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Showing 1–30 of 123 reference entries

Mathematics & logic · Physics · MeasurementRatios and rates

Distinguish part-to-part ratios, fractions of a whole and rates with units. Scale quantities together, compare unit rates, and explain when a relationship is proportional. Check zero cases, starting amounts and whether a result fits its context.

DefinitionMathematics & logic · Physics · MeasurementQuantities and units

Describe a quantity as a numerical value with a unit, and distinguish its physical kind from its dimension. Build length, area, volume and rate units, check meaningful combinations, and separate exact unit relations from measurement uncertainty.

DefinitionMathematics & logic · Physics · MeasurementUnit conversions

Convert quantities with exact unit ratios, track cancellation through compound units, and apply the correct powers to area and volume. Distinguish temperature readings from differences, check dimensions and context, and retain measurement uncertainty when reporting.

MethodMathematics & logic · Physics · MeasurementEstimation and uncertainty

Distinguish exact model values, rounded approximations and estimates from measurements. Declare the rounding rule, preserve information through calculations and unit changes, and interpret resolution, precision, accuracy and the stated uncertainty type without turning a report’s digits into guaranteed bounds.

DefinitionMathematics & logic · Physics · MeasurementReading graphs

Read a graph’s quantities, units, ticks and context before judging its visual impression. Calculate differences, reference-based percentages and interval rates from the represented values; distinguish legitimate zoom from distorted spacing; and keep samples, interpolation, missing information, uncertainty and causal explanations separate.

MethodPhysics · MeasurementObservables and measurement

Choose the physical quantity you want to investigate, specify the point, event or location involved, and explain how a reading relates to that quantity.

MethodPhysics · Information · MeasurementScientific records

Build an inspectable physics record, test and revise a bounded cart model, preserve processing history, and plan findable data with appropriate sharing conditions.

MethodPhysics · MeasurementSpeed of light in vacuum

c denotes the speed of light in vacuum. Its numerical value is fixed exactly in SI units.

DefinitionPhysics · MeasurementPlanck constant

h denotes the Planck constant. Its numerical value is fixed exactly in SI units.

DefinitionPhysics · MeasurementCaesium-133 defining frequency

ΔνCs denotes the unperturbed ground-state hyperfine transition frequency of caesium-133. Its numerical value is fixed exactly in SI units.

DefinitionMathematics & logic · MeasurementEuclidean right triangles and the Pythagorean theorem

In a Euclidean right triangle, squared leg lengths sum to the squared hypotenuse length.

Mathematical statementMathematics & logic · MeasurementConfidence interval for a population mean

A confidence level describes repeated-sampling coverage of an interval procedure.

MethodMeasurementSI base units

Seven named base units organize the SI quantity system.

DefinitionMeasurementSI decimal prefixes

Prefix symbols specify decimal scale factors.

DefinitionMeasurementMetrological traceability

Connect a result to a reference through documented calibrations.

DefinitionMeasurement · Mathematics & logicFirst-order uncertainty propagation

Combine input uncertainty through a measurement model.

MethodMeasurement · Physics · Mathematics & logicDimensional consistency

Use dimensions to detect impossible quantity equations.

MethodPhysics · MeasurementElectric current

Current measures charge crossing a chosen surface per unit time.

DefinitionPhysics · MeasurementElementary charge

The elementary charge has an exact SI numerical value.

DefinitionPhysics · MeasurementBoltzmann constant

The Boltzmann constant has an exact SI numerical value.

DefinitionMeasurement · Chemistry · PhysicsAvogadro constant

The mole is linked to a specified number of entities.

DefinitionMeasurement · PhysicsSI defining luminous efficacy

A specified frequency fixes the photometric SI reference.

DefinitionChemistry · MeasurementMole and amount of substance

The mole counts specified entities using the exact Avogadro constant.

DefinitionMeasurementCalibration

Relate indications to standards, then infer measurement results.

DefinitionMeasurementType A and Type B uncertainty evaluation

The classification describes how a component is evaluated.

MethodMeasurementExpanded uncertainty and coverage

A coverage factor scales standard uncertainty to a reported interval.

MethodMeasurement · Mathematics & logicCovariance in uncertainty models

Shared input variation belongs in the joint uncertainty description.

MethodMeasurementMeasurement models

Specify how input quantities determine the measurand.

MethodMeasurement · InformationMonte Carlo uncertainty propagation

Sample the joint input model to approximate the output distribution.

MethodMeasurementRepeatability and reproducibility

Precision depends on which measurement conditions are held or changed.

Definition
DefinitionSource checked

Mole and amount of substance

ChemistryMeasurement

The mole counts specified entities using the exact Avogadro constant.

Key knowledge

The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 10²³ specified elementary entities. The amount n and entity count N are related by n = N/N_A, where N_A = 6.02214076 × 10²³ mol⁻¹ exactly.

Values and equations

n = N/N_A

n
Amount of substance mol
N
Number of specified entities
N_A
Avogadro constant, exactly 6.02214076 × 10²³ mol⁻¹

Conditions and scope

  • Specify the entities being counted, such as atoms, molecules or ions.
  • Amount of substance and mass are different quantities; an exact unit definition does not remove measurement uncertainty.
  • N counts the same specified entities whose amount is n.
Sources · 2

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. SI base unit: mole (mol)Bureau International des Poids et Mesures (BIPM)Reference guidebipm.orgRead source
  2. 国際単位系（SI）第9版 · Japanese translation, V3.01National Metrology Institute of Japan, AISTReference guide · PDFunit.aist.go.jpRead source

Evidence and review

Exact SI definition and entity-count relation documented by BIPM; not a measurement of a sample.

2026-10-10 · English unit, exact decimal value and specified-entity scope checked against BIPM's mole definition.

Foundational review

2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.

Sources from other places

Agreement within this scope

Exact mole definition and specified-entity count.

The Japanese translation implements the same international SI standard.

Related reference entries

Explore relationships within this area of study and its connections to other areas.

Showing 1–3 of 3 relationships

Scientific relationships · 3 / 3

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Related to
    Relationship sources · 1

    Linked statements

    • Stoichiometric coefficients in a balanced chemical equation specify ratios of reactant consumption and product formation. These particle-number ratios also give mole ratios, so a known reacting amount can be converted into another reacting or produced amount.
    • The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 10²³ specified elementary entities. The amount n and entity count N are related by n = N/N_A, where N_A = 6.02214076 × 10²³ mol⁻¹ exactly.

    Balanced particle-number ratios also give reacting mole ratios.

  2. Uses definition
    Relationship sources · 2

    Linked statements

    • Molar mass M is mass divided by amount of substance for specified entities and composition, so n = m/M. For entities with mean mass m_entity, M = NA m_entity. Since the 2019 SI revision, NA is exact but the atomic mass constant in kilograms is measured: the molar mass constant Mu = NA mu is close to, and no longer exactly, 0.001 kg/mol.

    Mass–amount conversion requires a mole of specified entities and a stated composition.

  3. Uses definition
    Relationship sources · 3

    Linked statements

    • Amount concentration (molarity) is solute amount per solution volume; molality is solute amount per solvent mass. Mole fraction and mass fraction divide a component's amount or mass by the corresponding total. These scales are not interchangeable. Volume-based concentration can change with temperature through expansion even when composition and solute amount are unchanged.

    Amount concentration, molality and mole fraction require the amount of specified components.

Entry detailsPermanent link to this entry ↗
Record identity
chem-mole
Revision
core.1
Structured reference record
Essential core · first collection