Teach lesson
The PV constant challenge
Use five real pressure-volume pairs to decide whether one multiplication rule remains consistent throughout a full syringe compression.
New to LabsLand? Create your teacher account
Learning Outcomes
Collect five selected pressure-volume pairs from the 60 mL run.
Calculate PV in consistent units for each selected pair.
Judge whether PV is approximately constant using a clearly defined deviation criterion.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
Can multiplication reveal a pattern?
6 min
A compressed syringe produces many different pressure-volume pairs. At first they can look like an untidy collection of numbers. One operation may reveal a hidden regularity: multiply each pressure by its volume.
For a fixed amount of gas at approximately constant temperature, Boyle's law proposes that PV should stay approximately constant:
The rule you will test
P\,V \approx \text{constant}
P is the displayed pressure in kPa and V is the syringe-scale volume in mL, so PV is in kPa·mL. The available lab source does not identify the display as showing absolute or gauge pressure. Gas in the tubing or sensor may also add volume that is not shown on the syringe scale. Use the displayed pressure and syringe-scale volume consistently as working measurements. The word *approximately* matters: this run tests a practical pattern rather than claiming a perfect ideal-gas relationship.
Before calculating, what do you expect the five PV products to do?
Collect five pairs and calculate PV
16 min
Use the 60 mL syringe, trial 1. The video shows nine volumes, but this activity uses only five: 60, 50, 40, 30, and 20 mL. At each one, record the pressure before decreasing the volume again. Continue through 55, 45, 35, and 25 mL without adding them to the table.
Evidence comes from this display
Read the large pressure number beside kPa; it appears red in the current interface. If it uses a decimal comma, enter a decimal point in numeric fields.
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 60 mL run
Open the lab, then select the 60 mL syringe and trial 1.
Record initial pressure at 60 mL.
At each pause, select Decrease by 5 mL. Record again only at 50, 40, 30, and 20 mL.
For each row, calculate
PV = pressure × volumewith a calculator.If a reading is uncertain, replay the pause or mark it in the note column; do not replace it with an ideal number.
The five rows are already identified. Use the pressure as displayed and round each PV product to the nearest 0.1 kPa·mL. Leave the percentage-deviation column blank until you calculate the mean in the next phase; the table is completed in two stages. The optional note can be used to mark a difficult reading, such as a blurred digit or fluctuating display. Leave any extra interface row unused.
Five tests of PV
First copy the pressure and calculate PV. After finding the mean PV, complete the percentage deviation for every row.
| Volume mL | Pressure kPa | PV kPa·mL | Deviation from mean PV % | Reading note |
|---|---|---|---|---|
Decide what ‘constant’ can mean
8 min
An experimental constant does not require identical products. First calculate mean PV = sum of five PV products ÷ 5, using the products already rounded to 0.1 kPa·mL. Then complete the table's final numeric column with percentage deviation = |PV − mean PV| ÷ mean PV × 100, rounded to 0.1%. For this lesson, call a row a noticeable deviation when its percentage deviation exceeds 5%. This is a transparent classroom rule, not a universal law of nature.
Calculate the mean of your five PV products. Enter it rounded to 0.1 kPa·mL and show the sum divided by five.
How many of your five rows have a percentage deviation that exceeds 5%? Choose the one count that matches your completed table.
Which row has the largest percentage deviation from the mean PV? State its volume, PV, and percentage, then apply the 5% rule. If it is a noticeable deviation, give one possible cause related to the measurement or setup—such as a difficult reading, temperature change, leak, sensor response, or uncounted setup volume—without claiming that cause is proven.
Give the challenge verdict
5 min
Write a four-sentence verdict:
1. Decide whether the run supports approximately constant PV.
2. Cite at least two PV products from your table.
3. Report how many rows exceed 5% deviation and identify the row with the largest deviation.
4. Explain how the full data set supports or limits your verdict; do not present a possible cause of the deviation as proven.