Question 1
Photosynthesis is the process by which plants manufacture ………………… from raw materials using energy from ………………… .
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B15.3 — Sexual reproduction in plants (Part (a))
• Topic B6.1 — Photosynthesis (Part (b))
• Topic B4.1 — Biological molecules (Part (c))
▶️ Answer/Explanation
(a)(i) Test-tube A
Germination needs both water and oxygen present.
Test-tube A is the only one with both conditions met.
(a)(ii) A suitable temperature
Water and oxygen were tested in the table.
Temperature is the third requirement for germination that was not varied here.
(b)(i) carbohydrates; light
Photosynthesis converts raw materials into carbohydrates.
The energy used comes from light, absorbed by chlorophyll.
(b)(ii) carbon dioxide; water
The word equation is: \( \text{carbon dioxide} + \text{water} \rightarrow \text{glucose} + \text{oxygen} \).
So the two raw materials required are carbon dioxide and water.
(c) amino acids
Proteins are large molecules made of many smaller repeating units.
These smaller units are called amino acids.
Question 2
State the name of one other fossil fuel.
State why fractional distillation is a physical change and not a chemical change.
On Fig. 2.1, draw one line from each fraction to its use. One line has been drawn for you.
Describe the observation for an alkane and for an alkene.
State the name of the polymer made from ethene.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C11.3 — Fuels (Parts (a), (b), (c))
• Topic C11.5 — Alkenes (Part (d))
▶️ Answer/Explanation
(a) Coal / natural gas
Fossil fuels form from the remains of ancient organisms over millions of years.
Coal and natural gas are the two other common examples besides petroleum.
(b) The change is reversible / no new products are formed
Fractional distillation only separates the mixture based on differing boiling points.
No new chemical substances are produced, so it is a physical change.
(c) 
Each fraction of petroleum has different properties suited to different uses.
Bitumen is used for road surfaces and gas oil for diesel engine fuel.
(d)(i) Ethene contains a carbon-carbon double bond
Unsaturated compounds contain at least one C=C double bond.
This double bond allows ethene to undergo addition reactions.
(d)(ii) Test: aqueous bromine
Alkane: no change, stays orange/brown.
Alkene: decolourises (turns colourless), showing the double bond has reacted.
(d)(iii) Six atoms
\( C_2H_4 \) contains 2 carbon atoms and 4 hydrogen atoms.
Total atoms \( = 2 + 4 = 6 \).
(d)(iv) Structural formula of ethane
Ethane, \( C_2H_6 \), has a single C–C bond.
Each carbon is bonded to three hydrogen atoms, giving H₃C–CH₃.
(d)(v) Polyethene / polythene
Many ethene monomers join together in an addition polymerisation reaction.
This forms the long-chain polymer called polyethene (polythene).
Question 3
Calculate the speed of the submarine in m/s.
Ionising radiation is released in the reactor.
The reactor must be shielded to protect the crew from this radiation.
Pu-239 has a half-life of 24 000 years.
A small sample of Pu-239 has a mass of 1.0 g.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.5.1 — Forces: weight (Part (a))
• Topic P1.2 — Motion (Part (b))
• Topic P5.2.2 — Radioactivity: effects and shielding (Part (c))
• Topic P5.2.4 — Half-life (Part (d))
• Topic P3.2.1 — Reflection of light (Part (e))
▶️ Answer/Explanation
(a) Force C
Weight always acts vertically downward due to gravity.
In Fig. 3.1, force C points downward, so it represents the submarine’s weight.
(b) 5 m/s
Convert units: \( 36 \, \text{km} = 36\,000 \, \text{m} \) and \( 2 \, \text{hours} = 7200 \, \text{s} \).
Speed \( = \dfrac{\text{distance}}{\text{time}} = \dfrac{36\,000}{7200} = 5 \, \text{m/s} \).
(c)(i) Cancer / cell mutation
Ionising radiation can damage DNA within living cells.
This damage can cause mutations, which may lead to cancer.
(c)(ii) Lead
Lead is very dense and has a high atomic number.
This makes it effective at absorbing and stopping \( \alpha \)- and \( \beta \)-radiation.
(d) 0.0625 g
Number of half-lives \( = \dfrac{96\,000}{24\,000} = 4 \).
Mass remaining: \( 1.0 \rightarrow 0.5 \rightarrow 0.25 \rightarrow 0.125 \rightarrow 0.0625 \, \text{g} \).
(e) Light reflects off both mirrors
Light from the ship strikes the top mirror and reflects downward.
It then strikes the bottom mirror and reflects into the observer’s eye.
Question 4
The scientists calculate the average rate of diffusion for dye X after 30 seconds as:
\( \dfrac{\text{distance travelled}}{\text{time taken}} = \dfrac{11}{30} = 0.37 \, \text{mm/s} \).
Calculate the average rate of diffusion for dye Y after 30 seconds.
oxygen starch water
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B3.1 — Diffusion (Parts (a), (b))
• Topic B2.1 — Cell structure (Parts (c)(i), (d))
• Topic B12.1 — Respiration (Part (c)(ii))
▶️ Answer/Explanation
(a)(i) Distance travelled increases with time
Both dye X and dye Y spread further from the origin as time passes.
This shows diffusion continuing steadily over the 60-second period.
(a)(ii) 0.2 mm/s
From the graph, dye Y travels 6 mm after 30 seconds.
Rate \( = \dfrac{6}{30} = 0.2 \, \text{mm/s} \).
(b) From higher to lower concentration by random movement
Particles move from a region of higher concentration to a region of lower concentration.
This occurs due to the random motion of the particles themselves.
(c)(i) Cell membrane
The cell membrane is selectively permeable.
It controls which substances can enter or leave the cell.
(c)(ii) Glucose and oxygen
Respiration requires glucose as a fuel and oxygen for aerobic breakdown.
Both substances diffuse into cells to supply the reaction.
(d)
The vacuole contains cell sap that supports the plant cell.
Cytoplasm is where chemical reactions/enzymes are located.
The chloroplast is where photosynthesis occurs.
Question 5
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.2 — Atomic structure and the Periodic Table (Part (a)(i))
• Topic C10.1 — Water (Parts (a)(ii), (b)(ii), (b)(iii))
• Topic C6.2 — Rate of reaction (Part (a)(iii))
• Topic C10.2 — Air quality and climate (Part (a)(iv))
• Topic C2.5 — Simple molecules and covalent bonds (Part (a)(v))
• Topic C6.1 — Chemical reactions: thermal decomposition (Part (b)(i))
▶️ Answer/Explanation
(a)(i) NH₃
Ammonia is a compound of one nitrogen atom and three hydrogen atoms.
Its formula NH₃ matches this composition directly.
(a)(ii) Cl₂
Chlorine gas is added to water supplies to kill harmful bacteria.
This makes drinking water safe for use.
(a)(iii) CO
Incomplete combustion occurs when oxygen supply is insufficient.
This produces carbon monoxide (CO) instead of carbon dioxide.
(a)(iv) N₂
Nitrogen gas makes up about 78% of the Earth’s atmosphere.
It exists as a diatomic molecule, N₂.
(a)(v) CH₄
Methane has one carbon atom bonded to four hydrogen atoms.
Each C–H bond is a single covalent bond, giving four in total.
(b)(i) Carbon dioxide
Thermal decomposition: \( \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2 \).
So the other product formed alongside calcium oxide is carbon dioxide.
(b)(ii) Neutralises acidic soil
Calcium carbonate is a base that reacts with acids in the soil.
This raises the soil pH, making it less acidic for plant growth.
(b)(iii) Nitrogen; phosphorus; potassium
These three elements are essential nutrients for healthy plant growth.
They are commonly supplied together in fertilisers (often labelled N-P-K).
Question 6
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P3.4 — Sound (Parts (a), (c)(ii), (c)(iii))
• Topic P3.3 — Electromagnetic spectrum (Part (b))
• Topic P3.1 — General properties of waves (Part (c)(i))
▶️ Answer/Explanation
(a) Echo
A sound wave that bounces off a surface and returns is called an echo.
Bats use this reflected sound to locate objects such as moths.
(b)(i) 
The electromagnetic spectrum is ordered by wavelength and frequency.
UV has a shorter wavelength than infrared but longer than X-rays.
(b)(ii) Radio waves
Radio waves have the longest wavelength in the spectrum.
Since frequency and wavelength are inversely related, they have the lowest frequency.
(c)(i) 
Amplitude is the maximum displacement of points on a wave.
Frequency is the number of waves passing a fixed point per second.
Wavelength is the distance between the peaks of consecutive waves.
(c)(ii) 200 kHz is above the human hearing range
The typical human hearing range extends up to about 20 kHz.
Since \( 200 \, \text{kHz} \) is far above this limit, humans cannot hear it.
(c)(iii) Pitch increases
Pitch is directly related to frequency.
As the frequency rises from \( 200 \, \text{kHz} \) to \( 250 \, \text{kHz} \), the pitch increases.
Question 7
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B17.1 — Variation (Part (a))
• Topic B16.1 — Chromosomes and genes (Part (b), (c))
▶️ Answer/Explanation
(a)(i) 22.0–22.9 cm
This category has the tallest bar on the histogram, at 12 students.
It represents the most common hand-span range measured.
(a)(ii) 4
Reading the bar for the 19.0–19.9 cm category on Fig. 7.2 gives a height of 4.
So 4 students recorded a hand-span in this range.
(a)(iii) There is a range of values between two extremes
Continuous variation shows a spread of values rather than distinct categories.
The histogram shows overlapping ranges from 17 cm up to nearly 28 cm.
(a)(iv) Height
Height varies continuously across a population, with no distinct categories.
It is a classic example alongside hand-span, mass, and foot length.
(b)(i) Female gametes both X; offspring XX and XY in equal proportion
The female contributes an X chromosome to every egg cell.
Combined with the male’s X or Y sperm, this gives XX (female) or XY (male) offspring.
(b)(ii) 1 : 1
The Punnett square shows two XX and two XY combinations.
This gives an equal ratio of male to female offspring, 1:1.
(c) Smallest to largest: DNA, gene, chromosome, nucleus
DNA is the smallest, forming genes as specific coding sections.
Genes make up chromosomes, which are found inside the nucleus, the largest structure.
Question 8
A potassium atom has a total of ………………… electrons.
A potassium ion has a positive charge of ………………… .
Fig. 8.1 shows the electronic structure of a sodium atom and a chlorine atom.
- anode
- cathode
- electrolyte
State the name of the other electrode product.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C8.1 — Arrangement of elements (Part (a))
• Topic C2.4 — Ions and ionic bonds (Part (b))
• Topic C4.2 — Electrolysis (Part (c)(i), (ii), (iii))
▶️ Answer/Explanation
(a) Group 1; 19 electrons; charge of 1
Potassium is an alkali metal, placed in Group 1.
Its atomic number is 19, so it has 19 electrons, and it loses one to form \( K^+ \).
(b) 
Sodium loses its outer electron, leaving an electron arrangement of 2,8.
Chlorine gains that electron, giving an arrangement of 2,8,8, forming an ionic bond.
(c)(i) Anode is positive; cathode is negative; electrolyte is the NaCl solution
The anode is the positive electrode where oxidation occurs.
The cathode is the negative electrode where reduction occurs, and the electrolyte is the concentrated aqueous sodium chloride.
(c)(ii) Chlorine
Hydrogen gas is produced at the cathode from reduction of hydrogen ions.
Chlorine gas is produced at the anode from oxidation of chloride ions.
(c)(iii) Lighted splint test; gives a pop sound
A lighted splint is held near the gas being tested.
If hydrogen is present, it burns rapidly with a characteristic “pop” sound.
Question 9
The gravitational field strength, \( g \), is 10 N/kg.
The aircraft engines produce a constant horizontal thrust force of 1 200 000 N.
A constant frictional force of 500 000 N acts on the aircraft.
Calculate the value of \( X \).
The current passing through the monitor when in use is 0.060 A.
Calculate the potential difference across the monitor.
State the unit of your answer.
The fuse in the electrical supply to the monitor has to be replaced.
Several fuse ratings are available.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.3 — Mass and weight (Part (a))
• Topic P1.5.1 — EEffects of forces (Part (b))
• Topic P1.6.1 — Energy (Part (c)(i))
• Topic P4.2.4 — Resistance (Part (c)(ii))
• Topic P4.4 — Electrical safety (Part (c)(iii))
▶️ Answer/Explanation
(a) 4 000 000 N
Weight is calculated using \( W = m \times g \).
Substituting values: \( W = 400\,000 \, \text{kg} \times 10 \, \text{N/kg} = 4\,000\,000 \, \text{N} \).
(b)(i) 700 000 N
Resultant force is the difference between thrust and friction.
\( F = 1\,200\,000 – 500\,000 = 700\,000 \, \text{N} \).
(b)(ii) A resultant force acts on the aircraft
Since thrust exceeds friction, there is a non-zero resultant force.
By Newton’s second law, this resultant force causes the aircraft to accelerate.
(c)(i) X = 1 J
Total energy input equals total energy output: \( 200 = 80 + 119 + X \).
Solving gives \( X = 200 – 199 = 1 \, \text{J} \).
(c)(ii) 114 V
Using Ohm’s law: \( V = I \times R \).
\( V = 0.060 \, \text{A} \times 1900 \, \Omega = 114 \, \text{V} \).
(c)(iii) 100 mA
The fuse rating must be higher than the operating current of 60 mA.
100 mA is the smallest available rating above this, so it is the correct choice for safety.
Question 10
- ingestion occurs
- egestion occurs
- mechanical digestion occurs
- saliva is produced
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B7.2 — Digestive system (Parts (a), (b))
• Topic B7.1 — Diet (Part (c))
▶️ Answer/Explanation
(a)(i) Ingestion – K; Egestion – F; Mechanical digestion – K/C; Saliva produced – A
Ingestion is the taking in of food, which occurs at the mouth (K).
Egestion of undigested waste occurs at the anus (F), while mechanical digestion happens in the mouth (K) and stomach (C), and saliva is produced by the salivary glands (A).
(a)(ii) D – pancreas; H – gall bladder
The pancreas (D) secretes digestive enzymes into the small intestine.
The gall bladder (H) stores bile before it is released to aid fat digestion.
(b) 
Absorption is the movement of digested food molecules into the blood.
Assimilation is the movement of these absorbed food molecules into the cells where they are used.
(c) 
Carbohydrates are the main energy source, while fibre prevents constipation.
Iron is needed for haemoglobin, protein for growth and repair, and vitamin D for healthy bone growth.
Question 11
One of the properties of transition metals is that they form coloured compounds.
State two other properties of transition metals which are not properties of all metals.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C7.3 — Preparation of salts (Part (a)(i), (ii))
• Topic C2.5 — Simple molecules and covalent bonds (Part (a)(iii))
• Topic C5.1 — Exothermic and endothermic reactions (Part (a)(iv))
• Topic C6.2 — Rate of reaction (Part (a)(v))
• Topic C8.4 — Transition elements (Part (b))
• Topic C9.3 — Alloys and their properties (Part (c))
▶️ Answer/Explanation
(a)(i) Filtration
Excess unreacted copper carbonate is removed as an insoluble solid.
Filtration separates this solid from the copper sulfate solution.
(a)(ii) Copper sulfate
Copper carbonate reacts with dilute sulfuric acid.
This produces copper sulfate, water, and carbon dioxide.
(a)(iii) Two non-metals bonding, sharing electrons
Carbon and oxygen are both non-metal elements.
When non-metals bond, they share electrons, forming covalent bonds.
(a)(iv) Exothermic
A reaction that releases heat energy to the surroundings is exothermic.
This is shown by the rising temperature of the reacting mixture.
(a)(v) Rate of reaction decreases
Large pieces have a smaller surface area than powdered pieces.
This reduces the frequency of collisions between particles, decreasing the rate.
(b) High density; act as catalysts (any two, also variable valency)
Transition metals typically have a high density compared to other metals.
They are also often used as catalysts, and can show variable valency.
(c)(i) Alloy
Brass is formed by mixing copper and zinc together.
A mixture of two or more metals is called an alloy.
(c)(ii) Stronger than copper
Pure copper is relatively soft and easily deformed.
Brass is harder and stronger, making it more suitable for many uses.
Question 12
The astronomer uses a telescope which contains mirrors.
Fig. 12.2 is a speed-time graph for the meteorite as it approaches Earth.
The density of the meteorite is 7500 kg/m³.
Suggest a simple way for the scientist to test for iron in an object found on Earth.
Draw more circles in the boxes in Fig. 12.3 to show the arrangement and separation of particles in a solid and in a liquid.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P3.2.1 — Reflection of light (Part (a))
• Topic P1.2 — Motion (Part (b)(i), (iii))
• Topic P1.6.1 — Energy (Part (b)(ii))
• Topic P1.4 — Density (Part (c)(i))
• Topic C12.5 — Identification of ions and gases (Part (c)(ii))
• Topic P2.3.4 — Consequences of thermal energy transfer (Part (d)(i))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (d)(ii))
• Topic P2.1.2 — Particle model (Part (d)(iii))
▶️ Answer/Explanation
(a) Same size; upright
A plane mirror produces an image the same distance behind the mirror as the object is in front.
This image is the same size as the object and appears upright, not inverted.
(b)(i) S marked between 5 s and 12 s
The meteorite travels at a roughly constant speed until about 5–6 seconds.
After this point the curve falls, so an S should be placed anywhere the speed is decreasing, such as around 8–10 s.
(b)(ii) Kinetic energy
As the meteorite slows down, its kinetic energy decreases.
This energy is transferred to the surroundings mainly as heat due to air resistance.
(b)(iii) 36 000 m/s
Reading the graph, the speed stays constant near its highest value before decreasing.
This maximum plateau value is 36 000 m/s.
(c)(i) 3.0 m³
Volume is calculated as \( V = \dfrac{\text{mass}}{\text{density}} \).
\( V = \dfrac{22\,500}{7500} = 3.0 \, \text{m}^3 \).
(c)(ii) Use a magnet
Iron is a magnetic material, unlike most other metals.
If the object is attracted to a magnet, this confirms the presence of iron.
(d)(i) Conduction
The hot meteorite is in direct contact with the surrounding seawater.
Thermal energy transfers by conduction through this direct particle contact.
(d)(ii) Fastest, most energetic molecules escape the surface
The molecules with the most kinetic energy move fastest within the liquid.
These high-energy molecules escape from the surface into the air as vapour, cooling the remaining liquid.
(d)(iii) Solid: touching, regular arrangement; liquid: touching, irregular arrangement
In a solid, particles are closely packed in a fixed, regular pattern.
In a liquid, particles remain close together but are arranged randomly and can move past one another.