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.

Use b.0.0—units in calculations to connect the rule to the data and decision in the question.

This matters because b.0.0—units in calculations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.0—units in calculations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.0—Units in calculations is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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 b.0.1—decimal and standard form to connect the rule to the data and decision in the question.

This matters because b.0.1—decimal and standard form determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.1—decimal and standard form to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.1—Decimal and standard form is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.0.2—ratios, fractions and percentages to connect the rule to the data and decision in the question.

This matters because b.0.2—ratios, fractions and percentages determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.2—ratios, fractions and percentages to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.2—Ratios, fractions and percentages is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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 b.0.3—estimating calculation results to connect the rule to the data and decision in the question.

This matters because b.0.3—estimating calculation results determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.3—estimating calculation results to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.3—Estimating calculation results is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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.

Use b.0.4—powers, exponentials and logarithms to connect the rule to the data and decision in the question.

This matters because b.0.4—powers, exponentials and logarithms determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.4—powers, exponentials and logarithms to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.4—Powers, exponentials and logarithms is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.0.p—si unit prefixes to connect the rule to the data and decision in the question.

This matters because b.0.p—si unit prefixes determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.0.p—si unit prefixes to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.0.P—SI unit prefixes is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.1.1—significant figures to connect the rule to the data and decision in the question.

This matters because b.1.1—significant figures determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.1.1—significant figures to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.1.1—Significant figures is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.1.2—arithmetic and weighted means to connect the rule to the data and decision in the question.

This matters because b.1.2—arithmetic and weighted means determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.1.2—arithmetic and weighted means to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.1.2—Arithmetic and weighted means is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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.

Use b.1.3—measurement uncertainty to connect the rule to the data and decision in the question.

This matters because b.1.3—measurement uncertainty determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.1.3—measurement uncertainty to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.1.3—Measurement uncertainty is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.2.1—mathematical symbols to connect the rule to the data and decision in the question.

This matters because b.2.1—mathematical symbols determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.2.1—mathematical symbols to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.2.1—Mathematical symbols is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.2.2—changing the subject of an equation to connect the rule to the data and decision in the question.

This matters because b.2.2—changing the subject of an equation determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.2.2—changing the subject of an equation to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.

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

Use b.2.3—substitution into algebraic equations to connect the rule to the data and decision in the question.

This matters because b.2.3—substitution into algebraic equations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.2.3—substitution into algebraic equations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.

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

Use b.2.4—solving algebraic equations to connect the rule to the data and decision in the question.

This matters because b.2.4—solving algebraic equations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.2.4—solving algebraic equations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.

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

Use b.2.5—logarithmic quantities to connect the rule to the data and decision in the question.

This matters because b.2.5—logarithmic quantities determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.2.5—logarithmic quantities to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.2.5—Logarithmic quantities is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.3.1—translating between data forms to connect the rule to the data and decision in the question.

This matters because b.3.1—translating between data forms determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.3.1—translating between data forms to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.3.1—Translating between data forms is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.3.2—plotting two variables to connect the rule to the data and decision in the question.

This matters because b.3.2—plotting two variables determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.3.2—plotting two variables to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.3.2—Plotting two variables is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.3.3—slope and intercept of a linear graph to connect the rule to the data and decision in the question.

This matters because b.3.3—slope and intercept of a linear graph determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.3.3—slope and intercept of a linear graph to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.3.3—Slope and intercept of a linear graph is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.3.4—rate from a linear graph to connect the rule to the data and decision in the question.

This matters because b.3.4—rate from a linear graph determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.3.4—rate from a linear graph to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.3.4—Rate from a linear graph is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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.

Use b.3.5—tangents and instantaneous rates to connect the rule to the data and decision in the question.

This matters because b.3.5—tangents and instantaneous rates determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.3.5—tangents and instantaneous rates to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.3.5—Tangents and instantaneous rates is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.4.1—angles and regular structures to connect the rule to the data and decision in the question.

This matters because b.4.1—angles and regular structures determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.4.1—angles and regular structures to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.4.1—Angles and regular structures is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.4.2—representing two- and three-dimensional forms to connect the rule to the data and decision in the question.

This matters because b.4.2—representing two- and three-dimensional forms determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.4.2—representing two- and three-dimensional forms to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.4.2—Representing two- and three-dimensional forms is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

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

Use b.4.3—symmetry of shapes to connect the rule to the data and decision in the question.

This matters because b.4.3—symmetry of shapes determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b.4.3—symmetry of shapes to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: B.4.3—Symmetry of shapes is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.