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OCR · J250 · Gateway Science
Rᶠ value
The ratio of the distance travelled by a substance to the distance travelled by the solvent front, both measured from the baseline: Rf=distance travelled by substancedistance travelled by solvent frontR_f = \frac{\text{distance travelled by substance}}{\text{distance travelled by solvent front}}Rf=.
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Ribosome
A small sub-cellular structure where proteins are made.
Right-hand thumb rule
A method for finding the magnetic field direction around a straight wire: point your right thumb along the conventional current, and your curled fingers show the field direction.
Risk
The likelihood of harm occurring from a hazard, together with how serious that harm could be.
Risk assessment
Identifying hazards, considering the harm they could cause and deciding on precautions to reduce risk.
Risk factor
Something that increases the chance of developing a disease.
Risk perception
A person's judgement of how likely and serious a risk is, which may differ from an assessment based on scientific data.
Root hair cell
A specialised cell in the outer layer of a plant root, with a long extension that increases the surface area for absorbing water and mineral ions.
Rounding
Replacing a number with a nearby value expressed to a chosen number of significant figures or decimal places.
Salt
An ionic compound formed when the hydrogen ions of an acid are replaced by metal ions or ammonium ions.
Salt solution
An aqueous solution containing dissolved ions from a salt, including positive metal ions for a metal salt.
Sampling
Collecting observations or measurements from part of a larger group or area to learn about the whole.
Saturated solution
A solution containing the maximum amount of dissolved solute at a particular temperature.
Scalar
A physical quantity that has magnitude only, with no direction.
Scale
The numerical value represented by each division along a graph axis.
Scale drawing
A vector diagram in which arrow lengths represent force magnitudes according to a stated scale.
Scientific communication
The sharing of scientific methods, findings and explanations in a form that an intended audience can understand and use.
Scientific drawing
An observational drawing that records visible structures clearly and in proportion, with accurate labels.
Scientific evidence
Measurements or observations used to support or challenge a scientific explanation or claim.
Scientific explanation
An account of why something happens, using scientific ideas; it may apply a scientific theory to a particular situation.
Scientific knowledge
The understanding of the natural world developed by gathering evidence, testing explanations and reviewing conclusions.
Scientific limitation
A boundary on what scientific methods or the available evidence allow scientists to explain, establish or predict.
Scientific model
A representation used to explain observations and make predictions that can be tested against evidence.
Scientific quantity
A measurable property of an object or system, such as length, mass, time or temperature.
Scientific rationale
The scientific reasoning behind an investigation, explaining why its question is worth investigating and how it relates to existing knowledge.
Scientific terminology
A word or expression with a specific meaning in science, used to communicate an idea precisely.
Scientific theory
A general explanation supported by scientific evidence that applies to many situations.
Screening
Testing people for signs of a disease so that it can be detected early, potentially before symptoms appear.
Sebum
An oily substance on the skin surface that helps protect against bacterial and fungal pathogens.
Secondary coil
The output coil of a transformer, which supplies the connected circuit.
1,166 key terms
