Ideal gases and kinetic theoryEdexcel A-Level Physics: Flashcards

Exam questions on Ideal gases and kinetic theory

1. A rigid steel cylinder of volume 0.020 m³ contains 4.8 × 10²⁴ atoms of helium at a temperature of 300 K. The helium behaves as an ideal gas.
   The cylinder is heated until the temperature of the helium is 600 K. Explain, using the kinetic model, why the pressure of the gas increases.2 marks
2. A laboratory at 27 °C contains argon and helium, each behaving as an ideal gas. An argon atom has mass 6.63 × 10⁻²⁶ kg and a helium atom has mass 6.6 × 10⁻²⁷ kg.
   Compare the mean kinetic energy and the root mean square speed of the helium atoms with those of the argon atoms in the laboratory.2 marks
3. A student investigates how the volume of a fixed mass of air varies with its pressure. The air is trapped above oil in a uniform vertical glass tube that is sealed at the top and has cross-sectional area 1.5 × 10⁻⁴ m². A foot pump raises the pressure on the oil, which is read from a Bourdon gauge, and the length of the trapped air column is read from a scale. The laboratory temperature is 293 K. At a pressure of 1.00 × 10⁵ Pa the air column is 12.0 cm long, and at 2.00 × 10⁵ Pa it is 6.0 cm long.
   Describe how the student could use a full set of readings of pressure $p$ and column length $l$ to show that $p$ is inversely proportional to the volume $V$ of the air.3 marks