Chemistry and Biology: Science Aptitude
This section tests school-level science reasoning rather than deep theory. Chemistry topics are atomic structure, the periodic table, chemical formulae and simple equations, acids-bases-salts, and everyday chemistry (water, air, fuels). Biology topics are the cell, human body systems, nutrition, classification of living things, and basic ecology.
Chemistry essentials
- Protons define the element; neutrons change the isotope; electrons govern bonding.
- Acids turn litmus red, bases blue; acid + base → salt + water (neutralisation).
- Know formulae of common compounds: H₂O, CO₂, NaCl, H₂SO₄, and the difference between an element, a compound and a mixture.
Biology essentials
- The cell is the unit of life; plant cells have a cell wall and chloroplasts, animal cells do not.
- Photosynthesis: carbon dioxide + water → glucose + oxygen, requiring light and chlorophyll.
- Blood, digestion, respiration and excretion are the high-frequency systems.
Traps to expect
- Mixture vs compound - a mixture can be separated physically.
- Atom vs molecule used interchangeably.
- Plant vs animal cell features swapped.
- Chemical vs physical change - no new substance is formed in a physical change.
Rule of thumb
For any "which is correct" item, apply the definition test: state the definition of the key term silently and check whether the option satisfies it exactly.
Worked example: "Is dissolving salt in water a chemical change?" No - no new substance forms and the salt can be recovered by evaporation, so it is a physical change.