= Gas-syringe measurement of Boyle's law
Vernier's Boyle's Law: Pressure-Volume Relationship in Gases, Experiment 6 of Chemistry with Vernier, specifies a graduated $20\,\mathrm{mL}$ <gas syringe>, a <pressure sensor> and LabQuest recording. Preparation sets the disconnected syringe to $10.0\,\mathrm{mL}$, then attaches it to the sensor valve, trapping air. At several plunger positions, the displayed <pressure> is allowed to stabilize before the paired <volume (thermodynamics)> is entered. The analysis tests whether $pV$ remains approximately constant. It adds $0.8\,\mathrm{mL}$ to each syringe reading for the sensor's internal <volume (thermodynamics)>; this correction belongs to that apparatus. The worksheet supplies a blank results table, not measured values.<Chemistry with Vernier/6 Boyle's Law: Pressure-Volume Relationship in Gases>[Experiment 6, printed pp. 6–1 to 6–3: Figure 1, preparation 1b–c, procedure 3–6, blank data table, and Processing the Data 7–9]{ref}
\Image[/boyles-law-closed-gas-syringe.png]
{title=A closed gas syringe measures total trapped volume and absolute pressure after thermal settling}
The manufacturer's Gas Pressure Sensor User Manual identifies a membrane sensor referenced to a <vacuum>, hence an <absolute pressure> readout. Its calibration section uses the actual local <atmospheric pressure> for an ambient reference check, rather than a weather report corrected to sea level. Checking this baseline before sealing separates an offset error from compression physics.<Gas Pressure Sensor User Manual, Vernier>[Calibration: station pressure and one-point reference; Specifications: internal volume; How the Sensor Works: vacuum-referenced membrane and absolute-pressure output]{ref}
Additional controls follow from the model. Keep the same sealed <amount of substance>, connections and ambient <temperature>; persistent <pressure> drift at held <volume (thermodynamics)> after <thermal equilibrium> suggests a leak or another uncontrolled change. Small steps and waiting allow compression <heat> to leave the <gas>; avoiding hand warming reduces another <heat> input. Compare settled readings when approaching a position from either direction. Plunger <friction> affects the applied <force> and position reproducibility, so record actual <pressure> and actual plunger position rather than predicting <pressure> from the load. These are proposed controls, not reported experimental outcomes.
Nearly constant $pV$ across equilibrated states supports the fixed-<temperature> <ideal gas> approximation over the tested range. Stabilized <pressure> alone does not demonstrate uniform or constant <temperature>; the <isothermal gas syringe experiment> adds a <temperature> readout to distinguish a transient from its cooled endpoint. Finite sensor accuracy and uncertain total <volume (thermodynamics)> limit the test, and agreement does not establish ideal behavior at every <pressure>. Repeated return readings help distinguish reproducibility from a one-direction trend.
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