Overall Exam Verdict

The October/November 2025 examination session for Cambridge IGCSE Combined Science (0653) maintained a solid and fair standard. The core and extended papers provided comprehensive coverage across all three sciences. Questions tested both fundamental recall and higher-order application, including calculating area under speed–time graphs, balancing complex chemical redox and organic combustion equations, and constructing reaction pathway diagrams with appropriate activation energy and enthalpy arrows.

Where the Marks Were Found

  • Biology: High marks were concentrated in photosynthesis kinetics, leaf anatomy, food web dynamics, and pathogenic disease control including antibiotic resistance.
  • Chemistry: Key scoring areas included acid-base titrations with indicator colors, industrial extraction of iron in the blast furnace, covalent dot-and-cross structures for \(\text{CO}_2\), and alkane/alkene reactions.
  • Physics: Substantial marks stemmed from kinematics (speed–time graph interpretation and distance calculations), series/parallel electrical circuit calculations (\(R = V/I\), combined resistance), thermal radiation comparison, and stellar life cycles in Space Physics.

Examiner Pitfalls & Common Errors

  • Reaction Pathway Profiles: Candidates frequently drew incorrect arrows for overall energy change (\(\Delta H\)) or omitted activation energy peaks in exothermic profiles.
  • Circuit Calculations: Confusion between series and parallel resistance rules remains common, particularly when combining parallel branches with a series resistor.
  • Significant Figures & Units: Marks were lost on physics and practical papers for omitting standard units (e.g., \(\text{g/cm}^3\), \(\text{J}\)) or failing to round to the requested two significant figures.
  • Precision in Definitions: Imprecise phrasing in definitions such as electromotive force (e.m.f.) and captive breeding lost straightforward recall marks.

Preparation Strategy for Next Series

Ensure balanced revision across all three science disciplines. Pay particular attention to multi-step numerical calculations in Physics, state symbols and dot-and-cross diagrams in Chemistry, and 6-mark experimental planning questions in Paper 6.