Sciences (Physics, Chemistry, Biology)
Core ideas
Science combines Physics, Chemistry, and Biology. In Physics, master SI units, speed and acceleration, Newton's laws, energy transfers, electricity (V = IR, power), waves, and radioactivity. In Chemistry, understand atomic structure, the periodic table, ionic and covalent bonding, balanced equations, the mole, acids and bases, rates, and organic families. In Biology, learn cell structure, transport (diffusion, osmosis, active transport), enzymes, photosynthesis and respiration, genetics, homeostasis, and ecology.
Traps
Unit errors are the biggest source of lost marks: convert cm to m, g to kg, and minutes to seconds. In equations, balance atoms before calculating moles. Do not confuse mass with weight, or diffusion with osmosis. In genetics, separate genotype from phenotype and use a Punnett square. In electricity, ammeters go in series and voltmeters in parallel. Always give the direction of a force or the name of a variable, not just a number.
Worked example
A car travels 150 m in 12 s. Calculate its average speed. Speed = distance ÷ time = 150 m ÷ 12 s = 12.5 m/s. If the question asks for km/h, multiply by 3.6: 12.5 × 3.6 = 45 km/h.
Rule of thumb
Write the formula first, substitute with units, then solve. For any practical, state the independent variable, dependent variable, and one control variable.