Question 1
Place ticks (✓) in the boxes to show which blood vessels transport blood to these organs.
One row has been done for you.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B9.2 — Heart (Parts (a)(i)–(ii))
• Topic B9.3 — Blood vessels (Parts (b)(i)–(iii), (c))
• Topic B9.4 — Blood (Part (d))
▶️ Answer/Explanation
(a)(i) 43 beats per minute
Pulse rate at rest, read from Fig. 1.1, is \( 72 \) beats per minute.
Maximum pulse rate, read from the peak of the graph, is \( 115 \) beats per minute.
Difference \( = 115 – 72 = 43 \) beats per minute.
(a)(ii) 20 minutes
Exercise stops at \( t = 20 \) minutes, where the pulse rate is at its lowest point during recovery.
The pulse rate returns to the resting value of \( 72 \) bpm at \( t = 40 \) minutes.
Time taken \( = 40 – 20 = 20 \) minutes.
(b)(i) Valves
Valves are internal structures found inside veins that prevent the backflow of blood.
They would not be visible in a simple cross-sectional photomicrograph like Fig. 1.2.
(b)(ii) Any two from:
Arteries have a thicker wall than the vein shown.
Arteries contain more muscle and elastic fibres in their walls.
Arteries have no valves, unlike veins.
Arteries have a narrower lumen compared to veins.
(b)(iii) Function of capillaries
Capillaries allow the transfer of substances (such as oxygen, carbon dioxide, glucose, and waste products) to and from tissues/cells.
Their thin, one-cell-thick walls make this exchange efficient over short diffusion distances.
(c) Table completed as follows:
(d) Any two from:
Red blood cells.
White blood cells.
Plasma.
Platelets.
Question 2
State a method used to separate zinc sulfate from water.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.1 — Formulae, equations and atoms (Part (a))
• Topic C4.1 — Electrolysis (Part (b))
• Topic C7.1 — Acids, bases and salts (Part (c)(i)–(iii))
• Topic C12.4 — Separating techniques (Part (c)(iv))
▶️ Answer/Explanation
(a)(i) 3
The formula \( H_2SO_4 \) contains three different elements.
These are hydrogen (H), sulfur (S), and oxygen (O).
(a)(ii) 7
Counting all atoms in \( H_2SO_4 \): \( 2 \) hydrogen atoms, \( 1 \) sulfur atom, and \( 4 \) oxygen atoms.
Total \( = 2 + 1 + 4 = 7 \) atoms.
(b)(i) Gas P: oxygen, Gas Q: hydrogen
In the electrolysis of dilute sulfuric acid, oxygen is produced at the positive electrode (anode).
Hydrogen is produced at the negative electrode (cathode), shown as gas Q.
(b)(ii) Anode
The positive electrode in electrolysis is called the anode.
Negative ions (anions) are attracted to and discharged at this electrode.
(c)(i) Any number less than 7
Dilute sulfuric acid is a strong acid, so its pH is well below 7.
A typical suggested value would be pH 1 or pH 2.
(c)(ii) Copper
Copper is a metal below hydrogen in the reactivity series.
It does not react with dilute sulfuric acid to produce hydrogen gas.
(c)(iii) Hydrogen
Zinc reacts with dilute sulfuric acid in a metal–acid reaction: \( Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2 \).
The gas produced, hydrogen, pops with a lighted splint.
(c)(iv) Evaporation / crystallisation
Zinc sulfate solution can be separated from water by evaporating the water off.
Continuing to crystallisation point yields solid zinc sulfate crystals.
Question 3
State one difference between the magnetic properties of steel and the magnetic properties of soft iron.
The volume of the steel is \( 115 \, \text{cm}^3 \).
Calculate the density of the steel used to make the saucepan.
State the units of your answer.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P2.3.1 — Conduction (Part (a))
• Topic P2.2.2 — Boiling (Part (b))
• Topic P4.1 — Magnetism (Part (c)(i))
• Topic P1.4 — Density (Part (c)(ii))
• Topic P2.2.1 — Thermal expansion (Part (d))
▶️ Answer/Explanation
(a) Conduction
Thermal energy is transferred through a solid, such as the metal base of the saucepan, by conduction.
Vibrating particles pass kinetic energy to neighbouring particles, and free electrons in the metal also help transfer energy quickly.
(b)(i) 38 °C
From Fig. 3.2, the temperature at \( t = 0 \) minutes is \( 20\,^\circ\text{C} \).
At \( t = 2 \) minutes, the temperature is \( 58\,^\circ\text{C} \).
Temperature rise \( = 58 – 20 = 38\,^\circ\text{C} \).
(b)(ii)
The graph shows the temperature increasing steadily, then levelling off at \( 100\,^\circ\text{C} \).
This flat, horizontal section shows the temperature stops increasing, confirming that boiling is occurring at \( 100\,^\circ\text{C} \).
(c)(i)
Soft iron is magnetised quickly but also loses its magnetism quickly (temporary magnet).
Steel is magnetised more slowly but retains its magnetism for longer (permanent magnet).
(c)(ii) \( 7.83 \, \text{g/cm}^3 \)
Density is calculated using \( \text{density} = \dfrac{\text{mass}}{\text{volume}} \).
Density \( = \dfrac{900}{115} = 7.83 \, \text{g/cm}^3 \).
(d)(i)
Thermal expansion is useful in liquid-in-glass thermometers, where the liquid expands to show a temperature reading.
It is also used in bimetallic strips, which bend as different metals expand at different rates when heated.
(d)(ii)
Thermal expansion is a problem for structures like bridges, roads, and overhead electricity cables.
Gaps or sag allowances must be built in to prevent damage caused by expansion and contraction with temperature changes.
Question 4
Explain the effect this has on the population of rabbits.
Describe how an increase in plant population affects the concentration of carbon dioxide in the atmosphere.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B18.2 — Food chains and food webs (Parts (a), (b), (c))
• Topic B18.1 — Energy flow (Part (d))
• Topic B18.3 — Nutrient cycles (Part (e))
▶️ Answer/Explanation
(a)(i) Yucca plant or prickly pear
Producers are organisms that make their own food, typically through photosynthesis.
In Fig. 4.1, the yucca plant and prickly pear are the producers, since they are plants at the base of the food web.
(a)(ii) Rat or rabbit
Herbivores are organisms that only eat plants.
The rat and the rabbit both feed directly on producers (prickly pear and/or yucca plant), making them herbivores.
(a)(iii) Hawk
The hawk eats the rat and rabbit directly, making it a secondary consumer.
The hawk also eats the fox, which itself eats rats and rabbits, making the hawk a tertiary consumer too.
(a)(iv) Any correct four-organism chain, e.g. yucca plant → rabbit → fox → hawk
A valid chain must follow an arrow pathway shown in Fig. 4.1.
Other accepted answers include: prickly pear → rat → fox → hawk, or prickly pear → rabbit → fox → hawk.
Arrows must point in the direction of energy transfer (producer → consumer).
(b)
If a new species is introduced that eats yucca plants, there is less food available for rabbits.
This increases competition for food, causing the rabbit population to decrease.
(c) Decomposers
Decomposers break down dead organic matter (e.g. dead plants and animals) to obtain energy.
Examples include bacteria and fungi.
(d) The Sun
The Sun is the principal source of energy for almost all food chains.
Producers capture this light energy through photosynthesis, and it is then passed along the food chain.
(e)
An increase in plant population means more carbon dioxide is removed from the atmosphere.
This is because more carbon dioxide is used as a raw material for photosynthesis.
Question 5
State what is meant by the term hydrocarbon.
State the colour change when aqueous bromine reacts with an alkene.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C11.3 — Fuels / Fractional distillation (Parts (a), (b))
• Topic C11.5 — Alkenes and cracking (Part (c))
▶️ Answer/Explanation
(a)(i) Gasoline and bitumen
In the fractionating column, fractions are collected in order of decreasing volatility from top to bottom.
The missing fraction near the top (below refinery gas, above naphtha) is gasoline; the missing fraction at the bottom (below diesel oil) is bitumen.
(a)(ii)
Refinery gas is commonly used as a fuel for heating and cooking, such as in bottled gas (LPG).
(a)(iii)
Fractional distillation only separates the existing hydrocarbons based on their different boiling points.
No new substances are formed during the process, so it is a physical change.
(b)(i)
A hydrocarbon is a compound that contains carbon and hydrogen atoms only.
No other elements are present in the molecule.
(b)(ii) Carbon dioxide and water
Complete combustion of a hydrocarbon occurs in plentiful oxygen.
The products formed are carbon dioxide (\( CO_2 \)) and water (\( H_2O \)).
(c)(i) Cracking
Cracking is the process in which larger, less useful alkane molecules are broken down into smaller alkane and alkene molecules using heat and a catalyst.
(c)(ii)
Alkane molecules contain only single carbon-carbon bonds, making them saturated.
Alkene molecules contain at least one carbon-carbon double bond (\( C=C \)), making them unsaturated.
(c)(iii) From orange to colourless
Aqueous bromine is orange in colour before reacting with an alkene.
When it reacts with the double bond in an alkene, it becomes colourless, confirming the presence of unsaturation.
Question 6
Several fuse ratings are available.
Explain your answer.
Calculate the total resistance of the television.
On Fig. 6.3 mark and label one wavelength.
State the angle of incidence.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P4.4 — Electrical safety (Parts (a)(i), (b))
• Topic P4.2.4 — Resistance (Part (a)(ii))
• Topic P3.3 — Electromagnetic spectrum (Part (c)(i))
• Topic P3.1 — Wave properties (Part (c)(ii))
• Topic P3.2.1 — Reflection of light (Part (d))
▶️ Answer/Explanation
(a)(i) 5 A
A fuse must have a rating just above the normal working current so it does not blow during ordinary use.
Since the working current is \( 3 \, \text{A} \), the smallest available rating above this value is \( 5 \, \text{A} \).
(a)(ii) \( 40 \, \Omega \)
Resistance is calculated using \( R = \dfrac{V}{I} \).
\( R = \dfrac{120}{3} = 40 \, \Omega \).
(b)
The socket is positioned right next to a kitchen sink, so water could get into the socket or plugs.
This creates a danger of electrocution, since water is a good conductor of electricity.
(c)(i)
Radio waves have the longest wavelength in the electromagnetic spectrum.
They belong in the box at the far end of the spectrum, opposite X-rays.
(c)(ii)
A wavelength is the distance from one point on a wave to the identical point on the next wave.
It should be marked from one peak to the next peak (or one trough to the next trough).
(d)(i) Normal
Line X is drawn perpendicular (at \( 90^\circ \)) to the mirror surface at the point of incidence.
This reference line is called the normal.
(d)(ii)
The angle of reflection, labelled \( r \), is measured between the reflected ray and the normal.
It is found on the side of the normal opposite to the incident ray.
(d)(iii) \( 30^\circ \)
By the law of reflection, the angle of incidence equals the angle of reflection.
Since the angle of reflection is \( 30^\circ \), the angle of incidence is also \( 30^\circ \).
Question 7
Name the structure that stops plant cells bursting in very dilute sugar solutions.
Write numbers next to each part to show the correct order 1–4.
Number 1 has been done for you.
mesophyll cells ………….
root cortex cells ………….
root hair cells ……1…..
xylem ………….
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B3.2 — Osmosis (Part (a))
• Topic B2.1 — Cell structure (Part (b))
• Topic B6.1 — Uses of water in plants (Part (c))
• Topic B8.2 — Water pathway through plants (Part (d))
▶️ Answer/Explanation
(a)(i) C, D and E
A loss of mass means water has left the potato cubes.
From Table 7.1, solutions C, D, and E all show a negative difference in mass.
(a)(ii)
Water moves out of the potato cells by osmosis.
This occurs through the partially permeable cell membrane, from a region of higher water concentration (inside the cell) to a region of lower water concentration (the sugar solution).
(a)(iii) Solution B
Solution B shows a mass difference of \( 0.0 \, \text{g} \), meaning no net movement of water occurred.
This indicates solution B has the same concentration as the cell contents of the potato (isotonic).
(b) Cell wall
The rigid cell wall in plant cells resists the buildup of pressure caused by water entering the cell.
This prevents the cell from bursting, unlike an animal cell which lacks a cell wall.
(c) As a solvent; as a material for photosynthesis
Water dissolves substances for transport within the plant, acting as a solvent.
Water is also a raw material required for photosynthesis, alongside carbon dioxide.
(d) 4, 2, 1, 3
Water first enters through root hair cells (1), providing a large surface area for absorption.
It then passes through root cortex cells (2) into the xylem (3), before finally reaching the mesophyll cells (4) in the leaf where transpiration occurs.
Question 8
Both isotopes have a proton number of 26.
Iron-54 has a nucleon number of 54 and iron-56 has a nucleon number of 56.
Suggest one suitable material to use.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.2 — Atomic structure (Part (a)(i))
• Topic C2.3 — Isotopes (Part (a)(ii))
• Topic C6.3 — Extraction of metals (Part (b))
• Topic C9.5 — Rusting (Part (c))
▶️ Answer/Explanation
(a)(i) 26
In a neutral atom, the number of electrons equals the number of protons.
Since iron has a proton number of \( 26 \), one atom of iron-54 has \( 26 \) electrons.
(a)(ii) 2
Number of neutrons \( = \) nucleon number \( – \) proton number.
Iron-54: \( 54 – 26 = 28 \) neutrons. Iron-56: \( 56 – 26 = 30 \) neutrons. Difference \( = 30 – 28 = 2 \).
(b)(i)
Word equation: iron oxide + carbon monoxide \( \rightarrow \) iron + carbon dioxide.
Carbon monoxide reduces iron oxide, releasing molten iron and carbon dioxide gas.
(b)(ii) Carbon monoxide
Carbon monoxide gains oxygen during the reaction, forming carbon dioxide.
Gaining oxygen is oxidation, so carbon monoxide is the substance oxidised.
(c)(i)
Element: oxygen.
Compound: water — both oxygen and water must be present together for iron to rust.
(c)(ii) Paint
Coating iron with paint creates a barrier that keeps oxygen and water away from the metal surface.
Other acceptable coatings include oil, grease, or plastic.
Question 9
Calculate the mass of nickel-63 remaining in the sample after 300 years.
Draw lines to link each type of ionising radiation to its correct description.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P5.1 — Nuclear fission (Part (a))
• Topic P5.2.4 — Half-life (Part (b)(i))
• Topic P5.2.5 — Safety and disposal (Part (b)(ii))
• Topic P5.2.2 — Types of radiation (Part (b)(iii))
• Topic P2.1.1 — States of matter (Part (c))
▶️ Answer/Explanation
(a) Any two from:
Nuclear fission produces no carbon dioxide emissions during electricity generation.
Using nuclear fission conserves fossil fuels, leaving them available for other purposes.
(b)(i) 0.25 g
\( 300 \) years \( \div 100 \) years (half-life) \( = 3 \) half-lives.
Mass remaining \( = 2.00 \div 2^3 = 2.00 \div 8 = 0.25 \, \text{g} \).
(b)(ii)
Nuclear waste should be stored underground.
It should also be kept in lead-lined containers to absorb and block the ionising radiation.
(b)(iii)
\( \alpha \)-particle links to helium nucleus.
\( \beta \)-particle links to electron.
\( \gamma \)-ray links to electromagnetic wave.
(c)
Diagram Y represents a liquid because the particles are randomly arranged, with most particles touching each other.
Diagram Z represents a gas because the particles are widely spaced apart and arranged randomly, moving freely.
Question 10
Adrenaline increases pulse rate and ………………….. rate.
Adrenaline also causes pupils in the eye to ……………… .
‘A nerve impulse is a chemical signal that passes along nerve cells called connectors.’
Circle the two words in the student’s description that are not correct.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic B13.2 — Hormones (Parts (a), (b))
• Topic B13.1 — Nervous system (Parts (c), (d))
▶️ Answer/Explanation
(a)
Adrenaline is secreted in ‘fight or flight’ situations, preparing the body for sudden action.
It increases pulse rate and breathing rate, and causes pupils to widen, all to improve oxygen supply and awareness.
(b)
A hormone is a chemical substance, produced by a gland, carried by the blood, which alters the activity of target organs.
This is the only combination of sentence beginning and ending that is scientifically correct.
(c)
The two parts of the central nervous system are the brain.
The other part is the spinal cord.
(d)
The two incorrect words are “chemical” and “connectors”.
A nerve impulse is actually an electrical signal that passes along nerve cells called neurons.
Question 11
You only need to show the outer shell electrons.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C8.3 — Group VII properties (Parts (a), (b))
• Topic C2.5 — Covalent bonding (Part (c))
▶️ Answer/Explanation
(a)(i) \( I_2 \)
Like chlorine and bromine, iodine exists as a diatomic molecule.
Its formula is written as \( I_2 \).
(a)(ii)
A diatomic molecule is one that contains exactly two atoms bonded together.
A chlorine molecule consists of two chlorine atoms joined by a single covalent bond.
(a)(iii) Gas
Moving down Group VII, elements become less volatile: chlorine is a gas, bromine is a liquid, and iodine is a solid.
Since chlorine is above bromine in the group, it must exist as a gas at room temperature.
(a)(iv) Halogens
Group VII of the Periodic Table is known as the halogens.
These elements share similar chemical properties, such as being diatomic and reactive non-metals.
(b)(i)
Chlorine is added to drinking water to kill microorganisms and bacteria present in the water.
This makes the water safe to drink by preventing the spread of waterborne diseases.
(b)(ii)
Test: hold damp litmus paper in the gas.
Result: the litmus paper is bleached (turns white), confirming the presence of chlorine.
(c)(i) \( H_2 + Cl_2 \rightarrow 2HCl \)
One molecule of hydrogen reacts with one molecule of chlorine.
This produces two molecules of hydrogen chloride, balancing the atoms on both sides.
(c)(ii)
The hydrogen atom shares its one electron with the chlorine atom.
This forms one shared (bonding) pair of electrons, giving chlorine a complete outer shell of eight electrons (octet).
(c)(iii)
Hydrogen chloride is formed from two non-metal atoms bonding together.
Since both atoms share electrons rather than transferring them, the compound is covalent, not ionic.
Question 12
Explain your answer.
Calculate the mass of the aircraft in kg.
The gravitational field strength g is \( 10 \, \text{N/kg} \).
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.2 — Motion (Part (a))
• Topic P1.5.1 — Effects of forces (Part (b))
▶️ Answer/Explanation
(a)(i) 575 m
Distance travelled equals the area under a speed-time graph.
Using the triangular area from the graph: \( \text{distance} = \frac{1}{2} \times 25 \times 46 = 575 \, \text{m} \).
(a)(ii)
The greatest acceleration occurs during the interval from \( t = 0 \, \text{s} \) to around \( t = 34 \, \text{s} \).
This is where the graph has its steepest gradient, indicating the fastest rate of change of speed.
(a)(iii) Kinetic energy and gravitational potential energy
As the aircraft speeds up, it gains kinetic energy.
As the aircraft climbs and gains height, it also gains gravitational potential energy.
(b)(i)
Forces B and D are equal and opposite.
This must be true because the aircraft is travelling at a constant speed, meaning the horizontal forces (thrust and drag) are balanced.
(b)(ii) C
Weight always acts vertically downward on an object.
Force C points downward in Fig. 12.2, so it represents the weight of the aircraft.
(b)(iii) 100,000 kg
Mass is calculated using \( m = \dfrac{W}{g} \).
\( m = \dfrac{1 \times 10^6}{10} = 100{,}000 \, \text{kg} \).