Science
Science in the SAMPAD Grade 7 entrance test samples general science: matter, cells and living processes, force and energy, ecosystems, human body and health, and earth/space basics. It favours explanation and application over isolated definitions.
Core rules
- Matter has mass and volume; physical changes alter form or state, while chemical changes form new substances.
- Cells are the basic unit of life; chloroplasts carry out photosynthesis, and mitochondria release energy from food.
- Forces change motion or shape; weight = mass × gravitational field strength, about 9.8 N/kg on Earth.
- Energy transfers between forms but is conserved; food chains show energy flow from producers to consumers.
- Measure with correct units and convert carefully: 1 kg = 1000 g, 1 L = 1000 mL, 1 cm³ = 1 mL.
Worked example
A metal cube has side 3 cm and mass 81 g. Find its density.
Volume = side³ = 3 × 3 × 3 = 27 cm³. Density = mass ÷ volume = 81 g ÷ 27 cm³ = 3 g/cm³. State the unit; density is not the same as mass. The cube's mass stays 81 g wherever it is, but its weight would change on another planet.
Traps that cost marks
- Confusing mass (amount of matter, kg or g) with weight (force, N).
- Saying plants photosynthesise at night; they respire all the time and photosynthesise only in light.
- Reversing food-chain arrows; they point from the eaten organism to the eater.
- Calling melting or dissolving a chemical change.
- Using the wrong unit or forgetting to cube the side.
- Treating a battery as a source of charge rather than an energy transfer device.