The current IB Chemistry IA criteria assess the scientific investigation through four equally weighted areas: Research Design, Data Analysis, Conclusion, and Evaluation. Each criterion is worth 6 marks, giving a total of 24 marks, and the same criteria apply at SL and HL.
The report is assessed through broad markband descriptors rather than a checklist. Including a graph, uncertainty or improvement does not automatically earn credit. Each element must support the scientific purpose described by the relevant criterion.
The current Chemistry IA mark scheme
The scientific investigation contributes 20% of the final Chemistry grade at both SL and HL. According to the official IB Chemistry subject brief, it is allocated approximately 10 hours and produces an individual written report with a maximum of 3,000 words.
| Criterion | Maximum marks | Main focus |
|---|---|---|
| Research Design | 6 | Context, methodological decisions and reproducibility |
| Data Analysis | 6 | Recording, processing, uncertainty and presentation |
| Conclusion | 6 | Answering the question using evidence and accepted chemistry |
| Evaluation | 6 | Evaluating limitations and explaining improvements |
| Total | 24 | Complete scientific investigation |
The revised course was first assessed in 2025. Separate criteria for personal engagement, exploration and communication no longer exist, so older five-criterion rubrics are outdated. Independent thinking and clear communication still matter when they strengthen evidence under the four current criteria.
Conclusion and Evaluation together account for 50% of the IA marks. The IB Chemistry curriculum update connects this structure with the course's increased emphasis on higher-order thinking.
How best-fit marking works
Each criterion has four levels: 0, 1-2, 3-4, and 5-6. The teacher selects the descriptor that best represents the report as a whole for that criterion, then decides whether the work deserves the lower or upper mark within the band.
This is a best-fit model, not point-by-point marking. A report can reach the 5-6 band despite a minor weakness, but its overall evidence must resemble that descriptor more closely than the 3-4 descriptor. Excellent graphs, for example, cannot compensate fully for processing errors that restrict the conclusion.
Teachers initially assess the reports, and the IB externally moderates a sample from each school. Moderation checks the application of the global standard, so a school's marks may remain unchanged, rise or fall. The IB assessment guide explains this process.
Criterion 1: Research Design, 6 marks
Research Design assesses how effectively the report communicates the purpose and practice of the methodology. The marker considers the research question, chemical context, methodological reasoning and reproducibility.
| Markband | Typical evidence |
|---|---|
| 1-2 | Little context, decisions merely stated, and insufficient detail for reproduction |
| 3-4 | Broad context, relevant decisions described, and a mostly reproducible method with some omissions |
| 5-6 | Specific chemical context, important decisions explained, and a fully reproducible method |
A strong research question identifies the variables or correlated quantities, chemical system and measurement method. For example: “How does hydrochloric acid temperature from 20-50 °C affect its initial reaction rate with magnesium, determined from hydrogen volume collected over time?”
Include only background chemistry needed to understand the question and expected relationship. Explain why the measurement method, range, intervals and quantity of data are suitable. Identify controlled variables and clarify their chemical relevance rather than merely listing them.
Another investigator should be able to repeat the procedure using the report alone. Include quantities, concentrations, apparatus, measurement intervals and relevant safety or environmental considerations. Briefly indicate how the resulting data will be processed.
The IB does not universally require five values or three repeats. The requirement is sufficient relevant data for the chosen investigation. The RevisionDojo data collection guide explains how to choose an appropriate range and sampling plan.
Criterion 2: Data Analysis, 6 marks
Data Analysis considers whether recorded and processed data answer the research question clearly, precisely and accurately.
| Markband | Typical evidence |
|---|---|
| 1-2 | Unclear processing, limited uncertainty treatment and major problems obstructing a valid conclusion |
| 3-4 | Generally understandable work with significant omissions or inaccuracies |
| 5-6 | Clear, precise data communication, appropriate uncertainty treatment and accurate processing |
Clear means the route from raw measurements to processed results can be followed. Precise means conventions such as units, graph labels, significant figures and decimal places are used correctly.
Separate raw and processed data, give tables descriptive titles, place units and uncertainties in headings, and show representative calculations. Select processing that fits the question, such as means, gradients, rates, constants or standard deviations. Graphs should use justified models, meaningful error bars and correctly labelled axes.
Uncertainty must inform the interpretation rather than simply appear beside measurements. If an enthalpy change is reported as , discuss whether its interval agrees with the literature value and affects the conclusion. Statistical techniques should be used only when they suit the data and scientific question.
The data analysis guide and uncertainty guide provide further worked guidance.
Criterion 3: Conclusion, 6 marks
Conclusion assesses whether the answer is consistent with the analysis and justified through comparison with accepted scientific context.
| Markband | Typical evidence |
|---|---|
| 1-2 | A relevant claim unsupported by the analysis, with superficial scientific comparison |
| 3-4 | A relevant conclusion that is not fully consistent with the analysis, plus some meaningful comparison |
| 5-6 | A justified conclusion fully consistent with the analysis and accepted chemistry |
Begin by answering the research question directly. Support the answer with selected processed values, gradients, uncertainty intervals, statistics or graph features. Then explain the pattern using relevant chemistry.
Accepted scientific context may be a traceable literature value, theoretical model or established relationship. Writing that a result “matches collision theory” is too general. State what agreement was expected, whether the measured evidence supports it and how uncertainty affects that judgement.
Do not claim that a hypothesis was proved. Evidence may support, partly support or fail to support a prediction within the investigation's conditions. The RevisionDojo conclusion guide explains how to connect evidence, theory and uncertainty without overstating findings.
Criterion 4: Evaluation, 6 marks
Evaluation assesses the analysis of methodological weaknesses and limitations, together with realistic improvements.
| Markband | Typical evidence |
|---|---|
| 1-2 | Generic problems and basic improvements |
| 3-4 | Specific problems with relevant, realistic improvements |
| 5-6 | Relative impacts explained and targeted improvements justified |
The phrase relative impact matters. Identify which problem most seriously affected the evidence and justify that judgement using uncertainty, spread, residuals, literature discrepancy or observed behaviour.
A useful structure is: specific problem → evidence → effect on data → effect on conclusion → importance → improvement.
“Human reaction time” is too generic. A stronger evaluation explains that manual timing caused random variation at a subjective colour endpoint, particularly during faster reactions, reducing confidence in the calculated rate trend. Replacing visual judgement with a calibrated colorimeter and automatic data logging addresses that cause directly.
Distinguish a methodological weakness, such as gas leakage or temperature drift, from a limitation, such as a narrow concentration range that restricts generalization. “Do more trials” is incomplete unless you identify the random variation involved and explain how additional independent trials would improve estimates of the mean and spread. See the Chemistry IA evaluation guide for a fuller framework.
Common misconceptions
- Personal engagement is not a current criterion. A personal story earns no separate marks.
- Complex chemistry does not automatically score higher. A manageable, controlled investigation can produce stronger evidence.
- Every IA does not need identical statistics. Processing must suit the question and data.
- A high does not prove accuracy or causation. Consider uncertainty, residuals and chemical reasoning.
- Evaluation is not limited to random error. Systematic bias, assumptions and restricted scope may matter more.
- Presentation cannot replace reasoning. Attractive tables cannot rescue inappropriate processing.
A practical final check
Read the report as one connected scientific argument. The design should generate suitable evidence, the analysis should transform it into defensible findings, the conclusion should answer the question, and the evaluation should establish how much confidence the findings deserve.
Check that every major claim is explicit rather than implied. The RevisionDojo Chemistry IA marking toolkit and moderated Chemistry IA examples can help identify how particular strengths and omissions affect marks.
Conclusion
The Chemistry IA criteria reward a coherent scientific argument, not a collection of headings. Reaching the 5-6 bands requires justified design decisions, accurate processing, meaningful uncertainty treatment, a conclusion grounded in accepted chemistry, and an evaluation of specific limitations and their relative impact.
Because every criterion carries 6 marks, avoid spending most of the report on the procedure while rushing Conclusion and Evaluation. RevisionDojo's exemplars, Coursework Review and Jojo AI can help identify criterion-level gaps, but feedback should always be checked against the official rubric and your teacher's guidance.
Sources and referenced URLs
- Official IB Chemistry subject brief
- Official IB Chemistry curriculum update
- IB assessment guide
- RevisionDojo Chemistry IA data collection guide
- RevisionDojo Chemistry IA data analysis guide
- RevisionDojo uncertainty and error analysis
- RevisionDojo Chemistry IA conclusion guide
- RevisionDojo Chemistry IA evaluation guide
- RevisionDojo Chemistry IA marking toolkit
- RevisionDojo Chemistry IA examples