IB Chemistry HL Internal Assessment Example

While the research question is clear and embedded in a specific context of Coffea arabica roasting, the choice of roasting durations (1–20 min) lacks explicit justification relating to industrial roasting profiles. A brief rationale here would strengthen context specificity.

The student clearly states the research question within a well-defined context, specifying bean species, roast levels, and expected caffeine extraction outcomes.

Control variables are comprehensive and relevant; however, the rationale for five replicates lacks explanation about statistical power or expected variability reduction.

The identification and control of critical variables (bean mass, roast temperature, solvent volume) demonstrate careful methodological consideration to ensure relevant and sufficient data.

Apparatus list is detailed, but the specified EDTA range (0.1–0.5 g) introduces ambiguity in replication. Specify exact mass per batch to allow full reproducibility.

Allowing one week for crystallization is impractically long; consider specifying alternative faster evaporation conditions or a controlled evaporation setup.

The liquid–liquid extraction procedure is described clearly, but the ratio of phases (ethyl acetate to aqueous) could be justified with partition coefficient values.

The KOH addition step lacks concentration detail in the list and text; specify molarity in both locations to avoid ambiguity.

Method describes roasting at 200 °C, yet earlier the table states 190 °C. This inconsistency could confuse replication; ensure temperature values match throughout.

Solubility discussion is precise and includes relevant references; incorporating a brief mention of temperature dependence here would strengthen context for extraction conditions.

Raw data are clearly presented, but the units (mg (± 0.01 g)) mix mass and uncertainty units incorrectly; use consistent units for uncertainties (± 0.01 mg).

No propagation of uncertainties is presented alongside the calculated averages; include combined standard uncertainties to fully account for measurement errors.

Mean calculations are correct and formulas are clearly shown, aiding reproducibility of the data processing.

The graph’s axes are labeled but units are omitted from axis labels; ensure units appear directly on the axes to improve clarity.

Graph conveys the trend effectively, but lacks error bars or uncertainty shading; include these to reflect measurement precision.

Literature comparison highlights significant deviations, but absence of statistical analysis (e.g., percentage differences, significance testing) limits interpretation.

The acknowledgment of uncertainties is appropriate but appears here rather than in data analysis; integrate quantitative uncertainty discussion earlier in results for coherence.

Practical implications are well articulated, highlighting the significance of roasting optimization for caffeine content in industry.

The comparison to published studies is relevant, but discussion could deepen the mechanistic link between chlorogenic acid breakdown and caffeine availability quantitatively.

Conclusion restates findings coherently, directly linking roasting time and caffeine yield, which demonstrates consistency with the data presented.

The student accurately identifies key strengths, linking controlled variables and multiple trials to improved reliability.

Improvements are realistic and tied to weaknesses, but the description lacks quantitative impact assessment of each suggested change.

Random error source is well identified, but its likely magnitude and effect on final values is not quantified; include an estimate of variation introduced.

Noting calibration errors as systematic is insightful; consider specifying calibration frequency and tolerance thresholds to enhance evaluation depth.