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Question 1

(a) Table 1.1 shows the total number of teeth of different animals.
(i) State which animal in Table 1.1 has the largest number of teeth.
(ii) Calculate the difference in the number of teeth between a human and an elephant as shown in Table 1.1.
(b) Circle the name of the outermost layer of a tooth.
cement     dentine     enamel     nerves     pulp
(c) State the type of teeth responsible for grinding food.
(d) Describe one way to take care of teeth.
(e) Fig. 1.1 is a diagram of the alimentary canal and associated organs in a human.
(i) Identify the letter from Fig. 1.1 that represents where:
  • egestion occurs
  • the most absorption occurs
  • ingestion occurs
(ii) State the name of part C in Fig. 1.1.
(f) Complete the definition of digestion.
Digestion is the ………………………………………….. of large, insoluble food molecules into small, water-soluble molecules using ………………………………………….. and chemical processes.
(g) After the food is digested, nutrients pass into the blood.
State the part of the blood that transports soluble nutrients.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic B7.2 — Digestive system (Parts (a)–(g))

▶️ Answer/Explanation

(a)(i) fox

Table 1.1 lists the fox with 42 teeth, the highest value shown.
All other animals in the table have fewer teeth.

(a)(ii) 6

Human teeth = 32, elephant teeth = 26.
Difference = \(32 – 26 = 6\).

(b) enamel

Enamel is the hard, outermost layer of a tooth.
It protects the underlying dentine and pulp from wear and decay.

(c) molar / premolar

Molars and premolars have broad, flat surfaces.
This shape is suited to crushing and grinding food.

(d) brushing / using toothpaste / regular dentist visits / consume less sugary food or drink

Regular brushing with toothpaste removes plaque and food debris.
This reduces the bacterial activity that causes tooth decay.

(e)(i) egestion – D; most absorption – E; ingestion – H

D is the rectum/anus region, where undigested waste is egested.
E is the small intestine, the main site of nutrient absorption.
H is the mouth, where food is first ingested.

(e)(ii) pancreas

Part C lies between the stomach and small intestine, feeding into the duodenum.
This organ is the pancreas, which secretes digestive enzymes.

(f) breaking down; mechanical

Digestion is the breaking down of large, insoluble food molecules.
This occurs into small, water-soluble molecules using mechanical and chemical processes.

(g) plasma

Soluble nutrients absorbed from digestion enter the blood.
They are carried dissolved in the plasma, the liquid component of blood.

Question 2

(a) Methane is a hydrocarbon.
(i) State what is meant by the term hydrocarbon.
(ii) State the fossil fuel whose main constituent is methane.
(b) Complete the dot-and-cross diagram of a molecule of methane in Fig. 2.1.
Include the symbols for the chemical elements.
Show outer shell electrons only.
(c) (i) The combustion of methane is an exothermic reaction.
       State what is meant by exothermic.
(ii) State the two products of the complete combustion of methane in oxygen.
(iii) During the incomplete combustion of methane, carbon monoxide is sometimes made.
Describe one adverse effect of carbon monoxide on the health of humans.
(d) Ethane, \(C_2H_6\), is an alkane. Ethene, \(C_2H_4\), is an alkene.
(i) State the difference in structure between an alkane and an alkene.
(ii) Describe a chemical test that distinguishes between an alkane and an alkene.
Describe the observations for a positive result of the test in each case.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic C11.3 — Fuels (Parts (a)(i)–(ii))
• Topic C2.5 — Simple molecules and covalent bonds (Part (b))
• Topic C5.1 — Exothermic and endothermic reactions (Parts (c)(i)–(iii))
• Topic C11.4 — Alkanes (Part (d)(i))
• Topic C11.5 — Alkenes (Part (d)(ii))

▶️ Answer/Explanation

(a)(i) Contains carbon and hydrogen (atoms) only

A hydrocarbon is a compound made up of carbon atoms bonded to hydrogen atoms.
No other elements are present in a hydrocarbon.

(a)(ii) Natural gas

Natural gas is a fossil fuel found underground or under the seabed.
Its main component is methane, \(CH_4\).

(b)

Methane, \(CH_4\), has one carbon atom bonded to four hydrogen atoms.
Each bond is a shared pair of electrons (one from carbon, one from hydrogen), giving four bonding pairs around the central carbon.

(c)(i) Gives out (thermal) energy

An exothermic reaction releases energy to the surroundings.
This energy is usually released as heat.

(c)(ii) Carbon dioxide; water

Complete combustion of methane in oxygen follows: \(CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O\).
The two products formed are carbon dioxide and water.

(c)(iii) Poisoning / death / reduces oxygen-carrying capacity of red blood cells

Carbon monoxide binds to haemoglobin more strongly than oxygen does.
This reduces the blood’s ability to carry oxygen, which can cause poisoning or death.

(d)(i) Alkenes contain a double bond; alkanes only have single bonds

Ethane (\(C_2H_6\)) is saturated, with only single \(C\)-\(C\) bonds.
Ethene (\(C_2H_4\)) is unsaturated, containing one \(C=C\) double bond.

(d)(ii) Aqueous bromine (bromine water) test

Add bromine water to each hydrocarbon and observe the colour.
For an alkane: no colour change (remains orange).
For an alkene: the orange colour turns colourless (decolourises), because the double bond reacts with the bromine.

Question 3

Some examples of waves are listed.
γ-ray
infrared
microwave
radio
sound
visible light
X-ray
(a) Use words from the list to answer the following questions.
(i) State which wave in the electromagnetic spectrum has the highest frequency.
(ii) State which wave is emitted by a remote control for a television.
(b) Fig. 3.1 shows a ray of light passing through a rectangular glass block.
(i) State the effect shown by the ray of light at B.
(ii) State the name of the line labelled PQ.
(iii) State the value of angle \(x\).
(iv) The glass block in Fig. 3.1 is resting on a bench.
The glass block exerts a pressure on the bench.
State the two variables that must be measured to determine the pressure exerted.
(v) The mass of the glass block is \(156\,\text{g}\).
The volume of the glass block is \(60.0\,\text{cm}^3\).
Calculate the density of the glass block.
(c) α-particles, β-particles and γ-rays are all types of ionising radiation.
(i) Place these three radiations in order of their ionising ability.
(ii) State which one of these radiations is negatively charged.
(iii) State which one of these radiations is the most penetrating.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic P3.3 — Electromagnetic spectrum (Parts (a)(i)–(ii))
• Topic P3.2.2 — Refraction of light (Parts (b)(i)–(iii))
• Topic P1.7 — Pressure (Part (b)(iv))
• Topic P1.4 — Density (Part (b)(v))
• Topic P5.2.2 — The three types of nuclear emission (Parts (c)(i)–(iii))

▶️ Answer/Explanation

(a)(i) γ-ray

The electromagnetic spectrum is ordered by increasing frequency: radio, microwave, infrared, visible light, ultraviolet, X-ray, γ-ray.
Gamma rays have the shortest wavelength and therefore the highest frequency.

(a)(ii) Infrared

Television remote controls send signals using infrared radiation.
This is invisible to the human eye but detected by a sensor on the TV.

(b)(i) Refraction

The light ray bends at B as it passes from air into the denser glass.
This bending of light at a boundary is called refraction.

(b)(ii) Normal

PQ is drawn perpendicular to the surface of the glass block at the point of incidence.
This reference line is called the normal.

(b)(iii) \(x = 45°\)

As the ray exits the parallel-sided glass block, it refracts back to its original direction.
So the angle \(x\) on exit equals the original angle of incidence, \(45°\).

(b)(iv) Force (weight); area

Pressure is defined as \(\text{pressure} = \dfrac{\text{force}}{\text{area}}\).
So both the weight (force) of the block and its contact area with the bench must be measured.

(b)(v) \(2.60\,\text{g/cm}^3\)

Density is calculated using \(\rho = \dfrac{m}{V}\).
\(\rho = \dfrac{156}{60.0} = 2.60\,\text{g/cm}^3\).

(c)(i) Most ionising: α; then β; least ionising: γ

α-particles are large and heavily charged, giving strong ionising ability.
β-particles ionise less strongly, and γ-rays, being uncharged electromagnetic waves, ionise the least.

(c)(ii) β-particles

β-particles are fast-moving electrons emitted from the nucleus.
Being electrons, they carry a negative charge.

(c)(iii) γ-rays

γ-rays are high-energy electromagnetic waves with no mass or charge.
This allows them to penetrate most materials, including thick metal, more easily than α- or β-particles.

Question 4

(a) Fig. 4.1 is a photograph of a dissected flower.
(i) Table 4.1 shows the function of some of the parts labelled A–E in Fig. 4.1.
Complete Table 4.1.
(ii) State the name of part B in Fig. 4.1.
(b) Complete the sentence to describe fertilisation in plants.
Fertilisation occurs when a pollen nucleus fuses with the nucleus in the ………………… .
(c) Plants can reproduce asexually and sexually.
State two ways asexual reproduction is different from sexual reproduction.
(d) Reproduction is one of the characteristics of living organisms.
Tick (✓) two boxes that each show a characteristic of all living organisms.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic B15.3 — Sexual reproduction in plants (Parts (a)(i)–(ii), (b))
• Topic B15.1 — Asexual reproduction (Part (c))
• Topic B1.1 — Characteristics of living organisms (Part (d))

▶️ Answer/Explanation

(a)(i) D — attracts pollinators; E — where pollination occurs; A — produces pollen

D is a petal, which is often brightly coloured/scented to attract pollinators.
E is the stigma, where pollen lands during pollination.
A is the anther, which produces pollen grains.

(a)(ii) Filament

Part B is the stalk that supports the anther.
This structure is called the filament.

(b) Ovule

During fertilisation, a pollen nucleus travels down the pollen tube.
It fuses with the nucleus inside the ovule to form a zygote.

(c) Involves only one parent; produces genetically identical offspring

Asexual reproduction needs only one parent, unlike sexual reproduction which needs two.
It also produces offspring that are genetically identical to the parent (no fusion of gametes occurs).

(d) Excretion; sensitivity

All living organisms must remove waste products, which is excretion.
All living organisms also respond to changes in their environment, which is sensitivity.

Question 5

(a) An atom of iron has a proton number of 26 and a nucleon number of 56.
(i) State the number of electrons in this atom of iron.
(ii) State the number of neutrons in this atom of iron.
(iii) Another atom of iron has a nucleon number of 54. State the proton number of this atom of iron.
(b) Fig. 5.1 shows an aqueous solution of iron(III) chloride.
A student tests the solution to confirm that the label is correct.
State the test for aqueous iron(III) ions (\(Fe^{3+}\)) and give the observation for a positive result.
(c) Stainless steel is an alloy of iron.
(i) Define the term alloy.
(ii) State one use for stainless steel.
(iii) State the two conditions needed for the rusting of iron.
(iv) Describe and explain one method of rust prevention.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic C2.2 — Atomic structure and the Periodic Table (Parts (a)(i)–(iii))
• Topic C12.5 — Identification of ions and gases (Part (b))
• Topic C9.3 — Alloys and their properties (Parts (c)(i)–(ii))
• Topic C9.5 — Corrosion of metals (Parts (c)(iii)–(iv))

▶️ Answer/Explanation

(a)(i) 26

In a neutral atom, the number of electrons equals the number of protons.
Since the proton number is 26, there are 26 electrons.

(a)(ii) 30

Number of neutrons = nucleon number − proton number.
\(56 – 26 = 30\).

(a)(iii) 26

The proton number defines the element and is always the same for iron.
Even with a different nucleon number (54), the proton number remains 26 (this is an isotope of iron).

(b) Test: add sodium hydroxide solution; observation: orange/brown precipitate forms

Adding aqueous sodium hydroxide to a solution containing \(Fe^{3+}\) ions causes a precipitate to form.
This precipitate, iron(III) hydroxide, is orange-brown, confirming the presence of \(Fe^{3+}\) ions.

(c)(i) A mixture of a metal with one or more other elements

An alloy is formed by mixing a metal with another metal or non-metal element.
This mixing changes the properties of the pure metal, often making it harder or more resistant to corrosion.

(c)(ii) Cutlery / chemical plant equipment

Stainless steel resists corrosion and is durable.
This makes it suitable for cutlery or equipment used in chemical plants.

(c)(iii) Presence of oxygen; presence of water

Rusting is a chemical reaction between iron, oxygen and water.
Both oxygen and water must be present for rust (hydrated iron oxide) to form.

(c)(iv) Painting / galvanising / plating / greasing, with explanation

Painting the iron surface creates a physical barrier.
This barrier stops oxygen and water from reaching the iron, preventing rust from forming.

Question 6

(a) Fig. 6.1 shows two dolphins using sound waves to communicate with each other in the sea.
(i) Dolphins hear sounds in the frequency range from \(75\,\text{Hz}\) to \(100\,000\,\text{Hz}\).
State why humans can hear some of these frequencies but not all of them.
Refer to the human audible frequency range in your answer.
(ii) A dolphin changes the frequency of a sound it makes from \(1000\,\text{Hz}\) to \(2000\,\text{Hz}\).
State what happens to the pitch of the sound.
(iii) The sound waves travel \(80\,\text{m}\).
The speed of sound in water is \(1600\,\text{m/s}\).
Calculate the time taken for a sound wave to travel \(80\,\text{m}\) in water.
(b) Fig. 6.2 shows a speed–time graph for a dolphin travelling through water.
(i) Describe the motion of the dolphin between time = 0 and time = \(5\,\text{s}\).
(ii) State the maximum speed of the dolphin as shown on the graph.
(iii) Calculate the distance travelled by the dolphin between time = \(15\,\text{s}\) and time = \(30\,\text{s}\).
(c) The water in the sea is heated by the Sun.
Some molecules of water evaporate.
Describe the process of evaporation.
Use ideas about particles in your answer.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic P3.4 — Sound (Parts (a)(i)–(iii))
• Topic P1.2 — Motion (Parts (b)(i)–(iii))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (c))

▶️ Answer/Explanation

(a)(i) Humans can hear lower frequencies because the human range starts near 20 Hz; humans cannot hear above about 20 kHz

The human audible range is roughly \(20\,\text{Hz}\) to \(20\,000\,\text{Hz}\).
Dolphin sounds below \(20\,\text{Hz}\) are inaudible to humans, and dolphin sounds above \(20\,000\,\text{Hz}\) are too high-pitched for humans to hear.

(a)(ii) The pitch increases

Pitch depends directly on frequency.
Since the frequency rises from \(1000\,\text{Hz}\) to \(2000\,\text{Hz}\), the pitch of the sound gets higher.

(a)(iii) \(0.05\,\text{s}\)

Time is calculated using \(\text{time} = \dfrac{\text{distance}}{\text{speed}}\).
\(\text{time} = \dfrac{80}{1600} = 0.05\,\text{s}\).

(b)(i) The dolphin is accelerating (speed is increasing)

The graph line rises steadily between \(t=0\) and \(t=5\,\text{s}\).
An increasing gradient on a speed–time graph shows the dolphin’s speed is increasing, i.e. it is accelerating.

(b)(ii) \(6\,\text{m/s}\)

The graph shows the speed rising to a flat, constant section.
This highest, constant value on the graph is \(6\,\text{m/s}\).

(b)(iii) \(45.0\,\text{m}\)

Distance travelled equals the area under the speed–time graph.
Between \(15\,\text{s}\) and \(30\,\text{s}\) this forms a triangle: \(\text{area} = \dfrac{1}{2} \times 15 \times 6 = 45.0\,\text{m}\).

(c) The fastest-moving, most energetic particles escape from the surface of the liquid

In a liquid, particles have a range of energies and move at different speeds.
The most energetic particles near the surface can overcome the attractive forces holding them in the liquid and escape as vapour — this is evaporation.

Question 7

Fig. 7.1 shows part of the carbon cycle.
(a) (i) Draw an arrow on Fig. 7.1 to represent the process of decomposition.
(ii) Processes B and C are respiration. Describe the process of respiration.
(b) Process D in Fig. 7.1 is photosynthesis.
State three requirements for photosynthesis.
(c) Fig. 7.2 shows a food chain.
(i) Circle the two words from the list that can be used to describe the sheep in Fig. 7.2.
carnivore      consumer      decomposer      herbivore      producer
(ii) Identify the tertiary consumer in Fig. 7.2.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic B18.3 — Carbon cycle (Part (a)(i))
• Topic B12.1 — Respiration (Part (a)(ii))
• Topic B6.1 — Photosynthesis (Part (b))
• Topic B18.2 — Food chains and food webs (Parts (c)(i)–(ii))

▶️ Answer/Explanation

(a)(i) Arrow drawn from “dead organisms” to “carbon dioxide in the atmosphere”

Decomposition is carried out by decomposers acting on dead organisms.
This releases carbon dioxide back into the atmosphere, so the arrow links these two boxes.

(a)(ii) Chemical reaction in cells; releases energy; glucose and oxygen as reactants; carbon dioxide and water as products

Respiration is a chemical reaction that takes place inside living cells.
It releases energy from glucose, using oxygen as a reactant, and produces carbon dioxide and water as waste products.

(b) Carbon dioxide; water; light (any three from: carbon dioxide, water, chlorophyll, light, warm temperature)

Photosynthesis requires carbon dioxide and water as raw materials.
It also needs light energy and chlorophyll to absorb that light, with a suitably warm temperature for the enzymes involved.

(c)(i) Herbivore; consumer

The sheep feeds only on grass (a plant), making it a herbivore.
Since it obtains energy by consuming another organism, it is also classed as a consumer.

(c)(ii) Wolf

In the chain grass → sheep → fox → wolf, the sheep is the primary consumer and the fox is the secondary consumer.
The wolf, feeding on the fox, is therefore the tertiary consumer.

Question 8

(a) Table 8.1 shows a list of covalently bonded molecules: \(Cl_2\), \(CO_2\), \(H_2\), \(HCl\), \(H_2O\), \(NH_3\).
(i) Identify two molecules from Table 8.1 that are elements.
(ii) Identify one molecule from Table 8.1 that is diatomic.
(iii) Identify one molecule from Table 8.1 which is a greenhouse gas.
(b) (i) State the names of the two elements present in a molecule of ammonia, \(NH_3\).
(ii) Determine the total number of atoms in a molecule of ammonia, \(NH_3\).
(c) Water, \(H_2O\), is a solvent. State the meaning of the term solvent.
(d) Dilute hydrochloric acid reacts with calcium carbonate to produce carbon dioxide, water and a solution of a salt.
(i) State which salt is produced.
(ii) Suggest a method of obtaining a sample of the dry salt from this salt solution.
(iii) When calcium carbonate and dilute hydrochloric acid react, the rate of reaction is slow.
Suggest two ways of increasing the rate of reaction.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic C2.5 — Simple molecules and covalent bonds (Parts (a)(i)–(ii), (b)(i)–(ii))
• Topic C10.2 — Air quality and climate (Part (a)(iii))
• Topic C12.1 — Experimental design (Part (c))
• Topic C7.3 — Preparation of salts (Parts (d)(i)–(ii))
• Topic C6.2 — Rate of reaction (Part (d)(iii))

▶️ Answer/Explanation

(a)(i) \(Cl_2\) and \(H_2\)

Elements contain only one type of atom.
\(Cl_2\) contains only chlorine atoms and \(H_2\) contains only hydrogen atoms, so both are elements.

(a)(ii) \(HCl\) / \(Cl_2\) / \(H_2\)

A diatomic molecule contains exactly two atoms.
\(HCl\), \(Cl_2\), and \(H_2\) each consist of two atoms bonded together.

(a)(iii) \(CO_2\)

Carbon dioxide absorbs and re-emits infrared radiation from the Earth’s surface.
This traps heat in the atmosphere, making \(CO_2\) a greenhouse gas.

(b)(i) Nitrogen; hydrogen

Ammonia has the formula \(NH_3\).
This shows it is made from nitrogen (N) and hydrogen (H) atoms.

(b)(ii) 4

\(NH_3\) contains 1 nitrogen atom and 3 hydrogen atoms.
Total atoms = \(1 + 3 = 4\).

(c) A liquid in which other substances (solutes) dissolve

A solvent is the liquid component of a solution.
Solutes dissolve in the solvent to form a solution.

(d)(i) Calcium chloride

The reaction is: \(CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2\).
The salt produced is calcium chloride.

(d)(ii) Evaporation (of the water, followed by crystallisation)

Heating the salt solution evaporates the water.
This leaves behind dry crystals of calcium chloride.

(d)(iii) Increase temperature; increase surface area (smaller particles) / increase concentration of acid

Raising the temperature increases particle energy and collision frequency.
Using smaller particles (greater surface area) or a more concentrated acid also increases the collision rate, speeding up the reaction.

Question 9

Fig. 9.1 shows a refrigerator.
(a) The air inside the refrigerator is cooled by the freezing compartment.
On Fig. 9.1, draw one straight arrow to show the movement of the air cooled by the freezing compartment.
(b) Some ice is made from water in the freezing compartment.
Fig. 9.2 represents the arrangement of particles in a liquid and in a solid.
Describe two differences between the particle arrangement in a liquid and in a solid as shown in Fig. 9.2.
(c) There is a lamp inside the refrigerator. The supply voltage is \(240\,\text{V}\).
The current through the lamp is \(0.04\,\text{A}\).
(i) Show that the resistance of the lamp is \(6000\,\Omega\).
(ii) Two lamps, each with a resistance of \(6000\,\Omega\), are connected in parallel.
The combined resistance of the two lamps is one of the following values.
\(3000\,\Omega\)    \(6000\,\Omega\)    \(12\,000\,\Omega\)    \(24\,000\,\Omega\)
State the correct value and explain your answer.
(d) The refrigerator has a d.c. motor.
The turning effect of the motor can be increased by increasing the strength of the magnetic field.
State two other ways to increase the turning effect of the motor.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic P2.3.3 — Radiation (Part (a))
• Topic P2.1.1 — States of matter (Part (b))
• Topic P4.2.2 — Electric current (Part (c)(i))
• Topic P4.3.2 — Series and parallel circuits (Part (c)(ii))
• Topic P4.5.5 — The d.c. motor (Part (d))

▶️ Answer/Explanation

(a) Vertical arrow drawn downwards

Air cooled by the freezing compartment becomes denser.
Denser (cooler) air sinks, so the arrow should point downwards.

(b) Solid has a regular arrangement, liquid has an irregular arrangement; particles are further apart in a liquid

In a solid, particles are packed in a fixed, regular pattern.
In a liquid, particles are arranged randomly and are spaced slightly further apart, allowing them to move past one another.

(c)(i) \(R = \dfrac{V}{I} = \dfrac{240}{0.04} = 6000\,\Omega\)

Ohm’s law states \(R = \dfrac{V}{I}\).
Substituting \(V = 240\,\text{V}\) and \(I = 0.04\,\text{A}\) gives \(R = 6000\,\Omega\).

(c)(ii) \(3000\,\Omega\)

For two equal resistors in parallel, combined resistance is half of one resistor.
The combined resistance of two resistors in parallel is always less than either resistor alone, giving \(3000\,\Omega\).

(d) Increase the current; increase the number of turns on the coil

A larger current through the coil increases the force on each wire.
Adding more turns to the coil also increases the total turning effect (torque) of the motor.

Question 10

(a) Fig. 10.1 is a diagram of a plant cell.
(i) The boxes on the left show some labels from Fig. 10.1.
The boxes on the right show the names of some parts of a plant cell.
Draw lines to link each label with its correct name.
(ii) Identify three parts of a plant cell that are also found in an animal cell. Choose from the labels in Fig. 10.1.
(iii) Describe one difference in structure between a root hair cell and the cell shown in Fig. 10.1.
(iv) State one function of root hair cells.
(b) A plant cell is \(0.05\,\text{mm}\) in length.
An animal cell is \(0.02\,\text{mm}\) in length.
Calculate how many times longer this plant cell is compared to this animal cell.
(c) State which type of animal cell transports oxygen.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic B2.1 — Cell structure (Parts (a)(i)–(iv))
• Topic B2.2 — Size of specimens (Part (b))
• Topic B9.4 — Blood (Part (c))

▶️ Answer/Explanation

(a)(i) 

Label A is the boundary structure controlling movement into/out of the cell (cell membrane).
Label C is the outer rigid layer (cell wall) and label D is the organelle containing chlorophyll (chloroplast).

(a)(ii) B, E, F (e.g. cell membrane, nucleus, cytoplasm)

Plant-specific structures like the cell wall, chloroplast, and vacuole are not found in animal cells.
Structures such as the cell membrane, nucleus, and cytoplasm are common to both plant and animal cells.

(a)(iii) Elongated shape / no chloroplasts

A root hair cell has a long, thin extension to increase surface area.
Unlike the plant cell shown, root hair cells lack chloroplasts since they are underground and do not photosynthesise.

(a)(iv) Absorption of water and mineral ions

Root hair cells have a large surface area due to their elongated shape.
This adaptation allows efficient absorption of water and mineral ions from the soil.

(b) 2.5 times longer

Divide the plant cell length by the animal cell length.
\(\dfrac{0.05}{0.02} = 2.5\).

(c) Red blood cell

Red blood cells contain haemoglobin, which binds oxygen.
This allows them to transport oxygen around the body.

Question 11

(a) Table 11.1 shows a list of seven metals from the Periodic Table: calcium, copper, iron, lithium, magnesium, potassium, sodium.
(i) Identify three metals from Table 11.1 that have only one electron in their outer shell as a neutral atom.
(ii) Identify the two metals from Table 11.1 that are Group II metals.
(b) State three general physical properties that distinguish metals from non-metals.
(c) Copper is used in electroplating.
Use words from the list to complete the description of electroplating.
Each word may be used once, more than once or not at all.
electrode      electrolyte      negative      neutral      positive      solute
Electrolysis is used to electroplate objects with copper.
The object to be plated, such as a metal pan, is connected to the ………………. terminal of the power supply. This is called the cathode.
A piece of copper is connected to the …………….. terminal. This is called the anode.
The anode and cathode are placed in aqueous copper(II) sulfate. This aqueous copper(II) sulfate is called the …………… .

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic C8.2 — Group I properties (Parts (a)(i)–(ii))
• Topic C9.1 — Properties of metals (Part (b))
• Topic C4.1 — Electrolysis (Part (c))

▶️ Answer/Explanation

(a)(i) Lithium; potassium; sodium

Lithium, potassium, and sodium are all in Group I of the Periodic Table.
Group I elements have exactly one electron in their outer shell.

(a)(ii) Calcium; magnesium

Calcium and magnesium belong to Group II.
Group II elements have two electrons in their outer shell.

(b) Good thermal conductors; good electrical conductors; malleable (or relatively high melting/boiling point)

Metals conduct heat and electricity well due to free-moving delocalised electrons.
They are also malleable (can be hammered into shape) and generally have relatively high melting and boiling points compared to non-metals.

(c) Negative; positive; electrolyte

The object to be plated is made the cathode, connected to the negative terminal.
The copper anode is connected to the positive terminal, and the copper(II) sulfate solution acts as the electrolyte, allowing copper ions to move and plate the object.

Question 12

(a) Fig. 12.1 shows four forces, \(P\), \(Q\), \(R\) and \(S\), acting on a bus travelling along a level road at constant speed.
(i) State which force is the weight of the bus.
(ii) Force \(Q\) is \(500\,000\,\text{N}\). State the size of force \(S\).
(b) The bus uses stored chemical energy from fuel to accelerate up a hill.
Some of this energy is transferred to thermal energy and sound energy.
State two other forms of energy transferred to the bus as it accelerates up the hill.
(c) The bus gets very hot on a sunny day.
State the method of thermal energy transfer between the Sun and the Earth.
(d) Some of the bus is made of iron. Other parts are made of steel.
Iron and steel are both magnetic.
Describe one difference between the magnetic properties of soft iron and the magnetic properties of steel.
(e) The fuel used by the bus is produced from petroleum.
Petroleum is a non-renewable energy source.
Name one other non-renewable energy source and one renewable energy source.
(f) The air in the tyres of the bus warms up during a journey.
Describe how the motion of the molecules inside the tyres changes as the air warms up.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic P1.5.1 — Effects of forces (Parts (a)(i)–(ii))
• Topic P1.6.1 — Energy (Part (b))
• Topic P2.3.3 — Radiation (Part (c))
• Topic P4.1 — Simple phenomena of magnetism (Part (d))
• Topic C10.2 — Air quality and climate (Part (e))
• Topic P2.1.2 — Particle model (Part (f))

▶️ Answer/Explanation

(a)(i) R

Weight always acts vertically downwards on an object.
In Fig. 12.1, force R points downward, so R is the weight.

(a)(ii) \(500\,000\,\text{N}\)

The bus travels at constant speed, so the forces are balanced.
This means the forward force \(Q\) must equal the opposing force \(S\), both \(500\,000\,\text{N}\).

(b) Kinetic energy; gravitational potential energy

As the bus speeds up, some chemical energy becomes kinetic energy.
As it rises up the hill, some energy is also transferred to gravitational potential energy.

(c) Radiation

The Sun and Earth are separated by the vacuum of space.
Since no medium is present, energy transfer must occur by radiation (electromagnetic waves).

(d) Iron magnetises and demagnetises more quickly than steel

Soft iron gains and loses its magnetism quickly, making it useful for temporary magnets.
Steel is harder to magnetise but retains its magnetism for longer, making it suitable for permanent magnets.

(e) Non-renewable: coal / natural gas; renewable: hydroelectric / solar / wind / tidal / geothermal / biogas

Non-renewable sources, like coal or natural gas, are finite and will eventually run out.
Renewable sources, such as solar or wind power, are naturally replenished and will not run out.

(f) The molecules gain kinetic energy and move faster

As the air warms, its particles absorb thermal energy.
This energy increases their kinetic energy, so they move faster (and collide with the tyre walls more forcefully/frequently).

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