IB Chemistry HL Internal Assessment Example

The statement that “Vitamin C has a boiling point of 100 °C” conflates the boiling point of water with vitamin C and may mislead readers about the compound’s thermal properties.

The student provides a well‐structured, specific context for the research question, citing quantitative values and relevant literature about vitamin C stability in potatoes.

Both null and alternative hypotheses are clearly stated, demonstrating understanding of the experimental design and the expected direction of change.

The manipulated variable section is well justified with literature references and clear rationale for chosen time intervals.

The equipment list omits calibrated pipettes or volumetric pipettes necessary for precise measurement of iodine solution volumes.

Consider adding details on equipment calibration and verification, such as burette standardization and balance calibration procedures.

The description of starch indicator and iodine solution concentrations is thorough, supporting reproducibility.

Clarify preparation details such as mixing speeds, durations, and how solutions were filtered or allowed to stand, to remove any ambiguity.

The potato preparation procedure is clearly broken into discrete steps, allowing a competent chemist to follow the method.

The blending and straining steps lack details on blender speed, duration, and mesh size, which could affect extraction efficiency.

The procedure omits mention of sample randomization or homogenization between replicates, which may introduce systematic bias.

The protocol for repeat titrations is explicit, indicating how each trial is conducted and recorded.

The narrative notes that quantitative data are recorded into tables, demonstrating clear communication intent.

Qualitative observations are systematically listed, capturing color changes and reaction dynamics.

The qualitative observations are superficial; consider using a standardized color chart or spectrophotometric method to quantify endpoint.

Ensure table headings align correctly with rows; an orphaned datum (50.00, 49.60, 0.40) lacks a corresponding time label.

The mean iodine volumes table is accompanied by standard deviations, strengthening data transparency.

The calculated mean for 0 min is 7.52 cm³, but recalculation shows 6.70 cm³; this major inaccuracy propagates through subsequent results.

The concentration formula is printed as $$c=\frac{n}{n}$$, but it should read $$c=\frac{n}{V}$$; correct the formula to avoid confusion.

The mole calculation for iodine uses correct units and concentration, demonstrating sound stoichiometric reasoning.

Several values in the processed table are inconsistently rounded (e.g., 1.38 vs. 1.39 ×10⁻⁴ M); apply uniform significant‐figure rules.

The processed data table clearly lists mean volumes, concentrations, and scaled mg/100 g values, aiding interpretation.

Include the R² value directly on the scatter plot or in the caption for quick reference to correlation strength.

The x-axis label reads “Boiling Points” but the data represent boiling times; correct this to maintain clarity.

The formula for percentage uncertainty is correctly presented, guiding accurate error analysis.

Only burette reading uncertainties are considered; include uncertainties from balance, volumetric flask, and pipetting in the propagation analysis.

Recognizing the non‐significant p-value alongside strong correlation demonstrates nuanced interpretation of statistical results.

The p-value is reported, but the statistical test method and assumptions are not described, limiting interpretation of significance.

The student compares findings to two relevant studies, noting both agreements and discrepancies, strengthening contextualization.

The conclusion clearly states that vitamin C content decreases with boiling time and references data and correlation, aligning with evidence.

The evaluation identifies methodological strengths but does not quantify their relative impact on the results.

Consider quantifying how each identified limitation (e.g., 5 min increments) could shift vitamin C results, to strengthen the evaluation.