What is absolute zero?

0 K or −273 °C, the lowest possible temperature.

How do you convert °C to K?

Add 273: T/K = \theta/{}^\circC + 273.

What graph confirms Boyle's law?

p against 1/V, a straight line through the origin.

Why wait before taking a reading in Boyle's law experiment?

Compression heats the gas, so wait for it to return to the temperature of the surroundings.

Ideal gasesAQA A-Level Physics: Flashcards

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State Boyle's law.

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State Boyle's law.: For a fixed mass of gas at constant temperature, $pV$ is constant.
State Charles's law.: For a fixed mass of gas at constant pressure, $V/T$ is constant, with $T$ in kelvin.
What is absolute zero?: 0 K or −273 °C, the lowest possible temperature.
How do you convert °C to K?: Add 273: $T/\text{K} = \theta/{}^\circ\text{C} + 273$ .
State the ideal gas equation in terms of moles.: $pV = nRT$
State the ideal gas equation in terms of molecules.: $pV = NkT$
How are $R$ and $k$ related?: $k = R/N_A$
What is the value of the Boltzmann constant?: $1.38 \times 10^{-23}$ J K⁻¹
How is the number of molecules related to the number of moles?: $N = nN_A$
How is molecular mass related to molar mass?: $m = M/N_A$
State the equation for work done by a gas at constant pressure.: $W = p\Delta V$
What graph confirms Boyle's law?: $p$ against $1/V$ , a straight line through the origin.
Why wait before taking a reading in Boyle's law experiment?: Compression heats the gas, so wait for it to return to the temperature of the surroundings.

Exam questions on Ideal gases

A rigid sealed cylinder of volume 2.0 × 10⁻² m³ contains 0.80 mol of an ideal gas at a temperature of 300 K (27 °C). The molar gas constant is 8.31 J mol⁻¹ K⁻¹ and the Avogadro constant is 6.02 × 10²³ mol⁻¹.
Calculate the number of molecules of gas in the cylinder.2 marks
A student investigates a fixed mass of dry air trapped in a glass tube by a short thread of oil. In the first experiment the pressure on the air is varied using a pump while the temperature is kept constant. In the second experiment the tube is heated in a water bath at atmospheric pressure.
In the first experiment, the student waits for a short time after changing the pressure before each reading of the volume. Explain why.2 marks
A gas is trapped in a cylinder by a frictionless piston and kept at a constant pressure of 1.0 × 10⁵ Pa. Its initial volume is 2.0 × 10⁻³ m³ at a temperature of 290 K. The gas is heated slowly until its volume is 5.0 × 10⁻³ m³. Treat the gas as ideal, with $R$ = 8.31 J mol⁻¹ K⁻¹.
Calculate the work done by the gas as it expands.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).