Question 1
- carbohydrate
- protein
- vitamins
Tick (✓) the boxes to show the three chemical elements present in all cooking oils.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B7.1 — Human Nutrition, Diet (Parts (a)(i), (a)(ii), (b)(iii))
• Topic B4.1 — Biological Molecules (Parts (b)(i), (b)(ii), (c))
▶️ Answer/Explanation
(a)(i) carbohydrate: rice; protein: chicken; vitamins: green beans / cucumber / onions
Rice is rich in starch, the main carbohydrate in the meal.
Chicken is the main protein-rich food shown.
The vegetables (beans, cucumber, onion) are the main source of vitamins.
(a)(ii) acts as a solvent
Water is needed as a solvent for chemical reactions in the body.
It also helps transport substances and regulate body temperature.
(b)(i) blue-black
Iodine solution is orange-brown normally.
In the presence of starch it turns blue-black, a standard test for starch.
(b)(ii) glucose
Starch is a polysaccharide.
It is made of many glucose molecules joined together.
(b)(iii) prevents constipation / keeps food moving through the gut
Fibre cannot be digested by the body.
It adds bulk to food, helping muscles push waste through the gut and preventing constipation.
(c) carbon, hydrogen and oxygen
All fats and oils are lipids.
Lipids are made only of the elements carbon, hydrogen, and oxygen.
Question 2
crystallisation decomposition
electrolysis fractional distillation polymerisation
(i) in the treatment of drinking water
(ii) to separate a mixture of dyes
(iii) to extract aluminium from bauxite
(iv) to produce long chain molecules from monomer units.
Fig. 2.1 shows apparatus used to investigate the change in pH as the acid is added.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C10.1 — Chemistry of the Environment, Water (Part (a)(i))
• Topic C12.3 — Chromatography (Part (a)(ii))
• Topic C4.1 — Electrolysis (Part (a)(iii))
• Topic C11.7 — Polymers (Part (a)(iv))
• Topic C12.2 — Acid-Base Titrations (Part (b)(i))
• Topic C7.1 — Properties of Acids and Bases (Part (b)(ii), (b)(iii), (c))
▶️ Answer/Explanation
(a)(i) chlorination
Chlorine gas is added to drinking water.
It kills harmful microorganisms, making the water safe to drink.
(a)(ii) chromatography
Chromatography separates components of a mixture based on solubility.
Different dyes travel different distances on the paper, separating the mixture.
(a)(iii) electrolysis
Aluminium is too reactive to be extracted by reduction with carbon.
Molten aluminium oxide (from bauxite) is electrolysed to extract the metal.
(a)(iv) polymerisation
Polymerisation joins many small monomer molecules together.
This forms one long chain molecule called a polymer.
(b)(i) burette
A burette is used to add a measured, variable volume of acid.
It allows precise, controlled addition of the acid drop by drop.
(b)(ii) 7
At the point of exact neutralisation, the solution is neither acidic nor alkaline.
This corresponds to \( \text{pH} = 7 \).
(b)(iii) sodium chloride and water
The reaction is: \( \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \).
An acid plus a base always forms a salt and water.
(c) pale blue precipitate
Sodium hydroxide reacts with copper(II) ions in solution.
This forms insoluble copper(II) hydroxide, seen as a pale blue precipitate.
Question 3
Explain what is meant by non-renewable when describing an energy source.
Describe what happens to the nucleus of a plutonium-239 atom during nuclear fission.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.6.3 — Energy Resources (Part (a)(i), (a)(ii))
• Topic P5.2.5 — Nuclear Physics, Applications and Safety Precautions (Part (a)(iii), (b)(ii))
• Topic P5.2.3 — Nuclear Physics, Radioactive Decay (Part (b)(i))
• Topic P5.2.4 — Nuclear Physics, Half-life (Part (c))
▶️ Answer/Explanation
(a)(i) coal, gas, petroleum
Coal, gas, and petroleum are all fossil fuels.
Burning fossil fuels releases carbon dioxide, unlike HEP or nuclear power.
(a)(ii) existing as a finite quantity / used up faster than it can be replaced
Non-renewable resources exist in limited amounts.
They are used up much faster than natural processes can replace them.
(a)(iii) nuclear accidents / dangerous or harmful waste produced
Nuclear power stations can produce radioactive waste.
This waste is hazardous and must be stored safely for a long time.
(b)(i) the nucleus splits
In nuclear fission, a large unstable nucleus such as plutonium-239 splits apart.
This releases energy along with smaller nuclei and neutrons.
(b)(ii) store in a lead-lined container
Lead is a dense material that absorbs radiation effectively.
Storing radioactive material in a lead-lined container reduces exposure risk.
(c) 6.25%
\( 24 \, \text{hours} \div 6 \, \text{hours} = 4 \) half-lives.
Remaining fraction \( = \left(\frac{1}{2}\right)^4 = \frac{1}{16} \).
As a percentage, this is \( \frac{1}{16} \times 100\% = 6.25\% \).
Question 4
Fig. 4.1 shows her heart rate before, during and after the event.
The central nervous system has two parts: the …………… and the ……………….. .
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B13.2 — Coordination and Response, Hormones (Part (a), (c)(i)–(iv))
• Topic B9.4 — Transport in Animals, Blood (Part (b))
• Topic B13.1 — Coordination and Response, Nervous System (Part (d))
▶️ Answer/Explanation
(a) gland; organs
A hormone is produced by a gland.
It travels in the blood to act on specific target organs.
(b) plasma
Plasma is the liquid component of blood.
Hormones dissolve in the plasma and are carried around the body.
(c)(i) 4 minutes
The heart rate is steady at rest until it begins rising sharply.
From the graph, this rise begins at \( t = 4 \) minutes.
(c)(ii) 109 bpm
The peak of the graph shows the maximum heart rate.
This peak value is read as 109 bpm.
(c)(iii) adrenaline
Adrenaline is released in response to fear or stress.
It increases heart rate to prepare the body for “fight or flight”.
(c)(iv) widened pupils; increased breathing rate
Adrenaline widens the pupils to let in more light.
It also increases breathing rate to supply more oxygen to muscles.
(d) peripheral; brain; spinal cord
The nervous system has two divisions: central and peripheral.
The central nervous system (CNS) is made up of the brain and spinal cord.
Question 5
State the name of one other greenhouse gas.
Describe what is meant by an exothermic reaction.
State the name of this orange solution.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.5 — Covalent Bonds (Part (a)(i))
• Topic C5.1 — Exothermic and Endothermic Reactions (Part (a)(ii), (b))
• Topic C11.4 — Alkanes (Part (c))
• Topic C11.5 — Alkenes (Part (d)(i)–(iii))
▶️ Answer/Explanation
(a)(i) one shared pair of electrons between each carbon-hydrogen bond, all outer shells complete
Molecule C is methane, \( \text{CH}_4 \).
Each C–H bond is a single covalent bond, so each bond shows one shared pair of electrons.
The carbon atom ends up with 8 outer electrons and each hydrogen with 2.
(a)(ii) water vapour / carbon dioxide
Greenhouse gases trap heat in the Earth’s atmosphere.
Water vapour and carbon dioxide are both well-known greenhouse gases besides methane.
(b) thermal energy is released
In an exothermic reaction, energy is transferred from the chemicals to the surroundings.
This usually causes a rise in temperature of the surroundings.
(c) molecule B
Molecule B has the formula \( \text{C}_2\text{H}_6 \).
This matches ethane, which has two carbon atoms joined by a single bond, each carbon bonded to three hydrogens.
(d)(i) molecule A
Molecule A has two carbon atoms but only four hydrogen atoms.
This matches the general formula \( \text{C}_n\text{H}_{2n} \), showing a C=C double bond, so it is unsaturated.
(d)(ii) aqueous bromine (bromine water)
Bromine water is orange in colour.
It is used to distinguish saturated from unsaturated hydrocarbons.
(d)(iii) it decolourises
An unsaturated hydrocarbon reacts with the bromine across its double bond.
This causes the orange bromine water to turn colourless.
Question 6
Four forces A, B, C and D act on the boat.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P2.2.2 — Melting, Boiling and Evaporation (Part (a)(i)–(ii))
• Topic P1.5.1 — Effects of Forces (Part (b))
• Topic P1.2 — Motion (Part (c)(i)–(ii))
• Topic P3.1 — General Properties of Waves (Part (d)(i)–(iii))
▶️ Answer/Explanation
(a)(i) evaporation
Evaporation is the process by which a liquid changes into a gas at the surface.
It occurs below the boiling point of the liquid.
(a)(ii) fastest-moving/most energetic molecules escape from the surface
Water molecules move at different speeds due to random motion.
The molecules with the most kinetic energy escape from the surface of the liquid into the air.
(b) weight
Force C acts downwards on the boat.
This is the weight of the boat, caused by gravity.
(c)(i) 4.4 m/s
The graph shows the speed remaining constant at \(4.4 \, \text{m/s}\).
This is read directly from the flat part of the speed-time graph.
(c)(ii) 880 m
Distance = speed × time, or the area under the graph.
\( \text{distance} = 4.4 \, \text{m/s} \times 200 \, \text{s} = 880 \, \text{m} \).
(d)(i) 8 m
The wavelength is the distance between two identical points on consecutive waves, such as peak to peak.
Reading from the graph, this distance is \(8 \, \text{m}\).
(d)(ii) amplitude correctly indicated
The amplitude is the maximum displacement from the rest (zero) position.
It should be marked as a vertical double-headed arrow from zero to the peak (or trough).
(d)(iii) 2.0 waves
Number of waves = frequency × time.
\( 0.08 \, \text{Hz} \times 25 \, \text{s} = 2.0 \) wavefronts.
Question 7
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B6.1 — Plant Nutrition, Photosynthesis (Part (a)(i)–(iii), (b), (c) & (d))
▶️ Answer/Explanation
(a)(i) light and chlorophyll
Plant A had both light and chlorophyll present and photosynthesised.
Plants B, C, and D each lacked one or both of these and did not photosynthesise, showing both are required.
(a)(ii) carbon dioxide is required for photosynthesis
Carbon dioxide is one of the raw materials of photosynthesis.
An excess ensures it is not a limiting factor in the investigation.
(a)(iii) carbon dioxide + water → glucose + oxygen
This word equation summarises photosynthesis.
Light energy is absorbed by chlorophyll to drive this reaction.
(b) chloroplast
Chloroplasts contain chlorophyll, the pigment that absorbs light.
Photosynthesis takes place inside these organelles.
(c)
(d) nitrate
Nitrate ions supply nitrogen to the plant.
Nitrogen is needed to make amino acids, the building blocks of proteins.
Question 8
Describe what is meant by the term reduction.
Transition elements have high densities, high melting points and high boiling points. They are all metals.
State one other property of a transition element.
State the term used to describe a mixture of metals.
State the meaning of the term malleable.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.2 — Atomic Structure (Part (a)(i)–(ii), (d)(iii))
• Topic C6.3 — Redox (Part (b)(i)–(ii))
• Topic C7.2 — Oxides (Part (b)(iii))
• Topic C8.4 — Transition Elements (Part (c))
• Topic C9.3 — Alloys and Their Properties (Part (d)(i))
• Topic C9.1 — Properties of Metals (Part (d)(ii))
• Topic C4.1 — Electrolysis (Part (e)(i)–(ii))
▶️ Answer/Explanation
(a)(i) 29
In a neutral atom, the number of electrons equals the proton number.
Copper has a proton number of 29, so it has 29 electrons.
(a)(ii) 34
Number of neutrons = nucleon number − proton number.
\( 63 – 29 = 34 \) neutrons.
(b)(i) copper oxide + carbon → copper + carbon dioxide
Carbon displaces copper from copper oxide because carbon is more reactive.
Copper metal and carbon dioxide gas are produced.
(b)(ii) loss of oxygen
Reduction is defined as the loss of oxygen from a substance.
Here, copper oxide loses oxygen to form copper metal.
(b)(iii) it is a metal oxide that reacts with an acid to form a salt / neutralises an acid
Basic oxides are typically metal oxides.
Copper oxide reacts with acids to form a salt and water, showing basic behaviour.
(c) forms coloured compounds / acts as a catalyst / has variable valency
Transition elements have characteristic properties beyond density and melting point.
These include forming coloured compounds, acting as catalysts, and showing variable valency (oxidation states).
(d)(i) alloy
An alloy is a mixture of two or more metals (or a metal and another element).
Brass is an alloy of copper and zinc.
(d)(ii) can be beaten or bent into shape without breaking
Malleable means the metal can be hammered or pressed into different shapes.
It does not shatter or crack under this stress.
(d)(iii) Cu and Zn
Cu is the chemical symbol for copper.
Zn is the chemical symbol for zinc.
(e)(i) cathode (negative electrode)
In electroplating, the object to be plated is made the cathode.
Positive copper ions are attracted to and deposited onto the negative electrode.
(e)(ii) copper(II) sulfate solution
Copper(II) sulfate solution contains copper ions in solution.
These ions are deposited as a layer of copper metal onto the key during electrolysis.
Question 9
The potential difference across each lamp is 12 V.
Calculate the resistance of each lamp.
State the unit of your answer.
Fig. 9.2 shows a gap in the road surface in the middle of the bridge.
(i) State what happens to the gap as the temperature increases.
State two other forms of energy gained by the car as it accelerates up the hill.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P4.3.2 — Series and Parallel Circuits (Part (a)(i))
• Topic P4.2.4 — Resistance (Part (a)(ii))
• Topic P2.2.1 — Thermal Expansion (Part (b)(i)–(ii))
• Topic P3.4 — Sound (Part (c)(i)–(ii))
• Topic P1.6.1 — Energy (Part (c)(iii))
▶️ Answer/Explanation
(a)(i) two lamps in parallel with the battery, switch controlling both
Both lamps must be drawn as separate parallel branches connected to the battery.
A single switch must be placed in the main circuit so it controls both lamps together.
(a)(ii) 3 Ω (ohms)
Resistance is calculated using \( R = \dfrac{V}{I} \).
\( R = \dfrac{12}{4.0} = 3 \, \Omega \).
(b)(i) the gap becomes smaller / closes
As temperature increases, the metal of the bridge expands.
This expansion reduces the size of the gap.
(b)(ii) the bridge needs to expand on a hot day, or it could be damaged
Without a gap, expanding metal would have nowhere to go.
This could cause the bridge structure to buckle or crack.
(c)(i) amplitude increases
A louder sound corresponds to a larger amplitude of the sound wave.
As the engine gets louder, the amplitude increases.
(c)(ii) frequency increases
A higher pitch corresponds to a higher frequency of the sound wave.
As the pitch rises, the frequency increases.
(c)(iii) kinetic energy; gravitational potential energy
As the car speeds up, it gains kinetic energy.
As it moves up the hill, it also gains gravitational potential energy due to the increase in height.
Question 10
Complete Table 10.1 by placing ticks (✓) in the boxes to show all the terms that describe each organism.
Use only the information given in Fig. 10.1. One row has been done for you.
State the name of three other characteristics.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B18.2 — Food Chains and Food Webs (Part (a)(i)–(ii), (b))
• Topic B18.1 — Energy Flow (Part (c))
• Topic B1.1 — Characteristics of Living Organisms (Part (d))
• Topic B2.1 — Cell Structure (Part (e))
▶️ Answer/Explanation
(a)(i) cactus → desert rats → snake → desert fox
A food chain starts with the producer and shows the direction of energy flow.
The cactus (producer) is eaten by desert rats, which are eaten by snakes, which are eaten by desert foxes.
(a)(ii)
The cactus is a producer, since it is the base of the food chain.
Desert rats are herbivores (eat only the cactus); snakes are carnivores and secondary consumers (eat desert rats); desert foxes are carnivores (eat snakes).
(b) decomposer
Decomposers break down dead organisms and waste matter.
They release nutrients back into the environment through this process.
(c) the Sun
The Sun provides the light energy captured by producers during photosynthesis.
This energy then flows through the food chain to consumers.
(d) any three of: movement, respiration, sensitivity, growth, reproduction, excretion
Living things share several defining characteristics.
These are commonly remembered by the acronym MRS GREN (movement, respiration, sensitivity, growth, reproduction, excretion, nutrition).
(e) cells
Cells are the basic structural and functional units of life.
All living organisms are made up of one or more cells.
Question 11
Sodium chloride is a compound.
Describe what is meant by an element and a compound.
Balance the symbol equation for this reaction.
The electron configuration of a sodium atom is 2.8.1.
The electron configuration of a chlorine atom is 2.8.7.
State the electron configuration of a sodium ion and a chloride ion.
Describe the test for chloride ions and state the observation for a positive result.
Electrolysis is defined as the breakdown of an ionic compound when ………………… or in aqueous solution by the passage of ………………… .
The gas released at the negative electrode is ………………… and the gas released at the positive electrode is ………………… .
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.1 — Elements, Compounds, and Mixtures (Part (a))
• Topic C3.1 — Formulas (Part (b))
• Topic C2.4 — Ions and Ionic Bonds (Part (c), (d))
• Topic C12.5 — Identification of Ions and Gases (Part (e))
• Topic C4.1 — Electrolysis (Part (f))
▶️ Answer/Explanation
(a) element — contains only one type of atom; compound — contains two or more elements chemically combined
An element cannot be broken down into simpler substances, as it has only one type of atom.
A compound forms when two or more different elements chemically bond together in fixed proportions.
(b) \( 2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl} \)
The equation must be balanced so atoms of each element are equal on both sides.
Two sodium atoms react with one chlorine molecule (\(\text{Cl}_2\)) to form two formula units of sodium chloride.
(c) sodium ion: 2.8; chloride ion: 2.8.8
Sodium loses one electron to form \( \text{Na}^+ \), giving configuration 2.8.
Chlorine gains one electron to form \( \text{Cl}^- \), giving configuration 2.8.8, both achieving a stable full outer shell.
(d) an ionic compound has greater solubility in water than a covalent compound
Ionic compounds are generally more soluble in water due to the polarity of water molecules interacting with charged ions.
Covalent compounds are typically less soluble in water, especially non-polar ones.
(e) add acidified aqueous silver nitrate; a white precipitate forms for a positive result
Dilute nitric acid is added first to remove any interfering ions.
Silver nitrate solution is then added; chloride ions react with silver ions to form a white precipitate of silver chloride.
(f) molten; electricity; hydrogen; chlorine
Electrolysis breaks down an ionic compound when it is molten or in aqueous solution, by passing electricity through it.
At the negative electrode (cathode), hydrogen gas is released.
At the positive electrode (anode), chlorine gas is released.
Question 12
When one foot is lifted off the sand, the other foot sinks deeper into the sand.
Explain why this happens.
This sand has a density of \(1600 \, \text{kg/m}^3\).
The gravitational field strength, \(g\), is \(10 \, \text{N/kg}\).
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P3.3 — Electromagnetic Spectrum (Part (a))
• Topic P1.5.1 — Effects of Forces (Part (b))
• Topic P1.4 — Density (Part (c)(i))
• Topic P1.3 — Mass and Weight (Part (c)(ii))
• Topic P3.2.3 — Thin Converging Lens (Part (d)(i)–(iii))
▶️ Answer/Explanation
(a) 
The electromagnetic spectrum in order is: gamma-radiation, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves.
X-rays fit between gamma-radiation and ultraviolet; microwaves fit between infrared and radio waves.
(b) area decreases, so pressure increases
Pressure is calculated as \( P = \dfrac{F}{A} \).
When one foot is lifted, the same weight now acts through a smaller contact area, so the pressure exerted increases.
(c)(i) 5 m³
Volume is calculated using \( V = \dfrac{m}{\rho} \).
\( V = \dfrac{8000}{1600} = 5 \, \text{m}^3 \).
(c)(ii) 80 000 N
Weight is calculated using \( W = mg \).
\( W = 8000 \, \text{kg} \times 10 \, \text{N/kg} = 80\,000 \, \text{N} \).
(d)(i) rays meet at the focus (F)
Both incoming rays are parallel to the principal axis before hitting the lens.
After refraction through the convex lens, both rays converge and meet at the principal focus, F.
(d)(ii) principal focus
Point F is where parallel rays converge after passing through a convex lens.
This point is called the principal focus of the lens.
(d)(iii) focal length correctly identified
The focal length is the distance from the centre of the lens to the principal focus, F.
This should be marked as a double-headed arrow along the principal axis, from the lens centre to point F.