KS3 · YEARS 7–9 · ALL UNITS

KS3 Science
Question Bank

Concept summaries, key facts to memorise, and 20 exam-style questions across Biology, Chemistry, Physics & Earth Science.

📋 20 questions
⏱ 25 min timer
🎯 4 units
📊 MCQ format
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Key Concepts & Memorisation

REVISE FIRST

Tap each unit to expand the concept summary and key facts to memorise before attempting the quiz.

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Biology — Cells, Life Processes & Ecosystems
BIO
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Cell structure: Animal cells have a nucleus, cytoplasm, cell membrane, and mitochondria. Plant cells also have a cell wall (cellulose), vacuole, and chloroplasts.
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Cells → Tissues → Organs → Organ Systems → Organism (hierarchy)
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Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (light energy needed)
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Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
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Diffusion: movement of particles from HIGH to LOW concentration (no energy needed)
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Osmosis: diffusion of WATER through a semi-permeable membrane
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Food chains: Producer → Primary consumer → Secondary consumer → Tertiary consumer
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Human digestive system order: Mouth → Oesophagus → Stomach → Small intestine → Large intestine
Exam Example

Q: A plant cell is placed in a very dilute solution. In which direction does water move, and by what process?

✓ Water moves INTO the cell by osmosis (from high water concentration to low).
⚗️
Chemistry — Particles, Reactions & Materials
CHEM
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Particle model: Solids (fixed lattice, vibrating), Liquids (close, flowing), Gases (far apart, fast random motion). Increasing temp → particles move faster.
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Elements are made of ONE type of atom. Compounds are chemically joined elements. Mixtures are NOT joined.
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Physical change: reversible, no new substance (e.g. melting). Chemical change: irreversible, new substance (e.g. burning).
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Acid + metal → salt + hydrogen gas. Acid + carbonate → salt + water + CO₂.
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pH scale: 1–6 = acidic, 7 = neutral, 8–14 = alkaline. Indicators change colour.
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Law of conservation of mass: mass of reactants = mass of products.
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Periodic table: periods = rows (same number of shells), groups = columns (same number of outer electrons).
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Separation techniques: filtration (insoluble solid from liquid), distillation (liquid from solution), chromatography (different solutes).
Exam Example

Q: Hydrochloric acid reacts with calcium carbonate. Identify all the products.

✓ Calcium chloride (salt) + water + carbon dioxide gas.
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Physics — Forces, Energy & Waves
PHYS
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Key equations to memorise: Speed = distance ÷ time  |  Work done = force × distance  |  Pressure = force ÷ area  |  Power = energy ÷ time
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Newton's 1st Law: object at rest / constant velocity unless unbalanced force acts on it.
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Newton's 2nd Law: F = m × a (force = mass × acceleration).
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Gravity on Earth ≈ 10 N/kg. Weight (N) = mass (kg) × gravitational field strength (N/kg).
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Energy stores: kinetic, gravitational potential, chemical, thermal, elastic potential, nuclear.
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Energy is always conserved — it transfers between stores, never created or destroyed.
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Light travels at 3 × 10⁸ m/s in a vacuum. Reflection: angle of incidence = angle of reflection.
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Series circuit: same current everywhere. Parallel circuit: voltage same across each branch.
Exam Example

Q: A car of mass 1200 kg accelerates at 3 m/s². Calculate the force applied (ignore friction).

✓ F = m × a = 1200 × 3 = 3600 N
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Earth Science — Space, Geology & Climate
ES
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Rock cycle: Igneous (cooled magma) → Weathered → Sedimentary (compressed layers) → Metamorphic (heat/pressure) → Melts again. All rock types can transform into each other.
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Solar system order (Mercury → Neptune): My Very Excellent Mother Just Served Us Nachos.
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Earth's layers: crust → mantle → outer core (liquid) → inner core (solid iron/nickel).
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Tectonic plates move by convection currents in the mantle (heat from radioactive decay).
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Greenhouse gases: CO₂, methane (CH₄), water vapour. They trap outgoing infrared radiation.
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Earth orbits the Sun once per year. The Moon orbits Earth approximately every 28 days.
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Carbon cycle: photosynthesis removes CO₂; respiration, combustion, and decomposition release it.
Exam Example

Q: Explain why the Earth's surface gets warmer when atmospheric CO₂ increases.

✓ CO₂ absorbs infrared radiation emitted by Earth's surface and re-radiates it in all directions, including back towards Earth, so less heat escapes to space → enhanced greenhouse effect → warming.

20 Exam-Style Questions

MCQ QUIZ

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