IB Physics SL B 3 8 Ideal Gas Approximation Limits Questions

Practise IB Physics SL B.3.8 by identifying when real gases follow ideal-gas behaviour and why extreme compression breaks the model.

Exam points

Trace transformations among translational kinetic, near-Earth gravitational potential and elastic potential energy stores.
Use conservation of mechanical energy to calculate speeds, heights or elastic-energy changes and identify dissipative transfers where present.

[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 IB Physics SL B 3 8 Ideal Gas Approximation Limits Questions question 1 — IB Physics SL

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

The equation of the line of best fit is:

p=a+\frac{b}{H}

The equation above may be used to predict the pressure of the air at extremely large values of $\frac{1}{H}$ . Suggest why this will be an unreliable estimate of the pressure.

very large $\frac{1}{H}$ means very small volumes / very high pressures

at very small volumes the ideal gas does not apply

OR

at very small volumes some of the assumptions of the kinetic theory of gases do not hold

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IB Physics SL B 3 8 Ideal Gas Approximation Limits Questions question 1