Basic Sciences
Basic Sciences tests the physics, chemistry, biology and quantitative reasoning that underpin agricultural technology. Questions often apply school-level science to field and laboratory situations.
Core rules and concepts
- Use SI units and convert before calculating. Concentration can be expressed as mass per volume, percentage or molarity. Dilution obeys C1V1 = C2V2.
- pH = −log10[H+]; each pH unit is a tenfold change in hydrogen-ion concentration. A pH of 5 is ten times more acidic than pH 6.
- Photosynthesis converts light energy into chemical energy in chloroplasts; respiration releases energy; transpiration pulls water through xylem and cools leaves. Stomata regulate gas exchange.
- Cells contain nucleus, mitochondria, chloroplasts, endoplasmic reticulum and vacuoles. Mitosis maintains chromosome number; meiosis halves it and creates variation. DNA bases pair A–T and G–C.
- Mendel's monohybrid cross gives a 3:1 phenotype ratio in F2 for a dominant trait; the testcross ratio is 1:1.
Worked example
How many grams of NaCl (molar mass 58.44 g/mol) are needed for 500 mL of 0.20 M solution? Moles = molarity × volume in litres = 0.20 × 0.500 = 0.100 mol. Mass = moles × molar mass = 0.100 × 58.44 = 5.844 g. Dissolve and make up to 500 mL; do not add 500 mL water to the solid if final volume must be exact.
Traps that cost marks
Do not treat pH as linear. Do not forget to convert millilitres to litres. Do not confuse molarity with molality. Do not mix acid into concentrated base without proper procedure. Do not confuse mitosis with meiosis or photosynthesis with respiration.