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What the quantitative report has to contain

The shape of the work

The investigation runs over several weeks: you develop a purpose, plan and trial a procedure, analyse a set of samples, process the data and write a report.
What the report has to contain is unusually specific, so plan the report before you plan the chemistry.

What the report must contain

A complete report does all of the following. None of it is optional, and the list is worth checking off before you write.

A purpose naming a possible trend or pattern in the quantity of a substance.
A procedure you developed and carried out, reported in enough detail that someone else could duplicate it.
Quality data: the standard solution standardised, the significant variables controlled, and enough measurements to distinguish a trend from scatter.
The processing, with the mathematical steps visible — not just a table of answers — and with correct significant figures and units.
A conclusion that states the trend and answers the purpose in the same terms it was asked in.
A justification of each procedural step against the reactions occurring and the nature of the samples.
An evaluation of the reliability of the data, of how the data supports the conclusion, and of what the chemistry means beyond the experiment.
Notice where standardising the standard solution sits. It is the most commonly skipped step of the whole investigation, and it is not a refinement — the titrant's concentration multiplies into every result.

The trend-or-pattern requirement

The purpose must be about how a quantity changes across your samples, not about what a single quantity is.
The thing you vary 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?"

Two purposes are ruled out specifically: consumer testing and comparing manufacturers. A brand comparison is excluded because it is consumer testing, not because of the shape of its data.

A trend and a pattern are not the same thing

A trend comes from a continuous independent variable — one that takes any value along a scale.
- "How does chloride concentration change with distance inland from the coast?" Distance is continuous, so the result is a trend you can plot as a line and describe as rising, falling or levelling off.
A pattern comes from a discontinuous independent variable — a set of separate categories with no scale between them.
- "How does nitrate concentration differ between pasture, forestry and native bush catchments?" Land use is a category, not a number. The result is a pattern: an ordering of groups, with the differences between them either large enough to be real or not.
Both are valid investigations. Do not talk yourself out of a categorical design because it does not produce a line graph — a pattern across categories is as real a result as a trend along a scale.
The difference changes how you process and conclude:
- For a trend, plot the dependent variable against the independent variable and describe the shape of the relationship.
- For a pattern, take several samples within each category, compare the means, and check that the difference between categories is bigger than the spread inside one category. Without that check you cannot tell a pattern from scatter.

Choosing a technique

Two techniques carry the quantitative work:

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 does not work here. Its mole-ratio step does no work at all, so there is no stoichiometric reasoning to justify. Use a redox titration (permanganate, iodine/thiosulfate, dichromate), a back titration, or colorimetry.

The two technical minimums

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

The logbook

Keep a logbook 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 makes it a good report — why you changed the dilution, what the trial showed, which run was anomalous — exists only in the logbook.

What the quantitative report has to contain

Covers AS91387

The shape of the work

The investigation runs over several weeks: you develop a purpose, plan and trial a procedure, analyse a set of samples, process the data and write a report.
What the report has to contain is unusually specific, so plan the report before you plan the chemistry.

What the report must contain

A complete report does all of the following. None of it is optional, and the list is worth checking off before you write.

A purpose naming a possible trend or pattern in the quantity of a substance.
A procedure you developed and carried out, reported in enough detail that someone else could duplicate it.
Quality data: the standard solution standardised, the significant variables controlled, and enough measurements to distinguish a trend from scatter.
The processing, with the mathematical steps visible — not just a table of answers — and with correct significant figures and units.
A conclusion that states the trend and answers the purpose in the same terms it was asked in.
A justification of each procedural step against the reactions occurring and the nature of the samples.
An evaluation of the reliability of the data, of how the data supports the conclusion, and of what the chemistry means beyond the experiment.
Notice where standardising the standard solution sits. It is the most commonly skipped step of the whole investigation, and it is not a refinement — the titrant's concentration multiplies into every result.

The trend-or-pattern requirement

The purpose must be about how a quantity changes across your samples, not about what a single quantity is.
The thing you vary 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?"

Two purposes are ruled out specifically: consumer testing and comparing manufacturers. A brand comparison is excluded because it is consumer testing, not because of the shape of its data.

A trend and a pattern are not the same thing

A trend comes from a continuous independent variable — one that takes any value along a scale.
- "How does chloride concentration change with distance inland from the coast?" Distance is continuous, so the result is a trend you can plot as a line and describe as rising, falling or levelling off.
A pattern comes from a discontinuous independent variable — a set of separate categories with no scale between them.
- "How does nitrate concentration differ between pasture, forestry and native bush catchments?" Land use is a category, not a number. The result is a pattern: an ordering of groups, with the differences between them either large enough to be real or not.
Both are valid investigations. Do not talk yourself out of a categorical design because it does not produce a line graph — a pattern across categories is as real a result as a trend along a scale.
The difference changes how you process and conclude:
- For a trend, plot the dependent variable against the independent variable and describe the shape of the relationship.
- For a pattern, take several samples within each category, compare the means, and check that the difference between categories is bigger than the spread inside one category. Without that check you cannot tell a pattern from scatter.

Choosing a technique

Two techniques carry the quantitative work:

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 does not work here. Its mole-ratio step does no work at all, so there is no stoichiometric reasoning to justify. Use a redox titration (permanganate, iodine/thiosulfate, dichromate), a back titration, or colorimetry.

The two technical minimums

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

The logbook

Keep a logbook 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 makes it a good report — why you changed the dilution, what the trial showed, which run was anomalous — exists only in the logbook.