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Assessed mathematical skills and measurement conventions

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  1. B.0 Arithmetic and numerical computation

    1. B.0.0—Units in calculations

      Recognise and use appropriate units in calculations, including unit conversions. At A2 this includes units for equilibrium and rate constants and conversions between entropy in J mol⁻¹ K⁻¹ and enthalpy changes in kJ mol⁻¹.

    2. B.0.1—Decimal and standard form

      Recognise and use decimal, ordinary and standard form; choose appropriate decimal places; calculate with the Avogadro constant; and retain significant figures when converting between forms.

    3. B.0.2—Ratios, fractions and percentages

      Use ratios, fractions and percentages, including percentage yield, atom economy, and constructing or balancing equations from ratios.

    4. B.0.3—Estimating calculation results

      Estimate calculation results without a calculator and use estimates to evaluate whether results are reasonable. A2 applications include the effect of changed experimental parameters on measurable values such as Kc.

    5. B.0.4—Powers, exponentials and logarithms

      Use calculators to find and use power functions, including calculations with the Avogadro constant. Exponential and logarithmic functions, pH and pKa calculations, and buffer approximations are A2-only applications.

    6. B.0.P—SI unit prefixes

      Know and convert between the SI prefixes kilo, centi, milli, micro and nano, as clarified by Pearson for International A Level Chemistry candidates.

  2. B.1 Handling data

    1. B.1.1—Significant figures

      Use an appropriate number of significant figures and report calculated results consistently with the precision of the raw data and the least accurate measurement.

    2. B.1.2—Arithmetic and weighted means

      Calculate arithmetic and weighted means, including relative atomic mass from isotopic abundances, and select concordant titration data after identifying outliers.

    3. B.1.3—Measurement uncertainty

      Identify measurement uncertainties and use simple techniques to determine uncertainty when data are combined, including uncertainty from two burette readings used to calculate a titre.

  3. B.2 Algebra

    1. B.2.1—Mathematical symbols

      Understand and use =, <, ≪, ≫, >, ∝, ~ and the equilibrium sign.

    2. B.2.2—Changing the subject of an equation

      Change the subject of an equation in structured and unstructured chemical calculations. A2 applications include calculating a rate constant from a rate equation.

    3. B.2.3—Substitution into algebraic equations

      Substitute numerical values into algebraic equations using appropriate physical units, including mole calculations. A2 applications include rate and equilibrium-constant calculations.

    4. B.2.4—Solving algebraic equations

      Solve algebraic equations, including Hess's law calculations. A2 applications include calculating a rate constant from a rate equation.

    5. B.2.5—Logarithmic quantities

      Use logarithms for quantities spanning several orders of magnitude, including pH and pKa calculations.

  4. B.3 Graphs

    1. B.3.1—Translating between data forms

      Translate information between graphical, numerical and algebraic forms, including interpreting spectra. A2 applications include determining reaction order and deriving rate expressions from graphs.

    2. B.3.2—Plotting two variables

      Plot two variables from experimental or other data, including concentration–time graphs with an appropriate best-fit curve.

    3. B.3.3—Slope and intercept of a linear graph

      Determine the slope and intercept of a linear graph, including finding a zero-order rate constant from the gradient of a concentration–time graph.

    4. B.3.4—Rate from a linear graph

      Calculate rate of change from a graph showing a linear relationship, including finding a zero-order rate constant from a concentration–time gradient.

    5. B.3.5—Tangents and instantaneous rates

      Draw and use the slope of a tangent to a curve as a measure of rate of change, including determining reaction order by the initial-rates method.

  5. B.4 Geometry and trigonometry

    1. B.4.1—Angles and regular structures

      Recognise angles and shapes in regular two- and three-dimensional structures, including molecular shapes and bond angles.

    2. B.4.2—Representing two- and three-dimensional forms

      Visualise and represent two- and three-dimensional forms, including drawing isomers. Identifying chiral centres from such representations is an A2 application.

    3. B.4.3—Symmetry of shapes

      Understand the symmetry of two- and three-dimensional shapes. Identifying chiral centres from representations is an A2 application.