Active recall for chemistry: how to revise GCSE, IGCSE, Class 10 and AP chemistry so it stays, with the question banks, the retrieval schedule and the mistakes that make it fail

Most chemistry revision is re-reading: the notes, the textbook, the revision guide with the highlighter. It feels like learning, because the material looks familiar, and it produces almost nothing in the exam, because familiarity is not memory. Active recall for chemistry is the opposite: closing the book and pulling the material out, in writing, from memory, then checking. It is the single revision method with the strongest evidence behind it, and chemistry, being a subject of definitions, trends, equations and calculations, is where it pays most. This post explains how to do it topic by topic, the schedule that spaces it over a month, how to combine it with past papers, and the four mistakes that make students conclude it does not work.

Why re-reading fails and recall works

When you re-read a page, the words become familiar, and the brain mistakes familiarity for knowledge. In the exam nothing is familiar, because the page is not there. When you retrieve something from memory, the act of retrieving strengthens the memory and makes the next retrieval easier, which is exactly what the exam requires. Students who test themselves remember around twice as much a week later as students who re-read for the same time, and the gap grows over a month.

Turn each topic into questions

The whole method is questions. Each chemistry topic becomes a set of one-line questions that force a full answer, written on cards, in a notebook or in a free flashcard app. Examples by topic:

Atomic structure and the periodic table. Define an isotope. Give the electronic configuration of chlorine. State and explain the trend in reactivity down group 1. Why do the noble gases not react? (The first 30 elements are the prerequisite here.)

Bonding and structure. Why does sodium chloride have a high melting point? Why does graphite conduct and diamond not? Draw the dot-and-cross diagram for ammonia. Explain why simple molecular substances have low boiling points.

Quantitative chemistry. Calculate the moles in 8 g of oxygen molecules. Balance the equation for the combustion of ethane. 4.0 g of product from a theoretical 5.0 g: percentage yield? What is the concentration in mol/dm³ of 0.5 mol in 250 cm³?

Chemical changes. Write the ionic equation for zinc with copper sulfate solution. Describe how to make pure dry crystals of copper sulfate from copper oxide. What happens at each electrode in the electrolysis of molten lead bromide, with half-equations?

Rates and equilibrium. Explain, using collision theory, why increasing temperature increases rate. What does a catalyst do to the activation energy? State Le Chatelier's principle and apply it to the Haber process when pressure is increased.

Organic chemistry. Draw the displayed formula of butene. What is the test for an alkene? Write the equation for the complete combustion of propane. How is crude oil separated, and why do the fractions separate?

A GCSE or IGCSE course is about 300 such questions; Class 10 CBSE about 200; AP Chemistry about 500. Writing the questions is itself revision, and takes a weekend per subject.

Do the retrieval properly

• Write the answer down before checking. Answering in your head lets you believe you knew it.
• Check, then mark yourself honestly: right, partly, wrong. The partly ones are where the marks are lost in exams.
• Draw diagrams from memory: the fractionating column, the electrolysis cell, the reaction profile with activation energy, the dot-and-cross. A diagram copied is not learned; a diagram drawn wrong and corrected is.
• Explain aloud to a parent, a sibling or the wall. Explaining is retrieval with a witness.
• Calculations are questions too. Do the moles question from memory, including the method; check the method, not only the number.

The schedule: space it

A question answered correctly today is asked again tomorrow, then in three days, then in a week, then in a fortnight. A question answered wrong goes back to tomorrow. Over a month every question is retrieved four or five times at growing intervals, which is the pattern that makes memory last. A free app will schedule this automatically; a notebook with dates works as well.

In practice, for a subject with 300 questions: about 40 questions a day, 25 minutes, five days a week, for four weeks, and the whole course is secure. Compare that with the hours of re-reading that produce a familiar-looking page and a blank in the exam.

Combine with past papers

Recall builds the knowledge; past papers teach the format and the mark scheme. From week two, one timed past paper a week, marked to the real mark scheme, and every lost mark becomes a new recall question. A student who has done both by the exam is not revising on the last night; they are re-reading their summary sheet and sleeping.

The four mistakes that make it "not work"

1. Checking too early. Looking at the answer after five seconds of not knowing. Sit with the blank for thirty seconds; the struggle is the learning.
2. Only the easy questions. Students drift to the cards they know. The wrong pile is the revision; the right pile is the reward.
3. Questions that are too big. "Explain the periodic table" cannot be retrieved. "State the trend in atomic radius down a group and explain it" can.
4. Starting the week before. Spacing needs time; recall started three days before the exam is cramming with extra steps. Four weeks is the minimum; a term is better.

What we do

In our chemistry classes the question bank is built in class, topic by topic, as the course is taught, so that by exam term the student has 300 questions in their own words and has been retrieving them for months. Past papers are marked live to the mark scheme, and every lost mark goes into the bank. The free 30-minute class is a good place to bring the current topic and see the method on the whiteboard.

Questions parents ask

See how we teach this, 1-on-1 online →