IB Physics SL B.3.4 Empirical Gas Laws

Practise comparing fixed-mass gas states with PV/T constant, identifying which variable is held fixed and using graphs to test Boyle, Charles or pressure-law behaviour.

Syllabus
First assessment 2025
Objective
—
Level
SL

Exam points

  • apply P₁V₁/T₁ = P₂V₂/T₂ to a fixed gas sample with every temperature in kelvin
  • select the reduced relationship for constant pressure, volume or temperature before calculating
  • test ideal behaviour from linear graphs, constant PV values or an intercept near absolute zero

B.3.4—Empirical gas laws question 1

[Maximum number: 2]

The equipment shown in the diagram was used by a student to investigate the variation with volume, of the pressure p of air, at constant temperature. The air was trapped in a tube of constant cross-sectional area above a column of oil.

Figure for Question B.3.4—Empirical gas laws question 1 — IB Physics SL

The pump forces oil to move up the tube decreasing the volume of the trapped air.

Outline how the results of this experiment are consistent with the ideal gas law at constant temperature.

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