IAL Chemistry Unit 4: 14-Day WCH14 Revision Plan

A day-by-day WCH14 revision plan built from the paper's own mark split, three series of grade boundaries and what examiners say loses marks.

Table: WCH14 (IAL Chemistry Unit 4) grade boundaries, June 2024 to June 2025 — raw marks out of 90.

Look at the shape of that table rather than any single number. The E boundary barely moves — 39, 39, 38. The A boundary climbed nine marks across three sittings. The top of the paper is where the volatility lives, which means a student chasing an A is chasing a moving target and needs a genuine buffer, while a student chasing a pass is aiming at something stable.

Two practical consequences for your fortnight. If you are targeting an A, plan for roughly 80% of the paper, not 70% — assume a June 2025-style boundary and you will never be caught out. If you are targeting a C, the gap between the C and A boundaries in June 2025 was 18 marks, which is around three well-drilled calculation questions. That is a realistic fortnight's work if the fortnight is spent correctly.

The 14-day WCH14 plan, day by day

The plan runs in four blocks: rebuild the calculations, work the topics through questions, sit whole papers to time, then finish on mistakes only. Roughly two hours a day if you have school, four if you do not.

Before you start, set up the tracking system. I ask every student to keep three colours against every topic and every question type:

• Red — needs restudying from scratch
• Orange — known, but needs revision
• Green — fine, leave it alone

Everything you do over the fourteen days either confirms a colour or changes it. On the last day you look only at red. This is the single most useful thing on this page, and it costs nothing but a highlighter.

Days 1–4: rebuild the calculations from AS upwards

Start below Unit 4, not inside it. This surprises students every year, but it is where the marks hide.

Spend the first day and a half on AS chemistry calculations: mole conversions in both directions, concentration in mol dm⁻³ and g dm⁻³, the ideal gas equation pV = nRT, empirical and molecular formulae from experimental data. These are Unit 1 skills, they are examinable synoptically, and they sit underneath every Unit 4 calculation you are about to meet. A student who fumbles a mole conversion will fumble a Kp question for reasons that have nothing to do with equilibria.

Then shift into the Unit 4 calculations themselves, in this order:

• Rate equations — deducing orders from initial-rate data, calculating the rate constant with units, half-life
• Entropy — ΔS system, ΔS surroundings, ΔS total, and the temperature at which a reaction becomes feasible
• Born–Haber and lattice energy — cycles, enthalpy of solution, hydration enthalpies
• Kc and Kp — expressions first, values second, units last
• Acid–base — pH of strong acids, pH of weak acids from Ka, pH of strong bases from Kw, buffer calculations

Use condensed material for this, not a textbook — you do not have time to read chapters. Our Edexcel IAL Chemistry notes are built for exactly this compression, with the A2 content set out in the order the paper asks for it.

One rule for this whole block, and it applies to Born–Haber cycles above all: plan your work and sketch the cycle before you write anything. Do not write until you have a clear map in your head. Examiners repeatedly flag sign errors in these questions, and almost every one of them comes from a student who started calculating before they had drawn the diagram.

Days 5–9: topic by topic, through questions only

From day five you stop studying topics and start answering questions on them. One topic per day, worked entirely through past-paper questions with the mark scheme beside you.

• Day 5 — Kinetics, including the Arrhenius graph and the rate-determining step
• Day 6 — Entropy, energetics and Born–Haber
• Day 7 — Chemical equilibria, Kc and Kp
• Day 8 — Acid–base equilibria, titration curves, indicators and buffers
• Day 9 — Organic: carbonyls, carboxylic acids, chirality, NMR and chromatography

The method matters. Attempt the question with the paper closed. Mark it yourself against the mark scheme. Then — and this is the part students skip — write down why the mark scheme awarded what it did, in your own words. Update your red, orange and green as you go.

You want as many papers as you can get your hands on. WCH14 in its current form was first assessed in January 2020, so the complete set is not enormous and it is entirely realistic to work through all of it. Our classified IAL Chemistry past papers group every question by topic, which is what makes this block possible in five days rather than fifteen.

If, working through these, you find that the problem is not Unit 4 at all but the AS foundations underneath it, that is worth knowing now rather than in the exam hall. Our IAL AS Chemistry course rebuilds those Unit 1 and Unit 2 skills properly, and they will keep paying you back in Unit 5.

Days 10–13: whole papers, to time

Four days, four complete papers, each sat in one 105-minute block with a calculator, the Data Booklet and a ruler. No pausing, no looking things up, no starting again.

Mark each one the same day. Convert your raw mark using the boundary table above so you know where you stand — and use the June 2025 column, the harshest of the three, so that your estimate is conservative.

By the fourth paper you are not learning chemistry any more; you are learning the rhythm of the paper. That rhythm is the thing that turns a student who knows the content into a student who finishes.

Day 14: red only

Nothing new. Open your tracking sheet and look at what is still red. Rework those questions — the ones you have already got wrong, not fresh ones.

Reread your marked scripts rather than your notes. Your own crossed-out working teaches you more the day before an exam than any summary sheet, because it shows you the specific mistake your brain is inclined to make under pressure.

Which Unit 4 topics lose the most marks?

The multiple-choice section is not the easy 20 marks students assume: in January 2022 the mean score across Section A was 54.0%, meaning the average candidate got roughly nine of the sixteen questions right. If you have been treating Section A as a warm-up, that figure alone should change how you spend two of your fourteen days.

The examiner report for that series is unusually specific about the rest, and its closing advice to candidates is worth treating as a checklist:

• Apply knowledge to unfamiliar situations
• Read questions with great care, and do not assume what is being asked
• Practise drawing three-dimensional structures of organic molecules
• Understand bonding, structure and intermolecular forces as explanations for solubility and melting temperature
• Practise writing equations, including state symbols, for familiar and unfamiliar reactions

Two of these deserve expanding, because they are where I see marks disappear most often.

Misreading the question. This is the biggest single loss in my experience, and it bites hardest on Kp calculations. The examiner report describes candidates who were asked for the mathematical expression for Ka and instead wrote the chemical equation for the dissociation of the acid — a question they could have answered, thrown away by answering a different one. Underline the command word. Underline what the question is asking you to produce. Then start.

Mole to mole-fraction conversion. If you lose marks on Kp, this is almost always where it happens. Students get the moles at equilibrium right, then go straight to partial pressures without converting to mole fractions, or divide by the wrong total. Write the total moles down as a separate line before you touch the pressures. One extra line of working prevents the most common Kp error there is.

Three-dimensional organic structures. The examiner report makes a striking observation here — that this technique needs to be directly taught, because there are few resources that let candidates learn it independently. I teach it with simulations and 3D models on screen, because the wedge-and-dash convention only makes sense once you have seen the tetrahedron rotate. If you have nothing else, draw the same chiral molecule ten times from memory and compare them.

One caution on topic weighting. In the January 2023 paper the entire 19-mark Section C was a single acid–base question — Ka, pH, a titration curve, indicator choice and two buffer calculations. That was an unusual paper rather than a rule, and I would not build a fortnight around the assumption that it repeats. But it could repeat, and acid–base equilibria is cheap to secure. Do not leave it until day nine and hope.

How should you spend the 105 minutes on exam day?

The paper tells you itself: spend no more than 20 minutes on Section A. In the January 2023 WCH14 paper, Section A carried 20 marks across 16 questions, Section B carried 51 marks and Section C carried 19.

Do the arithmetic on that and the shape of the day becomes clear. Twenty minutes for twenty marks leaves 85 minutes for the remaining 70 marks — about 1.2 minutes per mark. A 15-mark question deserves roughly 18 minutes. A six-mark extended-writing question deserves seven, not fifteen.

Three habits worth drilling during your four timed papers:

• Show every step. The mark scheme awards intermediate steps. A wrong final answer with correct working still scores; a right answer with no working sometimes does not, particularly where the question expects you to demonstrate a method.
• Include units and signs. Rate constants, entropy changes and equilibrium constants all carry marks for units. Enthalpy answers carry marks for sign.
• Do not leave blanks. The paper's own advice is to try to answer every question. An attempt at a six-mark question costs you two minutes and can return two marks.

What if you have fewer than 14 days?

Compress the blocks rather than deleting them, and protect the calculations above everything else. With seven days: two days rebuilding calculations, three days of topic questions, two full papers. With three days: one day of calculations, two full papers with careful marking.

What you never cut is the whole-paper practice. It is tempting, when time is short, to think you cannot afford to spend 105 minutes on something that teaches you no new content. That instinct is exactly backwards, and it is the mistake the EEF trial exposes — recall practice without application practice moved nothing.

A word of proportion, though. The EEF itself notes that while cognitive science principles can improve learning, the evidence base has real limitations, with positive results often coming from small or tightly controlled studies. No revision plan, mine included, is a guarantee. What a plan does is stop you spending your last fortnight on the comfortable activity instead of the useful one.

I have taught many students who moved a grade in a short run-up to this paper. In every case it came down to the same two things: enough practice, and the right mindset going into it. Neither requires more time than you have. Both require you to start answering questions today rather than reading about them.

If you would like to see how this works before committing to anything, sit in on a free AS Chemistry class and bring a question you got wrong. If you would rather ask something directly, message me on WhatsApp at +965 5137 5709 or email admin@chem-bio.info.

Frequently asked questions

Is 14 days enough to pass IAL Chemistry Unit 4? Fourteen days is enough to pass and, from a reasonable starting point, enough to move a grade. The E boundary has sat at 38 to 39 marks out of 90 across the last three sittings, which is a realistic target for a focused fortnight spent on past papers.

How many marks do you need for an A in WCH14? In the last three published sittings an A required 63, 66 and 72 raw marks out of 90, with June 2025 the highest. Plan for around 80% of the paper if you are targeting an A, so that a harsh series does not catch you out.

What is the hardest topic in IAL Chemistry Unit 4? Most students find Kp calculations and Born–Haber cycles hardest, though the marks are usually lost to method rather than understanding — mole-to-mole-fraction conversion in Kp, and sign errors in Born–Haber. Both are fixed by sketching the structure of the answer before writing anything.

Should I do past papers or notes first for Unit 4? Do a short, targeted rebuild of your calculations first, then move to past papers and stay there. Re-reading notes improves recall, but WCH14 is examined on application to unfamiliar contexts, which only past-paper practice develops.