IB Chemistry SL Internal Assessment Example

The research question is clearly stated and framed within a specific context, linking caffeine polarity, partition behavior, and extraction cycles. This focus supports reproducibility and relevance.

Background material concisely explains caffeine polarity and DCM characteristics, grounding the study in relevant chemical principles.

The preliminary trials section documents methodological adjustments but omits justification for choosing three replicates. Explain why this sample size was considered sufficient.

The table of DCM volumes per cycle is clear, but the rationale for a total 30 mL volume is not explained. Justify why this volume was chosen chemically.

Coffee solution preparation describes 55 g for 5 trials, but earlier sections reference 11 g per trial. Resolve this inconsistency to ensure reproducibility.

Shaking 16 times is specified, but the basis for this number is unclear. Explain how this frequency was determined to balance mixing and emulsion control.

Carrying capacity L is set to the maximum observed mean but lacks theoretical justification. Discuss why saturation should occur at that value.

Weighing procedure uses three-digit scale uncertainty; random and systematic uncertainties should be separated in propagation for transparency.

Calculated mass table is well organized with uncertainties and units clearly shown, facilitating precise interpretation.

Raw data table mixes comma and point separators and includes blank header cells. Use a consistent decimal format and tidy the columns.

Total uncertainty shows correct propagation formula but mislabels Uₜ twice. Distinguish instrument and sample uncertainties clearly.

Mean calculation uses range/2 for uncertainty but omits standard deviation. Include an analysis of spread (σ) to better assess precision.

Table of uncertainties is comprehensive, presenting mean, absolute, and percentage uncertainties for each cycle clearly.

The percentage uncertainty formula uses commas in decimals (e.g., 7,7%). Adopt consistent use of decimal points to match SI conventions.

Graph 2 would benefit from a residual plot or discussion of deviations from linearity to validate the model fit.

Graph 1 lacks explicit axis labels and units, making it difficult to assess scale. Include full labeling for both axes.

Linearization table caption references ‘table blank.’ Ensure table numbering is correct and accompanying data is clearly labeled.

Interpreting 4.2 cycles in practical terms overextends discrete cycle data. Discuss limitations of applying continuous models to integer‐cycle experiments.

Conclusion restates findings clearly and links to analytical results. The use of logarithmic model and calculus adds depth to the interpretation.

The 5% optimization threshold is introduced without sensitivity analysis. Explain why this cutoff is chemically or economically justified.

Weakness table effectively links specific limitations to results but does not rank their relative impact. Quantify which error sources most affect reliability.