Cover teacher — you need no subject knowledge
Print: this sheet and the stimulus sheet "Raw results: marble chips and hydrochloric acid", one of each per pupil. No practical work happens in this lesson and no chemicals are needed — the results were collected last lesson and are printed on the stimulus sheet. If computers are available pupils type the report; if not, they write it on lined paper using the same headings. A calculator each is useful.
Run: 5 min read the raw results and spot the odd value · 10 min process the results table on this sheet · 25 min write the report under the six headings · 8 min evaluation paragraph · 2 min check the formatting checklist at the bottom.
Collect: this sheet with the processed table filled in, plus the report (printed or handwritten). You do not need to mark the chemistry — the marks are for the structure, the processing and the evaluation.
What you are doing
Another class collected results for the reaction between marble chips and hydrochloric acid but never wrote them up. You are going to process their raw times, work out a rate for each concentration, and produce a properly formatted investigation report with the six standard headings, a results table and a labelled graph. One of the fifteen raw readings is anomalous — find it, exclude it from your mean, and say why you excluded it.
Step by step
- 5 min — Read Table 1 on the stimulus sheet and the lab book notes underneath it. Ring the one reading that does not belong with its repeats.
- 10 min — Complete the processed results table below. Mean time to 1 decimal place; rate = 20 ÷ mean time, to 3 decimal places.
- 25 min — Write the report under the six headings listed below. Use the planning grid to get the variables right before you start.
- 8 min — Draw or insert the graph of rate against concentration, then write the evaluation paragraph.
- 2 min — Work through the formatting checklist and tick each line you can honestly tick.
Processed results
| Concentration (mol/dm³) |
Readings I used (s) |
Any reading excluded, and why |
Mean time (s) |
Rate = 20 ÷ mean time (cm³/s) |
| 0.5 | | | | |
|---|
| 1.0 | | | | |
|---|
| 1.5 | | | | |
|---|
| 2.0 | | | | |
|---|
| 2.5 | | | | |
|---|
In a spreadsheet, the mean of three repeats in cells B2, C2 and D2 is =AVERAGE(B2:D2). To exclude one repeat, average only the cells you trust, for example =AVERAGE(B5:C5). The rate is then =ROUND(20/E5,3).
Planning grid for the report
| Independent variable (what was changed) | |
|---|
| Dependent variable (what was measured) | |
|---|
| Two control variables (kept the same) | |
|---|
| My hypothesis, and the reason for it | |
|---|
| What the graph shape tells me | |
|---|
| One improvement I would make to the method | |
|---|
The six headings your report must use
- Aim — one sentence, naming both variables.
- Hypothesis — what you predict and why.
- Variables — independent, dependent, controlled.
- Method — numbered steps, past tense, no "you".
- Results — the processed table with a caption, then the graph with a caption.
- Conclusion and evaluation — answer the aim using your numbers, then judge the quality of the evidence.
Draw your graph here
Rate (cm³/s) up the side, concentration (mol/dm³) along the bottom. Plot the five points, then draw a single straight line of best fit — do not join the dots one by one.
Conclusion and evaluation
Success criteria
- My report uses all six headings, formatted as headings rather than just bold text in a paragraph.
- My results table has a caption, a header row and units in the column headings, not in every cell.
- My graph is captioned "Figure 1", has labelled axes with units, and is referred to by name in my writing.
- I processed the raw data myself: means to 1 decimal place, rates to 3, with the anomaly excluded and explained.
- My conclusion answers the aim using specific values, and my evaluation judges repeatability rather than saying "it went well".
Formatting checklist
- Heading styles used (Heading 1 for the title, Heading 2 for each section) so a contents list could be generated automatically.
- Spell check set to English (UK). Check that "metre", "litre" and "analyse" are not corrected to American spellings.
- Table and figure captions numbered in order, and every figure mentioned in the text.
- Your name, class and the date in the header or footer, and page numbers if the report runs to more than one page.
If you finish early
- Divide each rate by its concentration. The five answers are all close to the same number — what does that tell you about the relationship?
- Write the method for the repeat you would run to replace the anomalous reading, including the one thing you would do differently.
- The gas syringe is marked every 1 cm³ and the class could only react to about half a second. Work out which of those two limits matters more at 2.5 mol/dm³, where the whole run lasted 20 seconds.