Assessed mathematical skills and measurement conventions

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.

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.

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

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.

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.

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

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

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

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.

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

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

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

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

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

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

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

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

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

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.

B.4.1—Angles and regular structures

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

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.

B.4.3—Symmetry of shapes

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