Scientific Inquiry, Methodology, and the Nature of Science
What Domain I Tests
This domain asks you to reason like a scientist: form testable hypotheses, identify variables and controls, evaluate evidence, use units and significant figures correctly, and distinguish scientific theories from laws. GACE Chemistry questions often embed these skills inside lab scenarios, graphs, and data tables rather than asking definitions alone.
Core Rules and Concepts
- Hypothesis vs. prediction vs. theory: a hypothesis is a testable explanation; a theory is a broad, well-supported explanatory framework; a law describes a repeated relationship.
- Variables: the independent variable is manipulated; the dependent variable is measured; controlled variables are held constant; a control group receives no treatment or a baseline treatment.
- Accuracy vs. precision: accuracy is closeness to true value; precision is reproducibility. Random error affects precision; systematic error biases accuracy.
- Significant figures: nonzero digits count; captive zeros count; leading zeros do not; trailing zeros count only with a decimal point. For multiplication/division, round to the least number of sig figs; for addition/subtraction, round to the least decimal place.
- Dimensional analysis: multiply by conversion factors so unwanted units cancel.
- Graphing: put the independent variable on the x-axis and dependent on the y-axis; slope and intercept carry units and meaning.
Worked Example
A student finds the mass of a metal block to be 24.60 g and its volume by displacement to be 12.5 mL. Calculate density and percent error if the accepted density is 2.00 g/mL. Reasoning: density = mass/volume = 24.60 g / 12.5 mL = 1.968 g/mL. The volume has three significant figures, so report 1.97 g/mL. Percent error = |experimental − accepted| / accepted × 100 = |1.97 − 2.00| / 2.00 × 100 = 1.5%. The result is precise enough to report but slightly low, suggesting a systematic error such as trapped air bubbles in the volume reading.
Traps That Cost Marks
- Rounding too early in a multi-step calculation.
- Treating a control group as the same thing as a controlled variable.
- Calling a well-tested explanation a law or a descriptive relationship a theory.
- Mixing up precision and accuracy when interpreting replicate measurements.
- Forgetting that percent error uses the accepted value in the denominator and is often reported as an absolute value.