MYP Chemistry: Designing a Chemistry Investigation (Criterion B)

Designing a chemistry investigation is Criterion B in MYP Sciences — the strand where you turn a scientific question into a testable plan. You explain the problem, write a hypothesis backed by scientific reasoning, identify variables, and describe a safe, ethical method for collecting reliable data.

Criterion B has four strands assessed together out of 8 marks: explaining the problem or question, formulating and explaining a testable hypothesis, explaining how variables will be manipulated and data collected, and designing a method that's safe, ethical, and environmentally sound.

A testable hypothesis predicts a relationship between two variables and explains that prediction using chemistry you already know — not just a guess. Top-band answers use the structure: "If [independent variable] changes, then [dependent variable] will [effect], because [scientific reasoning]."

The independent variable is the one you deliberately change; the dependent variable is what you measure as a result; controlled variables are everything else you keep constant so the test is fair. Mixing these up is the single most common reason students lose marks on strand iii of Criterion B.

A 7-8 needs all four strands explained in depth, not just stated: a clearly justified research question, a hypothesis with real scientific reasoning, variables identified with a logical method for controlling them, and a plan naming specific safety, ethical, and environmental considerations for your exact experiment.

The three mistakes I see most often: hypotheses that predict but never explain why, methods that name variables without saying how they'll be controlled, and generic safety notes like "wear goggles" instead of hazard-specific ones tied to the actual chemicals in your experiment.

There's no word count — length isn't the criterion, reasoning is. A strong research question is one clear sentence naming both variables; a strong hypothesis is one or two sentences with a "because" clause explaining the prediction using chemistry content you've actually studied.

Most IB Chemistry teachers expect at least three repeats per data point so you can calculate a mean and spot anomalies. Criterion B rewards you for explaining why repeats improve reliability, not just stating a number — five repeats is safer for fast or hard-to-time reactions.

Criterion B is marked out of 8 using four achievement level bands (1-2, 3-4, 5-6, 7-8), each describing how fully you explain the problem, hypothesis, variables, and method. According to the IB's MYP: From Principles into Practice guide, all four criteria (A-D) combine for a final 1-7 subject grade using standard MYP grade boundaries.

Criterion B (Inquiring and designing) is about planning the investigation before you touch any equipment — hypothesis, variables, method. Criterion C (Processing and evaluating) is about what happens after: analysing results, calculating uncertainty, and evaluating validity. You can't score well on C with a weak Criterion B plan.

No — most MYP Chemistry courses assess Criterion B two or three times a year, not every unit, since a full investigation design takes real class time to teach properly. Your teacher will tell you which practicals count as summative Criterion B tasks versus which are just formative practice.

Yes — Criterion B builds exactly the skills the DP Chemistry internal assessment demands: a focused research question, a justified method, and identified variables. Students who've practised this rigorously in MYP 4-5 generally find the DP IA's exploration and method sections far less daunting in Year 12.

Yes, noticeably — MYP 4-5 expects independent scientific reasoning behind every choice, not just correct steps. Where MYP 1-3 might accept "I will change the temperature," MYP 4-5 wants "because increasing temperature raises particle kinetic energy, increasing collision frequency and rate," referencing named chemistry content.

Past practical write-ups, a copy of the Sciences subject-specific guidance for command terms, and worked exemplar investigations marked at the correct achievement level all help. On revisionprep.com, the MYP Chemistry Revision Notes and Topical Worksheets include practice research questions and sample hypotheses to mark against real level descriptors.