Question 1
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B9.3 — Blood vessels (Parts (a)(i), (a)(ii), (b), (c))
• Topic B9.1 — Circulatory systems (Part (a)(iii))
• Topic B9.2 — Heart (Part (a)(iv))
• Topic B9.4 — Blood (Part (d))
▶️ Answer/Explanation
(a)(i) A – aorta; C – renal artery
Vessel A carries oxygenated blood away from the heart towards the lungs’ side and down to the body.
In Fig. 1.1, A leaves the heart to supply the liver, intestines, kidneys and other organs, so it is the aorta.
Vessel C leads directly into the kidneys, so it is the renal artery.
(a)(ii) B – artery; D – vein; E – artery
Vessel B carries blood towards the intestines (away from the heart, oxygenated), so it is an artery.
Vessel D carries blood away from the liver back towards the heart, so it is a vein.
Vessel E carries blood away from the heart towards the lungs, so it is an artery.
(a)(iii) Valves
Valves are flap-like structures found in the heart and in veins.
They close to prevent the backflow of blood.
This ensures blood always flows in one direction only.
(a)(iv) Septum
The septum is the muscular wall inside the heart.
It separates the left side (oxygenated blood) from the right side (deoxygenated blood).
This prevents the two types of blood from mixing.
(b) 
Arteries have the thickest walls to withstand the high pressure of blood pumped from the heart.
Veins have thinner, less muscular walls since blood flows at lower pressure.
Capillaries have walls only one cell thick (\(0.0005\,\text{mm}\)) to allow efficient exchange of substances.
(c) Exchange of substances between blood and tissue cells
Capillaries have very thin, permeable walls (one cell thick).
This allows oxygen, glucose, and other substances to diffuse from the blood into tissue cells.
Waste products such as carbon dioxide diffuse from cells back into the blood.
(d) Any two from: red blood cells, white blood cells, plasma, platelets
Blood is made up of several components with different functions.
Red blood cells transport oxygen, white blood cells fight infection, plasma carries dissolved substances, and platelets help clotting.
Any two of these four components are accepted.
Question 2
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic C2.6 — Giant covalent structures (Part (a)(i))
• Topic C8.3 — Group VII properties (Part (a)(ii))
• Topic C9.2 — Uses of metals (Part (a)(iii))
• Topic C9.6 — Extraction of metals (Part (a)(iv))
• Topic C4.1 — Electrolysis (Part (a)(v))
• Topic C3.1 — Formulas (Part (b))
• Topic C7.2 — Oxides (Part (c))
• Topic B6.1 — Photosynthesis (Part (d))
▶️ Answer/Explanation
(a)(i) carbon
Carbon is the element that exists in different structural forms.
Diamond and graphite are both allotropes of carbon.
(a)(ii) chlorine
Halogens are the Group VII elements.
Chlorine is the only halogen in the given list.
(a)(iii) copper
Copper is commonly electroplated onto other metals.
This is done to improve appearance or resistance to corrosion.
(a)(iv) aluminium
Aluminium’s main ore is bauxite.
It is extracted from bauxite by electrolysis.
(a)(v) sulfur
Sulfur is burned to form sulfur dioxide.
Sulfur dioxide is then converted to sulfur trioxide and used to manufacture sulfuric acid.
(a)(vi) chlorine
Chlorine gas kills bacteria and microorganisms in water.
It is added in small amounts to make drinking water safe.
(b) phosphorus = 4, oxygen = 10
The formula \(\text{P}_4\text{O}_{10}\) shows the subscript number of each atom type per molecule.
So one molecule contains 4 phosphorus atoms and 10 oxygen atoms.
(c) Non-metal oxides are acidic
Phosphorus is a non-metal, so its oxide is a non-metal oxide.
Non-metal oxides dissolve in water to form acidic solutions.
(d) nitrogen and potassium
Fertilisers commonly supply the three key plant nutrients.
Alongside phosphorus, nitrogen and potassium are the two other elements typically found in fertilisers.
Question 3
Technetium-99 has a half-life of \(6\) hours.
Calculate how many atoms will have decayed after \(12\) hours.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic P3.4 — Sound (Part (a), speed of ultrasound)
• Topic P3.3 — Electromagnetic spectrum (Part (b), Part (c)(i))
• Topic P5.2.4 — Half-life (Part (c)(ii))
▶️ Answer/Explanation
(a) speed = 1500 m/s
Convert the distance to metres: \(13.5\,\text{cm} = 0.135\,\text{m}\).
Speed is calculated using \(\text{speed} = \dfrac{\text{distance}}{\text{time}} = \dfrac{0.135}{0.000090}\).
This gives \(\text{speed} = 1500\,\text{m/s}\).
(b)(i) X-rays are ionising radiation and can damage cells / DNA
X-rays carry enough energy to ionise atoms in living tissue.
This can damage or kill the developing cells of an unborn baby, so ultrasound (non-ionising) is used instead.
(b)(ii) e.g. observing broken bones
X-rays pass easily through soft tissue but are absorbed by dense bone.
This makes them useful in hospitals for imaging fractures or other bone/dental problems.
(c)(i) gamma-radiation goes in the first (leftmost) box
The table is arranged in order of increasing frequency from right to left.
Since gamma radiation has a higher frequency than X-rays, it belongs in the empty box to the left of “X-rays”.
(c)(ii) 960 atoms have decayed
\(12\) hours is equal to \(2\) half-lives (since the half-life is \(6\) hours).
After \(2\) half-lives, the number of undecayed atoms remaining is \(1280 \div 4 = 320\).
So the number of atoms decayed is \(1280 – 320 = 960\).
Question 4
The allele for no albinism is dominant and represented by the letter A.
The allele for albinism is recessive and represented by the letter a.
carrying genetic information in the form of …………………………… .
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic B16.3 — Monohybrid inheritance (Part (a)(i), (a)(ii))
• Topic B16.1 — Chromosomes and genes (Part (b)(i), (b)(ii), (b)(iii))
• Topic B15.4 — Sexual reproduction in humans (Part (c), (d))
▶️ Answer/Explanation
(a)(i)
Person 1 has albinism, so the genotype must be homozygous recessive: \(aa\).
Person 2 has genotype \(Aa\), which is heterozygous, giving the phenotype “no albinism” since A is dominant.
Person 3 has genotype \(AA\) (homozygous dominant), giving the phenotype “no albinism”.
(a)(ii)
Person 3 (\(AA\)) can only contribute an \(A\) gamete, and person 2 (\(Aa\)) can contribute \(A\) or \(a\).
Combining gametes gives offspring genotypes of \(AA\) and \(Aa\) in every box of the Punnett square.
So both rows read \(AA\) and \(Aa\).
(b)(i) DNA; genes
A chromosome is a thread-like structure made of DNA.
It carries genetic information in the form of genes.
(b)(ii) nucleus
In human cells, chromosomes are found inside the nucleus.
This is where the genetic material is stored and protected.
(b)(iii) X or Y
Human males have the sex chromosome combination \(XY\).
So a male gamete (sperm) carries either an \(X\) chromosome or a \(Y\) chromosome.
(c) sperm
The male gametes in humans are called sperm.
They are produced by meiosis and are adapted for swimming to reach the egg cell.
(d) testes
Male gametes are produced in the testes.
This is where sperm cells are made throughout a man’s reproductive life.
Question 5
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic C10.2 — Air quality and climate (Part (a), (c)(i), (c)(iii))
• Topic C8.5 — Noble gases (Part (b)(i), (b)(ii), (b)(iii))
• Topic C2.1 — Elements, compounds and mixtures (Part (c)(ii))
• Topic C7.1 — The characteristic properties of acids and bases (Part (d)(i), (d)(ii), pH scale)
▶️ Answer/Explanation
(a) 1%
Clean, dry air is approximately \(78\%\) nitrogen and \(21\%\) oxygen.
Adding these together gives \(78 + 21 = 99\%\).
So the remaining “other gases” make up \(100 – 99 = 1\%\).
(b)(i) 2,8,8
Argon has \(18\) electrons (proton number \(18\) from the Periodic Table).
These are arranged in shells as \(2, 8, 8\).
(b)(ii) argon has a full outer shell of electrons
The electronic structure \(2,8,8\) shows a complete outer shell of \(8\) electrons.
A full outer shell means argon has no tendency to gain, lose or share electrons, making it very unreactive.
(b)(iii) e.g. used in lamps / light bulbs
Argon’s lack of reactivity means it will not react with the hot filament inside a light bulb.
This makes it useful as an inert filling gas to prevent the filament from burning away.
(c)(i) e.g. combustion of fossil fuels
Burning carbon-containing fuels such as coal, oil, or petrol releases carbon dioxide.
This is one of the main sources of carbon dioxide in the atmosphere.
(c)(ii) an element contains only one type of atom; a compound contains atoms of two or more elements chemically bonded together
An element is a substance made of only one type of atom.
A compound is formed when atoms of two or more different elements are chemically combined, as in carbon dioxide (carbon and oxygen).
(c)(iii) e.g. methane
Methane is released from the decomposition of vegetation and from animal digestion.
Like carbon dioxide, it traps thermal energy in the atmosphere and contributes to global warming.
(d)(i) pH = 7
Pure water is neutral, neither acidic nor alkaline.
On the pH scale, neutral substances have a pH value of \(7\).
(d)(ii) pH = 4–6
Dissolved carbon dioxide forms a weak acid (carbonic acid) in rainwater.
This lowers the pH slightly below \(7\), typically to a value between \(4\) and \(6\).
Question 6
the …………………………………………………………………. of a body
and the …………………………………………………………………. of a body.
kinetic light
transferred to …………………………………………………… energy as the athlete moves.
As the athlete moves up the hill his store of …………………………………………………… energy increases.
The speed of the athlete is constant when moving up the hill, so his …………………………………………………… energy remains constant.
same size upright
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic P1.5.1 — Effects of forces (Part (a), (b))
• Topic P1.6.1 — Energy (Part (c))
• Topic P1.6.4 — Power (Part (d))
• Topic P3.2.3 — Thin converging lens (Part (e))
▶️ Answer/Explanation
(a) C = weight, D = drag / air resistance
Force C acts vertically downwards on the athlete, which is the athlete’s weight.
Force D acts backwards, opposing the athlete’s forward motion, which is drag (air resistance).
(b) size; shape (any two of size, shape, speed)
Forces can change the direction of motion of a body.
They can also change the size and the shape of a body (or its speed), depending on how the force acts.
(c) chemical potential → kinetic → gravitational potential → kinetic
Chemical potential energy stored in food is transferred to kinetic energy as the athlete moves.
As the athlete climbs the hill, gravitational potential energy increases due to the rise in height.
Since speed stays constant going up the hill, kinetic energy remains constant.
(d) rate of work done increases
Power is defined as the work done (or energy transferred) per unit time, \(P = \dfrac{W}{t}\).
Running faster means the athlete does the same or more work in less time, so the rate of work done — and therefore the power output — increases.
(e)(i) ray 1 refracts through F and meets ray 2 at the image sensor; ray 2 continues in a straight line to the same point
Ray 1 travels parallel to the principal axis before the lens, then refracts through the principal focus F.
Ray 2 passes straight through the centre of the lens without bending.
Both rays meet at the same point on the image sensor, forming the image.
(e)(ii) focal length correctly shown
The focal length is the distance from the centre of the lens to the principal focus F.
A double-headed arrow should span exactly this distance on the principal axis.
(e)(iii) inverted; diminished
A camera lens forms a real image that is smaller than the object, since the object is much further from the lens than the focal length.
This image is also inverted (upside down) compared to the object.
Question 7
Give your answer to \(1\) significant figure.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic B8.3 — Transpiration (Part (a)(i), (a)(ii), (a)(iii))
• Topic B8.2 — Water uptake (Part (b)(i), (b)(ii))
▶️ Answer/Explanation
(a)(i) 0.3 mm/min
Rate of transpiration = distance moved ÷ time taken.
Rate \(= \dfrac{7}{22} = 0.318\,\text{mm/min}\).
Rounded to \(1\) significant figure, this gives \(0.3\,\text{mm/min}\).
(a)(ii) e.g. humidity
Humidity affects how quickly water vapour diffuses out of the leaf.
Other acceptable factors include wind speed or light intensity, since all affect the rate of water loss from the leaf surface.
(a)(iii) loss of water vapour from a plant’s leaves, by evaporation from mesophyll cells followed by diffusion through the stomata
Water evaporates from the surfaces of the mesophyll cells inside the leaf.
This water vapour then diffuses out of the leaf through the stomata.
Transpiration is the overall term for this loss of water vapour from the plant’s leaves.
(b)(i) X = root hair cell, Y = root cortex cell
X is located at the surface of the root, in direct contact with soil water, identifying it as a root hair cell.
Y lies further along the pathway before the xylem, identifying it as a root cortex cell.
(b)(ii) osmosis
Water moves from a region of higher water potential (dilute soil water) to a region of lower water potential inside the root hair cell.
This movement of water across a partially permeable membrane, down a water potential gradient, is osmosis.
Question 8
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic C3.1 — Formulas (Part (a))
• Topic C11.2 — Naming organic compounds (Part (b))
• Topic C11.5 — Alkenes, reaction with steam (Part (c), “reaction of ethene with steam”)
• Topic C11.6 — Alcohols (Part (d), (f))
• Topic C11.3 — Fuels, definition of hydrocarbons (Part (e))
▶️ Answer/Explanation
(a) 3
The formula \(\text{C}_2\text{H}_5\text{OH}\) contains carbon, hydrogen, and oxygen atoms.
These are three different elements in one molecule of ethanol.
(b) 
Ethanol’s displayed formula shows two carbon atoms joined by a single bond.
Each carbon is bonded to hydrogen atoms, and one carbon is also bonded to an \(-\text{O}-\text{H}\) (hydroxyl) group.
All bonds must be shown as single lines, since ethanol is a saturated molecule.
(c) fermentation; reaction of ethene with steam
Ethanol can be produced by fermentation of sugar using yeast.
It can also be produced industrially by reacting ethene with steam in the presence of a catalyst.
(d) ethanol + oxygen → carbon dioxide + water
Complete combustion of a fuel occurs in a plentiful supply of oxygen.
Ethanol reacts with oxygen to produce carbon dioxide and water as the only products.
(e) ethanol contains oxygen
Hydrocarbons are compounds that contain only hydrogen and carbon atoms.
Ethanol also contains an oxygen atom (in its \(-\text{OH}\) group), so it cannot be classified as a hydrocarbon.
(f) e.g. solvent or fuel
Ethanol is widely used as a solvent, for example in perfumes, cosmetics, and inks.
It is also used as a fuel, either on its own or blended with petrol.
Question 9
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic P1.7 — Pressure (Part (a))
• Topic P2.2.2, Melting, boiling and evaporation (Part (b))
• Topic P1.5.1 — Effects of forces (Part (c)(i), resultant force)
• Topic P1.5.2 — Turning effect of forces (Part (c)(ii), moment)
▶️ Answer/Explanation
(a) tyre Y has a greater surface area in contact with the ground
Pressure is defined as force per unit area, \(p = \dfrac{F}{A}\).
Since the same weight (force) acts over a larger contact area for tyre Y, the pressure exerted on the ground is lower.
(b)(i) Celsius
The scale shown on the thermometer runs from \(-10\) to \(110\).
This range and labelling identify it as the Celsius temperature scale.
(b)(ii) volume (of the alcohol)
As temperature increases, the alcohol expands and its volume increases.
This change in volume causes the liquid column to rise or fall along the tube, allowing temperature to be read off the scale.
(b)(iii) melting point of ice / freezing point of water (0 °C); boiling point of water (100 °C)
The lower fixed point is the melting point of pure ice (\(0\,°\text{C}\)).
The upper fixed point is the boiling point of pure water at standard atmospheric pressure (\(100\,°\text{C}\)).
(c)(i) 350 N, to the right / forward
The resultant force is found by subtracting the smaller opposing force from the larger one: \(900 – 550 = 350\,\text{N}\).
Since the larger force (\(900\,\text{N}\)) acts to the right/forward, the resultant force also acts in that direction.
(c)(ii) 720 N cm
Moment is calculated using \(\text{moment} = \text{force} \times \text{perpendicular distance from the pivot}\).
Moment \(= 40\,\text{N} \times 18\,\text{cm} = 720\,\text{N cm}\).
Question 10
Place ticks (\(\checkmark\)) in the boxes to show the correct features of each process.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic B5.1 — Enzymes (Part (a)(i), (a)(ii))
• Topic B6.1 — Photosynthesis and Topic B12.1 — Respiration (Part (b))
• Topic B1.1 — Characteristics of living organisms (Part (c))
▶️ Answer/Explanation
(a)(i) a protein that functions as a biological catalyst
An enzyme is a type of protein molecule.
It functions as a biological catalyst, speeding up chemical reactions in living organisms without being used up.
(a)(ii) enzyme activity increases then decreases with increasing pH, peaking at pH 7
As pH rises from around \(5\) to \(7\), enzyme activity increases and reaches its optimum (maximum) at \(\text{pH} = 7\).
Beyond pH \(7\), as pH continues to rise towards \(9\), enzyme activity decreases again.
This shows enzyme A works best at a neutral pH of \(7\).
(b)
Photosynthesis occurs in plants, and produces oxygen as a product (it does not release carbon dioxide; it uses it up).
Aerobic respiration occurs in plants too (as well as animals), and it releases carbon dioxide but does not produce oxygen — it uses oxygen up.
(c) any three from: movement, sensitivity, growth, excretion, nutrition, reproduction
Living organisms show movement, the ability to change position.
They also show sensitivity (detecting and responding to changes), growth (a permanent increase in size), excretion (removal of waste), nutrition (taking in materials for energy), and reproduction (producing more of the same organism).
Question 11
The observations are shown in Table 11.1.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic C9.3 — Alloys and their properties (Part (a))
• Topic C8.4 — Transition elements (Part (b))
• Topic C12.5 — Identification of ions and gases (Part (c), iron(II) test)
• Topic C9.5 — Corrosion of metals (Part (d))
• Topic C2.3 — Isotopes (Part (e))
• Topic C9.4 — Reactivity series (Part (f))
▶️ Answer/Explanation
(a) alloy
A mixture made from a metal combined with one or more other elements is called an alloy.
Alloys are usually harder and stronger than the pure metal alone.
(b) transition elements / transition metals
Period 4 contains a block of metals between Groups II and III.
Iron belongs to this block, known as the transition elements.
(c) test: add aqueous sodium hydroxide; observation: green precipitate
Adding aqueous sodium hydroxide to a solution containing iron(II) ions produces a precipitate.
A positive result for iron(II) ions is shown by the formation of a green precipitate, insoluble in excess.
(d) oxygen and water
Rusting is a reaction between iron, oxygen, and water.
Both oxygen and water (moisture) must be present at the same time for iron to rust.
(e)(i) neutrons = 32, electrons = 26
Number of neutrons = nucleon number − proton number \(= 58 – 26 = 32\).
In a neutral atom, the number of electrons equals the number of protons, so electrons \(= 26\).
(e)(ii) atoms of the same element with the same number of protons but different numbers of neutrons
Isotopes are atoms of the same element.
They have the same proton number but different numbers of neutrons, giving them different nucleon numbers.
(f) most reactive: lithium; calcium; iron; least reactive: silver
The rate of bubbling with dilute hydrochloric acid indicates reactivity: faster bubbling means a more reactive metal.
Lithium bubbles fastest (most reactive), followed by calcium, then iron (only a few bubbles), with silver producing no bubbles at all (least reactive).
Question 12
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):
• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a))
• Topic P4.2.4 — Resistance (Part (b)(i))
• Topic P4.4 — Electrical safety (Part (b)(ii))
• Topic P2.3.1 — Conduction (Part (c)(i))
• Topic P2.3.2 — Convection (Part (c)(ii))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (d))
• Topic P1.6.3 — Energy resources (Part (e))
▶️ Answer/Explanation
(a) fuse symbol inserted in the gap in the circuit
A fuse is normally placed in the live wire of a mains circuit, close to the supply.
The standard fuse symbol (a rectangle on the wire) should be drawn in the gap shown in Fig. 12.1.
(b)(i) resistance = 80 Ω
Resistance is calculated using \(R = \dfrac{V}{I}\).
\(R = \dfrac{240}{3} = 80\,\Omega\).
(b)(ii) a fuse must have a rating slightly higher than the normal operating current
The heater draws a normal current of \(3\,\text{A}\).
A \(3\,\text{A}\) fuse would blow during normal use, so a \(5\,\text{A}\) fuse (just above the operating current) is chosen instead, so it only blows if the current becomes dangerously high.
(c)(i) conduction
Thermal energy passes through the solid floor material by conduction.
This is because conduction is the main method of thermal energy transfer through solids.
(c)(ii) convection
Air heated near the floor becomes less dense and rises, while cooler air sinks to take its place.
This circulation of air, known as convection, spreads thermal energy throughout the room.
(d) faster-moving (most energetic) molecules escape from the surface of the liquid
In the water, molecules move with a range of different speeds.
The fastest-moving, most energetic molecules near the surface have enough energy to overcome the forces holding them in the liquid and escape as vapour, which is evaporation.
(e) advantage: renewable / does not produce carbon dioxide; disadvantage: only works during daylight / needs sunlight
Solar cells generate electricity using a renewable energy source and produce no carbon dioxide during operation.
However, they only generate electricity when sunlight is available, so output depends on daylight and weather conditions.