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What this standard actually asks for

How this standard is assessed

AS91387 is internally assessed over several weeks: you develop a purpose, plan and trial a procedure, analyse a set of samples, process the data and write a report.
The criteria are unusually specific about what the report must contain, so plan the report before you plan the chemistry.

Grade	What you must do
Achieved	Explore a possible trend or pattern; develop and carry out a procedure; collect and record sufficient data; process it to reach a conclusion; report purpose, procedure, data summary and conclusion
Merit	Quality data — standardise your standard solution(s) and control significant variables; accurate processing to a valid conclusion; show the mathematical steps; procedure detailed enough to duplicate; conclusion linked to the purpose; explain how the procedure gave quality data
Excellence	Correct significant figures and units; justify the procedural steps in relation to the reactions and the samples; a comprehensive evaluation

Notice that Merit names standardising the standard solution explicitly. This is the most commonly skipped requirement at Level 3, exactly as it is at Level 2.

The purpose must be about how a quantity changes, not about what a quantity is.
The variable you change is your independent variable; the quantity you measure is the dependent variable.

Not acceptable	Acceptable
"How much vitamin C is in this juice?"	"How does the vitamin C content of juice change with days after opening?"
"Which brand of antacid neutralises most acid?"	"How does the neutralising capacity of an antacid change with the age of the tablet?"
"How much iron is in this supplement?"	"How does the iron(II) content of a supplement change with exposure to air?"
"Is this bore water safe?"	"How does chloride concentration change with distance inland from the coast?"

The NZQA clarification names two purposes to avoid specifically: consumer testing and comparing manufacturers. Both produce a list of numbers with nothing connecting them.

EN5 names two:

Technique	Best for	Watch out for
Titration — redox or back titration	anything that reacts stoichiometrically	a 1 : 1 acid–base is not suitable
Colorimetry	coloured species, low concentrations	needs a valid standard curve

A straight 1 : 1 acid–base titration will cap your grade. Use a redox titration (permanganate, iodine/thiosulfate, dichromate), a back titration, or colorimetry.

Titres of at least 5 mL. Below that, the fixed ±0.05 mL reading uncertainty becomes an unacceptably large percentage of the result. Aim for 15–25 mL.
For colorimetry, an appropriate standard curve range — your samples' absorbances must fall within the range covered by your standards, not beyond either end.

EN3 requires a logbook kept throughout the investigation, containing:
- the development of the purpose — including the ideas you rejected,
- the procedure as it evolved,
- the raw data, including the results that went wrong,
- the calculations.
The report is written from the logbook. Most of what earns Merit and Excellence — why you changed the dilution, what the trial showed, which run was anomalous — exists only in the logbook.

AS91387 is internally assessed over several weeks: you develop a purpose, plan and trial a procedure, analyse a set of samples, process the data and write a report.
The criteria are unusually specific about what the report must contain, so plan the report before you plan the chemistry.

Grade	What you must do
Achieved	Explore a possible trend or pattern; develop and carry out a procedure; collect and record sufficient data; process it to reach a conclusion; report purpose, procedure, data summary and conclusion
Merit	Quality data — standardise your standard solution(s) and control significant variables; accurate processing to a valid conclusion; show the mathematical steps; procedure detailed enough to duplicate; conclusion linked to the purpose; explain how the procedure gave quality data
Excellence	Correct significant figures and units; justify the procedural steps in relation to the reactions and the samples; a comprehensive evaluation

Notice that Merit names standardising the standard solution explicitly. This is the most commonly skipped requirement at Level 3, exactly as it is at Level 2.

The purpose must be about how a quantity changes, not about what a quantity is.
The variable you change is your independent variable; the quantity you measure is the dependent variable.

Not acceptable	Acceptable
"How much vitamin C is in this juice?"	"How does the vitamin C content of juice change with days after opening?"
"Which brand of antacid neutralises most acid?"	"How does the neutralising capacity of an antacid change with the age of the tablet?"
"How much iron is in this supplement?"	"How does the iron(II) content of a supplement change with exposure to air?"
"Is this bore water safe?"	"How does chloride concentration change with distance inland from the coast?"

The NZQA clarification names two purposes to avoid specifically: consumer testing and comparing manufacturers. Both produce a list of numbers with nothing connecting them.

EN5 names two:

Technique	Best for	Watch out for
Titration — redox or back titration	anything that reacts stoichiometrically	a 1 : 1 acid–base is not suitable
Colorimetry	coloured species, low concentrations	needs a valid standard curve

A straight 1 : 1 acid–base titration will cap your grade. Use a redox titration (permanganate, iodine/thiosulfate, dichromate), a back titration, or colorimetry.

Titres of at least 5 mL. Below that, the fixed ±0.05 mL reading uncertainty becomes an unacceptably large percentage of the result. Aim for 15–25 mL.
For colorimetry, an appropriate standard curve range — your samples' absorbances must fall within the range covered by your standards, not beyond either end.

EN3 requires a logbook kept throughout the investigation, containing:
- the development of the purpose — including the ideas you rejected,
- the procedure as it evolved,
- the raw data, including the results that went wrong,
- the calculations.
The report is written from the logbook. Most of what earns Merit and Excellence — why you changed the dilution, what the trial showed, which run was anomalous — exists only in the logbook.