How to Write a Level 7 IB Chemistry IA: Scientific Investigation Guide

The IB Chemistry Internal Assessment (IA) is worth 20% of your final IB Chemistry grade, making it an important opportunity to earn marks outside your final exams.

But getting a high score isn't just about conducting a successful experiment. Your scientific investigation needs to demonstrate strong experimental design, accurate data analysis, scientific reasoning and critical evaluation.

So, what does a top-scoring IB Chemistry IA actually look like?

In this guide, we'll break down the IB Chemistry IA structure, marking criteria and worked examples to help you write a scientific investigation that targets the highest mark bands.

🎯 Want To Score Top Marks in IB Chemistry?

We've helped over 5000 students discover the power of KIS Personalised Tutoring - now it's your turn!

Start a Free Trial Lesson →

What Is the IB Chemistry Scientific Investigation?

The IB Chemistry IA is an independent scientific investigation in which you develop a research question, collect and analyse data, and present your findings in a written report.

Under the current IB Chemistry syllabus (first assessed in 2025), your investigation is assessed against four criteria:

Key things to know:

• Weighting: 20% of your final Chemistry grade.
• Word limit: 3,000 words.
• HL vs SL: Both levels use the same IA criteria.
• Investigation types: Laboratory experiments, simulations and database investigations are possible.

Your teacher marks your IA, which is then subject to external IB moderation.

Important: Your Chemistry IA is marked out of 24, not graded separately from 1–7. Achieving high marks can contribute towards a final grade of 7, but there is no single IA score that guarantees it.

1. How to Choose a Strong IB Chemistry IA Research Question

Your research question is the foundation of your entire investigation.

A strong question should be specific, measurable and achievable with the equipment and time available to you.

For example:

Weak research question:

"How does acid concentration affect reaction rate?"

This question is too vague. Which acid? Which chemical reaction? How will you measure the rate?

Stronger research question:

"How does hydrochloric acid concentration (0.50–2.50 mol/L) affect the average rate of hydrogen gas production when reacting with magnesium ribbon at 25°C?"

This is better because it identifies:

• Independent variable: Hydrochloric acid concentration.
• Dependent variable: Average rate of hydrogen gas production.
• Controlled variables: Temperature, magnesium mass and surface area, solution volume and measurement procedure.

It also allows you to explore collision theory and reaction kinetics.

IB Chemistry IA Research Question Examples

Need some inspiration? Here are a few investigation ideas:

1. Reaction kinetics: How does temperature affect the rate constant of a chosen chemical reaction?
2. Acid-base chemistry: How does temperature affect the pH of a buffer solution?
3. Electrochemistry: How does copper(II) ion concentration affect the potential of a copper concentration cell?
4. Energetics: How does alcohol chain length affect the experimentally determined molar enthalpy of combustion?
5. Analytical chemistry: How does storage temperature affect the vitamin C concentration of orange juice over time?

These are starting points. Each question needs a clearly defined method, suitable variable ranges and enough chemical depth to support a meaningful investigation.

Our tip: The best Chemistry IA topics aren't necessarily the most complicated. A relatively simple experiment with reliable measurements, strong calculations and thoughtful evaluation can be more successful than an ambitious experiment with unreliable data.

2. IB Chemistry IA Structure: How to Write Each Section

Although there is no mandatory report-heading structure, your IA should clearly address all four assessment criteria.

Let's walk through each criterion using our magnesium and hydrochloric acid investigation as an illustrative example.

Criterion 1: Research Design (6 Marks)

Your research design should explain what you're investigating, the chemistry behind it and how your experiment will produce sufficient data to answer your research question.

Include:

• A focused research question.
• Relevant chemical theory and balanced equations.
• Independent, dependent and controlled variables.
• A reproducible methodology with justified experimental choices.
• Relevant safety and environmental considerations.

Example — Chemical background

Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas, according to the equation:

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

According to collision theory, increasing the concentration of hydrochloric acid increases the frequency of collisions involving hydrogen ions at the magnesium surface. This is expected to increase the rate of reaction, provided other factors remain constant.

Notice how this explanation connects the independent variable to the underlying chemistry rather than simply predicting that the reaction will become faster.

Example — Methodology

For our investigation, we could:

1. Prepare hydrochloric acid solutions with concentrations of 0.50, 1.00, 1.50, 2.00 and 2.50 mol/L.
2. Add an equal volume of each solution to a suitable reaction flask connected to a gas syringe.
3. React each solution with the same measured mass and surface area of magnesium ribbon.
4. Record the time required to collect 20.0 mL of hydrogen gas.
5. Repeat each concentration five times and calculate the mean reaction time.

A strong methodology would also explain how temperature is maintained, how gas loss at the start is minimised, how measurements are timed and why the selected concentration range and number of replicates are appropriate.

Safety is particularly important because hydrochloric acid is hazardous and hydrogen gas is flammable. This investigation should only be carried out under appropriate laboratory supervision and risk controls.

🔥 Key takeaway: Don't just describe your procedure. Explain why each important experimental choice helps produce reliable, relevant data.

Criterion 2: Data Analysis (6 Marks)

This is where Chemistry students can gain valuable marks by demonstrating accurate calculations and a strong understanding of uncertainty.

Your data analysis should include:

• Clearly labelled raw and processed data tables.
• Appropriate calculations with correct units and significant figures.
• Graphs showing relevant relationships.
• Analysis of measurement uncertainties.
• Interpretation of trends and anomalies.

Let's imagine we obtained the following data.

Example — Processed results (illustrative data only)

For this investigation, we can calculate the average rate of hydrogen gas production using:

Average rate (mL/s) = Volume of hydrogen produced (mL) ÷ Time taken (s)

For the 1.00 mol/L hydrochloric acid solution:

Average rate = 20.0 ÷ 36.0 = 0.556 mL/s

This gives us a quantitative measure of how quickly hydrogen gas was produced over the measured interval.

However, calculations alone aren't enough!

To strengthen your analysis, you should also:

• Calculate the mean and standard deviation of your replicate measurements.
• Plot average reaction rate against acid concentration.
• Include appropriate error bars and explain what they represent.
• Account for gas-syringe, timing and concentration uncertainties.
• Discuss whether the relationship is linear or nonlinear and what this suggests about the reaction.

Remember that the calculated value represents the average gas production rate over the measured interval, not necessarily the initial reaction rate.

Our tip: One of the biggest differences between an average and excellent Chemistry IA is how well the student handles uncertainty. Don't simply list equipment uncertainties. Explain how they affect your calculations and the reliability of your conclusions.

Criterion 3: Conclusion (6 Marks)

Your conclusion should directly answer your research question using quantitative evidence, while explaining your findings through accepted chemical theory.

Compare these two responses.

Weak conclusion:

Increasing hydrochloric acid concentration increased the reaction rate. This supports collision theory, so the hypothesis was correct.

This identifies the trend, but doesn't provide much supporting evidence or consider the limitations of the findings.

Stronger conclusion example:

The results indicate that increasing hydrochloric acid concentration increased the average rate of hydrogen gas production. Between 0.50 and 2.50 mol/L, the average rate increased from 0.303 mL/s to 1.176 mL/s, representing approximately a 3.9-fold increase. This trend is consistent with collision theory, as higher acid concentrations increase the frequency of collisions between reacting particles. However, the rate did not increase in direct proportion to concentration across the entire range, suggesting that other factors, such as changes in the exposed magnesium surface, may have influenced the results.

Why is this stronger?

It directly answers the research question, uses numerical evidence, connects the findings to chemical theory and acknowledges that the results may have more than one explanation.

For a top-band conclusion, you should also discuss the strength of the evidence, measurement uncertainties and how your findings compare with relevant scientific literature.

Key takeaway: Your conclusion should explain not just what happened, but why it happened and how confidently your results support your interpretation.

Criterion 4: Evaluation (6 Marks)

Your evaluation demonstrates whether you understand the limitations of your investigation.

Simply writing "human error affected the results" is not enough!

You need to identify specific methodological weaknesses, explain their effects and propose realistic improvements.

Example — Chemistry IA Evaluation Table

Now compare these two evaluation responses.

Weak evaluation:

Some hydrogen gas may have escaped, making the results inaccurate. Better equipment should be used next time.

Stronger evaluation example:

A potential systematic limitation was the loss of hydrogen gas during the initial sealing of the reaction vessel. This would cause the recorded gas volume to underestimate the amount produced, particularly during faster reactions at higher acid concentrations. As a result, the calculated average reaction rates may have been underestimated. Initiating the reaction only after the apparatus is sealed would minimise this source of error and improve the validity of the concentration comparison.

The second response explains the cause, consequence and a specific improvement.

That's exactly the kind of reasoning your evaluation should demonstrate.

3. Common IB Chemistry IA Mistakes That Cost Students Marks

Even a promising investigation can lose marks through avoidable mistakes.

1. Choosing an overly complicated topic

Make sure you understand the chemistry behind your investigation. Complex experiments are not automatically rewarded with higher marks.

2. Poor control of variables

Factors such as temperature, concentration, reaction time and surface area can significantly affect results. Clearly explain how relevant variables were controlled.

3. Ignoring measurement uncertainty

Using precise equipment doesn't eliminate uncertainty. Consider the limitations of your measurements and how these affect calculated values.

4. Presenting graphs without interpreting them

A graph isn't an analysis on its own. Explain gradients, trends, anomalies and their chemical significance.

5. Making unsupported conclusions

Always support your findings with quantitative evidence and relevant chemical principles. Avoid claiming your hypothesis has been proven.

6. Writing generic evaluations

Focus on specific weaknesses that actually matter to your experiment, rather than listing every imaginable source of error.

4. Final IB Chemistry IA Checklist

Before submitting your Chemistry scientific investigation, check that you can confidently tick off the following:

• My research question is focused, measurable and chemically relevant.
• My background theory explains the chemistry behind the investigation.
• My independent, dependent and controlled variables are clearly identified.
• My methodology is detailed, justified and reproducible.
• My results include appropriate raw data and processed calculations.
• My graphs have labelled axes, units and relevant uncertainty information.
• I've interpreted the trends and considered anomalous results.
• My conclusion answers the research question using quantitative evidence.
• My evaluation explains meaningful limitations and specific improvements.
• My sources are appropriately referenced.
• My report follows the 3,000-word limit and current IB criteria.

Need Help With Your IB Chemistry IA?

Struggling to choose a research question? Not sure how to analyse your results or improve your evaluation?

At KIS Academics, our experienced IB Chemistry HL tutors and IB Chemistry SL tutors can help you build confidence in your chemistry knowledge, understand the IA requirements and develop the skills to complete your own scientific investigation.

Find your perfect IB Chemistry tutor at KIS Academics and take the next step towards your academic goals!

Frequently Asked Questions About the IB Chemistry IA

Want more personalised guidance to help support you through your studies? Find a KIS Academics tutor today!

What Our Students & Parents Say

600+ Five-Star reviews across all our tutoring programs — hear why below !👇