Every formal report in this course uses the same eight sections. Learn the shape once and it carries you through every science course after this one — and through anything you ever have to write where somebody needs to check your reasoning rather than take your word for it.
Some of the examples below come from investigations you have not run yet. They are here because this is the page you will come back to all semester, and it is more useful complete than it is convenient.
The sections
| Section | What belongs there | Common mistake |
|---|---|---|
| Question | What you set out to find out, in one sentence | Restating the title |
| Prediction | What you expect and the mechanism you expect it from | ”I think it will work” |
| Variables | Independent, dependent, and everything you held constant | Listing two and forgetting the third |
| Materials and procedure | Numbered steps, with quantities, concentrations, and the glassware named | Written as a story afterwards |
| Observations | Raw readings, tables, qualitative notes — no interpretation | Recording only the calculated answer |
| Analysis | One sample calculation in full, then the rest | Repeating the table in sentences |
| Conclusion | The answer, and the evidence that supports it | Claiming more than the data supports |
| Limitations | What the method could not settle, and which way each one pushed | A list of things you feel bad about |
Grade 10 merged the last two. This course separates them, because they do different jobs: the conclusion says what you found, and the limitations section says what your finding is worth. Marks live in both and they are not the same marks.
Predictions need a mechanism, and now a direction
A prediction without a “because” is a guess with a confident tone.
❌ We will not get all the product.
âś… We will recover less than the calculated mass because some of the precipitate stays on the filter paper and on the walls of the beaker, and neither of those ends up on the balance.
The second version can be wrong in a useful way. If you recover more than the calculated mass, the first version tells you nothing; the second tells you that something other than losses is in play, and sends you to look for water you did not dry off.
Where you can, put a number on it. “Somewhere in the eighties” is a real prediction and it is checkable. “It will be lower” is a direction, which is the minimum. “It might be different” is not a prediction at all.
Write the prediction before you measure
Not after, and not “roughly what I was expecting”. Record it, with its reasoning, in your Chemistry Journal before the first reading. That record is the only way to find out whether your reasoning about mechanism is improving, which is the actual skill this course is teaching.
Variables are yours now
Last year a procedure was handed to you and the variables came with it. This year you design the investigation, which means you decide what to change, what to measure, and what to hold still.
Name all three, and for the controlled variables say how you held each one — not “temperature was controlled”, but “all four trials were run in the same water bath, checked at 22 °C before each”. A controlled variable you did not actually control is a limitation, and it belongs in the last section rather than this one.
If you cannot name all three, you do not yet have an experiment. You have an activity.
Procedure: written so it can be repeated
Past tense, numbered, with quantities, concentrations, and the glassware named specifically. “25.0 mL of 0.100 mol/L sodium carbonate solution was delivered with a volumetric pipet”, not “some sodium carbonate was added”. A beaker, a graduated cylinder, and a pipet are three different claims about how well you know that volume — see Measuring Well.
The test is not whether it reads well. It is whether another group could follow it and get your result without asking you a single question.
Observations, and the sample calculation
Observations hold the numbers the instruments gave you, before any arithmetic, with units, in a table. State each instrument’s resolution once, at the top: balance to 0.01 g; burette read to two decimal places, good to about ±0.02 mL. That one line does a great deal of work later.
Analysis holds one calculation written out in full, with units carried through every line, followed by a table of the results of repeating it. Nobody wants to read the same arithmetic five times, and nobody can check any of it if you show none.
Three significant figures there, because the mass had three. If you are not sure why that is the rule, or why it would be a different rule if those quantities were being added, Significant Figures in Practice is the page.
Conclusions: answer, evidence, and whether the difference is real
Three moves, in order, and the third is the Grade 11 one.
The reaction produced 1.31 g of precipitate against a calculated maximum of 1.42 g, a percentage yield of 92%. This supports the prediction that the recovered mass would fall short of the calculated value.
The other two groups reported 90% and 94%. Weighing by difference on a balance reading to 0.01 g puts roughly ±0.02 g on each recovered mass, which is about ±2 percentage points on the yield, so all three results agree to within the precision of the measurement. There is one result here, measured three times, not three different results.
That second paragraph is where the marks are. It does not say the numbers “were close”. It says how close they had to be before closeness meant anything, and then checks.
Limitations: which way did each one push?
Naming a limitation is Grade 10. Saying what it did to your number is this course.
| Limitation | Direction it pushes | So your result is |
|---|---|---|
| Precipitate left on the filter paper and beaker walls | Recovered mass down | A floor — the true yield is higher |
| Precipitate not completely dried before weighing | Recovered mass up | Inflated, and this is how a yield above 100% happens |
| Reading the top of the meniscus rather than the bottom | Every volume recorded too large | Wrong in the same direction every time — systematic, so repeating will not help |
| Overshooting the endpoint of a titration | Titrant volume up | Concentration of the unknown calculated too high |
| A burette rinsed with water and not with the titrant | Titrant is diluted, so more is needed | Concentration of the unknown calculated too high |
Every row has a direction. That is not a coincidence — a limitation you cannot assign a direction to is usually one you have not thought about yet, and working out the direction is often what tells you how to fix it.
A limitation is not a blunder, and they get different treatment
A limitation would still be there if you ran the method perfectly: the resolution of the balance, solid you cannot get off the filter paper, a variable you had no way to control. It belongs in this section, and it earns marks.
A blunder is a mistake: you used the wrong solution, you misread 2.35 as 2.53, you knocked the flask. It belongs in your notes and in a repeated trial, not here. Listing “human error” as a limitation is claiming credit for the wrong thing — and it is the single most common sentence I strike out. See Mistakes Are Data for sorting one from the other.
Before you submit
- Prediction states a mechanism, has a direction, and was recorded first
- All three kinds of variable named, and controls say how
- Glassware named specifically wherever a volume was measured
- Every measurement carries a unit and the right number of significant figures
- Instrument resolutions stated once, near the data
- One sample calculation shown in full, with units on every line
- Conclusion answers the question using your own numbers
- Any comparison between numbers checked against the uncertainty
- Every limitation carries a direction
- One specific change you would make, not “be more careful”
Language: Writing About Chemistry. Assessment: How Marks Work.
Curriculum connection
A1.10
draw conclusions based on inquiry results and research findings, and justify their conclusions with reference to scientific knowledge
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A1.11
communicate ideas, plans, procedures, results, and conclusions orally, in writing, and/or in electronic presentations, using appropriate language and a variety of formats (e.g., data tables, laboratory reports, presentations, debates, simulations, models)
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