KS3 Science · Year 7–9

Science
Key Concepts

20-Question Exam Practice

All topics · Biology, Chemistry & Physics
Multiple Choice · Exam-Style Questions
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🧬 Biology ⚗️ Chemistry ⚡ Physics

Core Concepts & Key Facts

Memorise these before attempting the quiz

🧬 Biology
CELLThe basic unit of all living things. Plant cells have a cell wall, chloroplasts and a large vacuole; animal cells do not.
PHOTOPhotosynthesis: CO₂ + H₂O → glucose + O₂. Occurs in chloroplasts; requires light energy.
RESPAerobic respiration: glucose + O₂ → CO₂ + H₂O + energy (ATP). Occurs in mitochondria.
DNADNA carries genetic information. It is a double helix made of four bases: A-T and C-G pair together.
FOODFood chains show energy flow. Producers (plants) → Primary consumers → Secondary consumers. Only ~10% of energy passes to each level.
ADAPTOrganisms adapt over many generations via natural selection. Individuals with favourable traits survive and reproduce more.
⚗️ Chemistry
ATOMAtoms contain protons and neutrons in the nucleus, and electrons in shells. Atomic number = number of protons.
ELEMElements are pure substances made of one type of atom only. Compounds are two or more elements chemically bonded.
REACTIn a chemical reaction, mass is conserved. Atoms are rearranged, not created or destroyed.
ACIDAcids have pH < 7, alkalis pH > 7, neutral pH = 7. Acid + alkali → salt + water (neutralisation).
PERPeriodic Table: elements arranged by atomic number. Groups (columns) share similar properties. Period 1 has 2 elements.
METALMetals are malleable, conduct heat/electricity. Non-metals are generally poor conductors. Most elements are metals.
⚡ Physics
FORCEForce = mass × acceleration (F = ma). Measured in Newtons (N). Balanced forces → no change in motion.
ENERGYEnergy is conserved: it cannot be created or destroyed, only transferred. Unit: Joule (J).
WAVEWaves transfer energy, not matter. Transverse waves oscillate perpendicular to direction of travel (light); longitudinal waves oscillate parallel (sound).
ELECV = IR (Ohm's Law). Series circuits: same current throughout. Parallel circuits: same voltage across each branch.
SPEEDSpeed = distance ÷ time. Velocity is speed in a given direction. Acceleration = change in velocity ÷ time.
LIGHTLight travels at ~3×10⁸ m/s in a vacuum. It reflects off surfaces (angle of incidence = angle of reflection) and refracts when it changes medium.
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