Cambridge IGCSE™

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COMBINED SCIENCE 0653/03

Paper 3 Theory (Core) For examination from 2025
SPECIMEN PAPER 1 hour 15 minutes

You must answer on the question paper.

No additional materials are needed.

INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.
● Take the weight of 1.0 kg to be 9.8 N (acceleration of free fall = 9.8 m / s2).

INFORMATION
● The total mark for this paper is 80.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.

This document has 24 pages. Any blank pages are indicated.

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1 (a) Fig. 1.1 shows an animal cell and a plant cell.

B E

C F

D G

Fig. 1.1

Table 1.1 shows the names and functions of some of the structures of the cells labelled in
Fig. 1.1.

Complete Table 1.1.

Table 1.1

letter in name of structure function

Fig. 1.1
controls the movement of substances
A .................................................. into and out of cells

D mitochondria ..................................................

.......... vacuole ..................................................

 [4]

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(b) Fig. 1.2 shows some structures organised in order of increasing size, starting with the smallest
size.

cell

.....................................

.....................................

.....................................

organism

Fig. 1.2

Use the words from the list to complete Fig. 1.2.

organ organ system tissue

[2]

(c) The heart is the organ that pumps blood around the body.

(i) State the name of an upper chamber of the heart.

....................................................................................................................................... [1]

(ii) State the type of blood vessel that transports blood to the heart.

....................................................................................................................................... [1]

(iii) State the function of red blood cells.

....................................................................................................................................... [1]

(d) White blood cells defend the human body against pathogens.

State one other way the human body defends itself against pathogens.

............................................................................................................................................... [1]
 [Total: 10]
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2 (a) A student investigates photosynthesis using the set-up shown in Fig. 2.1.

plant X plant Y

clear plastic
bag

substance substance
that releases that absorbs
carbon dioxide carbon dioxide
into the air from the air

Fig. 2.1

The student puts the plants in the same warm room with plenty of light.

After three days, the student uses iodine solution to test a leaf from each plant.

Fig. 2.2 shows the results.

plant X plant Y

blue-black colour yellow-brown colour

Fig. 2.2

(i) Complete the sentences to explain the results in Fig. 2.2.

The colour of the iodine solution shows that only the leaf from plant X contains

.................................................. .

This investigation shows that photosynthesis requires the presence of

.................................................. .
[2]

(ii) State the name of the green pigment needed for photosynthesis.

....................................................................................................................................... [1]

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(b) Photosynthesis is an enzyme-controlled reaction.

Fig. 2.3 shows the effect of temperature on the rate of photosynthesis for three different
plants.

rate of plant R
photosynthesis

plant Q

plant S
0 10 20 30 40 50
temperature / °C

Fig. 2.3

(i) Identify the temperature at which the rate of photosynthesis for plant Q is highest.

....................................................... °C [1]

(ii) In a desert, temperatures are often higher than 40 °C.

Explain why plant S would not survive in a desert.

Use the word enzyme in your answer.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

....................................................................................................................................... [2]

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(c) Fig. 2.4 shows a drawing of the carpel from an insect-pollinated flower.

ovule

Fig. 2.4

(i) Identify the part labelled X on Fig. 2.4.

....................................................................................................................................... [1]

(ii) Describe fertilisation in an ovule.

............................................................................................................................................

............................................................................................................................................

....................................................................................................................................... [1]

 [Total: 8]

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BLANK PAGE

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3 (a) Fig. 3.1 shows a food web.

fox

puffin

squid
fish

zooplankton

phytoplankton

Fig. 3.1

(i) Identify the producer in Fig. 3.1.

....................................................................................................................................... [1]

(ii) Place a tick () in each box that describes the puffin in Fig. 3.1.

carnivore

herbivore

primary consumer

secondary consumer

tertiary consumer
[2]

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(iii) Pollution in the ocean can kill squid.

Explain how this may reduce the number of foxes.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

....................................................................................................................................... [2]

(iv) Pollution is one reason why squid may become endangered.

State two other reasons why squid may become endangered.

1 .........................................................................................................................................

............................................................................................................................................

2 .........................................................................................................................................

............................................................................................................................................
 [2]

(b) Decomposers are important organisms in ecosystems.

Complete the description of a decomposer.

A decomposer is an organism that gets its .................................................. from dead or

waste .................................................. material.

[2]

 [Total: 9]

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4 Fig. 4.1 shows the electrolysis of concentrated aqueous sodium chloride using inert electrodes.

low voltage
d.c. supply

negative positive
electrode electrode

concentrated aqueous
sodium chloride

Fig. 4.1

(a) State the name of the positive electrode.

............................................................................................................................................... [1]

(b) Identify the gases produced at the electrodes.

positive electrode ............................................................

negative electrode ...........................................................

 [2]

(c) The electrolysis of concentrated aqueous sodium chloride produces a solution containing
an alkali.

(i) State what is meant by an alkali.

............................................................................................................................................

....................................................................................................................................... [1]

(ii) State what colour change is observed when methyl orange is added to a solution
containing an alkali.

from orange to ........................................................... [1]

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(d) The electrolysis shown in Fig. 4.1 produces the alkali sodium hydroxide.

Aqueous sodium hydroxide reacts with dilute sulfuric acid.

(i) Complete the word equation for this reaction.

sodium
+ sulfuric acid → +
hydroxide .......................... ..........................

[1]

(ii) The reaction between aqueous sodium hydroxide and dilute sulfuric acid is exothermic.

State what is meant by an exothermic reaction.

............................................................................................................................................

....................................................................................................................................... [2]

 [Total: 8]

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5 Petroleum is a mixture of hydrocarbons.

The mixture is separated using the fractional distillation apparatus shown in Fig. 5.1.

refinery gas

gasoline

naphtha

gas oil

petroleum

bitumen

Fig. 5.1

(a) Two fractions obtained from the distillation of petroleum are refinery gas and gasoline.

State one use of each of these fractions.

refinery gas ................................................................................................................................

gasoline .....................................................................................................................................
 [2]

(b) Fig. 5.2 shows two hydrocarbon molecules.

H H H H H
H
H C C C H H C C C
H
H H H H
hydrocarbon A hydrocarbon B

Fig. 5.2

(i) State the molecular formula of hydrocarbon A.

....................................................................................................................................... [1]

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(ii) State which hydrocarbon is saturated.

Give a reason for your answer.

hydrocarbon .......................................................................................................................

reason ................................................................................................................................

............................................................................................................................................
 [1]

(iii) State the chemical test that is used to distinguish between hydrocarbon A and
hydrocarbon B.

State the observation for each hydrocarbon.

test .....................................................................................................................................

observation for hydrocarbon A ...........................................................................................

............................................................................................................................................

observation for hydrocarbon B ...........................................................................................

............................................................................................................................................
 [2]

(c) The symbol equation for the complete combustion of the hydrocarbon methane, CH4, is
shown.

CH4(g) + ..........O2(..........) → CO2(..........) + ..........H2O(l)

Complete the balanced equation and write the missing state symbols. [2]

(d) Methane is a simple molecular compound.

State one physical property of methane.

............................................................................................................................................... [1]

 [Total: 9]

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6 The symbol for an atom of iron is shown.

Fe
56

26

(a) Deduce the number of electrons and the number of neutrons in this atom.

electrons ...................................................

neutrons ....................................................
 [2]

(b) Iron(II) ions, Fe2+, are formed from atoms of iron, Fe.

(i) Describe how Fe2+ ions are formed from iron atoms.

............................................................................................................................................

....................................................................................................................................... [1]

(ii) Describe what is observed when aqueous sodium hydroxide is added to

aqueous iron(II) ions.

............................................................................................................................................

....................................................................................................................................... [2]

(c) Iron reacts with dilute hydrochloric acid to form hydrogen and a salt.

(i) Explain why this is a chemical change.

............................................................................................................................................

....................................................................................................................................... [1]

(ii) State the test for hydrogen and give the observation for a positive result.

test .....................................................................................................................................

observation ........................................................................................................................

............................................................................................................................................
[1]

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(d) Iron is used as a catalyst in some chemical reactions.

Describe what is meant by a catalyst.

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

............................................................................................................................................... [2]

 [Total: 9]

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7 (a) Fig 7.1 shows an electric heater connected in a circuit.

M
X

Fig. 7.1

(i) State the name of component X.

....................................................................................................................................... [1]

(ii) The current in component X is 0.5 A.

The current in the heater is 8.3 A.

Circle the value of the current from the source.

0.5 A 7.8 A 8.3 A 8.8 A

[1]

(iii) The electric heater uses 2.0 kW of electrical power.

Electrical energy costs $0.15 per kW h.

Calculate the cost of using the heater for 5.5 hours.

cost = $............................................................ [2]

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(b) Fig. 7.2 shows a wind turbine used to generate electricity from the power of the wind.

Fig. 7.2

The wind turbine produces electrical power of 2200 W at a voltage of 240 V.

Calculate the energy transferred by the wind turbine in 15 seconds.

energy = ........................................................ J [2]

(c) Solar power can also be used to generate electricity.

(i) Visible light from the Sun contains all the colours of the visible spectrum.

State the colour with the longest wavelength.

....................................................................................................................................... [1]

(ii) Most of the energy from the Sun is radiated in three regions of the electromagnetic
spectrum.

One of these regions is visible light.

State the name of one of the other two regions.

....................................................................................................................................... [1]

 [Total: 8]

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8 (a) (i) A spacecraft has a mass of 3.1 × 103 kg.

Calculate the weight of the spacecraft on the surface of the Earth.

Include the unit in your answer.

 weight = .......................... unit .......... [3]

(ii) The spacecraft is launched into space. The spacecraft accelerates as it moves upwards
through the Earth’s atmosphere.

State what is meant by accelerates.

....................................................................................................................................... [1]

(iii) The spacecraft travels from the Earth to the Moon in 3.2 days.

Calculate the number of hours in 3.2 days.

number of hours = ........................................................... [1]

(iv) The distance from the Earth to the Moon is 384 000 km.

Use your answer to (a)(iii) to calculate the average speed of the spacecraft in km / h.

speed = ................................................. km / h [2]

(v) The spacecraft is controlled by radio waves sent from the Earth.

State whether the radio waves travel to the spacecraft faster, slower or at the same
speed as visible light.

Give a reason for your answer.

speed .................................................................................................................................

reason ................................................................................................................................
 [1]

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(b) The Earth orbits the Sun as part of the Solar System.

State the name of the planet that orbits closest to the Sun.

............................................................................................................................................... [1]

(c) State the name of the galaxy that contains the Sun.

............................................................................................................................................... [1]

 [Total: 10]

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9 Table 9.1 gives some data about five substances.

Table 9.1

aluminium ethanol poly(ethene) sulfur water

density in
2.7 0.8 0.9 2.0 1.0
g / cm3
state at
solid liquid solid solid liquid
25 °C
electrical
conductor insulator insulator insulator
property

(a) State the electrical property of poly(ethene).

Give a reason for your answer.

electrical property .......................................................

reason ........................................................................................................................................
 [1]

(b) A ball made of poly(ethene) has a density of 0.9 g / cm3.

Predict what happens to the ball when placed in a beaker of water and in a beaker of ethanol.

Use the data in Table 9.1 to explain your answer.

water ..........................................................................................................................................

ethanol .......................................................................................................................................

explanation.................................................................................................................................

....................................................................................................................................................
[2]

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(c) Fig. 9.1 shows the arrangements of particles in ethanol and sulfur at a temperature of 25 °C.

X Y

Fig. 9.1

Use Fig. 9.1 and information from Table 9.1 to state which diagram, X or Y, shows the
structure of ethanol and of sulfur at 25°C.

Explain your answer in terms of particles.

ethanol ............................................................

sulfur ............................................................

explanation ................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................
[2]

(d) A thin, flat piece of aluminium is used as a mirror.

(i) The piece of aluminium has a mass of 9.0 g.

Use information from Table 9.1 to calculate the volume of the piece of aluminium.

volume = .................................................... cm3 [2]

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(ii) Fig. 9.2 shows a person’s eye looking at the reflection of an object placed in front of the
aluminium mirror.

object

eye

mirror

Fig. 9.2

On Fig. 9.2:

draw the normal line and label the angle of incidence of the incident ray with
•
the letter i.
• draw the reflected ray to show how the eye is able to see the reflected image of
the object.
[2]

 [Total: 9]

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© Cambridge University Press & Assessment 2022 0653/03/SP/25

 The Periodic Table of Elements
Group
I II III IV V VI VII VIII
1 2

H He
hydrogen helium
Key 1 4
3 4 atomic number 5 6 7 8 9 10

of the University of Cambridge.

Li Be atomic symbol B C N O F Ne
lithium beryllium name boron carbon nitrogen oxygen fluorine neon
7 9 relative atomic mass 11 12 14 16 19 20
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
23 24 27 28 31 32 35.5 40
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

© Cambridge University Press & Assessment 2022

potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
85 88 89 91 93 96 – 101 103 106 108 112 115 119 122 128 127 131
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
24

caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
133 137 178 181 184 186 190 192 195 197 201 204 207 209 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118

0653/03/SP/25
actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson
– – – – – – – – – – – – – – – – –

57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity.
lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
139 140 141 144 – 150 152 157 159 163 165 167 169 173 175
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232 231 238 – – – – – – – – – – –

The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).

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