Cambridge IGCSE Co-ordinated Sciences 0654/62 is the May/June 2026 Paper 6 (Alternative to Practical), variant 2. It lasts 1 hour 30 minutes, is worth 60 marks and is sat by Core and Extended candidates whose school enters them for the written alternative rather than Paper 5. It had six compulsory questions, two each in biology, chemistry and physics, and the biggest was Question 3, a 15-mark calculation of the water of crystallisation in washing soda. This guide goes through the paper question by question and shows what the official mark scheme gave marks for. The paper and its mark scheme are free on the Tutopiya Learning Portal.

For an overview of all six 0654 papers from this series, see IGCSE Co-ordinated Sciences 0654 May/June 2026 past papers: what came up and how it was marked.

Paper 6 used the same six investigations as Paper 5, in the same order. Where Paper 5 students took their own readings, Paper 6 gave you diagrams to read and added extra questions on apparatus and technique. The 0654 Paper 52 guide shows how the hands-on version was marked.

0654/62 at a glance

Question	Topic	Marks	Main command word
1	Biology: catalase in celery puree, foam height with 2 cm³ and 1 cm³ of puree	13	Record, state, suggest
2	Biology: planning, height and recovery time after exercise	7	Plan
3	Chemistry: finding x in washing soda, Na₂CO₃·xH₂O, by heating	15	State, calculate
4	Chemistry: identifying the ions in aqueous L from test results	5	State, suggest, describe
5	Physics: spring constant from stop-watch times for 10 oscillations	13	Record, calculate, plot
6	Physics: temperature changes when hot and cold water are mixed	7	Record, calculate, suggest
	Total	60

Question-by-question walkthrough

Question 1: catalase in celery puree, biology (13 marks)

A student added hydrogen peroxide to celery puree with detergent and measured the total height h of mixture and foam after 90 seconds, using 2 cm³ of puree, then 1 cm³ of puree with 1 cm³ of water. Trial 1 heights were given as 5.3 cm and 3.2 cm.

• Reading trial 2 from the actual-size drawings (3 marks): 5.0 cm for 2 cm³ (1) and 3.5 cm for 1 cm³ (1), each allowed ±0.1 cm, plus both to one decimal place (1). Writing 5.0 matters: 5 alone got the reading mark but not the decimal-place mark.
• Averages (1 mark): 5.2 cm and 3.4 cm (5.15 and 3.35, or 5.1 and 3.3, were also accepted), with both to the same number of significant figures.
• Enzyme volume and height (1 mark): as the volume increases, the height increases (or the reverse). Both variables had to be comparative. “Proportional” was not allowed, and “positive correlation” was ignored.
• Enzyme volume and rate (1 mark): as the volume increases, the rate increases, or the reaction is faster. “Proportional” was ignored.
• Results at 4 °C (1 mark): lower heights. “Slower” and “smaller results” were ignored.
• Why stir the puree (1 mark): so the celery cells or enzyme are evenly spread, or so all the hydrogen peroxide meets the enzyme. “Evenly mix” was ignored because it repeats the question.
• Why liquidise the celery (1 mark): to increase the surface area, or to break open the cells and release the enzyme.
• Source of error and improvement (2 marks): a matched pair, such as the top of the foam is uneven or the bubbles burst (1), so measure the gas volume with a syringe and no detergent, or measure to the topmost part each time (1); or the ruler’s zero is not at its end (1), so measure the foam only (1); or the bottom of the boiling tube is curved (1), so use a measuring cylinder, beaker or conical flask (1). If neither mark was earned, parallax with a description of reading at eye level to the reading scored one.
• Measuring 2 cm³ of hydrogen peroxide (1 mark): a measuring cylinder or syringe (a graduated or volumetric pipette or a burette was also allowed). “Pipette” on its own was ignored, and a dropping pipette was rejected.
• Testing for reducing sugar (1 mark): add Benedict’s solution and heat.

Question 2: planning a recovery-time investigation, biology (7 marks)

Identical to Paper 5 Question 2 and marked the same way: plan an investigation into whether height affects how long the pulse takes to return to resting after exercise. One mark from each of five sections, then any two more.

• Apparatus: a stop-watch, a pulse meter (heart rate monitor, smart watch or ECG accepted) or a tape measure, each with its use in the method.
• Method: resting pulse, exercise, time to return to resting, at least two heights.
• Measurements: pulse before and just after exercise; each person’s height; the time to return to resting; repeats at the same height to spot anomalies; at least five heights.
• Control variables: the same sex, age or fitness; the same exercise time or named type of exercise. Weight was ignored.
• Processing: plot recovery time against height, say how to read the graph, and look at whether recovery time rises, falls or stays the same with height.

Question 3: finding x in washing soda, chemistry (15 marks)

A student heated washing soda crystals in an evaporating basin until only dry sodium carbonate was left. The empty basin (M1) was 42.1 g.

• Using a shared balance (1 mark): tare or zero it before weighing. “Clean it” and “make sure nothing is on it” were ignored.
• Another reason for a blue flame (1 mark): it doesn’t leave soot on the bottom of the basin. “Faster evaporation” was ignored.
• Recording M2 and M3 (2 marks): 51.12 g and 45.67 g to three significant figures are 51.1 g (1) and 45.7 g (1).
• Mass of water (1 mark): 51.1 − 45.7 = 5.4 g (5.45 g from the unrounded readings was also accepted).
• Moles of water (1 mark): 5.4 ÷ 18 = 0.30 mol.
• Mass of sodium carbonate (1 mark): 45.7 − 42.1 = 3.6 g.
• Moles of sodium carbonate (1 mark): 3.6 ÷ 106 = 0.034 mol, to at least 2 significant figures.
• x (2 marks): 0.30 ÷ 0.034 = 8.8 (1), then 9 to one significant figure (1). An answer of 9 scored both marks, and every step carried your own earlier answers forward.
• Mass of powder larger than expected (1 mark): water is still there, so heat to constant mass (or heat again, or for longer).
• Making crystals (1 mark): evaporate some of the water (or heat until saturated) and leave to cool and crystallise. Heating or leaving to dryness was rejected; “crystallisation” alone was not enough.
• Test for water (2 marks): anhydrous copper(II) sulfate turning white to blue, or anhydrous cobalt(II) chloride turning blue to pink. The colour mark depended on the right reagent.
• Why the method fails for JCO₃·yH₂O (1 mark): carbon dioxide is also given off and has mass. “Carbon monoxide” was rejected.

Question 4: the ions in aqueous L, chemistry (5 marks)

The results were given: a white precipitate with sodium hydroxide that gave a colourless solution in excess, a yellow precipitate with nitric acid and silver nitrate, and a white precipitate with nitric acid and barium nitrate.

• The ions (1 mark): zinc, iodide and sulfate (Zn²⁺, I⁻, SO₄²⁻). Names and formulae had to match if you gave both. “Iodine” was not allowed.
• Why add nitric acid in tests 2 and 3 (1 mark): to remove any carbonate, so it can’t give a precipitate.
• Why not hydrochloric acid in test 2 (1 mark): it would give a white precipitate with the silver nitrate, which would hide the colour of the iodide precipitate. “It contains chloride ions” on its own was not enough.
• How to do a flame test (2 marks): dip a wire or splint (a cotton bud, rod or loop was also allowed) into the solution and put it into the flame (1), using a blue, roaring or non-luminous Bunsen flame (1). Spraying into the flame and using a spoon or spatula were ignored.

Question 5: spring constant from oscillations, physics (13 marks)

A student timed 10 oscillations for masses of 100 g to 500 g. Three rows were filled in; you completed the rows for 200 g and 300 g from two stop-watch displays.

• Reading the stop-watches (2 marks): 5.57 s and 7.04 s to the nearest 0.1 s are 5.6 s (1) and 7.0 s (1).
• T (1 mark): t ÷ 10 gives 0.56 s and 0.70 s (0.7 was also allowed).
• T² to two decimal places (1 mark): 0.31 and 0.49 s². Rounding 0.7 up to give 0.50 was rejected.
• Plotting (3 marks): axes labelled with quantity and unit, T² / s² and m / g (1); sensible linear scales with the points covering at least half the grid (1); and points within half a small square, with one error allowed (1). The question also told you to start both axes at the origin.
• Line (1 mark): a straight line of best fit with points on both sides. The mark scheme also allowed a line through the origin that missed the 200 g point, or one through the other points that missed the 100 g point.
• Gradient (2 marks): a triangle using at least half the line (1) and a value in the expected range of 0.0013 to 0.0017 (1).
• Spring constant (1 mark): k = 0.039 ÷ gradient, to at least 2 significant figures in N/m, carried forward from your gradient. A gradient of 0.0015, for example, gives 26 N/m.
• Is T² proportional to m? (1 mark): a yes or no with a reason that matches your own line: yes, because the straight line passes through the origin, or T² ÷ m is constant; or no, because your line misses the origin, T² ÷ m is not constant, or doubling m does not double T². “Straight line” without mentioning the origin was ignored.
• Why 20 oscillations is better (1 mark): your reaction time is spread over more oscillations, so it has less effect. “Accuracy” on its own and “easier to measure” were ignored.

Question 6: mixing hot and cold water, physics (7 marks)

The cold water was 19.0 °C. You read the other two temperatures from thermometer diagrams.

• Reading the thermometers (2 marks): hot water 68.0 °C (68 also allowed) and mixture 29.5 °C.
• Temperature changes (1 mark): cold water 29.5 − 19.0 = 10.5 °C and hot water 68.0 − 29.5 = 38.5 °C.
• Is the hot change double the cold change? (1 mark): no, with a calculation: 10.5 × 2 = 21, not 38.5; or 38.5 ÷ 2 = 19.25, not 10.5; or 38.5 ÷ 10.5 = 3.67, not 2.
• Hazard and precaution (1 mark): both together, such as hot water or a hot beaker burning your hands, with heatproof gloves or tongs as the precaution.
• Two thermometer mistakes (1 mark): the bulb is not fully under the water and the thermometer is touching the beaker. Both were needed.
• Reading straight from a 4 °C fridge sample (1 mark): a value above 4 °C and below 19 °C, because the thermometer has not finished falling.

Where the marks are on 0654/62

• “Calculate” parts carried 13 marks: the averages in 1(a)(ii), the washing soda chain in 3(b) (6), T, T², the gradient and k in Question 5 (5) and the temperature changes in 6(b).
• “Suggest” and “identify” parts carried 10 marks: 1(a)(v), 1(b)(i), 1(b)(ii), 1(b)(iii) (2), 3(c), 4(b), 4(c), 6(e) and 6(f).
• Reading and recording values from diagrams carried 9 marks: foam heights in 1(a)(i) (3), balance readings in 3(a)(iii) (2), stop-watches in 5(a)(i) (2) and thermometers in 6(a) (2).
• “State” parts carried 8 marks: 1(a)(iii), 1(a)(iv), 1(b)(iv), 3(a)(i), 3(a)(ii), 4(a), 6(c) and 6(d).
• The plan carried 7 marks, all in Question 2.
• “Describe” parts carried 6 marks: the reducing sugar test in 1(b)(v), making crystals in 3(d), the test for water in 3(e) (2) and the flame test in 4(d) (2).
• Plotting and drawing the graph carried 4 marks in 5(b)(i) and (ii).
• “Explain” parts carried 3 marks: 3(f), 5(b)(v) and 5(c).

That is 13 + 10 + 9 + 8 + 7 + 6 + 4 + 3 = 60. Question 3 (15 marks) and Questions 1 and 5 (13 each) make up over two-thirds of the paper.

How to self-mark 0654/62 with the mark scheme

1. Learn the abbreviations first. A semicolon separates marking points, a slash shows alternatives, ALLOW means accept, IGNORE means the words neither gain nor lose credit, DO NOT ALLOW means reject, ORA means the reverse argument also scores and ecf means error carried forward.
2. Check your readings against the fixed values: 5.0 and 3.5 cm, 51.1 and 45.7 g, 5.6 and 7.0 s, 68.0 and 29.5 °C.
3. Mark the decimal places separately. 5.0 rather than 5 in 1(a)(i), and T² to two decimal places in 5(a)(iii), each decide a mark.
4. Follow the washing soda chain with ecf. If you misread a balance, still award the later marks you calculated correctly from your own numbers, and remember that 9 alone earns both marks for x.
5. Check the graph in three parts: labels with units, scales that use half the grid from the origin, and points within half a small square.
6. Mark 5(b)(v) against your own line. “Yes” scores only if your line goes through the origin, and “no” scores if it doesn’t.
7. Watch for answers on the ignore list. “Pipette” alone in 1(b)(iv), “proportional” in 1(a)(iii), “HCl contains chloride ions” in 4(c) and “accuracy” in 5(c) earned nothing.

Sit 0654/62 as a timed mock

The paper allows 90 minutes for 60 marks, about one and a half minutes per mark. A workable plan:

Block	Marks	Time
Question 1 (catalase)	13	18 minutes
Question 2 (plan)	7	12 minutes
Question 3 (washing soda)	15	20 minutes
Question 4 (ions in L)	5	7 minutes
Question 5 (spring and graph)	13	21 minutes
Question 6 (hot and cold water)	7	9 minutes
Check units, decimal places and the graph	–	3 minutes

Draw the graph in pencil, and write the plan under the five headings from the question so you don’t miss a section.

Other May/June 2026 0654 papers

• 0654 Paper 12 (Core Multiple Choice)
• 0654 Paper 22 (Extended Multiple Choice)
• 0654 Paper 32 (Core Theory)
• 0654 Paper 42 (Extended Theory)
• 0654 Paper 52 (Practical Test)

Practise and download

• Download 0654/62 and its mark scheme on the Learning Portal →
• All 0654 May/June 2026 papers: overview and marking patterns
• Try a free IGCSE Co-ordinated Sciences quiz

Need help with a 0654 topic? Book a free trial lesson with an IGCSE Co-ordinated Sciences tutor →

Frequently asked questions

What topics were on 0654 Paper 62 May/June 2026? +

Six questions, two per science. Biology: catalase in celery puree (13 marks) and a plan linking height to recovery time after exercise (7). Chemistry: finding x in washing soda (15) and the ions in solution L (5). Physics: the spring constant from oscillation times (13) and mixing hot and cold water (7).

How many marks is 0654/62 and how long is it? +

It is out of 60 marks and lasts 1 hour 30 minutes. Question 3, on washing soda, is the biggest at 15 marks.

What was the value of x in washing soda on 0654/62? +

The balance readings were 51.1 g and 45.7 g to three significant figures, with an empty basin of 42.1 g. That gives 5.4 g of water (0.30 mol) and 3.6 g of sodium carbonate (0.034 mol), so x = 8.8, which is 9 to one significant figure. An answer of 9 scored both marks.

What were the readings to record on 0654/62? +

Foam heights of 5.0 cm and 3.5 cm for trial 2; balance readings of 51.1 g and 45.7 g; stop-watch times of 5.6 s and 7.0 s; and thermometer readings of 68.0 °C for the hot water and 29.5 °C for the mixture.

Is 0654/62 the same as 0654/52? +

They use the same six investigations in the same order. Paper 6 gives you the readings as diagrams instead of asking you to take them, and adds questions on measuring 2 cm³, the test for reducing sugar, taring a balance, the blue flame, why nitric acid is used, the flame test, proportionality and a safety hazard.

Where can I download 0654/62 May/June 2026 and its mark scheme? +

Both are free to download and print on the Tutopiya Learning Portal, on the Cambridge IGCSE Co-ordinated Sciences 0654 past papers page.

Ready to Excel in Your Studies?

Get personalised help from Tutopiya's expert tutors. Whether it's IGCSE, IB, A-Levels, or any other curriculum — we match you with the perfect tutor and your first session is free.

Book Your Free Trial