Grade 9 Natural Science is the final year of the Senior Phase and covers the most sophisticated content yet across all four strands. Learners study genetics and evolution, chemical bonding and reactions, electricity and electromagnetism, and Earth's history in depth. They are expected to plan and conduct independent investigations, write formal scientific reports and critically evaluate evidence. Grade 9 Natural Science provides the direct foundation for Physical Sciences and Life Sciences in Grade 10.
- DNA: structure (double helix, base pairs A-T, C-G), location in cell, function
- Genes and chromosomes: gene → chromosome → nucleus
- Heredity: dominant and recessive alleles — genotype and phenotype
- Punnett squares: monohybrid crosses — predict offspring ratios
- Inherited and environmental variation: examples in humans and other organisms
- Natural selection: Darwin's theory — variation, selection pressure, survival of fittest
- Evidence for evolution: fossil record, comparative anatomy, DNA evidence
- Human evolution: key hominid species — Australopithecus, Homo habilis, Homo sapiens
- Ionic bonding: metal + non-metal, transfer of electrons, formation of ions
- Examples: NaCl, MgO, CaCl₂ — draw electron diagrams
- Covalent bonding: non-metal + non-metal, sharing of electrons
- Examples: H₂O, CO₂, O₂, CH₄ — draw shared electron diagrams
- Metallic bonding: sea of electrons model — explains conductivity, malleability
- Properties of ionic, covalent and metallic substances — compare
- Chemical reactions: balancing equations — conservation of mass
- Types of reactions: synthesis, decomposition, single and double displacement
- Ohm's Law: V = IR — calculate voltage, current, resistance
- Series circuits: current same, voltage splits — calculate total resistance
- Parallel circuits: voltage same, current splits — calculate total resistance
- Power: P = VI — calculate electrical power and energy cost
- Electrostatics: charge, attraction, repulsion, electric field
- Magnetism: magnetic fields, domain theory, permanent magnets
- Electromagnetism: a current produces a magnetic field — right-hand rule
- Electromagnetic induction: changing magnetic field produces current — generator principle
- Age of the Earth: radioactive dating — concept and application
- Geological time scale: eons, eras, periods — key events
- Fossil formation: conditions needed, types of fossils, what they reveal
- Plate tectonics: evidence — continental fit, fossil distribution, seafloor spreading
- Rock types: igneous, sedimentary, metamorphic — formation and examples in SA
- Natural resources: SA's mineral wealth — gold, platinum, diamonds, coal
- Mining impacts: acid mine drainage, land degradation, community impacts in SA
- Sustainable use of resources: renewable vs non-renewable — future challenges
Punnett squares follow a fixed method. Write the alleles of each parent across the top and side. Fill in each box. Count the ratio. Always show your working.
Balancing equations: atoms in = atoms out. Count each type of atom on both sides. Adjust coefficients (not subscripts) until they are equal.
Ohm's Law triangle. Cover what you want to find: V = IR, I = V/R, R = V/I. Draw the triangle and use it every time.
Electromagnetism is cause and effect. Current → magnetic field. Changing magnetic field → current. Know which causes which.
DNA → gene → chromosome → nucleus. This hierarchy is always tested. Know it in both directions.