ELECTROCHEMISTRY BASICS:
  Electrolysis: decomposition by electric current
    Cathode (-): cations deposit (reduction)
    Anode (+): anions discharge (oxidation)
  Electrolytic refining: impure metal anode dissolves, pure metal deposits at cathode
  Electroplating: deposit thin layer of one metal on another
    Chrome plating: protect from rust and give shiny appearance
    Silver plating: on jewellery, utensils

CORROSION:
  Rusting of iron: Fe + O₂ + H₂O → Fe₂O₃.xH₂O (iron oxide = rust)
  Conditions needed: both water AND oxygen (neither alone causes rusting)
  Prevention: painting, galvanizing (zinc coat), alloying, oiling/greasing
  Galvanization: coat iron with zinc | zinc oxidizes preferentially (sacrificial anode)

ALLOYS:
  Bronze: Cu + Sn (tin) | Brass: Cu + Zn | Stainless steel: Fe + Cr + Ni
  Solder: Pb + Sn (low melting, used in electronics)
  Amalgam: Hg alloy (dental fillings, mirrors)

LIGHT — ADVANCED:
  Refraction: light bends when entering different medium (change in speed)
  Refractive index: n = c/v = sin i / sin r (Snell's law)
  Total internal reflection: when light goes from denser to rarer at > critical angle
    Applications: optical fibres, diamonds, mirages
  
  Human eye:
    Cornea: refraction | Iris: controls pupil | Lens: accommodation (changes shape)
    Retina: image formation (cones: colour, rods: dim light)
    Defects: Myopia (near-sightedness → concave lens) | Hypermetropia (far-sightedness → convex lens)
    Presbyopia: old age, both near and far | Cataract: cloudy lens → surgery
  
  Scattering:
    Blue sky: blue light scatters more (short wavelength) → sky appears blue
    Red sunrise/sunset: blue scattered away, red reaches us at shallow angle
    White clouds: all wavelengths scatter equally → white
    Tyndall effect: light scattering by colloidal particles

MAGNETIC EFFECTS:
  Magnetic field around current-carrying wire: Right-hand thumb rule
  Force on current in magnetic field: F = BIL (B = field, I = current, L = length)
    Direction: Fleming's left-hand rule (current, field, force)
  Electromagnetic induction: Faraday's law, Lenz's law
    AC generator: coil rotating in magnetic field generates alternating current
    Transformer: step up (increase V, decrease I) | step down (decrease V, increase I)
    Power transmission: high voltage for long distance (reduces I² R losses)

HEREDITY AND EVOLUTION:
  Mendel's experiments with pea plants:
    Traits: tall/dwarf, round/wrinkled seeds, yellow/green seeds
    Law of Dominance: TT and Tt both tall (T dominant over t)
    Law of Segregation: Tt × Tt → 1TT:2Tt:1tt → 3:1 phenotype ratio
  
  Human sex determination:
    Female: XX | Male: XY
    Father (XY) determines sex: gives X → daughter | gives Y → son
    X-linked diseases: colour blindness (recessie), haemophilia — more in males
  
  Evolution:
    Darwin's natural selection: survival of the fittest
    Variation: genetic mutations, sexual reproduction → raw material for evolution
    Speciation: reproductive isolation leads to new species
    Evidence: fossil record, homologous organs, vestigial organs, embryology
    Human evolution: Africa (Australopithecus → Homo habilis → Homo erectus → Homo sapiens)

ENVIRONMENT:
  Food chain: Producer → Primary consumer → Secondary → Tertiary
  Energy transfer: only 10% reaches next level (90% lost as heat)
  Ozone layer: O₃ in stratosphere absorbs UV radiation
    Depletion: CFCs from ACs and refrigerators
  Greenhouse effect: CO₂, CH₄, N₂O trap heat → global warming → climate change
  Biodegradable vs non-biodegradable: plastics take 400-1000 years to degrade