How the voltage supplied (4,6,8,10,12,14V) to aluminium cathode in aqueous sulfuric acid affects the increase in mass (in grams) of aluminium oxide deposited at the aluminium anode.SL
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4
Official IB Result
11/24
Criteria A: Research Design
3/6
0
3
6
Criteria Strands
A.1Research question context
Moderate
A.2Methodological considerations
Moderate
A.3Methodology description
Moderate
Criteria Feedback
- Clear articulation of the research question with well-defined variables
- Balanced and correctly balanced electrochemical equations demonstrating theoretical understanding
- Comprehensive control variables table and hypothesis stated with null and alternative
- Procedure, apparatus table and photographs sufficient for basic reproducibility
- Context remains broad and not specific to the chosen experimental conditions
- Lacks plan for current monitoring and exact electrode dimensions
- Ambiguities in temperature control and rinse solvent grade
- Incorrect units for current density
1.1·Strength
Page 1
The research question is clearly stated with a specific dependent and independent variable, demonstrating good understanding of the investigation’s aim.
1.2·Suggestion
Page 1
Background theory could be strengthened by citing Faraday’s constant with its numerical value to support the link between charge and mass deposition.
1.3·Weakness
Page 1
Contextual background remains broad; consider integrating quantitative industrial parameters or specific alloy compositions to narrow the scope.
1.4·Strength
Page 2
Equations for anode and cathode reactions are correctly balanced, reflecting solid understanding of electrochemical processes.
1.5·Weakness
Page 2
Method lacks explicit plan for current monitoring; without current measurements, charge passed cannot be directly related to oxide mass.
1.6·Weakness
Page 3
Definition of current density in joules is incorrect; current density should be in A m⁻². Revise units and formula accordingly.
1.7·Suggestion
Page 3
Including a worked example of electric field strength calculation for a given voltage and separation would reinforce the rationale for electrode spacing.
1.8·Weakness
Page 4
Hypothesis narrative is overly detailed and mixes predictions with explanations; consider separating concise testable hypothesis from background rationale.
1.9·Strength
Page 4
Hypothesis is clearly articulated with both null and alternate statements, demonstrating rigor in experimental planning.
1.10·Strength
Page 5
Justification of voltage range references preliminary trials and clear measurable trends, reflecting thoughtful design.
1.11·Suggestion
Page 5
Consider quantifying the effect of electrode separation on cell resistance using Ohm’s law to justify the chosen 7 cm spacing.
1.12·Strength
Page 6
Control variables table is extensive and demonstrates strong effort to ensure a fair test.
1.13·Suggestion
Page 7
Specify the method and solvent used to remove old oxide layers between trials to ensure consistent surface preparation.
1.14·Suggestion
Page 9
Maintain current constant using a regulated power supply and report its stability over each 5 min trial.
1.15·Weakness
Page 9
Stepwise method is detailed, supporting reproducibility, but lacks specification of rinse solvent grade.
1.16·Strength
Page 17
The extension proposes investigating electrolyte concentration and temperature effects, offering a clear pathway for future research.
Criteria B: Data Analysis
3/6
0
3
6
Criteria Strands
B.1Communication of data recording and processing
Moderate
B.2Consideration of uncertainties
Poor
B.3Data processing quality
Moderate
Criteria Feedback
- Raw data table is neatly organized for traceability
- Uncertainty propagation for mass readings is correctly applied
- Linear regression, r², and p-value are calculated and interpreted accurately
- Graph with fitted line is present
- Formatting issues (merged cells, truncated headings) impair precision
- No uncertainty on voltage or combined uncertainty for the mean
- Lack of an ammeter and its uncertainty limits processing accuracy
- Missing error bars on the voltage axis and incomplete equation references
2.1·Weakness
Page 5
Hypothesized graph is useful, but axes lack units and labels, limiting clarity of the predicted relationship.
2.2·Weakness
Page 6
Merged cells and inconsistent row structure in the control table impair precise communication of methods and apparatus.
2.3·Strength
Page 8
Apparatus uncertainties table lists percentage uncertainties, aiding transparent error analysis.
2.4·Weakness
Page 8
No current measurement device is listed; including an ammeter with its uncertainty would improve data processing accuracy.
2.5·Suggestion
Page 9
Include uncertainty propagation for volumetric preparation steps (M₁V₁=M₂V₂) to capture dilution errors.
2.6·Suggestion
Page 11
Add units to each term in equations to ensure clear communication of derived quantities.
2.7·Strength
Page 11
Uncertainty propagation is correctly applied to mass readings, showing appropriate error calculation.
2.8·Weakness
Page 11
Percentage uncertainty calculation omits voltage error impact on regression slope; include voltage uncertainty propagation.
2.9·Weakness
Page 11
Placeholder Equation 5 is empty; remove or complete it to avoid ambiguity in sample calculations.
2.10·Strength
Page 11
Sample calculation clearly shows mass change determination, reinforcing correct data processing.
2.11·Suggestion
Page 12
Include regression equation, R² value, and p-value alongside processed table entries for comprehensive data presentation.
2.12·Weakness
Page 12
Processed data graph lacks error bars on voltage axis; adding these would reflect voltage uncertainty.
2.13·Strength
Page 12
Raw data table is neatly organized, facilitating clear traceability of individual trials.
2.14·Weakness
Page 15
The method used to compute the p-value is unspecified; clarify the statistical test and degrees of freedom to bolster credibility.
2.15·Strength
Page 15
P-value interpretation is accurate and supports rejecting the null hypothesis, strengthening statistical validity.
Criteria C: Conclusion
3/6
0
3
6
Criteria Strands
C.1Conclusion relevance and support
Moderate
C.2Scientific context comparison
Poor
Criteria Feedback
- Conclusion links observed linear trend to Faraday’s law and theory
- Regression statistics are used to support the mass-voltage relationship
- Consistent interpretation of processed data
- Omits discussion of small mass changes relative to measurement uncertainty
- Superficial comparison to broader industrial context
- Does not reconcile expected non-linear behavior at high voltages
3.1·Strength
Page 13
Conclusion effectively links the trendline to Faraday’s law, demonstrating consistency between theory and results.
3.2·Weakness
Page 13
The conclusion omits discussion of small mass changes relative to measurement uncertainty, limiting critical assessment of trend significance.
3.3·Suggestion
Page 14
Discuss potential non‐linear trends quantitatively, for example by extending anodization time or voltage beyond the current range.
Criteria D: Evaluation
2/6
0
3
6
Criteria Strands
D.1Methodological weaknesses
Poor
D.2Suggested improvements
Poor
Criteria Feedback
- Identification of realistic improvements such as using an analytical balance and automating timing
- Specific weaknesses (voltage range, precision of balance) are noted
- Descriptions of methodological limitations remain general without estimating their impact on data quality
- Explanations of how proposed improvements would quantitatively enhance validity are brief
- Does not analyze the relative impact of individual weaknesses on the final conclusions
4.1·Weakness
Page 15
Strengths highlight control variables well but misstate varying temperatures; ensure consistency in describing experimental conditions.
4.2·Strength
Page 16
Using an analytical balance with ±0.0001 g precision is a strong improvement suggestion to lower absolute and percentage uncertainties.
4.3·Suggestion
Page 16
Estimate how improved balance precision would reduce overall percentage uncertainty to quantify the impact of this change.