Science: Biology, Chemistry, Physics, and Scientific Reasoning
What the section tests
Science items test core concepts in biology, chemistry, and physics plus scientific reasoning: interpreting experiments, identifying variables, and drawing conclusions from data. Expect questions on cells, ecosystems, matter and atomic structure, chemical reactions, forces and motion, energy, and experimental design.
Concepts to master
- Cells and life processes: cell structures (nucleus, mitochondria, chloroplasts), photosynthesis vs. respiration, and the role of DNA.
- Ecosystems: food chains, producers and consumers, energy flow (about 10% transfers between trophic levels).
- Matter and atoms: atomic number = protons; mass number = protons + neutrons; states of matter and phase changes.
- Chemical reactions: conservation of mass; balancing equations; acids and bases (pH below 7 acidic, above 7 basic).
- Forces and motion: Newton's laws; speed = distance / time; gravity and friction.
- Energy: forms of energy, conservation, and transfer (conduction, convection, radiation).
- Experimental design: independent variable (changed), dependent variable (measured), controlled variables (kept constant).
Common traps
- Confusing independent and dependent variables.
- Assuming a correlation proves causation.
- Mixing atomic number with mass number.
- Forgetting that mass is conserved in a reaction even when a gas escapes.
- Treating a hypothesis as a proven conclusion.
Worked example
A student tests whether light affects plant growth, giving one group full light and another no light, keeping water and soil equal. Independent variable: light. Dependent variable: plant growth. Controlled variables: water, soil, temperature. Conclusion is valid only if all else is held constant. Rule of thumb: name what you changed, what you measured, and what you kept the same.