Overview
A strong IB Chemistry IA research question is focused, measurable, and tied to chemistry theory. The reliable format is "How does [independent variable] affect [dependent variable] of [system]?" — one thing you change, one thing you measure, everything else held constant, generating numerical data you can process and evaluate. A vague prompt like "the chemistry of soap" fails because there is nothing to plot; "How does temperature affect the initial rate of the iodine clock reaction?" works because the variables, the maths and the safety are all under your control. Below are example research questions grouped by topic area, plus how to get from a rough interest to a question a moderator will reward.
This post is about choosing and phrasing the question. For the write-up itself — criteria, structure, uncertainties and evaluation — see the full IB Chemistry IA guide.
What the IB Chemistry IA is (briefly)
The Internal Assessment is an individual scientific investigation of roughly 10 hours, worth 20% of your final Chemistry grade, marked on five criteria: personal engagement, exploration, analysis, evaluation, and communication. You design it around a research question you choose — and everything downstream (your data, graphs and error analysis) depends on that question being answerable with the equipment and time you actually have. Topic choice is the highest-leverage decision in the whole IA.
What makes a strong research question
For the IB Diploma Programme, four things separate a top-band question from one that quietly caps your marks:
- Focused — one independent variable (IV) and one dependent variable (DV). Not "what affects reaction rate" (three variables at once) but "how does concentration affect rate."
- Measurable — the DV must give quantitative data (a volume, a mass, a temperature change, a voltage, a time), ideally across at least five values of the IV with repeats.
- Controlled — you can name and hold the other variables constant (temperature, volume, particle size, apparatus).
- Theory-linked — the trend should connect to syllabus chemistry: collision theory, bond enthalpies, Hess's law, Ka, standard electrode potentials. This is what lifts analysis and evaluation above "the graph went up."
If you can fill in this sentence, you have a workable question: "How does __ (IV, with units and range) affect __ (DV, measured how) of __ (specific system)?"
How to turn an interest into a research question
For the IB Diploma Programme, start from something you genuinely care about, then narrow relentlessly:
- Pick a context — food, sport, the environment, cleaning products, your own diet.
- Find a measurable property inside it — an enthalpy, a rate, a concentration, a voltage.
- Choose one variable to change and check you can control the rest.
- Pressure-test feasibility — do you have the reagents, the apparatus, and the time to run repeats safely?
Example: "I drink a lot of orange juice" → vitamin C is measurable by titration → does storage temperature change it? → "How does storage temperature affect the vitamin C concentration of orange juice, measured by titration against DCPIP?" That is a real IA.
Example research questions by area
For the IB Diploma Programme, each of these is phrased as a usable RQ. Adapt the specifics to your lab.
Rates of reaction
- How does temperature (10–60 °C) affect the initial rate of the iodine clock reaction? — clean DV (time to colour change → rate), textbook collision-theory link, easy repeats.
- How does the concentration of hydrogen peroxide affect its rate of decomposition catalysed by manganese(IV) oxide? — measure gas volume over time; strong for a rate-vs-concentration graph and reaction order.
- How does surface area of calcium carbonate (chips vs powder) affect its rate of reaction with hydrochloric acid? — mass loss on a balance; simple, reliable.
- How does temperature affect the rate of vitamin C degradation in fruit juice? — connects everyday chemistry to kinetics; titration gives the DV.
Why they work: rate is measurable several ways (gas volume, mass loss, time-to-endpoint), the IVs vary in controlled steps, and every trend maps to collision theory or activation energy.
Energetics
- How does carbon chain length affect the enthalpy of combustion of straight-chain alcohols (methanol to pentanol)? — spirit burner + calorimetry; a clear trend against relative molecular mass and bond enthalpies.
- How does the identity of the acid affect the enthalpy of neutralisation with sodium hydroxide? — compare strong vs weak acids; links to degree of dissociation.
- How does concentration affect the enthalpy change of dissolving a salt (e.g. ammonium nitrate)? — simple calorimetry with a lattice-energy discussion.
Why they work: calorimetry gives a numerical ΔH to compare against database values, and the discrepancy (heat loss, incomplete combustion) is rich material for evaluation.
Acids and bases
- How does the concentration of acetic acid vary between different brands of vinegar, determined by titration against standardised NaOH? — precise, quantitative, great for uncertainty analysis.
- How does citric acid content vary across citrus fruits (lemon, lime, orange, grapefruit)? — titration DV, relatable context.
- How does dilution affect the measured pH of a weak acid, and how does this compare to the theoretical value from Ka? — pairs experiment with calculation for a strong analysis mark.
Why they work: titrations produce highly repeatable data with small, quantifiable uncertainties — ideal for the analysis and evaluation criteria.
Electrochemistry
- How does electrolyte concentration affect the voltage of a zinc–copper voltaic cell? — voltmeter DV, ties to the Nernst relationship at a qualitative level.
- How does the choice of metal electrode affect the cell potential relative to a copper half-cell? — links directly to standard electrode potentials.
- How does current affect the mass of copper deposited during electrolysis of copper(II) sulfate? — mass DV, connects to Faraday's laws.
Why they work: voltage and deposited mass are direct numerical readings, and the theory (electrode potentials, Faraday's constant) gives you a predicted value to compare against.
Solubility and equilibrium
- How does temperature affect the solubility of potassium nitrate in water? — measure the saturation point on cooling; produces a clean solubility curve.
- How does temperature affect the position of an equilibrium such as the cobalt chloride colour change? — colorimetry gives a quantitative DV.
- How does common-ion addition affect the solubility of calcium hydroxide? — titration DV, direct link to the solubility product Ksp.
Why they work: solubility and equilibrium extent are measurable by titration or colorimetry, and both connect cleanly to Le Chatelier or Ksp.
Using secondary data or a database
Database (secondary-data) IAs are allowed and can score full marks — but only if you add a strong processing angle. Plotting numbers from a spreadsheet is not enough. You need a genuine research question, a justified selection of the data, and real chemical processing: calculating trends, testing a relationship against theory, propagating uncertainty from the source. A weak database IA describes; a strong one interrogates. Be as rigorous about your data source and its limitations as you would be about apparatus error in the lab.
Common mistakes when choosing a topic
This section covers Common mistakes when choosing a topic — what IB examiners reward most often in past papers and coursework.
- Too broad — "the chemistry of caffeine" is a topic, not a question. Narrow to one measurable relationship.
- Not measurable — if the DV is a colour you can only describe, or an effect with no number, you cannot graph or evaluate it.
- No clear IV/DV — changing several things at once makes the data uninterpretable.
- Unsafe — anything involving concentrated acids at high temperature, toxic gases, or reagents your school won't stock. If your teacher won't sign the safety form, it is not your IA.
- Done to death with no twist — the marble-chips-and-acid classic can still score well, but only if your control and analysis are genuinely careful. Add a specific, personal angle so your engagement mark is real.
How to refine your research question
For the IB Diploma Programme, once you have a draft, tighten it:
- Add ranges and units — "temperature" becomes "temperature from 20 °C to 70 °C in 10 °C steps."
- Name the system precisely — which acid, which brand, which concentration.
- State how the DV is measured — "by titration against DCPIP," "by gas volume over 120 s."
- Check the theory link — write one sentence predicting the trend from chemistry. If you can't, the question is too thin.
- Do a mini pilot — one rough run shows whether the effect is even detectable before you commit ten hours.
How MarkScheme helps
Draft your research question and background, then [get an answer marked](/mark) against IB assessment language to see whether your exploration and communication read at the level you want — while the question is still cheap to change. Pair that with the free [IB Chemistry SL course](/ib/courses/chemistry-sl) or [HL course](/ib/courses/chemistry-hl) to keep your theory link solid, and read [how to get a 7 in IB Chemistry](/blog/ib-chemistry-how-to-get-a-7) for the wider grade strategy.
Frequently asked questions
For the IB Diploma Programme, a single independent variable, a measurable quantitative dependent variable, controllable conditions, and a clear link to syllabus chemistry — phrased as "How does X affect Y of Z?" so the whole investigation has one clear focus.
What makes a good Chemistry IA research question?
Can I do a database IA in Chemistry?
Yes. Secondary-data IAs are permitted and can reach the top band, but they must have a real research question and substantial processing — trend analysis, comparison to theory, and uncertainty from the source — not just a plotted spreadsheet.
How many values of my variable should I test?
Aim for at least five values of the independent variable with repeats at each, so you can plot a meaningful trend and quantify reliability. Fewer than five makes a convincing graph hard to justify.
Is a titration or a rates experiment better for a high mark?
Neither is inherently better — both give clean numerical data. Titrations shine for precision and uncertainty analysis; rates experiments shine for theory links to collision theory. Choose the one you can control most carefully.
How do I know if my idea is safe enough?
If it needs concentrated corrosives at high temperature, toxic gases, or reagents your school does not stock, redesign it. Your teacher must approve the risk assessment — check with them before committing time.