An IB Chemistry IA energetics investigation should examine a focused chemical relationship through measurable energy changes. The most practical approaches are calorimetry studies of combustion, neutralisation, or dissolution, provided that you collect enough repeated data and treat heat loss and uncertainty critically.
A familiar experiment is not automatically a weak investigation. Its quality depends on whether the independent variable has a chemical rationale, the method produces meaningful quantitative data, and the analysis answers a precise research question.
What the current IB Chemistry IA requires
Under the Chemistry course first assessed in 2025, the IA is formally called the scientific investigation. It is an open-ended investigation in which students gather and analyse data to answer their own research question. The individual report has a maximum of 3,000 words, contributes 20% of the final Chemistry grade, and is assessed using four criteria: research design, data analysis, conclusion, and evaluation.
The revised criteria place substantial emphasis on interpreting results and evaluating the investigation. This means that a sophisticated apparatus is less important than a defensible method, well-processed data, and specific discussion of limitations. The RevisionDojo IB Chemistry IA guide explains the current structure, while the Chemistry IA exemplars show how investigations can be evaluated against the criteria.
Strong IB Chemistry IA energetics ideas
The following ideas are starting points rather than ready-made research questions. Adapt the substances, variable range, and method to your laboratory's equipment and safety requirements.
| Area | Possible independent variable | Dependent variable | Chemical rationale | Main challenge |
|---|---|---|---|---|
| Combustion | Carbon-chain length of alcohols | Experimental molar enthalpy of combustion | More oxidizable carbon and hydrogen bonds generally increase energy released per mole | Heat loss and incomplete combustion |
| Combustion | Degree of branching among alcohol isomers | Molar enthalpy of combustion | Isomers have different relative stabilities | Differences may be small compared with experimental error |
| Neutralisation | Identity of a weak acid | Molar enthalpy of neutralisation | Energy is required to ionise weak acids before H⁺ reacts with OH⁻ | Acids must be compared at controlled concentration |
| Neutralisation | Initial acid or alkali concentration | Experimental enthalpy per mole of water formed | Dilution and non-ideal solution effects may influence measured energy changes | Total volume and mole ratios must be controlled |
| Dissolution | Identity of an ionic salt | Molar enthalpy of solution | Enthalpy depends on competition between lattice separation and ion hydration | Solubility and hydration state differ among salts |
| Dissolution | Water-to-solute mole ratio | Enthalpy change per mole dissolved | The extent of hydration and final concentration can affect the measured process | Complete dissolution must be confirmed |
| Dissolution | Anhydrous versus hydrated salts | Molar enthalpy of solution | Crystal water changes lattice structure and dissolution energetics | Hygroscopic samples may change composition |
Enthalpy of combustion
A common research question is: How does the number of carbon atoms in primary alcohols affect their experimentally determined molar enthalpy of combustion? A spirit burner heats a measured mass of water, and the burner's mass loss gives the amount of fuel consumed.
Calculate the energy absorbed by the water using:
q = mcΔT
The experimental molar enthalpy is then approximately:
ΔH = −q/n
Here, n is the amount of fuel burned. The negative sign represents an exothermic process.
School combustion calorimetry usually underestimates the magnitude of combustion enthalpy because energy heats the container and surrounding air, while incomplete combustion may produce carbon monoxide or soot. Fuel evaporation can also make the measured mass loss larger than the mass actually burned. These are systematic limitations, not problems solved simply by adding more repeats.
Enthalpy of neutralisation
Neutralisation experiments are generally more controlled because reactions occur inside an insulated cup. A chemically meaningful investigation could compare ethanoic acid and other weak acids reacting with the same strong alkali.
For a strong acid and strong base, the central reaction is:
H⁺(aq) + OH⁻(aq) → H₂O(l)
Weak acids must ionise as neutralisation proceeds, so their measured enthalpy can differ. Calculate the amount of water formed from the limiting reagent, rather than dividing by the total amount of acid and base added. Keep initial temperatures, concentrations, total volumes, mole ratios, stirring, and calorimeter geometry consistent.
Enthalpy of dissolution
Dissolution calorimetry can compare salts or investigate a structural property such as ionic charge density. Dissolution may be exothermic or endothermic because separating an ionic lattice requires energy, while hydrating the released ions gives out energy.
A strong question might examine how cation identity affects the molar enthalpy of solution within a carefully selected family of salts. Avoid comparing unrelated compounds without explaining differences in charge, ionic radius, lattice structure, hydration, and solubility. Confirm the formula and hydration state of every salt because these determine molar mass and the thermochemical process being measured.
RevisionDojo's measuring energy changes notes and energetics Questionbank can help you check the underlying calculations before processing IA data.
Designing a reliable calorimetry method
For solution calorimetry, use nested polystyrene cups with a fitted lid and a temperature probe passing through a small opening. Measure the mass of the final solution when practical instead of assuming every aqueous solution has a density of exactly 1.00 g cm⁻³. Stir consistently without allowing the probe to touch the container.
Collect temperature readings at regular intervals before and after mixing. A graph of temperature against time allows extrapolation toward the mixing time, producing a better estimate of the corrected temperature change than simply recording the highest or lowest displayed value.
A useful investigation normally includes:
- A justified range of at least several independent-variable levels
- Repeated trials at each level
- Controlled reactant amounts, initial temperature, insulation, stirring, and timing
- Apparatus uncertainties recorded with raw measurements
- Quantitative observations plus relevant qualitative evidence, such as soot or incomplete dissolution
- A pilot study confirming that temperature changes are large enough to measure reliably
Controlling heat loss
No school calorimeter is perfectly insulated. Improve control by using a lid, nesting cups, reducing transfer time, keeping the same solution volume, and recording temperatures electronically where possible. For combustion, a draught shield and fixed burner-to-can distance improve consistency, but sufficient oxygen must still reach the flame.
A stronger correction is to determine the calorimeter's heat capacity through calibration. The energy balance can then include both solution and calorimeter:
q absorbed = (m solution × c solution × ΔT) + (C calorimeter × ΔT)
Heat exchange with the wider environment may still remain. State clearly which effects the calibration addresses and which it does not.
Handling uncertainty correctly
Record uncertainties for mass, volume, concentration, and temperature. Because ΔT = Tfinal − Tinitial, its absolute uncertainty must reflect both temperature measurements. The uncertainty in q then depends on the uncertainties in mass and ΔT, plus any experimentally determined uncertainty in heat capacity.
Use repeated trials to calculate a mean and a measure of spread, such as standard deviation. Instrument uncertainty and trial-to-trial variation answer different questions, so do not substitute one for the other. Follow one justified propagation convention consistently and explain it, particularly if your school expects conservative addition or root-sum-square propagation.
Heat loss, incomplete combustion, and assuming every solution has water's specific heat capacity are usually systematic limitations. They should be analysed by direction and likely importance rather than placed in an uncertainty calculation without justification. The RevisionDojo data analysis guide provides further guidance on tables, graphs, error bars, and propagated uncertainty.
Common mistakes to avoid
- Calling a measured value a standard enthalpy change when standard-state conditions were not established
- Changing both substance identity and concentration without separating their effects
- Using only three substances or one trial per condition
- Treating accepted values as evidence that experimental data should be altered
- Listing generic errors without explaining their effect on the result
- Claiming that repeats eliminate heat loss or another systematic bias
- Removing anomalous data without a documented scientific reason
Your conclusion should answer the research question using processed results, uncertainties, and chemical theory. Your evaluation should connect each important weakness to its effect on the data and propose a realistic improvement. The IB Chemistry IA grader can help identify missing reasoning, but feedback should support rather than replace your own analysis.
Conclusion
The strongest IB Chemistry IA energetics topics combine a clear chemical relationship with a calorimetry method capable of testing it. Neutralisation and dissolution often produce cleaner data than simple combustion, although combustion can still support a good investigation when its systematic limitations are treated honestly.
Choose a question only after pilot testing the temperature change, repeatability, and safety of the method. RevisionDojo's IA guide, exemplars, Study Notes, Questionbank, IA Feedback, and Jojo AI can then help you check the chemistry and refine the clarity of your report.
Sources and referenced URLs
- Official IB Chemistry subject brief, first assessment 2025
- Official IB Chemistry curriculum updates
- Chemguide guidance on measuring enthalpy changes
- Chemistry LibreTexts calorimetry and thermochemistry procedure
- RevisionDojo IB Chemistry IA guide
- RevisionDojo Chemistry IA exemplars
- RevisionDojo measuring energy changes notes
- RevisionDojo measuring energy changes Questionbank
- RevisionDojo Chemistry IA data analysis guide
- RevisionDojo Chemistry IA grader