Queensland's senior sciences (Chemistry, Physics, Biology) all share the same assessment skeleton: a data test worth 10%, a Student Experiment worth 20%, a Research Investigation worth 20%, and the external exam at 50%. Which means two written investigations decide 40% of your result, and they are completed and locked in long before exam block.
Students consistently underestimate both tasks, partly because they look like "assignments" rather than exams, and partly because the two get blurred together. They are very different tasks.
IA2: the Student Experiment
The Student Experiment asks you to take an experiment you have met in class and modify it, then carry out your modified methodology and collect primary data: your own measurements, from your own hands.
The marks are not really in the lab work. They are in the reasoning around it:
- The rationale. Why this modification? A strong report explains what the change is designed to reveal and connects it to the unit's subject matter. "We changed the temperature because it seemed interesting" is a rationale-shaped hole.
- Justified modifications. Changes to the method need reasons tied to validity or reliability, not novelty.
- Uncertainty and error, treated honestly. Every measurement has limits. Reports that quantify uncertainty, discuss how it propagates, and connect it to the confidence of the conclusion sit in the top band. Reports that end with "human error may have occurred" do not.
- A conclusion the data can actually carry. The claim you make at the end must be sized to the evidence you collected, no bigger.
IA3: the Research Investigation
The Research Investigation flips the direction: no lab, no primary data. You take a claim, sharpen it into a focused research question, and evaluate it using secondary evidence: published data and scientific sources you gather and analyse.
Different task, different failure modes:
- An unfocused question. "Are batteries bad for the environment?" cannot be answered in a report. The question must be narrow enough that specific published evidence bears on it directly.
- Sources collected, not interrogated. The task is evaluation, not summary. Top responses weigh the quality of the evidence: sample sizes, methodology, agreement between independent sources.
- The claim disappears. Every section should be visibly in service of the verdict on the claim. Reports that wander into general background lose the thread and the marks.
What markers reward in both
Across both IAs, the same spine appears in every top-band report: a clear line of reasoning from question to conclusion, choices that are justified rather than asserted, and limitations acknowledged with their consequences spelled out. Scientific writing is argument, not decoration; the students who internalise that early tend to find the external exam's short-response reasoning easier too.
Next steps
This is exactly the territory where experienced eyes matter: a rationale that sounds fine to you can have a hole a marker will find in ten seconds. In Dr Lee's Chemistry class, investigation planning and drafting are worked through as part of the program, and our high school group tutoring supports the same tasks in Physics and Biology.
If an IA2 or IA3 is coming up this term, bring the task sheet: enrol here or ask at either campus.
Written by the tutors and teachers at Lee Excellence Education. Assessment weightings per QCAA senior science syllabuses as of mid-2026; your school's task sheets are authoritative on scope and dates.