Teach lesson
Pressure limit: how far can we compress?
Turn three readings from a real syringe run into an engineering recommendation with a pressure limit and safety margin.
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Learning Outcomes
Collect pressure readings around a 150 kPa design limit.
Identify the observed passing/failing bracket between tested settings.
Recommend a setting that includes a defensible safety margin.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
A decision with consequences
7 min
Imagine designing a small air chamber to protect a sensor. For this fictional classroom scenario, the displayed LabQuest pressure must not exceed 150 kPa. It is not a certified equipment safety limit. More compression uses less space, but moving too close to the threshold leaves less room for measurement uncertainty.
Your job is not to control an exact pressure. Use the volumes offered by the real syringe to identify the smallest observed volume that meets the limit and choose a recommendation with a safety margin.
Before measuring, which volume do you predict will be the smallest that stays at or below 150 kPa?
Explain in one sentence why you chose that volume.
Measure around the limit
13 min
Use the 60 mL syringe, trial 1. Decrease the volume from 60 mL and record only 40, 35, and 30 mL. These three points test the design limit. Record the pressure before decreasing the volume again.
The display that informs the decision
The large number beside kPa is pressure; it appears red in the current interface. The syringe scale shows the current volume; check both before completing a row.
Lab-screen note: the introduction may mention pressure and temperature. In this Boyle run, syringe volume changes, pressure is measured, and temperature is treated as approximately constant.
Open the limit-test run
Open the lab and select the 60 mL syringe, trial 1.
Advance through the pauses until you reach 40 mL and record the pressure.
Decrease to 35 mL and record again.
Decrease to 30 mL and record the third pressure.
Replay a pause if a digit is unclear. Use decimal points in numeric fields.
Complete exactly three rows. In Meets the ≤150 kPa limit?, choose yes or no based on the observed pressure. Leave any extra interface row empty.
Test of the 150 kPa limit
One row per volume. Copy the pressure and decide whether P ≤ 150 kPa.
| Volume mL | Observed pressure kPa | Meets the ≤150 kPa limit? |
|---|---|---|
Distinguish the observed bracket from your recommendation
9 min
The smallest observed volume that meets the limit comes directly from the table. For this scenario, a recommendation with margin must be at least 10 kPa below 150 kPa in the observed run. That 10 kPa rule is a classroom decision criterion, not a general engineering safety standard.
Classify each tested volume against the limit. If adjacent tested volumes fall on opposite sides, report the observed bracket and both pressures; otherwise state that no crossing was observed. Do not claim an exact physical boundary.
Using the classroom rule, which is the smallest measured volume at least 10 kPa below 150 kPa? Choose "none" if no measured setting meets that margin.
Explain why a reading near 150 kPa deserves more caution than one at least 10 kPa below it. Name one possible measurement uncertainty. Do not use trial-to-trial variation as your example, because this lesson measured only one trial.
Summarize your decision in four sentences
6 min
Write exactly four sentences, one for each item:
1. Recommendation: choose one of the volumes you measured by applying the 10 kPa classroom margin.
2. Evidence: report the pressure you measured at that volume.
3. Observed change: if the result changed, name the two consecutive volumes between which it happened (one with P ≤ 150 kPa and one with P > 150 kPa). If it did not change, say so clearly.
4. Limitation: explain why one run with one setup cannot establish a general safety rule.
You are reporting the result of this classroom scenario, not certifying the real laboratory's safety.