IB Chemistry IA Research Question and Pilot: Make the Study Testable

One of the most expensive mistakes in an IB Chemistry IA—the Scientific Investigation in the current course—is collecting full data too early. A student finds an interesting topic, writes a broad question and only then discovers that the change is too small, the reaction too fast, the instrument insufficiently sensitive or a supposed control variable moves with another factor.

Use this order: interest → filtered research question → pilot → decision → full data collection. A pilot is not a miniature final experiment. It is inexpensive information about which parts of the design work.

Eight filters for a viable research question

Revisit the filters with the initial idea, the method outline and the completed pilot. Attach a record or measurement to each decision; an unresolved answer identifies the next specific task.

From interest to testable wording

Too broad: “The effect of temperature on reaction rate.”

The system, measurement method, range and rate quantity are all undefined.

Better, but incomplete: “How does temperature affect the rate of reaction between sodium thiosulfate and hydrochloric acid?”

There is now a system, but “rate” remains unoperationalised and the range is open.

Testable starting point: “How does temperature from 20.0 to 50.0 °C affect the reciprocal of the time required to reach a defined optical threshold in the reaction of sodium thiosulfate and hydrochloric acid of specified concentrations, while total volume and initial reactant concentrations are held constant?”

This is not automatically final. The pilot must test whether the optical endpoint is reproducible, the 20–50 °C range is usable and the reciprocal-time analysis is defensible.

Good wording is not good because it is long. It is good because it exposes the major method and analysis decisions.

Here 1/t is a rate proxy derived from time to a fixed optical threshold, with unit s⁻¹, not automatically an initial reaction rate. The signal can depend on sulfur-particle formation, mixing and geometry. Even with fixed threshold, concentrations and volume, check that the endpoint represents comparable progress and measure actual solution temperature.

What a pilot must find out

A useful pilot is not a full data set. A few extreme and middle points with limited repetition can test five decisions.

• Range: is there a measurable change between the lowest and highest values?
• Resolution: is the signal between neighbouring levels larger than measurement scatter?
• Timing: is there enough time for reliable readings, or is the investigation too slow for the available session?
• Control: can temperature, concentration, mixing, pH or another condition actually remain stable?
• Data path: will the derived quantity and graph from the raw measurements answer the question?

Suppose that in a 20–50 °C pilot the difference between 20 and 25 °C is barely larger than scatter, while at 50 °C the reaction has already advanced substantially before timing can begin reliably. Do not hide these as “bad data”. They reveal that the method provides unequal information quality at the two ends of its range.

A defensible response might be to use 25–45 °C, reduce intervals where the response changes quickly, replace a subjective visual endpoint with an automated light sensor, or add repeats where signal and scatter are similar. The right decision depends on available equipment and the chemical question.

Do not change everything at once. If the pilot leads to a new range, concentration, endpoint and instrument, run a short second pilot; otherwise the new combination remains untested. Record the date and reason for each change, then apply the approved method consistently during full data collection.

Preserve pilot data even if they do not enter the final analysis. The notes document how range and repeat count were chosen and later support a specific evaluation. Do not automatically combine pilot and final data when the method changed materially between them.

Five red flags

1. The question contains no numerical range. A major method decision is probably still unresolved.
2. The dependent variable is “reaction”, “colour” or “effect”. It is unclear which measurement will become data.
3. Control variables appear only as a list. There is no plan for how, or to what precision, they remain constant.
4. The pilot is expected to look “good”. Its purpose is not to confirm a hypothesis; it is to find weaknesses in the method.
5. Analysis will be chosen later. If there is no visible route from data to answer, extensive measurement may produce little evidence.

Also stop if the plan assumes a hazardous condition, equipment that cannot be authorised or precision beyond the instrument available in school.

One-page decision sheet before full data collection

Use the worksheet to compare the question, measurement plan and pilot evidence. Short entries fit a compact print layout; longer text may require additional pages. Entries remain only on this open page.

Record whether to keep the plan, change and retest it, or redesign it. Discuss the decision with your supervisor; filling the sheet does not substitute for institutional approval.

Before full collection, state which pattern would strengthen or weaken your expectation. This is a planned interpretation rule, not an invented result. If the data show another pattern, analyse that pattern.

Return to the Scientific Investigation guide for the complete process. Research decisions, analysis and submitted writing must remain your own. Clearly acknowledge any permitted quoted material or assistance and follow the school’s current integrity rules.