Nature of Science
What the exam expects
Nature-of-science questions test whether you can reason about how chemistry knowledge is built, not just recall facts. Core concepts: the scientific method as a flexible cycle (observation, question, hypothesis, experiment, analysis, revision); the difference between hypothesis, theory, and law (a theory explains why; a law describes what happens, often mathematically - neither is a stepping stone to the other); variables (independent = manipulated, dependent = measured, controlled = held constant); and the role of peer review, replication, and falsifiability.
Traps to watch for
- "Theory" in everyday vs. scientific usage. In science, a theory is a well-supported explanatory framework (atomic theory, kinetic-molecular theory), not a guess. Questions often bait with "just a theory."
- Confusing law and theory. A law does not become a theory or vice versa.
- Correlation vs. causation and anecdotal vs. controlled evidence.
- Significant figures, unit conversions, and percent error - these are quantitative reasoning skills grouped under this domain.
- Measurement uncertainty: precision (repeatability) vs. accuracy (closeness to true value).
Rule of thumb
When a question describes an experiment, ask three questions: What was changed? What was measured? What was held constant? If a proposed explanation cannot be tested, it is not a scientific hypothesis.
Worked example
A student measures a 10.00 g sample three times: 10.52 g, 10.51 g, 10.53 g. Are the results accurate or precise? They are precise (tight clustering) but not accurate (all off by ~0.5 g, suggesting systematic error, e.g., a miscalibrated balance). Percent error = |10.52 − 10.00| / 10.00 × 100 ≈ 5.2%.