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ZIMSEC O Level · 4003/1 · N2025

Combined Science Paper 1 November 2025

Questions
40
Syllabus code
4003/1

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Questions
40
Pass mark
24
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Answer every question in the printed order, get marked at the end, then see the answers.

The questions

Question 1

Biology

The diagram shows a plant cell.

Which part maintains the shape of the cell?

  1. AA
  2. BB
  3. CC
  4. DD

Question 2

Biology
By which process does water enter root hair cells?
  1. Aosmosis
  2. Bdiffusion
  3. Cactive uptake
  4. Dtranslocation

Question 3

Biology
Which instrument is used to measure the rate of transpiration?
  1. Abarometer
  2. Bmanometer
  3. Chydrometer
  4. Dpotometer

Question 4

Biology
The diagram shows part of the carbon cycle.
Which process, A, B, C or D, represents photosynthesis?
  1. AA
  2. BB
  3. CC
  4. DD

Question 5

Biology
Which statement describes the structure of a blood capillary?
  1. AIt contains valves.
  2. BIt is one cell thick.
  3. CIt has a wide lumen.
  4. DIt has a thick elastic layer.

Question 6

Biology
The digestion of protein produces
  1. Aglucose.
  2. Bglycerol.
  3. Camino acids.
  4. Dfatty acids.

Question 7

Biology
Which nutrient prevents constipation?
  1. Afat
  2. Bprotein
  3. Croughage
  4. Dcarbohydrate

Question 8

Biology

The diagram shows a food web.

In the food web, the lizard is

  1. Aa carnivore.
  2. Ba herbivore.
  3. Can omnivore.
  4. Da decomposer.

Question 9

Biology
Which sequence correctly shows the flow of energy in an ecosystem?
  1. Asun → secondary consumer → primary consumer → producer
  2. Bsecondary consumer → tertiary consumer → producer → sun
  3. Cproducer → primary consumer → tertiary consumer → sun
  4. Dsun → producer → primary consumer → secondary consumer

Question 10

Biology
Which substance builds up in muscles as a result of anaerobic respiration?
  1. Aoxygen
  2. Bethanol
  3. Clactic acid
  4. Dcarbon dioxide

Question 11

Biology
Which condition is mainly caused by tobacco smoking?
  1. Aliver cirrhosis
  2. Bemphysema
  3. Challucinations
  4. Ddamaged muscles

Question 12

Biology
The release of a mature ovum from the ovary into the oviduct takes place during
  1. Amenstruation.
  2. Bfertilisation.
  3. Cimplantation.
  4. Dovulation.

Question 13

Biology
Which one is a sign of puberty in girls?
  1. Awidening of the pelvic girdle
  2. Bbroadening of shoulders
  3. Cdevelopment of beard
  4. Ddeepening of voice

Question 14

Biology
Which disease is water-borne?
  1. Abilharzia
  2. Bmalaria
  3. Cherpes
  4. Debola

Question 15

Chemistry
Which is the best method used to separate two liquids which have different densities?
  1. Asieving
  2. Bfiltration
  3. Cdistillation
  4. Ddecanting

Question 16

Chemistry

The diagram shows apparatus that are used in paper chromatography.

What is the purpose of liquid Y?

  1. Ato give colour to the dyes
  2. Bto separate the dyes
  3. Cto provide a sweet scent
  4. Dto make the paper wet

Question 17

Chemistry
Which diagram, A, B, C or D, shows the electronic configuration of a chlorine atom, 1737Cl^{37}_{17}Cl?
  1. AA
  2. BB
  3. CC
  4. DD

Question 18

Chemistry

The element carbon exists as carbon-12, 612C^{12}_{6}C and carbon-14, 614C^{14}_{6}C.

The two carbon atoms have

  1. Athe same number of electrons.
  2. Bthe same number of neutrons.
  3. Cdifferent number of protons.
  4. Ddifferent chemical properties.

Question 19

Chemistry
Which statement correctly describes covalent compounds?
  1. AThey are soluble in water.
  2. BThey conduct electricity.
  3. CThey generally have low melting points.
  4. DThey are usually solids at room temperature.

Question 20

Chemistry
Which one is the correct formula for calculating the concentration of a solution?
  1. Aconcentration = molesvolume\frac{moles}{volume}
  2. Bconcentration = volumemoles\frac{volume}{moles}
  3. Cconcentration = moles x volume
  4. Dconcentration = moles + volume

Question 21

Chemistry

The diagram shows the apparatus used in the electrolysis of water.

Why is the water acidified?

  1. Ato reduce its electrical conductivity
  2. Bto increase the formation of ions
  3. Cto produce fumes
  4. Dto give it scent

Question 22

Chemistry
A compound
  1. Ais a mixture of substances.
  2. Bcan be separated by physical means.
  3. Chas different substances that are chemically combined.
  4. Dis formed without either the gain or release of heat energy.

Question 23

Chemistry
When sulphuric acid reacts with a base, the salt formed is a
  1. Anitrate.
  2. Bchloride.
  3. Csulphate.
  4. Dcarbonate.

Question 24

Chemistry

The diagram shows the blast furnace which is used in the extraction of iron.

Which reaction occurs at X?

  1. Acarbon + oxygen → carbon dioxide
  2. Bcarbon dioxide + oxygen → carbon monoxide
  3. Ciron (III) oxide + slag → carbon monoxide + iron
  4. Diron (III) oxide + carbon monoxide → carbon dioxide + iron

Question 25

Chemistry
Zinc, iron, copper and magnesium are metals.
Which one is the least reactive?
  1. Airon
  2. Bzinc
  3. Ccopper
  4. Dmagnesium

Question 26

Chemistry
A biogas digester operates best at a pH range of
  1. A12 to 14.
  2. B6 to 8.
  3. C4 to 5.
  4. D1 to 3.

Question 27

Chemistry
Which organic molecule, A, B, C or D, is an alkane?
  1. AA
  2. BB
  3. CC
  4. DD

Question 28

Physics

The flow diagram shows steps in a thermal power station.

coal → boiler → turbines → generator → power cables

Which row shows the energy conversions in the thermal power station?

  1. Aheat → sound → chemical → electrical
  2. Bkinetic → heat → sound → electrical
  3. Cchemical → heat → kinetic → electrical
  4. Dsound → heat → chemical → electrical

Question 29

Physics

Forces acting on a box are shown in the diagram.

What is the resultant force acting on the box?

  1. A5 N
  2. B10 N
  3. C15 N
  4. D25 N

Question 30

Physics
The law of conservation of energy states that
  1. Awork done is equal to energy used.
  2. Bgravitational potential energy is equal to force pulling objects down.
  3. Cthe source of all energy is the carbohydrates produced by green plants through photosynthesis.
  4. Denergy cannot be created or destroyed but can be converted from one form to another.

Question 31

Physics
Which statement correctly describes what happens in a petrol engine?
  1. Aonly air is compressed
  2. Bthe piston is compressed
  3. Conly petrol is compressed
  4. Dthe air and petrol mixture is compressed

Question 32

Physics
Poor conductors of heat and electricity are called
  1. Ainsulators.
  2. Belectrolytes.
  3. Cradiators.
  4. Delectrodes.

Question 33

Physics

The diagram shows an open 3-pin plug.

What is the colour of the cable P?

  1. Ablue
  2. Bgreen
  3. Cyellow
  4. Dbrown

Question 34

Physics
Which method of heat transfer does not need a medium?
  1. Aconduction
  2. Bradiation
  3. Cconvection
  4. Dreflection

Question 35

Physics
Which material is magnetic?
  1. Airon fillings
  2. Bcopper fillings
  3. Cglass powder
  4. Dchalk dust

Question 36

Physics

The diagram shows an electric circuit.

What is the current flowing in the circuit?

  1. A0.25 A
  2. B4.00 A
  3. C18.00 A
  4. D60.00 A

Question 37

Physics
What is the Standard International (SI) unit of power?
  1. Apascal
  2. Bjoule
  3. Cvolt
  4. Dwatt

Question 38

Physics
The unit cost of electricity is 20 cents. A household uses 210 kWh per month.
What is the total cost of electricity for the household per month?
  1. A$10.50
  2. B$42.00
  3. C$190.00
  4. D$4200.00

Question 39

Physics

The diagram shows a Blair pump.

What happens to the valves during upstroke?

  1. Aboth valves are closed
  2. Bboth valves are open
  3. Cvalve L is closed while valve K is open
  4. Dvalve L is open while valve K is closed

Question 40

Physics
A force of 300 N is exerted on a surface of 75 m².
What is the pressure exerted on the surface?
  1. A4 Pa
  2. B225 Pa
  3. C375 Pa
  4. D22 500 Pa

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