IGCSE Paper 6 (Alternative to Practical): The Complete Guide for 2026

Paper 6 is worth 20% of your IGCSE science grade, and it is the paper almost nobody revises properly. Students drill Paper 2 and Paper 4 for months, then walk into Alternative to Practical having done two past papers and hoping for the best.

That is a strange way to treat a fifth of your grade — especially because Paper 6 is the most predictable paper Cambridge sets. The theory papers can ask you anything on the syllabus. Paper 6 asks the same eight or nine things every single session, in a slightly different costume.

This guide covers what Paper 6 actually is, how it differs from Paper 5, the recurring question types that make up most of the paper, and the specific places where marks leak out.

What Paper 6 actually is

Cambridge assesses practical skills in every IGCSE science. It offers schools two routes to do it, and they carry identical weight:

Why "alternative" does not mean "easier"

There is a persistent staffroom myth that Paper 6 is the soft option. The grade data does not support it. Paper 6 removes the parts of practical work students find easy — physically doing the thing — and keeps the parts they find hard: describing method precisely, handling data honestly, and criticising an experiment they did not design.

In a real lab you can see that the liquid went cloudy. In Paper 6 you have to read that it went cloudy, know what that implies, and write the observation in the language the mark scheme accepts. That is a language skill as much as a science one.

The six question types that make up the paper

Go through five years of Paper 6 for any Cambridge science and the same skeleton appears. The context changes — a pendulum becomes a cooling curve becomes a titration — but the questions do not.

1. 1. Name the apparatus
   You are shown a diagram, or told what the experiment needs, and asked to identify or choose equipment. Measuring cylinder versus pipette versus burette. Stopwatch versus stopclock. This is free marks if you know the names, and zero if you have only ever seen the apparatus, never named it.
2. 2. Complete or draw a results table
   Almost guaranteed. Headings need the quantity and the unit, usually as length / cm. Every reading in a column needs the same number of decimal places. Calculated columns need consistent significant figures.
3. 3. Plot a graph
   Axes labelled with units, a sensible scale that uses at least half the grid, points plotted accurately, and a best-fit line — a thin single line, not a dot-to-dot and not a sausage. Then read a value off it, showing your construction lines.
4. 4. Identify the anomaly
   One point sits off the trend. You are asked to circle it, and often to suggest why. "The student misread the scale" is a reason. "It was wrong" is not.
5. 5. Variables and fair testing
   What is the independent variable, the dependent variable, and what must be kept constant. The control variables are where marks go missing — you need specific ones for this experiment, not a generic list.
6. 6. Errors and improvements
   The hardest section and the biggest mark-loser. You must give a source of error tied to this experiment and a change that would genuinely fix it.

Where the marks actually leak

Examiner reports for Paper 6 are unusually repetitive. The same failures appear year after year, across subjects and across countries. Here are the ones that cost the most.

"To make it more accurate"

This is the single most common wasted answer in Alternative to Practical. It scores nothing, in any subject, in any year. It describes a goal, not a method.

The mark scheme wants a mechanism. Compare:

The pattern is always the same: name the change, then name the error it removes. Two clauses. If your improvement sentence has only one clause, it is probably worth nothing.

Table headings without units

A results table headed Time instead of time / s loses a mark that requires no knowledge whatsoever. Cambridge's convention is quantity / unit — a forward slash, not brackets, though brackets are usually tolerated. The unit belongs in the heading and must never be repeated next to every number in the column.

Inconsistent decimal places

If you measured to the nearest 0.1 cm, then every value in that column ends in one decimal place — including the ones that came out whole. Writing 12.0, 14.5, 16, 17.5 loses the mark. It should be 12.0, 14.5, 16.0, 17.5. The reading did not suddenly become more precise because the number was round.

Graph scales that waste the grid

If your plotted points occupy less than half the printed grid, you lose a mark for scale — even if every point is plotted perfectly. Choose a scale that spreads the data out. And avoid awkward scales like 3 units per square; stick to 1, 2, 5 or 10, because everything you do afterwards is easier and less error-prone.

The subject-specific half

Everything above applies to all three sciences. On top of it, each subject has its own recurring content — and this is where a generic revision guide stops being useful.

Chemistry 0620 leans heavily on qualitative analysis — identifying unknown ions and gases from observations. This is the highest-value single topic in the whole paper, and it works differently from how most students assume. We cover it in detail in the Chemistry Paper 6 guide.

Physics 0625 is about precision. Reading instruments correctly, repeating for a mean, plotting cleanly and calculating a gradient. The experiments recur — pendulums, springs, resistance wires, lenses, cooling curves — with small variations. See the Physics Paper 6 guide.

Biology 0610 centres on food tests (Benedict's, iodine, biuret, ethanol emulsion), controlled comparisons, and describing a trend from data without simply restating the numbers.

A four-week Paper 6 plan

Paper 6 rewards short, frequent, deliberate practice far more than long sessions. Twenty minutes, four times a week, beats one three-hour Sunday.

1. Week 1 — Learn the shape
   Map the question types across four past papers as described above. Then learn your subject's core content: the qualitative analysis table for Chemistry, the standard apparatus list for Physics, the food tests for Biology.
2. Week 2 — Drill the mechanical marks
   Tables and graphs only. Take the data from six past papers and just build the table and plot the graph. Do not answer anything else. These are the most reliable marks in the paper and they are pure habit.
3. Week 3 — Drill errors and improvements
   Take every "suggest an improvement" question you can find and answer them all in the two-clause format. Mark yourself against the scheme brutally. This is where the grade is won.
4. Week 4 — Full papers to the clock
   One hour, no notes, no pauses. Paper 6 has real time pressure because of the drawing. Then mark against the scheme and log every lost mark by type, not by topic.

Common questions

The one-line version

Paper 6 is 20% of your grade, it asks the same six questions every year, and most of the marks students lose are lost to habits rather than to gaps in knowledge. Fix the habits — units in headings, consistent decimal places, two-clause improvements, a scale that fills the grid — and you will pick up marks in a fortnight that would take a term to earn on the theory papers.

Then go deeper on your subject: Chemistry 0620 and Physics 0625.