IB Chemistry HL Internal Assessment Example

The research question is clearly stated but lacks quantitative background (e.g., typical ΔH values for commercial alcohols or combustion theory) to frame its significance in a chemical context.

The narrative introduction offers strong personal motivation but delays the chemical context until later. Consider condensing personal anecdote and introducing relevant chemistry background sooner.

Restating the research question in 1.2 is helpful for clarity, but refine wording to specify the expected trend (e.g., “increase in enthalpy per CH₂ unit”) to sharpen focus.

The background section defines alcohols well but would benefit from skeletal structures of ethanol, propan-2-ol and butanol to reinforce structural differences discussed.

The combustion definition lacks a balanced chemical equation (e.g., C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O). Include these to link theory to your measurements.

Step lacks specification of the flame-to-beaker distance. State the exact vertical separation (e.g., 2 cm) to ensure reproducibility.

The units for specific heat capacity are split across two blocks. Integrate “c in J·kg⁻¹·K⁻¹” in one equation line to improve precision and clarity.

Mass of alcohol is inferred from volume without using density (ρ). Record actual mass on the balance rather than assuming 1 cm³ equals 1 g.

Number of trials differs for each alcohol (6, 5, 3), compromising statistical reliability. Use equal replicate trials for fair comparison.

Raw data tables list initial and final water volumes but never change; measuring mass of water instead would be more relevant for Q calculations.

No uncertainties or error margins are included in any data processing. Quantify instrument uncertainties and propagate them to ΔH_c.

Temperature change steps use imprecise notation (e.g., “63 23 = 40.0”). Include subtraction symbol and units consistently for clear communication.

Volume-to-mass conversion for alcohol ignores density differences (e.g., ρ_ethanol ≈ 0.789 g/cm³). Use actual mass measurements for accurate mole calculations.

The specific heat calculation block shows garbled fraction notation. Ensure each mathematical step is typeset correctly in LaTeX for precision.

Calculated Q values (~16 kJ) are consistent across all alcohols and far too low by two orders of magnitude; indicates misunderstanding of heat calculation.

ΔH_c values for all trials are identical or nearly so, suggesting copying errors rather than genuine measurement differences.

Propan-2-ol ΔH_c values are constant at –20.1 kJ/mol across trials, an implausible result. Verify each trial’s Q and mole calculation independently.

Butanol ΔH_c calculations replicate ethanol Q values, indicating data was copied rather than recalculated. Recompute Q using measured temperature changes and mass.

The final paragraph restates success but lacks forward-looking research questions. Outline specific next steps or experiments to deepen understanding.

The conclusion asserts butanol as best fuel without discussing combustion rate vs. energy trade-offs or error margins. Add nuance by integrating uncertainties.

In evaluation, heat-loss and incomplete combustion are identified but not quantified. Estimate error percentages for each source to discuss their relative impact.

The soot formation is noted well, but consider calculating how much energy was lost to incomplete combustion versus heat absorbed by soot.

Trial numbers vary across alcohols, hindering statistical comparison. Repeat each alcohol to the same number of trials for valid trend analysis.

The conclusion refers to “real-world ramifications” but lacks comparison to theoretical or literature ΔH_c values. Incorporate literature data to contextualize findings.