Executive Verdict: Moderate Difficulty with Practical Hurdles
The October/November 2025 examination series for Cambridge IGCSE Combined Science (0653) presents a standard difficulty level (rated 3.2 out of 5). The paper balances basic conceptual recall (such as identifying cell parts and food chain levels) with challenging multi-step quantitative calculations in Physics and structural representation in Chemistry. Students who rely on memorisation alone will find the transitions to application-heavy theory and experimental design demanding.
Where Marks Were Won and Lost
A significant portion of the marks lay within three major areas: Electricity, Motion, Forces and Energy, and The Periodic Table. In the Physics sections, many students successfully solved direct formula applications like finding resistance \( R = \frac{V}{I} \) or power \( P = VI \). However, marks were frequently lost in more complex scenarios, such as determining parallel resistance combinations and calculating total charge \( Q = It \) where candidates failed to convert the time from minutes into seconds (e.g., \( 2.0 \text{ minutes} = 120 \text{ s} \)).
In Chemistry, candidates performed well on Periodic Table trends but struggled with the ionic dot-and-cross diagram for magnesium chloride (MgCl\(_2\)). Common omissions included failing to represent the correct charges on the ions or drawing covalent sharing lines instead of demonstrating electron transfer. In Biology, definitions of basic concepts like transpiration were occasionally incomplete; examiners seek the precise loss of water vapour from leaves rather than merely water.
Practical and Planning Insights (Paper 6)
Paper 6 (Alternative to Practical) highlighted the importance of graphical skills. Students lost marks by drawing non-linear scales or lines of best-fit that did not ignore identified anomalous points. The 7-mark experimental planning task on the inverse relationship between wooden beam deflection and its width required a systematic structure. Successful scripts explicitly stated independent, dependent, and controlled variables, alongside a clear description of the processing method (such as plotting \( \frac{1}{h} \) against \( w \)).
Preparation Strategy & Syllabus Predictions
To secure a top grade in future sittings, students must prioritise the following:
- Rigorous Unit Tracking: Always convert time to seconds, mass to kilograms, and volume to cm\(^3\) or dm\(^3\) before calculating.
- Precise Chemical Vocabulary: Clearly differentiate between hydrocarbons (containing carbon and hydrogen *only*) and other organic derivatives.
- Practical Mechanics: Learn the standard testing methodologies for anions, cations, and gases.
Based on the underrepresentation of certain topics in this series, there is a high likelihood of upcoming papers placing a larger weight on Stoichiometry, Electrochemistry, and Plant Transport mechanisms.