IB Chemistry HL Internal Assessment Example

The student provides a rich personal and industrial context for the research question, linking health motivations, commercial pasteurization practices, and cited literature effectively.

Ensure consistency between the research question’s stated units (g dm⁻³) and the units actually used later (mol dm⁻³); clarify or convert as needed.

It would strengthen the design to control oxygen exposure during heating and storage, as atmospheric O₂ can oxidize ascorbic acid independently of temperature.

The dependent variable description uses 0.025 cm³ instead of 0.025 dm³; correct this volume unit to prevent confusion in reproducibility.

The independent variable section clearly justifies the temperature range and increments in the context of food processing, demonstrating sound methodological consideration.

The procedure omits details on filtration conditions (e.g., vacuum pressure or filter pore size); include these to ensure complete reproducibility.

Describe how the sample is held at the set temperature during titration (e.g., in a water bath or insulated flask) to prevent cooling before measurement.

The Procedure header lacks any mention of heating duration or equilibration time; specify how long each sample is maintained at target temperature.

Consider recording the time to endpoint for each titration as qualitative data; this could reveal kinetic differences at different temperatures.

Present balanced reaction equations clearly with correct stoichiometry and LaTeX formatting (e.g. $C_6{H}_8{O}_6+I_2\to C_6{H}_6{O}_6+2I^{-}+2H^{+}$).

The concordant averages at 60°C and 70°C are identical (26.70 and 25.50), suggesting a possible transcription or calculation error in the raw data table.

The raw data table is overly complex; consider separating trials from concordant values and using a simplified summary table to improve clarity.

Concentration values at 70 °C match exactly those at 60 °C, indicating a likely copy–paste or calculation slip; verify and correct as needed.

Include percentage uncertainties alongside each concentration in the final data table to convey measurement precision directly.

Temperature measurement uncertainty (±0.5 °C) is not propagated into concentration uncertainty; include this contribution in error analysis.

Ensure the caption for Table 9 is properly placed and distinct from headers, to avoid confusion with subsequent sample calculations.

Given the known kinetics of ascorbic acid degradation, consider fitting an exponential or logarithmic model in addition to a linear trend to better capture reaction behavior.

The interpretation text clearly explains the negative slope and high R², showing strong understanding of the relationship between temperature and Vitamin C degradation.

Expand the discussion of literature context by comparing with other studies or discussing matrix effects to justify your experimental deviation.

The assumption that 242 mg/100 g (literature) equals 242 mg/100 ml may introduce error; discuss density or matrix differences explicitly.

Align the stated percent reduction in the conclusion with the regression analysis results to maintain consistency.

The conclusion states a 50% reduction but the data show a drop from 0.0080 to 0.0036 mol dm⁻³ (55%); recalculate and correct the reported percentage.

The evaluation section effectively highlights key strengths such as multiple trials and pipette usage, demonstrating reflection on reliability.

For each methodological weakness, explain its relative impact on accuracy or precision (e.g., which error contributes most to overall uncertainty).

The systematic-errors table proposes realistic improvements (water bath, standardization); these are well linked to identified biases, strengthening the evaluation.