Science (Physical and Biological Sciences)
Physical science you must be able to state
- Motion: speed = distance/time; velocity has direction; acceleration = change in velocity/time.
- Newton's laws: inertia; F = ma; every action has an equal and opposite reaction.
- Light: angle of incidence equals angle of reflection; light bends towards the normal on entering a denser medium.
- Electricity: Ohm's law V = IR; resistances add in series; in parallel their reciprocals add.
- Matter: three states, separation techniques, acids and bases on the pH scale, metals and non-metals.
Biological science
The cell is the structural and functional unit of life; plant cells have a cell wall, a large vacuole and chloroplasts, animal cells do not. Photosynthesis is carbon dioxide plus water giving glucose plus oxygen in the presence of chlorophyll and sunlight. At the human-body level, know the main organs of digestion, respiration, circulation and excretion and their functions.
Worked example
A 12 V battery is connected across a 4 ohm resistor. Find the current. I = V/R = 12/4 = 3 A. If a second identical resistor were joined in series, total resistance becomes 8 ohm and the current falls to 1.5 A; in parallel the combined resistance is 2 ohm and the current rises to 6 A. The contrast shows why household appliances are wired in parallel.
Traps that cost marks
- Mass (kilogram, constant) versus weight (newton, varies with gravity).
- Reversing the products of photosynthesis and respiration.
- Forgetting that current is not "used up" in a circuit; energy is.
- Naming the cell wall as an animal-cell feature.