MYP Chemistry: Evaluating a Chemistry Experiment

Evaluation asks you to judge your own method critically, not just describe what happened — a different skill from writing a conclusion. Most students I teach can say whether their hypothesis was supported but freeze when asked to weigh up reliability, validity and realistic improvements together, tied to their actual data.

Criterion C — Processing and evaluating — is one of four MYP Sciences criteria, marked out of 8, and evaluation is its final strand. It asks you to judge the validity of your hypothesis and your method, then explain specific, realistic improvements — not just "use better equipment".

A conclusion states what your results show and whether they support your hypothesis, using actual numbers. An evaluation goes further — it critiques how reliable and valid that method was, names specific weaknesses in your procedure, and proposes concrete changes you'd make if you repeated the experiment.

Accuracy is how close a result sits to the true or literature value; precision is how consistent repeated readings are with each other. Reliability means your method would give similar results if repeated; validity means the experiment actually tests what it claims to. Mixing these up costs marks every year.

Start by judging your hypothesis against the actual data, then assess the method's reliability and validity, name specific limitations tied to your results, and finish with targeted improvements. A strong evaluation always references numbers from your own experiment — never a generic line like "human error occurred".

Look at your raw data first — where do the anomalies or biggest deviations from the literature value sit? Trace each one back to a specific step: was it a timing issue, a poorly calibrated instrument, or an uncontrolled variable? A genuine limitation names the exact step, not "the equipment wasn't good enough".

Match every improvement to a limitation you've already identified — vague fixes like "repeat the experiment more times" rarely earn top marks alone. Instead, name the specific change: use a data logger instead of a stopwatch, control room temperature, or swap a measuring cylinder for a burette to reduce volume error.

A systematic error shifts every reading in the same direction, usually from uncalibrated equipment, while a random error causes unpredictable scatter around the true value, often from reaction time or reading a scale. Naming which type affected your result — and why — shows you actually understand your own data.

Criterion C is marked out of 8 across four bands, and the top band (7–8) specifically requires you to evaluate the validity of both your method and hypothesis, then explain detailed, realistic improvements. Landing in the 5–6 band usually means your evaluation is present but not specific enough to your own data.

Criterion C — Processing and evaluating — has five strands covering data presentation, interpretation and evaluation, and teachers award a single best-fit level from 0 to 8 using task-specific clarifications written for each investigation. Schools then combine this with Criteria A, B and D to calculate your final 1–7 subject grade.

Good results don't automatically produce a good evaluation — Criterion C rewards how well you critique the method itself, not whether your hypothesis was confirmed. I've marked investigations with near-perfect data that scored low here simply because the student never questioned reliability or named a genuine limitation.

Yes — the on-screen MYP Sciences eAssessment includes scenario-based questions giving you data from an unfamiliar experiment and asking you to evaluate its method, reliability or validity, so this isn't only a coursework skill. Practising past on-screen exam-style questions is the fastest way to build this before exam day.

MYP evaluation skills map directly onto DP Chemistry's internal assessment and data-based exam questions, where you're expected to discuss systematic and random error, propose improvements and judge conclusion validity independently. Students who master Criterion C in MYP 4-5 usually find those DP questions far less daunting.

The most useful thing isn't checking the chemistry — it's asking questions that force specificity: "Which exact reading was anomalous?" or "What would you actually change, and why?" A vague answer means the evaluation isn't finished yet, whatever level it currently has pencilled in.

Yes — a reliable evaluation template covers four moves: judge the hypothesis, judge the method's reliability and validity, name specific limitations, then propose targeted improvements, each tied to actual data. Revision Notes and Topical Worksheets on revisionprep.com walk through this structure using real MYP-style investigations rather than generic checklists.