Catalyst
A substance that increases a reaction rate without being consumed as a reactant. Enzymes such as catalase are biological catalysts.
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Science glossary
Short definitions connect to the lessons where each concept is used. Search terms or browse the full list.
Showing 16 of 16 terms
Claim–Evidence–Reasoning (CER)
A way to explain a result: state a claim, point to relevant evidence, and explain why that evidence supports the claim.
Confounding variable
A factor that changes alongside the tested variable and could offer another explanation for the measured result.
Control group
A comparison condition that does not receive the treatment being studied, or receives the standard condition, helping interpret the treatment result.
Dependent variable
The outcome a researcher measures or observes in response to a planned change.
Diffusion
Net movement of particles from a region of higher concentration toward a region of lower concentration, caused by random motion.
Evidence
Observations or measurements used to evaluate a claim. Evidence is stronger when methods, units, conditions and uncertainty are clear.
Hypothesis
A testable, reasoned prediction about a relationship between variables. A result can support or fail to support it; a hypothesis is not proven by one trial.
Independent variable
The factor deliberately changed in an investigation. A fair test usually changes one planned factor at a time.
Inference
An interpretation drawn from observations and prior knowledge. It should be distinguished from what was directly observed.
Osmosis
Net movement of water across a selectively permeable membrane driven by differences in water potential or solute concentration. Water molecules still move in both directions.
Peer review
Evaluation of a research report by other knowledgeable researchers before publication. It can identify weaknesses but does not guarantee that a finding is correct.
Percent change
The change relative to the starting value, expressed as a percentage: (final − start) ÷ start × 100.
Replication
Repeating measurements or an investigation with additional samples or trials to assess variability and whether a pattern recurs.
Selectively permeable membrane
A barrier that allows some substances to cross more readily than others. Real cell membranes have complex transport processes.
Uncertainty
The range of doubt associated with a measurement or estimate. Repeated trials, calibrated equipment and clear precision help describe it.