AQA GCSE Chemistry Past Papers

Indiscriminate Use of Particle Terminology

The most frequent error is the imprecise use of the terms atoms, ions, and molecules, which are often used interchangeably or omitted entirely. For example, students often refer to "calcium" and "chlorine" reacting rather than specifying calcium atoms and chlorine atoms.

Referring to Intermolecular Forces in Giant Structures

Students often incorrectly state that intermolecular forces exist in giant structures like diamond, graphite, or metals. These substances are held together by strong covalent, ionic, or metallic bonds, not intermolecular forces.

Mathematical Errors in Mole Calculations

A recurring high-demand mistake is failing to convert volumes from cm³ to dm³ before calculating moles in titration questions. Additionally, many students divide by the sum of mass numbers rather than 100 when calculating relative atomic mass from percentages.

Incomplete Definitions of Weak Acids

The definition of a weak acid is often given as "partially ionised," but students frequently omit the essential detail that this occurs in aqueous solution. Some also incorrectly state the acid is "ionising" (acting on something else) rather than being "ionised" itself.

““partially ionised”

Errors in Atomic Theory Timelines

Students often lose credit by referring to protons and neutrons when describing early models like the Plum Pudding or the Bohr model. At the time these models were developed, these subatomic particles had not yet been discovered.

Confusing Conductivity Mechanisms

Many students believe that electric current in a solution is conducted by delocalised electrons rather than mobile ions. Conversely, when describing metals, they often fail to state that electrons move through the structure in a specific direction rather than just "throughout" it.