How to write the IB Chemistry IA

The Chemistry IA is the one piece of coursework your Chemistry grade is marked on internally — worth 20% of your final grade at both SL and HL. Most students lose marks not because they can't do chemistry, but because they pick a weak question or never learn what each marking criterion actually rewards. This guide walks you through the whole thing: what the IA is, how it's marked, exactly how to write each part, and what separates a top-band investigation from an average one.

The IB Chemistry IA at a glance

Under the current syllabus (first assessment 2025) the Chemistry IA is called the Scientific Investigation: a single, focused, individual investigation reported concisely — typically 6–12 pages within the 3,000-word guideline. It is marked out of 24 across four equally weighted criteria, and the same criteria are used for Biology, Physics and Environmental Systems & Societies. There is no separate mark for "personal engagement" any more — your engagement should show through the relevance and ownership of your investigation.

How the Chemistry IA is marked: the four criteria

Every mark comes from one of these four criteria, each worth 6. Write your IA criterion by criterion and check what each rewards:

How to write a Chemistry IA, step by step

1. Choose a topic with a real chemical reaction. A purely physical change is not a valid Chemistry IA. Pick one variable you can change over a range and one you can measure.
2. Write a focused research question. "How does [independent variable, range + units] affect [dependent variable, how measured]?" — then ground it in the background chemistry.
3. Identify and control your variables. Name at least three control variables and explain, in prose, how each is held constant and how it would distort the result if it drifted.
4. Write a referenced risk assessment. Assess every chemical and procedure with a real hazard, a control measure and a source.
5. Develop the method through preliminary trials. Use trials to fix concentrations, ranges and timings; report what you changed and why.
6. Collect enough raw data. At least five values of the independent variable across a sensible range, each repeated at least three times, recorded with units and uncertainties.
7. Process the data with uncertainty. Calculate means, then propagate absolute and percentage uncertainty through every step (add absolute uncertainties when adding/subtracting; add percentage uncertainties when multiplying/dividing).
8. Plot a graph with error bars and a gradient. Add error bars, a best-fit line and maximum/minimum gradients so the uncertainty in the gradient is quantified.
9. Write a justified conclusion. Answer the question with the trend and gradient, then compare to a literature value with a percentage difference.
10. Evaluate honestly. Weigh limitations by impact, name the biggest error, and propose specific improvements and an extension.

Chemistry IA structure: what goes in each section

There is no single mandated layout, but the clearest structure that maps onto the criteria is:

• Research question & background — the question, the chemistry behind it, and why it is worth investigating.
• Variables — independent (range + units), dependent (how measured), and controlled (in prose).
• Risk assessment & ethics — hazards, controls, environmental disposal, referenced.
• Apparatus & method — equipment with uncertainties, and a reproducible procedure.
• Raw data — a clear table with units and uncertainties, plus qualitative observations.
• Data processing — sample calculations with uncertainty propagation.
• Graph — processed data with error bars, best-fit line and gradients.
• Conclusion — answer, justification, comparison to literature.
• Evaluation — limitations by impact, improvements, extension.
• References — a consistent citation style throughout.

What a strong vs weak Chemistry IA looks like

The fastest way to lift your marks is to see the difference. Here is the same work done two ways.

The research question

Data processing

Evaluation

Common mistakes that cost marks

• No real chemical reaction. A physical change (e.g. dissolving, evaporation alone) is not a valid Chemistry IA.
• Too narrow a range. Five points crammed into a small range hide the trend — spread them out.
• No uncertainty. Raw and processed data without absolute and percentage uncertainty caps Data analysis.
• Graph with no error bars or gradients. The gradient and its uncertainty are where the marks are.
• No literature comparison. A conclusion that never compares to an accepted value can't reach the top band.
• "Human error." Examiners read this as "I didn't analyse my method." Always name a specific, real weakness.
• Going over 3,000 words. Examiners stop reading at the limit — be concise.

Chemistry IA — frequently asked questions

Guidance written by experienced IB examiners and aligned to the current Chemistry guide (first assessment 2025). Not affiliated with or endorsed by the International Baccalaureate Organization.