Cambridge IGCSE Co-ordinated Sciences 0654/12 is the May/June 2026 Paper 1 (Multiple Choice, Core), variant 2. It has 40 questions worth one mark each, lasts 45 minutes and is sat by every Core candidate. Questions 1 to 13 were biology, 14 to 27 chemistry and 28 to 40 physics. Most questions tested recall, but a handful needed working: a magnification, a molecular formula from a structure, electron shells, melting and boiling point data and a stop-watch reading. This guide gives the official answer for every question, the topic it tested and the reasoning behind the trickier ones. 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.

0654/12 at a glance

Syllabus area	Questions	Number of questions
Biology: cells, biological molecules and enzymes	1–4	4
Biology: nutrition and transport in plants and humans	5–8	4
Biology: reproduction, inheritance and ecology	9–13	5
Chemistry: ions, electronic configuration and formulae	14–16	3
Chemistry: electrolysis, energy changes and physical change	17–19	3
Chemistry: indicators, salts and the Periodic Table	20–22	3
Chemistry: metals, water, air and organic chemistry	23–27	5
Physics: measurement, forces, work and power	28–30	3
Physics: thermal physics	31–32	2
Physics: light and the electromagnetic spectrum, sound	33–35	3
Physics: magnetism and electricity	36–38	3
Physics: nuclear and space physics	39–40	2
Total		40

Each correct answer scores one mark, so the total is 40. The paper gives the weight of 1.0 kg as 9.8 N and prints the Periodic Table at the back.

Answer key and topic for every question

Question	What it tested	Answer
1	Actual size of a cell from image size and magnification	B
2	Process that needs energy from respiration	D
3	Molecule containing carbon, hydrogen, oxygen and nitrogen	B
4	Optimum temperature read from an enzyme activity graph	C
5	Process that needs chlorophyll	B
6	Nutrient supplied by citrus fruits	C
7	Pathway of water from soil to leaf	C
8	Blood component that carries urea	A
9	Features of insect- and wind-pollinated flowers	A
10	What the letters T and t stand for in a cross	A
11	Choosing sheep for selective breeding from a table	D
12	Trophic levels in a marine food chain	A
13	Reasons little egrets spread north	D
14	Correct statement about ions	A
15	Counting Group IV elements from electron shell diagrams	C
16	Molecular formula from a displayed structure	D
17	What happens to aqueous potassium iodide in electrolysis	B
18	Changes during an endothermic reaction	A
19	Which change is physical	C
20	Colours of litmus and methyl orange in sodium hydroxide	B
21	Order of steps to make copper(II) chloride crystals	D
22	Properties of the noble gases	A
23	Metal that reacts with hot water and is extracted with carbon	D
24	Impure water samples from melting and boiling points	B
25	Composition of clean, dry air	C
26	Which formulae are hydrocarbons	C
27	Process that separates petroleum	D
28	Time elapsed between two stop-watch readings	A
29	Quantity affected by gravitational field strength	D
30	Units of work done and power	B
31	What the random motion of dust particles is evidence for	C
32	Which rod conducts heat to melt the wax	A
33	Diagram showing dispersion by a prism	D
34	Radio waves and X-rays: shorter wavelength and ionising	D
35	Why sound from the Sun is not heard on Earth	A
36	How a magnetic material responds to each pole	A
37	Statements about a two-lamp circuit with switches and an ammeter	B
38	Purpose of a 3 A fuse	B
39	Why long tongs are used for radioactive sources	B
40	Meaning of 4.2 light-years	A

What the paper tested, topic by topic

Biology (Questions 1–13)

• Magnification (Question 1): actual size = image size ÷ magnification = 4 mm ÷ 100 = 0.04 mm. Dividing the wrong way round (100 ÷ 4) gives the 25 mm distractor, and dividing by 1000 gives 0.004 mm.
• Respiration and transport (Question 2): of the processes listed, only active transport uses energy from respiration. Diffusion and osmosis are passive, so any option that includes them is wrong.
• Biological molecules and enzymes (Questions 3 and 4): proteins contain nitrogen as well as carbon, hydrogen and oxygen; fats, reducing sugars and starch do not. On the enzyme graph, activity peaks at 60 °C and falls sharply by 80 °C, so read the peak, not the end of the curve.
• Plants (Questions 5 and 7): chlorophyll is needed for photosynthesis. Water moves from root hair cells to the root cortex, into the xylem and then to the mesophyll cells of the leaf. The other options put these in the wrong order.
• Humans (Questions 6 and 8): citrus fruits are a main source of vitamin C, and urea is carried dissolved in the plasma.
• Reproduction and inheritance (Questions 9 and 10): insect-pollinated flowers keep their anthers inside the flower, while wind-pollinated flowers have them hanging outside. In a cross written as TT × tt, the letters stand for alleles.
• Selective breeding (Question 11): the farmer wants a high fleece yield and fine wool, and needs a female and a male. Sheep 3 is the only high-yield female, and it has fine wool. Of the males, only sheep 6 combines fine wool with a medium (rather than low) yield. So the pair is 3 and 6. Options A and C fail because 1 and 3 are both female, and sheep 4 has a low yield.
• Food chain (Question 12): the chain runs phytoplankton → char → capelin → harbour seal → orca. The phytoplankton is the producer and the char the primary consumer, so the capelin eats another animal and is a carnivore. The seal is the tertiary consumer, not the orca, and the seal is not a herbivore.
• Environment (Question 13): less food in the south and a warmer northern climate could both drive the birds north. More monitoring of the southern population would not make them move, so the answer is 2 and 3 only.

Chemistry (Questions 14–27)

• Ions (Question 14): ions are charged atoms (or groups of atoms). Cations are positive, metal ions are positive and non-metal ions are negative, so the other three statements are reversed.
• Electronic configuration (Question 15): count the electrons in the outer shell of each diagram. Two of the four have four outer electrons (2,4 and 2,8,4), so they are in Group IV. The other two are 2,8,2 and 2,8,8. The answer is 2. Count shell by shell: it is easy to add an inner-shell pair to the outer shell.
• Molecular formula (Question 16): the structure has a nitrile group (C≡N) at each end and two CH₂ groups in the middle. Counting gives 4 carbon, 4 hydrogen and 2 nitrogen atoms, so C₄H₄N₂.
• Electrolysis (Question 17): passing a current through aqueous potassium iodide breaks it down, so electrolysis is decomposition.
• Endothermic reactions (Question 18): thermal energy is absorbed from the surroundings, so the temperature of the surroundings decreases.
• Physical change (Question 19): dissolving sodium chloride in water is physical. Combustion, rusting and polymerisation all make new substances.
• Indicators (Question 20): sodium hydroxide is an alkali, so litmus turns blue and methyl orange turns yellow.
• Making crystals (Question 21): heat the solution to reduce the volume of water, cool it so crystals form, filter them off, then dry them. That is 4, 1, 3, 2.
• Noble gases (Question 22): they are in Group VIII and have full outer shells. They exist as single atoms, not diatomic molecules, and they are unreactive.
• Metals (Question 23): zinc reacts with hot water and is extracted from its oxide by heating with carbon. Sodium is too reactive to extract with carbon, copper does not react with water, and aluminium is extracted by electrolysis.
• Purity (Question 24): pure water boils at 100 °C and melts at 0 °C. Sample 2 boils at 102 °C and sample 3 melts at −6 °C, so samples 2 and 3 are impure. Samples 1 and 4 match the values for pure water.
• Air and fuels (Questions 25–27): clean, dry air is about 78% nitrogen, 21% oxygen and 1% noble gases and carbon dioxide. A hydrocarbon contains only carbon and hydrogen, so CH₄ and C₂H₂ qualify but the two formulae with oxygen do not. Petroleum is separated by fractional distillation.

Physics (Questions 28–40)

• Stop-watch (Question 28): 3 min 25 s − 0 min 45 s = 2 min 40 s. Adding the readings instead gives the 4 min 10 s distractor, so subtract carefully across the minute.
• Mass and weight (Question 29): only weight depends on gravitational field strength. Mass stays the same wherever the object is.
• Units (Question 30): work done is measured in joules and power in watts.
• Particles (Question 31): the random motion of dust particles in air is evidence for the kinetic particle model of matter, caused by air molecules hitting the dust.
• Conduction (Question 32): copper is a metal and the best thermal conductor of the four rods, so the wax melts on the copper rod. Glass, plastic and wood are poor conductors.
• Light and waves (Questions 33–35): in dispersion, blue light is refracted more than red, so it bends further and comes out below the red light, as in diagram D. X-rays have the smaller wavelength of the two regions, and they are also the ionising radiation. Sound from the Sun cannot reach us because sound cannot travel through the vacuum of space.
• Magnetism and circuits (Questions 36–38): a magnetic material that is not itself a magnet is attracted to both poles. In the circuit, the two lamps are in parallel and each has its own switch, so statement 1 is correct. The ammeter sits in only one branch, so it does not measure the current in both lamps, and the circuit is not a series circuit. A 3 A fuse melts to stop the current rising above 3 A; it does not hold the current steady.
• Radioactivity and space (Questions 39–40): long tongs increase the distance between the source and the scientist. A star 4.2 light-years away is so far that its light takes 4.2 years to reach the Earth; a light-year is a distance, not a time for a journey or an orbit.

Where the marks are on 0654/12

• Chemistry carried 14 marks, and biology and physics 13 each. The three sciences appear in that fixed order, so you can see your score per science straight from the answer sheet.
• Only two questions needed arithmetic: the magnification (1) and the stop-watch (28). Neither needed a calculator, but both have distractors built from the wrong operation.
• Five questions turned on reading a diagram, graph or table: the enzyme graph (4), the sheep table (11), the electron shells (15), the displayed formula (16) and the melting and boiling point table (24). The prism (33) and circuit (37) questions also depended on the drawings.
• Several questions used combined statements (Questions 13, 22 and 37). For these, judge each numbered statement on its own first, then find the option that matches.
• Pairs-in-a-table questions (Questions 9, 18, 20, 25, 30 and 34) need both halves of the row to be right. The wrong rows usually get one half right, so check both before you choose.

How to self-mark 0654/12

1. Check each answer against the key above or the official mark scheme. Count one mark per correct letter.
2. Split your score by science: Questions 1–13 biology, 14–27 chemistry, 28–40 physics. This tells you which science to revise first.
3. Tag every wrong answer by reason: knowledge (for example, not knowing which nutrient citrus fruits supply), misread (missing “impure” in Question 24 or “both lamps” in Question 37) or working (dividing by the wrong number in Question 1, or miscounting shells in Question 15).
4. Redo the working questions with every step written down: the formula first in Question 1, a shell-by-shell count in Question 15 and an atom-by-atom count in Question 16.
5. Revise knowledge gaps first, then retry the statement-style questions by marking each statement true or false before looking at the options.

Sit 0654/12 as a timed mock

You have 45 minutes for 40 questions, a little over one minute each. Answer the quick recall questions first, mark any that need a diagram or working, then come back to them.

Block	Questions	Time
Biology	1–13	13 minutes
Chemistry	14–27	14 minutes
Physics	28–40	13 minutes
Second pass and check the answer sheet	–	5 minutes

Keep the second pass for the diagram questions, such as the electron shells (15) and the circuit (37), where a careful recount often changes the answer.

Other May/June 2026 0654 papers

• 0654 Paper 22 (Extended Multiple Choice)
• 0654 Paper 32 (Core Theory)
• 0654 Paper 42 (Extended Theory)
• 0654 Paper 52 (Practical Test)
• 0654 Paper 62 (Alternative to Practical)

Practise and download

• Download 0654/12 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

How was 0654 Paper 12 May/June 2026 split between the sciences? +

Questions 1 to 13 were biology, 14 to 27 chemistry and 28 to 40 physics. That is 13 biology marks, 14 chemistry marks and 13 physics marks out of 40.

How many marks is 0654/12 and how long is it? +

It has 40 multiple choice questions, and each correct answer scores one mark, for a total of 40 marks. You have 45 minutes and you may use a calculator.

Is 0654/12 the Core or Extended paper? +

Core. Paper 1 is the Core multiple choice paper, sat alongside Paper 3 (Core Theory) and either Paper 5 or Paper 6. Extended candidates sit Paper 2 instead.

What was the answer to the magnification question on 0654/12? +

B, 0.04 mm. Actual size = image size ÷ magnification, so 4 mm ÷ 100 = 0.04 mm.

What was the answer to the Group IV electronic configuration question on 0654/12? +

C, two. Of the four diagrams, two had four electrons in the outer shell (2,4 and 2,8,4). The other two had two and eight outer electrons, so they were not in Group IV.

Where can I download 0654/12 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.

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