Scientific Inquiry and the Nature of Science
The vocabulary of inquiry
Inquiry questions reward precision about how science works. Know the hierarchy: an observation is a recorded measurement or sensory fact; an inference is a conclusion drawn from observations; a hypothesis is a testable, falsifiable proposed explanation; a theory is a broad explanatory framework supported by many independent lines of evidence; a law is a concise statement of a regular relationship that describes but does not explain. The commonest trap is treating "theory" as a synonym for "guess" - describing a well-supported explanation as "only a theory" is always the wrong choice. A second trap is confusing hypothesis with prediction: the prediction is the if–then consequence you actually test.
Variables, data, and error
Identify the independent variable (what the investigator manipulates), the dependent variable (what is measured), and controlled variables (held constant). A control group receives no treatment so the treatment's effect can be isolated. Watch for confounding variables and for conclusions that outrun the data - a correlation between two variables never by itself proves causation.
Distinguish random error (scatter, reduced by repeated trials and larger samples) from systematic error (a consistent offset such as a miscalibrated balance, which repetition will not fix). Report values with correct units and significant figures, and always place the independent variable on the x-axis.
Worked example
A mineral's density is measured as 2.6 g/cm³; the accepted value is 2.70 g/cm³. Percent error = |2.6 − 2.70| ÷ 2.70 × 100 = 3.7%. The sign is dropped; only the magnitude is reported. Note also that density itself is a ratio problem: mass ÷ volume.