Writing Results and Data Visualization
Week 8 · 2105620 Research Communication Skills for Chemical Engineers · 09:00–12:00
8 October 2026
Is conversion enough?
Write one sentence, then discuss: what other measurement would you want?
The reaction case
Research question: How do conversion of A and selectivity to B change with temperature at a residence time of 2.0 s?
- A forms desired product B and by-products.
- Test 300–375 °C; assume other conditions are fixed.
- All values are synthetic teaching data.
Evidence for the first sentence
| Temperature (°C) | Conversion (%) | Selectivity to B (%) |
|---|---|---|
| 300 | 40 ± 2 | 90 ± 1 |
| 325 | 55 ± 2 | 86 ± 1 |
| 350 | 70 ± 2 | 78 ± 1 |
| 375 | 80 ± 2 | 65 ± 1 |
Mean ± sample SD, n = 3 independent runs per temperature. Synthetic data.
Today’s writing task
By the end of class, you will:
- Write Results (120–180 words) with a finding, magnitude and scope.
- Sketch a figure and write a caption (40–70 words) that defines the marks and n.
- Revise one claim using specific feedback and explain the change.
Definitions for this case
Conversion = A consumed / A fed × 100%
Selectivity = B formed / A consumed × 100%
Assumption: one mole of A can form one mole of B.
Yield = conversion × selectivity / 100
Observation, implication and hypothesis
Observation
Mean conversion increased from 40% to 80% between 300 and 375 °C.
Implication
Conversion alone cannot decide the operating condition because selectivity also changes.
Hypothesis
Competing pathways may contribute to the trade-off. The present data do not test this explanation.
The structure of a Results paragraph
Finding
Conversion increased with temperature, while selectivity to B decreased.
Evidence
From 300 to 375 °C, conversion rose by 40 percentage points and selectivity fell by 25.
Scope
The comparison applies at a residence time of 2.0 s over the tested temperature range.
Percent and percentage points
Conversion changes from 40% to 80%.
| Change | Calculation |
|---|---|
| +40 percentage points | 80 − 40 = 40 |
| +100% relative to the initial value | (80 − 40) / 40 × 100 = 100% |
Quick check: selectivity changes from 90% to 65%. State both changes.
One quantitative sentence
- Include the temperature range and the residence time.
- State the direction and magnitude for both responses.
- Keep the sentence within what the data show.
Check: could your reader recover the comparison without seeing the table?
A claim that needs revision
Temperature dramatically improved reactor performance.
Conversion increased significantly, proving that the catalyst became more active.
Therefore, 375 °C is optimal for industrial operation.
Deliberately flawed example for critique.
In pairs: underline each unsupported claim, then name the evidence it would need.
What evidence is missing?
- “Dramatically” needs a stated magnitude.
- “Significantly” needs a defined statistical basis.
- Catalyst activity needs additional measurements.
- Industrial optimum needs an objective and constraints.
A revision grounded in the measurements
At a residence time of 2.0 s, mean conversion increased from 40% at 300 °C to 80% at 375 °C.
Mean selectivity to B decreased from 90% to 65% over the same range.
These measurements show a trade-off between conversion and selectivity.
The question determines the display
| Question | Useful display |
|---|---|
| How does response vary with temperature? | Scatter plot, optionally with connecting lines |
| How variable are repeated runs? | Individual points with a defined summary |
| What are the exact values? | A table with units and uncertainty |
Connecting lines guide the eye unless a fitted model is explicitly stated.
Conversion rises while selectivity falls
Synthetic means at a residence time of 2.0 s. Variability omitted here for the design exercise.
Break
15 minutes
Resume at 10:30
Axis limits change the visual impression
Same conversion means in both panels. Axis limits must remain visible.
Independent runs and repeated readings
n = 3 means three independent runs in this exercise.
Three readings from one run do not establish three independent experiments.
The sampling unit belongs in the caption.
Sample SD describes variation between runs
Run values: at 300 °C, conversion is 38%, 40% and 42%.
Summary: mean = 40%. Sample SD = 2 percentage points.
Report as mean ± SD: (40 ± 2)%.
SD: spread between runs. SE: precision of the estimated mean; here, SD/√n ≈ 1.15 percentage points.
Neither is a 95% confidence interval. SD-bar overlap alone does not test significance.
Means with sample SD
Synthetic data, n = 3 independent runs per temperature. Bars show ±1 sample SD.
A caption makes the figure interpretable
- System and variable: temperature in the hypothetical reaction
- Conditions: residence time 2.0 s
- Display: points are means, bars are ±1 sample SD
- Replication: three independent runs per temperature
Check: can the reader identify every mark without reading the main text?
A caption linked to the marks on the figure
What and where
Figure 1. Conversion of A (left) and selectivity to B (right) versus temperature at a residence time of 2.0 s.
Summary and n
Points are means of three independent runs per temperature. Bars show ±1 sample SD.
Other marks
Lines guide the eye. The data are synthetic and were constructed for teaching.
Writing workshop
35 minutes
- First 10 min: sketch Figure 1 with labels, units and defined error bars.
- Next 20 min: write Results (120–180 words) and a caption (40–70 words).
- Last 5 min: underline the finding and check every numerical claim.
Ready for review: Figure 1 is cited; conditions, units, n and error-bar meaning are explicit; no untested mechanism is claimed.
Peer review
20 minutes
- Read your partner’s paragraph and figure for 5 minutes.
- Check numbers and units, claim strength, and caption–figure agreement.
- Write two specific revisions: quote the sentence, explain the issue and propose a fix.
Discuss which change most improves the match between claim and evidence.
Results with a clear finding and scope
Finding
At a residence time of 2.0 s, conversion increased with temperature while selectivity to B decreased.
Magnitude
From 300 to 375 °C, mean conversion rose by 40 percentage points and selectivity fell by 25.
Scope
The measurements show a conversion–selectivity trade-off within the tested range.
Exit ticket
7 minutes
- Submit the revised Results paragraph and caption.
- State one supported finding and one conclusion the data cannot establish.
- Identify one sentence you changed after peer review and explain why.
How was today?
Before you leave
Identify one point that is still unclear.
Name one change you will make in your writing or figure.
Complete the short anonymous feedback form.
