The Nature of Science: Inquiry, Evidence, and Fair Tests
What to know
Science is a way of answering questions using evidence, not opinion. Students must distinguish observations (what you see, hear, measure with a tool) from inferences (explanations you reason out from observations). A hypothesis is a testable prediction based on prior knowledge, not a random guess.
A fair test changes only one thing at a time:
- Independent variable - the one thing the scientist deliberately changes.
- Dependent variable - the thing measured as a result.
- Controlled variables (constants) - everything kept the same so the comparison is fair.
Investigations need repeated trials, and results are only trustworthy when they can be reproduced. Data belong in tables and then in graphs: bar graphs compare categories, line graphs show change over time, and the axes must be labeled with units. Models stand in for things too large, too small, or too dangerous to study directly, and every model has limitations. Scientific theories explain why something happens; laws describe a pattern. In engineering design, the cycle is: define the problem, design a solution, build a prototype, test it, and improve it.
Traps
- Calling a guess a hypothesis - a hypothesis must be testable and measurable.
- Believing one successful trial proves an idea; scientists repeat and compare.
- Mixing up the independent variable with a constant.
- Labeling an inference ("the rock was smoothed by water") as an observation ("the rock is smooth").
- Treating a model as an exact copy of reality.
Rule of thumb
Ask: What did I change? What did I measure? What stayed the same? If more than one thing changed, the test was not fair.