Physical and Natural Sciences
What the exam expects
Sciences are tested across physics, chemistry and biology, with emphasis on concepts and their quantitative use. Physics: kinematics and dynamics (Newton's laws), work and energy, electricity (Ohm's law, series and parallel circuits, power), optics (reflection, refraction, lenses), and waves. Chemistry: atomic structure, the periodic table, chemical bonding, stoichiometry, acids and bases, pH, oxidation-reduction, and organic functional groups. Biology: cell structure, genetics (Mendel's laws, DNA), human physiology (digestion, respiration, circulation, reproduction), ecology and the classification of living organisms.
Traps that recur
- Confusing mass and weight; forgetting that weight depends on gravitational field strength.
- Mixing series and parallel rules: in parallel, the voltage is common and currents add; in series, the current is common and voltages add.
- Forgetting to balance equations before stoichiometric calculation.
- Confusing pH with acidity direction: lower pH means more acidic.
- Confusing mitosis (two identical daughter cells) with meiosis (four haploid gametes).
- Treating dominant and recessive as "strong" and "weak" rather than as expression patterns.
Rule of thumb
In stoichiometry, always work in moles. Convert mass to moles, use the balanced equation's coefficients, then convert back to the requested quantity.
Worked example
How many moles of water form when 4 g of hydrogen (H₂, M = 2 g/mol) burn completely? Moles of H₂ = 4/2 = 2 mol. The equation 2H₂ + O₂ → 2H₂O gives a 1:1 ratio, so 2 mol of H₂O form, i.e. 36 g.