Question 1
most absorption occurs
egestion occurs
ingestion occurs
saliva is produced.
Digestion is the ………………………………………… of large, insoluble food molecules into small, water-soluble molecules using mechanical and ………………………………………… processes.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B7.2 — Digestive system (Part (a)(i))
• Topic B7.2 — Digestive system (Part (a)(ii))
• Topic B7.3 — Digestion (Part (a)(iii))
• Topic B7.1 — Diet (Part (b))
• Topic B7.1 — Diet (Part (c))
▶️ Answer/Explanation
(a)(i) most absorption — F; egestion — E; ingestion — J; saliva produced — A
Most absorption of digested food occurs in the small intestine, labelled F.
Egestion of undigested waste occurs at the anus, labelled E.
Ingestion (taking food into the mouth) occurs at J.
Saliva is produced by the salivary glands, labelled A.
(a)(ii) D — pancreas; H — liver
D is the pancreas, which secretes digestive enzymes into the small intestine.
H is the liver, which produces bile to help digest fats.
(a)(iii) breakdown; chemical
Digestion is the breakdown of large, insoluble food molecules into small, water-soluble molecules.
This occurs using mechanical and chemical processes.
(b) 
Carbohydrate is mainly obtained from starchy foods such as rice.
Vitamin C is mainly obtained from fruits such as grapefruit.
Tuna fish is a principal source of protein, not carbohydrate or vitamin C, so it is not connected.
(c) making haemoglobin / prevents anaemia
Iron is needed by the body to make haemoglobin, the oxygen-carrying pigment in red blood cells.
A lack of dietary iron can lead to anaemia.
Question 2
Rusting involves the oxidation of iron.
State what is meant by the term oxidation.
Explain how this method prevents the iron nail from rusting.
Metal ores are a finite resource and therefore, metals need to be …………………………………. .
(i) Suggest why steel is used for making cars instead of pure iron.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C6.3 — Redox (Part (a)(i))
• Topic C9.5 — Corrosion of metals (Part (a)(ii))
• Topic C9.6 — Extraction of metals (Part (b))
• Topic C8.4 — Transition elements (Part (c))
• Topic C9.3 — Alloys and their properties (Part (d))
• Topic C9.1 — Properties of metals (Part (e))
▶️ Answer/Explanation
(a)(i) gain of oxygen
Oxidation is defined as the gain of oxygen by a substance.
Iron gains oxygen (and water) from the air to form iron oxide (rust).
(a)(ii) e.g. paint it — stops contact with air and water
Method: painting the iron nail (or greasing/oiling/galvanising).
Explanation: the coating creates a barrier that stops the iron coming into contact with air and water, which are both needed for rusting.
(b) recycled
Since metal ores are finite (non-renewable), metals extracted from them should be recycled to conserve the limited supply of ore and save energy.
(c) iron acts as a catalyst ✓; iron forms coloured compounds ✓
Transition elements, including iron, commonly act as catalysts.
Transition elements also typically form coloured compounds.
Iron actually has a high density, a high melting point, and is grey/silver in colour, so the other three statements are incorrect.
(d)(i) stronger
Steel (an alloy) is harder and stronger than pure iron.
This makes it more suitable for the structural demands of car manufacturing.
(d)(ii) 65 kg
Percentage of iron = \(100 – (1 + 18 + 2 + 2 + 12) = 65\%\).
Mass of iron = \(\dfrac{65}{100} \times 80 = 52 \, \text{kg}\).
(e) can be shaped or bent (without breaking)
Malleable means the metal can be hammered, pressed, or bent into different shapes without cracking or breaking.
Question 3
When she wears her skis, she can stand on the snow without sinking.
Explain these observations.
Ultraviolet radiation is a form of ionising radiation.
Describe one danger to humans of being exposed to large quantities of ultraviolet radiation.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.7 — Pressure (Part (a)(i))
• Topic P3.4 — Sound (Part (a)(ii))
• Topic P1.5.1 — Effects of forces (Part (b))
• Topic P1.2 — Motion (Part (c))
• Topic P3.3 — Electromagnetic spectrum (Part (d))
▶️ Answer/Explanation
(a)(i) skis increase surface area, so pressure is less
Wearing skis spreads the skier’s weight over a much larger surface area.
Since \(\text{pressure} = \dfrac{\text{force}}{\text{area}}\), a larger area gives a lower pressure on the snow, so she does not sink.
(a)(ii) the sound wave is reflected
The sound wave reflects off the high wall and travels back to the skier.
This reflected sound is heard as an echo.
(b)(i) L
Weight acts vertically downward on the snowmobile and skier, which is force L in Fig. 3.2.
(b)(ii) K
Friction opposes the direction of travel (which is to the left), so it acts to the right — this is force K.
(c)(i) 5 m/s
The graph shows the speed levelling off at its highest value of \(5 \, \text{m/s}\) between \(t = 20\,\text{s}\) and \(t = 90\,\text{s}\).
(c)(ii) the line has a positive slope/gradient
During the first 20 s, the speed–time graph is a straight line sloping upward.
An increasing gradient (or any positive slope) on a speed–time graph shows the speed is increasing, i.e. the skier is accelerating.
(c)(iii) distance = area under graph
Distance travelled = area under the speed–time graph for the first 20 s.
Area = \(\frac{1}{2} \times 20 \, \text{s} \times 5 \, \text{m/s} = 50 \, \text{m}\).
(d) skin cancer
Large exposure to ultraviolet radiation can cause skin cancer.
UV radiation is ionising and can damage the DNA in skin cells, leading to uncontrolled cell division.
Question 4
The two biggest sources of pollution are …………………………………… and …………………………………… .
The total percentage of pollution caused by chemical waste is …………………………………… %.
The percentage of pollution caused by discarded rubbish is …………………………………… %.
A scientist measures the height of two pea plants, A and B, for one month.
Plant A is given unpolluted water.
Plant B is given polluted water.
Table 4.1 shows the increase in height for each plant.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B19.1 — Habitat destruction (Part (a)(i))
• Topic B19.1 — Habitat destruction (Part (a)(ii))
• Topic B8.2 — Water uptake (Part (b)(i))
• Topic B15.3 — Sexual reproduction in plants (Part (b)(ii))
▶️ Answer/Explanation
(a)(i) agriculture and (untreated) sewage; 41%; 5%
The two biggest sources shown in the pie chart are agriculture (27%) and untreated sewage (27%).
Total chemical waste = \(9 + 14 + 18 = 41\%\).
Discarded rubbish accounts for 5% of pollution, read directly from the chart.
(a)(ii) spread of disease
Untreated sewage contains harmful microorganisms.
These can spread diseases to humans through contaminated water.
(b)(i) 18 cm
Difference = \(29 – 11 = 18 \, \text{cm}\).
(b)(ii) warm/suitable temperature; oxygen
Besides water, seeds also require a suitable/warm temperature to germinate.
Seeds also require oxygen for respiration during germination.
Question 5
Explain the importance of purity in the manufacture of substances used in food additives.
(i) Describe the difference between an element and a compound.
Electrolysis is the breakdown of molten lead(II) bromide by the passage of …………………………………… .
The gas released at the positive electrode is …………………………………… and …………………………………… is formed at the negative electrode.
The negative electrode is called the …………………………………… .
The student’s observations are shown in Table 5.1.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C12.4 — Separation and purification (Part (a))
• Topic C12.4 — Separation and purification (Part (b))
• Topic C2.1 — Elements, compounds and mixtures (Part (c)(i))
• Topic C4.1 — Electrolysis (Part (c)(ii))
• Topic C9.4 — Reactivity series (Part (d))
▶️ Answer/Explanation
(a) 
Chromatography separates different dyes based on their differing solubility/movement through paper.
Fractional distillation separates a mixture of liquids (like petroleum fractions) with different boiling points.
Crystallisation separates a dissolved solid (salt) from its solution by evaporating the solvent.
Distillation separates the solvent (water) itself from a solution.
(b) to avoid poisoning
Food additives must be pure so that they do not contain harmful impurities.
Impure substances could poison or otherwise harm the people who consume the food.
(c)(i) an element contains only one type of atom; a compound consists of atoms of two or more elements chemically combined
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 together.
(c)(ii) electricity; bromine; lead; cathode
Electrolysis is the breakdown of a molten (or dissolved) ionic compound by the passage of electricity.
Bromine gas is released at the positive electrode (anode).
Lead is formed at the negative electrode, which is called the cathode.
(d) calcium, magnesium, lead, copper
Calcium reacts very quickly, so it is the most reactive.
Magnesium reacts quickly, lead reacts very slowly, and copper does not react at all, giving the order calcium > magnesium > lead > copper.
Question 6
Nuclear fission releases …………………………………… energy which heats up water in a boiler.
When the turbine and generator are turning, they have …………………………………… energy.
The generator produces …………………………………… energy.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.6.3 — Energy resources (Part (a)(i))
• Topic P5.1 — The nucleus (Part (a)(ii))
• Topic P5.2.2 — The three types of nuclear emission (Part (b)(i))
• Topic P5.2.3 — Radioactive decay (Part (b)(ii))
• Topic P5.2.4 — Half-life (Part (b)(iii))
▶️ Answer/Explanation
(a)(i) thermal; kinetic; electrical
Nuclear fission releases thermal (heat) energy, which is used to heat water into steam.
The turbine and generator, once spinning, possess kinetic energy.
The generator converts this kinetic energy into electrical energy.
(a)(ii) the nucleus splits
During nuclear fission, a large, unstable nucleus (such as uranium or plutonium) splits into two smaller nuclei, releasing energy and neutrons.
(b)(i) +2 (positive)
An α-particle is identical to a helium nucleus, consisting of 2 protons and 2 neutrons, giving it a charge of \(+2\).
(b)(ii) protons decrease by 2 (to 92); neutrons decrease by 2 (to 143)
Emitting an α-particle removes 2 protons and 2 neutrons from the nucleus.
Plutonium-239 has 94 protons and 145 neutrons, so after decay the uranium nucleus has \(94 – 2 = 92\) protons and \(145 – 2 = 143\) neutrons.
(b)(iii) 0.75 g
\(72\,000 \div 24\,000 = 3\) half-lives.
Mass remaining = \(6.0 \, \text{g} \div 2^3 = 6.0 \div 8 = 0.75 \, \text{g}\).
Question 7
• Identify the part where photosynthesis takes place with a label line and the correct name.
• Identify the part that contains the genetic material with a label line and the letter X.
glycogen glycerol
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B6.2 — Leaf structure (Part (a))
• Topic B2.1 — Cell structure (Part (b))
• Topic B6.1 — Photosynthesis (Part (c))
• Topic B4.1 — Biological molecules (Part (d))
• Topic B8.2 — Water uptake (Part (e))
• Topic B8.1 — Xylem and phloem (Part (f))
▶️ Answer/Explanation
(a) A — cuticle; B — (lower) epidermis; C — stoma/stomata
A is the waxy cuticle covering the upper surface of the leaf.
B is the lower epidermis, the outer layer of cells on the underside of the leaf.
C is a stoma (plural: stomata), a pore in the lower epidermis that allows gas exchange.
(b) chloroplast labelled with correct name; nucleus labelled with X
The chloroplasts (shown as the oval structures) are where photosynthesis takes place, as they contain chlorophyll.
The nucleus, labelled X, contains the genetic material (DNA) of the cell.
(c) process to manufacture glucose, from carbon dioxide and water, using light energy
Photosynthesis is the process used by plants (producers) to manufacture glucose.
It uses the raw materials carbon dioxide and water.
The reaction requires light energy, which is absorbed by chlorophyll and converted into chemical energy.
(d) amino acid
Nitrate ions are needed by plants to make amino acids, which are then used to build proteins.
Starch, glycogen and fatty acids/glycerol do not require nitrate ions for their synthesis.
(e) root hair cell
Root hair cells have a large surface area that increases the absorption of mineral ions (and water) from the soil.
(f) xylem
Mineral ions dissolved in water are transported up the stem in the xylem vessels, along with the transpiration stream.
Question 8
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.5 — Simple molecules and covalent bonds (Part (a)(i))
• Topic C2.5 — Simple molecules and covalent bonds (Part (a)(ii))
• Topic C11.3 — Fuels (Part (b))
• Topic C10.2 — Air quality and climate (Part (c))
▶️ Answer/Explanation
(a)(i) 1 shared pair of electrons between C and each H
Each hydrogen atom shares one electron with the carbon atom.
Carbon shares one of its four outer-shell electrons with each of the four hydrogen atoms, forming four single covalent bonds, each shown as a shared pair of dots and crosses.
(a)(ii) covalent; bonding between non-metals involving shared electron pairs
The bonding present is covalent bonding.
This occurs between non-metal atoms (carbon and hydrogen), where electron pairs are shared rather than transferred.
(b) methane + oxygen → carbon dioxide + water
Complete combustion of a hydrocarbon fuel requires oxygen.
The products of complete combustion are carbon dioxide and water: \(\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}\).
(c)(i) carbon monoxide
Incomplete combustion occurs when there is insufficient oxygen, producing carbon monoxide instead of carbon dioxide.
(c)(ii) poisonous
Carbon monoxide is poisonous/toxic.
It combines with haemoglobin in red blood cells more readily than oxygen, reducing the blood’s ability to carry oxygen around the body.
Question 9
• a motor to pump the hot water through the machine.
The circuit symbol for a heater is
The circuit symbol for a motor is
Complete the circuit diagram on Fig. 9.2.
The resistance of the motor is \(80 \, \Omega\).
Identify from the list the most likely value for the combined resistance of the heater and motor connected in parallel.
Explain your answer.
This turning effect can be increased by increasing the number of turns on the coil.
State two other ways to increase this turning effect.
During evaporation, water changes state from a liquid to a gas.
(i) Complete the diagrams in Fig. 9.3 to show the arrangement and separation of molecules in a liquid and in a gas.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a)(i))
• Topic P4.2.4 — Resistance (Part (a)(ii))
• Topic P4.2.2 — Electric current (Part (a)(iii))
• Topic P4.5.4 — Force on a current-carrying conductor (Part (a)(iv))
• Topic P2.1.2 — Particle model (Part (b)(i))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (b)(ii))
▶️ Answer/Explanation
(a)(i) heater and motor in parallel, each with its own switch
The heater and motor are drawn as two separate parallel branches connected across the 240 V supply.
Each branch contains its own switch in series with the heater or motor component.
(a)(ii) 16 Ω
For resistors in parallel, the combined resistance is always less than the smallest individual resistance.
Since the smallest resistance here is \(20\,\Omega\), the combined resistance must be less than \(20\,\Omega\), so \(16\,\Omega\) is the only possible value from the list.
(a)(iii) electrons
The current in metal wires is a flow of free/delocalised electrons.
(a)(iv) increase the current; increase the strength of the magnetic field
Increasing the current flowing through the coil increases the turning effect (torque).
Using a stronger magnet increases the strength of the magnetic field, which also increases the turning effect.
(b)(i) liquid: molecules touching, randomly arranged; gas: molecules widely separated, randomly arranged
In the liquid box, molecules should be drawn touching each other but in a random (not regular) arrangement.
In the gas box, molecules should be drawn much further apart (no more than about seven molecules), moving randomly.
(b)(ii) 100 °C
The boiling point of water at standard atmospheric pressure is \(100\,^{\circ}\text{C}\).
Question 10
State the name of the other part of the central nervous system.
One neurone measures 1.5 m in length.
One plant cell measures 0.1 mm in length.
Calculate how many times longer the neurone is than the plant cell.
They are carried in the blood.
They are produced by glands.
They are electrical signals.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B13.1 — Coordination and response (Part (a)(i))
• Topic B13.1 — Coordination and response (Part (a)(ii))
• Topic B13.1 — Coordination and response (Part (a)(iii))
• Topic B2.2 — Size of specimens (Part (b))
• Topic B13.2 — Hormones (Part (c))
• Topic B13.2 — Hormones (Part (d))
▶️ Answer/Explanation
(a)(i) stimulus — (change in) temperature; effector — muscle (in arm)
The stimulus detected by the receptor in the skin is a change in temperature (heat from the hot pan).
The effector is the muscle in the arm that contracts to pull the hand away.
(a)(ii) motor neurone
Neurone X carries the impulse from the spinal cord (central nervous system) to the effector, so it is a motor neurone.
(a)(iii) brain
The central nervous system consists of the brain and the spinal cord.
(b) \(1.5 \times 10^4\)
Convert to the same units: \(1.5 \, \text{m} = 1500 \, \text{mm}\).
Number of times longer = \(\dfrac{1500}{0.1} = 15\,000 = 1.5 \times 10^4\).
(c) hormones; hormones; nerve impulses
Hormones are carried in the blood.
Hormones are produced by glands.
Nerve impulses are electrical signals.
(d) increased breathing rate/depth; increased pulse/heart rate; widened pupils
Adrenaline increases the depth and rate of breathing, supplying more oxygen to muscles.
Adrenaline also increases the heart rate/pulse rate, increasing blood flow to muscles.
(Any two effects, e.g. widened pupils, are acceptable.)
Question 11
Limestone is mixed with water and poured through filter paper.
Limestone is mainly calcium carbonate which reacts with acid.
Fig. 11.1 shows the apparatus used.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C12.4 — Separation and purification (Part (a)(i))
• Topic C7.1 — The characteristic properties of acids and bases (Part (a)(ii))
• Topic C10.2 — Air quality and climate (Part (b)(i))
• Topic C10.2 — Air quality and climate (Part (b)(ii))
• Topic C6.2 — Rate of reaction (Part (c))
▶️ Answer/Explanation
(a)(i) limestone particles are larger than the holes in the filter paper
The holes in the filter paper are too small for the (larger) limestone particles to pass through, so they are retained as the residue.
Water particles are much smaller than the holes, so they pass through the filter paper as the filtrate.
(a)(ii) use universal indicator
Add universal indicator (paper or solution) to the filtrate.
Compare the resulting colour to a pH colour chart to determine the pH number.
(b)(i) combustion of carbon-containing fuels
Burning fossil fuels (carbon-containing fuels) releases additional carbon dioxide into the atmosphere.
(b)(ii) global warming/climate change
Increased carbon dioxide enhances the greenhouse effect, trapping more heat and causing global warming/climate change.
(c)(i) 45 cm³
The graph levels off (plateaus) at a volume of \(45 \, \text{cm}^3\), which is the total volume of gas released.
(c)(ii) 190 s
The reaction finishes at the point where the graph first becomes flat/horizontal, which occurs at \(t = 190 \, \text{s}\).
(c)(iii) steeper line, levelling off at the same 45 cm³
At a higher temperature, the reaction is faster, so the new line should rise more steeply than the original.
Since the amount of acid and limestone is unchanged, the line should still level off at the same final volume of \(45 \, \text{cm}^3\), but sooner.
(c)(iv) decrease particle size (increase surface area); increase acid concentration
Using powdered limestone instead of a single piece increases the surface area, speeding up the reaction.
Using a higher concentration of hydrochloric acid also increases the rate of reaction.
Question 12
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.4 — Density (Part (a))
• Topic P2.3.4 — Consequences of thermal energy transfer (Part (b)(i) & (ii))
• Topic P3.4 — Sound (Part (b)(iii))
• Topic P3.3 — Electromagnetic spectrum (Part (c))
• Topic P3.1 — General properties of waves (Part (d))
▶️ Answer/Explanation
(a) \(1.4 \times 10^{27} \, \text{m}^3\)
Volume = mass ÷ density.
Volume = \(\dfrac{1.97 \times 10^{30}}{1410} = 1.397 \times 10^{27} \approx 1.4 \times 10^{27} \, \text{m}^3\).
(b)(i) convection
Inside the Sun, hot gas rises and cooler gas sinks, transferring thermal energy from the core to the surface by convection.
(b)(ii) radiation
Infrared waves travel from the Sun to the Earth through the vacuum of space by (electromagnetic) radiation, which does not require a medium.
(b)(iii) sound waves need a medium/cannot travel through a vacuum
Sound is a mechanical wave and requires particles of a medium to travel.
Space is a vacuum (contains no particles), so sound cannot travel from the Sun to the Earth.
(c)(i) infrared to the right of visible light
In the electromagnetic spectrum arranged by increasing frequency (with X-rays and visible light shown), infrared radiation has a lower frequency than visible light, so it is placed to the right of (after) visible light.
(c)(ii) gamma radiation
Gamma radiation has the shortest wavelength and therefore the highest frequency in the electromagnetic spectrum.
(c)(iii) all electromagnetic waves travel at the same speed
Infrared and visible light are both electromagnetic waves.
All electromagnetic waves travel at the same speed through a vacuum, so they take the same time to travel the same distance from the Sun to the Earth.
(d)(i) & (ii) amplitude and wavelength correctly labelled
Amplitude (A) is the maximum displacement of the wave from its rest/midline position, shown as a vertical double-headed arrow from the midline to a peak.
Wavelength (W) is the distance between two corresponding points on successive waves (e.g. peak to peak), shown as a horizontal double-headed arrow.