About this GCSE Science practice test

Combined or Triple Science means keeping three quite different subjects fresh at once, and this set moves between them the way the real exam does — from circuit diagrams to rate-of-reaction calculations to cell structure in a single sitting. Each worked answer explains the reasoning, not just the fact, so you can check your logic without going back to the textbook.

GCSE Science Practice Test sample questions

These starter questions help you launch a science mock test quickly. Swap them with your own worksheet, notebook, or textbook questions any time.

1. 1. Biology: Cell biology: Under a microscope, a cell has an actual width of 0.05 mm and its magnified image measures 25 mm across. Calculate the magnification used.

2. 2. Biology: Transport in cells: A plant cell is placed in a strong salt solution. Explain, in terms of water movement, what happens to the cell.

3. 3. Biology: Organisation: Name the enzyme that breaks down starch into sugars and state where in the digestive system it is produced.

4. 4. Biology: Organisation: Describe one feature of an artery's structure and explain how it is adapted to carry blood at high pressure.

5. 5. Biology: Organisation: Write the word equation for anaerobic respiration in muscle cells during vigorous exercise.

6. 6. Biology: Infection and response: Explain how a vaccine gives a person long-term immunity to a particular pathogen.

7. 7. Biology: Bioenergetics: State two factors that can limit the rate of photosynthesis in a plant.

8. 8. Biology: Homeostasis: Explain how the body responds when blood glucose concentration rises after eating a meal.

9. 9. Biology: Inheritance: In pea plants, tall (T) is dominant over short (t). Two heterozygous tall plants (Tt) are crossed. Calculate the percentage of offspring expected to be short.

10. 10. Biology: Ecosystems: A student places 10 quadrats, each 1 m², at random across a 500 m² field and counts an average of 6 daisies per quadrat. Estimate the total daisy population in the field.

11. 11. Chemistry: Atomic structure: An atom of chlorine-35 has an atomic number of 17. Calculate the number of neutrons it contains.

12. 12. Chemistry: Bonding: Explain, in terms of electron transfer, how an ionic bond forms between sodium and chlorine atoms.

13. 13. Chemistry: Quantitative chemistry: Calculate the number of moles in 22 g of carbon dioxide (relative formula mass of CO2 = 44).

14. 14. Chemistry: Chemical changes: Predict what you would observe when magnesium ribbon is added to copper sulfate solution, and name the type of reaction taking place.

15. 15. Chemistry: Chemical changes: State the products formed at each electrode during the electrolysis of molten lead bromide.

16. 16. Chemistry: Energy changes: A reaction releases 150 kJ of energy when 2 moles of reactant react completely. Calculate the energy released per mole.

17. 17. Chemistry: Rates of reaction: In an experiment, 24 cm³ of gas was collected in 60 seconds. Calculate the mean rate of reaction.

18. 18. Chemistry: Organic chemistry: State the general formula for the alkane homologous series and name its first member.

19. 19. Chemistry: Chemical analysis: Describe a chemical test used to identify carbon dioxide gas, including the expected positive result.

20. 20. Chemistry: Earth's atmosphere: State two human activities that have increased the concentration of carbon dioxide in the atmosphere since the Industrial Revolution.

21. 21. Physics: Forces: A trolley of mass 2.5 kg accelerates at 4 m/s². Calculate the resultant force acting on it.

22. 22. Physics: Forces: Calculate the momentum of a 900 kg car travelling at 15 m/s.

23. 23. Physics: Energy: Calculate the kinetic energy of a 0.2 kg ball moving at 6 m/s.

24. 24. Physics: Energy: Explain, in terms of energy transfers, why a falling skydiver eventually reaches a constant (terminal) velocity.

25. 25. Physics: Waves: A wave has a time period of 0.02 seconds. Calculate its frequency.

26. 26. Physics: Waves: Explain, using the wave model of light, why a ray of light changes direction as it passes from air into glass.

27. 27. Physics: Electricity: A kettle operates at 230 V and draws a current of 10 A. Calculate the power of the kettle.

28. 28. Physics: Electricity: Explain why adding a resistor in parallel to a circuit decreases the circuit's total resistance.

29. 29. Physics: Magnetism: State two ways of increasing the strength of an electromagnet.

30. 30. Physics: Particle model: A radioactive sample has a half-life of 8 days and an initial activity of 800 Bq. Calculate its activity after 24 days.

Answer key & quick explanations

Short answers for the sample questions above. Use this to self-check before generating a fresh AI-built mock test.

1. 1. Magnification calculation (cell width)

   ×500

   Magnification = image size ÷ actual size = 25 mm ÷ 0.05 mm = 500. So the image was magnified 500 times its real size. Always convert both measurements to the same units before dividing.

2. 2. Osmosis in a plant cell in salt solution

   Water leaves the cell by osmosis, causing the cell to become flaccid or plasmolysed

   The salt solution has a lower water concentration (more solutes) than the cell's cytoplasm, so water moves out of the cell down its concentration gradient across the partially permeable membrane by osmosis. This causes the cell membrane to pull away from the cell wall, a process called plasmolysis, leaving the cell flaccid.

3. 3. Enzyme that digests starch

   Amylase, produced in the salivary glands and the pancreas

   Amylase is a carbohydrase enzyme that catalyses the breakdown of starch into simpler sugars such as maltose. It is secreted in saliva in the mouth and also produced by the pancreas, acting in the small intestine.

4. 4. Artery structure adaptation

   Arteries have thick, muscular walls with elastic fibres

   Arteries carry blood away from the heart at high pressure, so their walls contain thick layers of muscle and elastic fibres that can withstand and smooth out the pressure surges from each heartbeat, preventing the vessel from bursting.

5. 5. Word equation for anaerobic respiration in muscles

   Glucose -> lactic acid

   During vigorous exercise, oxygen supply cannot keep up with demand, so muscle cells respire anaerobically. Unlike aerobic respiration, this incomplete breakdown of glucose produces lactic acid and releases much less energy, without needing oxygen.

6. 6. How vaccines give immunity

   They trigger the immune system to produce memory (white blood) cells specific to the pathogen's antigen

   A vaccine contains a dead, inactive, or harmless form of a pathogen's antigen. This stimulates white blood cells to produce antibodies and, importantly, memory lymphocytes. If the real pathogen is encountered later, these memory cells allow a much faster, stronger secondary immune response before the person becomes ill.

7. 7. Limiting factors of photosynthesis

   Light intensity, carbon dioxide concentration, and temperature (any two)

   The rate of photosynthesis can be restricted by light intensity, because light provides the energy for the reaction; carbon dioxide concentration, because CO2 is a raw material; and temperature, because photosynthesis is enzyme-controlled and slows outside the optimum range.

8. 8. Blood glucose regulation after eating

   The pancreas releases insulin, which causes cells to take up glucose and the liver to convert it to glycogen

   When blood glucose rises after a meal, the pancreas detects this and secretes insulin into the blood. Insulin causes body cells, especially liver and muscle cells, to take up more glucose and convert excess glucose into glycogen for storage, lowering blood glucose back towards normal.

9. 9. Tt x Tt cross - percentage short offspring

   25%

   A Punnett square cross of Tt x Tt gives genotype ratio 1 TT : 2 Tt : 1 tt. Only the tt genotype is short, since short is recessive, so 1 out of 4 offspring (25%) are expected to be short.

10. 10. Quadrat population estimate

    3000 daisies

    Mean density = 6 daisies per m². Total population estimate = mean density × total area = 6 × 500 = 3000 daisies. This assumes daisies are distributed evenly across the field.

11. 11. Neutrons in chlorine-35

    18 neutrons

    Number of neutrons = mass number − atomic number = 35 − 17 = 18. The atomic number gives the number of protons, and mass number is protons plus neutrons.

12. 12. Ionic bonding between sodium and chlorine

    Sodium transfers one electron to chlorine, forming Na+ and Cl- ions held together by electrostatic attraction

    Sodium has one electron in its outer shell and readily loses it to form a stable Na+ ion. Chlorine has seven outer electrons and gains that one electron to complete its outer shell, forming a Cl- ion. The oppositely charged ions are then held together by a strong electrostatic force of attraction, forming an ionic bond.

13. 13. Moles in 22 g of CO2

    0.5 mol

    Moles = mass ÷ relative formula mass = 22 g ÷ 44 = 0.5 mol. The relative formula mass of CO2 is calculated as 12 + (16 × 2) = 44.

14. 14. Magnesium added to copper sulfate solution

    The blue solution fades and reddish-brown copper is deposited; this is a displacement reaction

    Magnesium is more reactive than copper, so it displaces copper from copper sulfate solution, forming magnesium sulfate and copper metal. The blue colour of the solution fades as copper(II) ions are removed, and a layer of reddish-brown copper is deposited.

15. 15. Electrolysis products of molten lead bromide

    Lead forms at the cathode (negative electrode); bromine forms at the anode (positive electrode)

    In molten lead bromide, Pb2+ ions are attracted to the negative cathode where they gain electrons (reduction) to form molten lead. Br- ions are attracted to the positive anode where they lose electrons (oxidation) to form bromine gas.

16. 16. Energy released per mole

    75 kJ/mol

    Energy per mole = total energy released ÷ number of moles = 150 kJ ÷ 2 mol = 75 kJ/mol.

17. 17. Mean rate of reaction from gas volume

    0.4 cm³/s

    Mean rate of reaction = volume of gas produced ÷ time taken = 24 cm³ ÷ 60 s = 0.4 cm³ per second.

18. 18. General formula and first alkane

    CnH2n+2; the first member is methane (CH4)

    Alkanes are saturated hydrocarbons with the general formula CnH2n+2, where n is the number of carbon atoms. The simplest alkane, with one carbon atom, is methane, CH4.

19. 19. Test for carbon dioxide gas

    Bubble the gas through limewater; it turns cloudy/milky if CO2 is present

    Carbon dioxide reacts with the calcium hydroxide in limewater to form insoluble calcium carbonate, which makes the limewater turn cloudy (milky white). This is the standard positive test for CO2.

20. 20. Human causes of rising atmospheric CO2

    Burning fossil fuels and deforestation (any two valid activities)

    Burning fossil fuels such as coal, oil and gas for energy and transport releases large amounts of stored carbon as CO2. Deforestation also increases atmospheric CO2 because fewer trees are available to remove it through photosynthesis, and burning cleared vegetation releases additional CO2.

21. 21. Resultant force on accelerating trolley

    10 N

    Using Newton's second law, F = m × a = 2.5 kg × 4 m/s² = 10 N.

22. 22. Momentum of a car

    13500 kg m/s

    Momentum = mass × velocity = 900 kg × 15 m/s = 13500 kg m/s.

23. 23. Kinetic energy of a moving ball

    3.6 J

    Kinetic energy = 0.5 × m × v² = 0.5 × 0.2 kg × (6 m/s)² = 0.5 × 0.2 × 36 = 3.6 J.

24. 24. Why falling objects reach terminal velocity

    Air resistance increases with speed until it equals weight, giving zero resultant force

    As a falling object speeds up, the air resistance acting against it increases. When air resistance becomes equal in size to the object's weight, the resultant force on the object is zero, so it stops accelerating and falls at a constant, terminal velocity.

25. 25. Frequency from time period

    50 Hz

    Frequency = 1 ÷ time period = 1 ÷ 0.02 s = 50 Hz.

26. 26. Why light changes direction entering glass

    Light refracts because it changes speed when moving between materials of different density

    Glass is a denser medium than air, so light waves slow down as they enter it. This change in speed causes the wave to change direction (refract) at the boundary, bending towards the normal when it enters glass from air.

27. 27. Power of a kettle

    2300 W (2.3 kW)

    Power = voltage × current = 230 V × 10 A = 2300 W.

28. 28. Why parallel resistors decrease total resistance

    Parallel branches provide additional paths for current, reducing overall resistance

    Adding a resistor in parallel creates an extra pathway for current to flow, so the total current from the supply increases for the same voltage. Since resistance is inversely related to the number of available current paths, the overall resistance of the parallel combination is lower than any single resistor's value.

29. 29. Increasing electromagnet strength

    Increase the current through the coil, or increase the number of turns on the coil (any two valid methods)

    The strength of an electromagnet's magnetic field can be increased by increasing the current flowing through the coil, or by increasing the number of turns of wire in the coil, both of which increase the magnetic field produced.

30. 30. Activity after three half-lives

    100 Bq

    Each half-life halves the activity: after 8 days, 800 Bq becomes 400 Bq; after 16 days, 400 Bq becomes 200 Bq; after 24 days (three half-lives), 200 Bq becomes 100 Bq.

Curriculum Mapping & Learning Guide

Use this breakdown to identify which skills each question tests and guide post-test review.

GCSE Science units covered

1. Chapter 1: Biology: Cell biology, transport in cells
2. Chapter 2: Biology: Organisation (digestion, circulation, respiration)
3. Chapter 3: Biology: Infection and response, bioenergetics
4. Chapter 4: Biology: Homeostasis, inheritance, variation, ecosystems
5. Chapter 5: Chemistry: Atomic structure, bonding, quantitative chemistry
6. Chapter 6: Chemistry: Chemical changes, energy changes, rates of reaction
7. Chapter 7: Chemistry: Organic chemistry, chemical analysis, Earth's atmosphere
8. Chapter 8: Physics: Forces, energy, waves
9. Chapter 9: Physics: Electricity, magnetism, particle model, atomic structure

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