Science (Physics, Chemistry, Biology)
Science is set as one paper covering Physics, Chemistry and Biology, weighted towards applying a law or equation to a short situation rather than reciting definitions.
Physics
- Equations of motion: v = u + at, s = ut + ½at², v² = u² + 2as. With uniform acceleration, distance = average velocity × time.
- Newton's laws, especially F = ma and the fact that an action–reaction pair acts on two different bodies.
- Work, power, Ohm's law (V = IR), series and parallel resistance, laws of reflection.
Chemistry
- Mole: n = mass ÷ molar mass. One mole holds 6.02×10²³ particles and, for a gas at STP, occupies 22.4 L.
- Balance the equation before using any mole ratio. pH is logarithmic, so pH 3 is ten times more acidic than pH 4.
- Periodic trends: atomic radius falls across a period, ionisation energy rises.
Biology
- Organelles and their jobs; plant versus animal cell differences.
- Photosynthesis (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, in chloroplasts, needs light) versus respiration (mitochondria, releases energy).
- Mendel's ratios, blood groups, and the broad outline of the digestive, circulatory and excretory systems.
Worked example
A car speeds up uniformly from 10 m/s to 30 m/s in 5 s. Find the acceleration and the distance covered. a = (v − u)/t = (30 − 10)/5 = 4 m/s². Distance = average velocity × time = ((10 + 30)/2) × 5 = 100 m.
Traps
- Forgetting to convert grams to moles, or millilitres to litres.
- Writing the photosynthesis equation for respiration.
- Reversing the sign of acceleration when a body slows down.