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Chemistry IA Exemplar: Magnesium Salt Solubility and Crystallisation… | RevisionDojo
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IB Chemistry HL Internal Assessment Example
How does the temperature of the water affect the solubilities of magnesium salts magnesium dichloride hexahydrate and magnesium nitrate hexahydrate, as measured by the crystallisation temperatures of the solution at manipulated concentrations?
6
Official IB Result
18/24
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Criteria A: Research Design
5/6
0
3
6
Criteria Strands
Excellent
Research question context
Excellent
Methodological considerations
Good
Methodology description
Criteria Feedback
Research question framed within a specific, real-world context of dietary magnesium supplements
Comprehensive methodological rationale, including control variables linked to scientific justifications
Responsive adaptations (e.g., switching to volumetric pipette, using bungs to prevent evaporation) to improve data quality
Detailed plan with sufficient trials and justification for concentration range
Procedure omits precise stirring rate, heating time, and thermometer reading intervals
Control of hot-water bath temperature not specified in enough detail
Minor repetition in research question wording impacting conciseness
1.1·Strength
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The research question is framed within a specific context of dietary magnesium supplements, providing clear relevance and scope.
1.2·Weakness
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The research question repeats terms unnecessarily; consider refining wording for conciseness and clarity.
1.3·Strength
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The background effectively contextualizes magnesium’s physiological role and justifies investigating supplement solubility in varying water temperatures.
1.4·Strength
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The rationale for selecting magnesium dichloride and nitrate hydrates over other salts is thorough, demonstrating sound methodological consideration.
1.5·Suggestion
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Include quantitative values for ΔH and ΔS or reference literature sources to strengthen the Gibbs free energy analysis.
1.6·Suggestion
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Clarify the precise rate and method of stirring during heating and cooling to improve reproducibility of crystallization observations.
1.7·Weakness
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The description of the independent and dependent variables is clear, but control of the hot water bath temperature requires more detail (e.g., thermostat settings).
1.8·Suggestion
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Consider using a volumetric flask for initial dilution steps to reduce cumulative pipetting uncertainties.
1.9·Weakness
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The procedure omits specifics on stirring speed and duration; specify these to allow precise replication.
1.10·Strength
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The controlled variables table systematically links each control to its scientific rationale, demonstrating comprehensive methodological consideration.
1.11·Strength
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Adapting the concentration range mid-investigation shows responsiveness to preliminary data and optimizes the experimental design.
1.12·Strength
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Implementing a volumetric pipette and using a bung to prevent evaporation illustrates thoughtful procedural refinements.
Criteria B: Data Analysis
5/6
0
3
6
Criteria Strands
Excellent
Communication of data recording and processing
Good
Consideration of uncertainties
Moderate
Data processing quality
Criteria Feedback
Data tables and graphs are both clear and precise, with consistent units, labels, legends, and error bars
Comprehensive communication of data processing steps, including conversion of mass to moles and calculation of standard deviations
Appropriate consideration of uncertainties in measurements, with propagation into concentration and display in visualizations
Effective use of scatterplots showing all data points and fitted trendlines enhances interpretability
Uncertainty propagation is done additively rather than using quadrature methods
No justification provided for the polynomial order chosen in trendline fitting
Inconsistent formatting of unit notation (e.g., “moldm⁻3”)
2.1·Strength
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The qualitative description of crystal formation and comparative solubility provides clear, precise communication of observed trends.
2.2·Weakness
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The unit notation 'moldm⁻3' is inconsistently formatted; ensure consistent unit formats to maintain clarity.
2.3·Suggestion
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Quantify uncertainties in molar mass or justify their omission to enhance transparency of uncertainty propagation.
2.4·Weakness
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Uncertainties are combined additively rather than via quadrature; use correct propagation methods to improve accuracy.
2.5·Weakness
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Combining percentage uncertainties by simple addition overestimates total uncertainty; consider quadrature for independent error sources.
2.6·Strength
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Presenting all individual data points in scatterplots with error bars enhances precision and clarity in data visualization.
2.7·Weakness
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Trendlines are applied without justification of polynomial order; include rationale or fit diagnostics (e.g., R2) to support the chosen model.
2.8·Strength
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Calculating standard deviations using raw data demonstrates appropriate consideration of data variability and uncertainties.
Criteria C: Conclusion
4/6
0
3
6
Criteria Strands
Good
Conclusion relevance and support
Moderate
Scientific context comparison
Criteria Feedback
Conclusion directly answers the research question and is fully consistent with observed trends
Integration of thermodynamic reasoning (Le Chatelier’s principle, Gibbs free energy) to support findings
Acknowledgment of discrepancies with literature solubility values and attribution to systematic error
Lacks quantitative reference to uncertainty ranges when justifying the conclusion
Discussion of deviation magnitudes from literature is superficial and could be deepened
No exploration of future research directions to extend the investigation
3.1·Weakness
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The comparison to literature solubilities identifies discrepancies, but the discussion remains superficial; deepen analysis of divergence magnitudes.
3.2·Weakness
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The conclusion restates qualitative trends but lacks quantitative integration of uncertainty ranges; strengthen by referencing error margins.
3.3·Suggestion
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Suggest outlining potential future research directions (e.g., other salt types or narrower temperature intervals) to extend the investigation’s scope.
Criteria D: Evaluation
4/6
0
3
6
Criteria Strands
Good
Methodological weaknesses
Moderate
Suggested improvements
Criteria Feedback
Specific methodological weaknesses are identified and linked to their impact on data accuracy
Realistic improvements are suggested for each limitation, demonstrating critical reflection
Use of an evaluation table shows systematic consideration of methodological issues
Some suggested improvements lack depth, feasibility discussion, or cost analysis
A few entries in the improvements table are incomplete or insufficiently explained
No quantification of the expected magnitude of improvement for each suggestion
4.1·Weakness
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Several improvement cells are left blank or lack depth; provide realistic, detailed mitigation strategies and consider feasibility and resource constraints.
4.2·Strength
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The evaluation section lists specific methodological limitations and links them to impacts on data, showing detailed critical reflection.
