrong variable.
Log entry.
- Cause: particle idea matched to the wrong variable.
- Repair: write the chain for each variable. More particles in the same volume, so more frequent collisions, so more successful collisions each second, so a higher rate.
- Retest in 3 days: a fresh question that changes the pressure of a gas instead of the concentration of a solution. The chain is the same, so the retest shows whether you can transfer it.
A log entry should always finish with a retest date. Without it, the entry is a record rather than a repair.
How does a weekly revision cycle work?
One workable cycle uses four blocks a week.
- Retrieve. Answer questions from last week’s topic without notes, then mark honestly.
- New or returning topic. Study one topic through its lessons and a short practice set.
- Repair. Work on the most frequent cause in your log, using a lesson and two new questions.
- Mixed check. Use the original mixed-practice builder or the original practice page to test several topics together.
If you have only three blocks, drop the new topic before you drop repair. For the order of topics, see the study route.
What about facts and calculations?
Keep them apart. Facts, such as the tests for gases and the reactivity order, need short daily retrieval, with cards or a blank table you fill in.
Calculations need full-line practice. Write the ratio line, the units and the check every time, even when the question is easy. Speed comes from a routine, not from skipping lines.
When does revision need a teacher?
Revision by yourself works well for missing facts and for errors you can see in the mark scheme.
It is harder when the error sits in how you think. If you keep choosing the wrong substance for a ratio, a teacher can ask you to reason aloud and catch the moment it goes wrong.
That is what online one-to-one Chemistry tuition is for. The Chemistry learning guide shows which topics feed which.