General Science - Concepts, Units and Applied Reasoning
This domain tests school-level science as it supports technical work: matter and its changes, acids, bases and salts, metals and non-metals, the cell and human body systems, basic electricity and magnetism, light, force, work and energy, and correct SI units.
Core concepts
- Physical change alters state or shape without new substances; chemical change forms new substances with new properties.
- Acid + base → salt + water (neutralisation). pH below 7 is acidic, 7 neutral, above 7 basic; litmus turns red in acid and blue in base.
- Cell: nucleus controls activity, mitochondria release energy, ribosomes make proteins; a rigid cell wall is present in plant cells, absent in animal cells.
- Electricity: Ohm’s law V = IR; power P = VI = I²R.
- SI units: force newton (N), pressure pascal (Pa), energy joule (J), power watt (W), current ampere (A), resistance ohm (Ω), frequency hertz (Hz).
- Mass is measured in kilograms and is constant; weight is a force in newtons and changes with gravity.
Worked example
A 12 V battery is connected across a 4 Ω resistor. Find the current and the power dissipated.
- Apply Ohm’s law: I = V/R = 12/4 = 3 A.
- Power: P = VI = 12 × 3 = 36 W (or I²R = 9 × 4 = 36 W). Reasoning shown: identify the known quantities, choose the law that links them, then verify with a second formula so an arithmetic slip is caught.
Traps that cost marks
- Writing the unit of force as kg - kilograms measure mass.
- Confusing conduction with convection when a question says “in solids”.
- Mixing up the anode and cathode in a simple cell.
- Naming an indicator’s colour change in the wrong direction.
- Ignoring that water boils at 100 °C only at standard pressure.