General Science
Scope
General Science tests basic physics, chemistry, biology and everyday science, with health and environment applications. Questions are usually conceptual, so understand the principle rather than memorise long derivations.
Core rules
- Physics: speed is scalar, velocity is vector; force = mass × acceleration; weight = mass × g. Density determines floating: an object floats if its average density is less than the fluid's.
- Chemistry: pH below 7 is acidic, 7 neutral, above 7 basic. Acids react with metals to release hydrogen; bases neutralise acids.
- Biology: plant cells have a cell wall and chloroplasts; animal cells do not. Blood groups follow ABO and Rh systems. Vitamins are needed in small amounts; deficiency causes specific diseases.
- Environment: photosynthesis uses CO₂ and releases O₂; combustion and deforestation increase atmospheric CO₂.
Worked example
A solution has pH 3. Is it acidic or basic, and what is its hydrogen-ion concentration? pH 3 is acidic because pH < 7. By definition, pH = −log[H⁺], so [H⁺] = 10⁻³ mol/L. The reasoning is logarithmic: each unit below 7 means ten times more H⁺ than the next higher pH.
Traps
- Confusing mass (kg) with weight (N).
- Saying plants respire only at night; they respire continuously.
- Mixing up vitamins and deficiency diseases.
- Treating pH 5 as 'slightly basic' because 5 is a small number.
- Ignoring units in force, pressure and density.