QCE Chemistry IA2 Student Experiment: 2026 guide

What IA2 is

IA2 is the Student Experiment, a QCAA-mandated internal assessment in Unit 3 (continuing into early Unit 4). Students modify or extend an existing chemistry investigation, conduct it, analyse the data, and report.

The deliverable is a scientific report of up to 10 pages including diagrams. Worth 20 percent of the subject result, the largest of the three internal assessments.

Assessment criteria

QCAA's four IA2 criteria:

1. Research and Planning. Quality of the research question, hypothesis, methodology, identification of variables, justification of choices.
2. Analysis of Evidence. Quality of data collection, tabulation, processing, graphing, uncertainty.
3. Interpretation and Evaluation. Quality of analysis, conclusion, evaluation of methodology, limitations, suggestions for improvement.
4. Communication. Scientific writing, structure, referencing.

Research question construction

A strong research question is specific and testable.

Components:

• Independent variable (what you vary).
• Dependent variable (what you measure).
• Range of values.
• Controlled variables (what you keep constant).
• Conditions (temperature, environment).

Example (rate). "How does the concentration of HCl (0.05, 0.10, 0.20, 0.30, 0.50 M) affect the initial rate of reaction with excess CaCO3 (1.00 g, 2 mm particles) at 25 degrees C, measured by mass loss?"

Example (equilibrium). "How does temperature (15, 25, 35, 45, 55 degrees C) affect the position of equilibrium of the iron(III) thiocyanate complex, measured by absorbance at 450 nm?"

Example (acid-base). "How does the structure of three organic acids (methanoic, ethanoic, propanoic) affect their dissociation constant Ka at 25 degrees C, measured by titration with 0.100 M NaOH?"

Methodology

A complete methodology includes:

1. Apparatus and reagents with quantities and uncertainties (50 mL volumetric flask plus or minus 0.05 mL).
2. Procedure as numbered steps reproducible by another student.
3. Risk assessment (hazards, controls).
4. Identification and control of variables.
5. Sample size: minimum 5 trials per condition; minimum 5 conditions.

Controls. Match temperature, particle size, reaction volume across all trials. Use the same brand of reagent. Calibrate instruments.

Data collection

Tabulate raw data immediately with units, uncertainties, and sig fig consistent with instrument precision.

Repeat each measurement. Three replicates minimum per condition; five preferred. Reject outliers using the Q-test or by inspection (cite reasoning).

Process data. Calculate means and standard deviations. Derive quantities (rate from mass-time, Kc from equilibrium concentrations, Ka from titration data).

Graphing and regression

A graph should have:

• Title.
• Axis labels with units.
• Appropriate scale, gridlines.
• Data points with uncertainty bars.
• Line of best fit (or curve as warranted).
• Gradient and intercept with units.

Linear regression. Report slope, intercept, R squared. Slope often has chemical meaning (rate constant, Ka).

Non-linear data may need transformation. Rate versus 1/T gives the Arrhenius plot ($\ln k$ versus $1/T$).

Uncertainty analysis

QCAA expects propagation of uncertainty.

Rules:

• Absolute uncertainty for addition or subtraction.
• Percentage uncertainty for multiplication or division.
• Quote final answer with the same sig fig as the smallest sig fig in input.

Report each measurement's uncertainty from instrument precision (half the smallest division for analog, instrument spec for digital).

Interpretation and evaluation

Interpretation. State the trend with specific numbers: "Initial rate increased from $2.4 \times 10^{-3}$ to $1.9 \times 10^{-2}$ mol/L/s as HCl concentration increased from 0.05 to 0.50 M, an approximately linear relationship suggesting first order in [HCl]."

Conclusion. Answer the research question. State the relationship and the chemistry that explains it.

Evaluation. Identify limitations of the method. Quantify their impact where possible. Suggest specific improvements: "The mass-loss method underestimates rate by not capturing CO2 dissolved in the solution; an inverted-cylinder gas collection apparatus would capture this and improve accuracy."

Compare with theoretical or accepted values where available. Calculate percentage error and discuss its sources.

Communication

QCAA marks scientific writing. Use:

• Third-person passive (in formal writing).
• Past tense for what was done.
• Present tense for general principles.
• Numbered sections (Introduction, Methodology, Results, Discussion, Conclusion).
• Captions on figures and tables.
• IUPAC nomenclature consistently.

Reference scientifically: APA or QCAA-prescribed style. Cite the source of any non-trivial method or value.

Common pitfalls

Research question too broad. "How does temperature affect the iron(III) thiocyanate reaction" is too broad; specify a range, a measurement method, and a condition.

Insufficient replicates. Three is the QCAA minimum; five is more defensible.

Methodology under-controlled. List every variable and how it is held constant.

Inadequate uncertainty analysis. Quote uncertainties on every measurement and propagate.

Conclusion divorced from data. The conclusion must cite specific numerical findings and link them to the research question.

Discussion limited to listing errors. Evaluate their direction and magnitude. Suggest specific improvements.

Timeline

Week -8 (start of IA2 period). Identify topic, draft research question with teacher feedback.

Week -7. Finalise research question. Begin methodology draft.

Weeks -6 to -4. Conduct experiments. Refine method based on pilot results.

Weeks -3 to -2. Complete data collection and processing. Begin discussion.

Week -1. Draft full report. Get teacher draft-feedback.

Submission week. Polish, proofread, submit.

In one sentence

QCE Chemistry IA2 rewards a tightly scoped research question, a reproducible methodology with at least five conditions and five replicates, rigorous data processing with uncertainty propagation and graphical regression, and an evaluation that quantifies error and proposes specific improvements.