IB Chemistry Extended Essay
The criteria on this page are the ones for exams from May 2027, when the Extended Essay is marked out of 30. See what changed. If you sit your exams in November 2026, the older 34-mark criteria are summarised after them.
The IB Chemistry Extended Essay (EE) is a 4,000-word independent research paper built on a focused investigation of a chemistry topic, using primary data from your own experiments or secondary data from databases and the literature. Its grade, combined with your TOK grade, decides up to three bonus points on your Diploma score, and it shows the kind of analytical thinking university chemistry courses value. This guide covers how to choose a research question that works, what each assessment criterion requires, and which topic areas consistently produce high-scoring Chemistry EEs.
What makes Chemistry a good EE subject
Chemistry lends itself naturally to the EE because it produces measurable, quantitative data and connects directly to existing peer-reviewed literature. Unlike subjects where the research question is more open-ended (such as history or literature), a Chemistry EE research question has a clear method: an experimental design with a specific dependent variable, or a well-defined set of published data to analyse. This makes the framework (Criterion A) and the analysis and discussion (Criteria C and D) more straightforward to address, provided the method is rigorous and you compare your results with published values.
Choosing a research question for Chemistry EE
A strong Chemistry EE research question specifies the system being studied, the variable being manipulated, the variable being measured, and the conditions under which the experiment is conducted. It should be narrow enough to be answered in 4,000 words, but significant enough to justify investigation.
Examples of strong Chemistry EE research questions
- How does the concentration of ascorbic acid in orange juice change with oxidation time when exposed to air at 25 degrees C, as determined by iodometric titration?
- To what extent does the chain length of primary alcohols (C1-C5) affect the enthalpy of combustion, as measured by calorimetry?
- How does pH (3, 5, 7, 9, 11) affect the rate of hydrolysis of aspirin in aqueous solution, measured by UV-Vis absorbance at 296 nm?
- What is the relationship between metal ion concentration and the rate of the iodine clock reaction in a phosphate-buffered solution?
Research question mistakes in Chemistry EE
The most common error is a question that is essentially confirming a known result without adding analytical depth. "How does temperature affect the rate of a reaction?" is not an EE question. "What is the activation energy of the saponification of ethyl acetate, found from the rate constant k between 20 and 70 degrees C?" is an EE question: it asks one thing, and the result can be tested against the literature value.
IB Chemistry EE assessment criteria
From May 2027, the Chemistry EE is marked out of 30 on five criteria:
- Criterion A: Framework for the essay (6 marks). A clear, focused research question, a detailed and reproducible method with a justified choice of variables and equipment, and a structure that serves the question.
- Criterion B: Knowledge and understanding (6 marks). Accurate chemistry, going beyond the syllabus where the question needs it. Correct use of IUPAC nomenclature, mechanisms and theory, with relevant, reliable sources.
- Criterion C: Analysis and line of argument (6 marks). Analysis that goes beyond describing data: standard quantitative and statistical processing, with trends tied to the question in a coherent argument (clearly processed data and uncertainties in calculations are structural conventions under Criterion A).
- Criterion D: Discussion and evaluation (8 marks). The highest-weighted criterion. Do you compare experimental results with literature values, discuss systematic error and alternative explanations, and evaluate what your method could and could not establish?
- Criterion E: Reflection (4 marks). Marked on the reflective statement in your RPF. It rewards evaluative reflection, with specific examples, on how the investigation changed you as a learner.
If you sit your exams in November 2026, the essay is marked out of 34 instead: Focus and method (6), Knowledge and understanding (6), Critical thinking (12), Presentation (4) and Engagement (6, marked on the three RPPF reflections). The advice above carries over, because research, analysis, and discussion and evaluation together make up Critical thinking.
Grade boundaries for the new scale are set only after the May 2027 session is marked; on the older scale, 27 or more out of 34 has been a grade A in recent sessions. Chemistry essays often lose discussion and evaluation marks by presenting data without context: they calculate a rate constant but do not compare it to a published value, or they note an anomaly but do not investigate whether it reflects a systematic error or a genuine chemical phenomenon.
How to structure a Chemistry EE
- Introduction (400-500 words): State the research question precisely. Provide chemical context: why is this system interesting, and what does published literature say about it? State a hypothesis derived from theory, not intuition.
- Background Chemistry (500-700 words): Explain the chemistry your investigation depends on, going beyond the syllabus where the question needs it: Michaelis-Menten theory for enzyme kinetics, for example, or the Nernst equation for cell potentials that change with concentration. Criterion B marks are won here.
- Methodology (500-700 words): Write a reproducible method. State which variables are independent, dependent, and controlled. Justify your choice of analytical technique (why titration rather than spectrophotometry?). State replicate numbers and justify them statistically.
- Results and Analysis (800-1,000 words): Present raw data, processed data, and appropriate statistical analysis. Include error propagation for calculated values. Use graphs with error bars. Identify and investigate anomalous data points.
- Discussion (600-800 words): Compare your results to published literature values with explicit citations. If your result differs from the literature, propose specific chemical explanations. Evaluate the methodology: what systematic errors exist, and how do they affect the conclusion? Evaluate as you go, not only here: the guide wants evaluation integrated throughout the essay.
- Conclusion (200-300 words): Answer the research question directly. State the degree of confidence in your answer given the limitations identified.
Chemistry EE topics that score well
- Kinetics and reaction rates: Iodine clock reactions, enzyme-catalysed reactions, or acid-catalysed hydrolysis. These produce clean quantitative data and connect to the Arrhenius equation and activation energy theory.
- Electrochemistry: Investigating how concentration, temperature, or electrode material affects cell potential or electrolysis efficiency. Strong connection to the Nernst equation (Criterion B).
- Colorimetry and spectrophotometry: Measuring concentration of coloured species (permanganate, iron complexes, anthocyanins) as a function of an experimental variable. Produces reliable Beer-Lambert data with statistical analysis potential.
- Analytical chemistry: Determining the concentration of a substance in a real-world sample (vitamin C in juice, iron in water) using titration or spectrophotometry. Strong for Criterion D because you can compare your results to certified reference values.
- Thermochemistry: Measuring enthalpy changes for related reactions (homologous series, isomers, reaction conditions) and comparing to theoretical values from Hess's law or bond enthalpies.
Analyse your Chemistry EE with IBLens
IBLens reads Extended Essays against the assessment criteria for your session. Paste a draft of your Chemistry EE to receive criterion-by-criterion feedback that shows where you are losing marks, including discussion and evaluation (Criterion D) and the precision of your research question under Criterion A.
An AI check is outside help on your EE, so ask your supervisor before you use IBLens or any other tool, and tell them if you do.
Analyse your Chemistry EE with IBLens