Physical Science
Physical Science questions test matter, motion, energy, and waves, often through simple data or apparatus.
Core content
- Matter: Density = mass ÷ volume. Physical changes (melting, dissolving) do not create new substances; chemical changes do. Mass is conserved in a closed system.
- States: Particles in solids vibrate in fixed positions, liquids slide past one another, gases move freely. Heating increases particle motion; it does not make particles expand.
- Forces and motion: Net force determines acceleration. Balanced forces mean no change in motion. Friction opposes relative motion; gravity pulls masses together. Speed = distance ÷ time; velocity includes direction.
- Energy: Energy is conserved but transforms and transfers. Heat moves from warmer to cooler objects by conduction, convection, or radiation.
- Waves and circuits: Sound needs a medium; light travels through a vacuum. A closed circuit is needed for current; series and parallel circuits behave differently.
Worked example
A block has mass 60 g and volume 20 cm³. Density = 60 ÷ 20 = 3 g/cm³. Since 3 g/cm³ is greater than water’s 1 g/cm³, the block sinks. If the block were cut in half, each piece would still have density 3 g/cm³ because both mass and volume halve.
Traps
- Confusing mass with weight; weight changes with gravity, mass does not.
- Saying energy is “used up” rather than transferred or transformed.
- Thinking a constant force is needed to keep an object moving at constant speed.
- Confusing speed with velocity, or amplitude with frequency.