Structure 1.5—Ideal gases

Structure 1.5.1—An ideal gas consists of moving particles with negligible volume and no intermolecular forces. All collisions between particles are considered elastic.

Structure 1.5.2 —Real gases deviate from the ideal gas model, particularly at low temperature and
high pressure.

Structure 1.5.3—The molar volume of an ideal gas is a constant at a specific temperature and

Structure 1.5.4—The relationship between the pressure, volume, temperature and amount of an ideal gas is shown in the ideal gas equation PV = nRT and the combined gas law:

What You’ll Learn:

  • Recognize the key assumptions in the ideal gas model.
  • Explain the limitations of the ideal gas model.
  • Investigate the relationship between temperature, pressure and volume for a fixed mass of an ideal gas and analyse graphs relating these variables.
  • Solve problems relating to the ideal gas equation.
  • Units of volume and pressure should be SI only. The value of the gas constant R, the ideal gas equation, and the combined gas law, are given in the data booklet.

AHL Only

  • None


ideal gas, moving particles, negligible volume, no intermolecular forces, elastic collisions, real gases, deviation, low temperature, high pressure, molar volume, constant, specific temperature, specific pressure, pressure, volume, temperature, amount, ideal gas equation, PV=nRT, combined gas law

Syllabus Links

Structure 2.2—Under comparable conditions, why do some gases deviate more from ideal behaviour than others?

Nature of science, Tools 2 and 3, Reactivity 2.2—Graphs can be presented as sketches or as accurately plotted data points. What are the advantages and limitations of each representation?

Tool 1, Inquiry 2—How can the ideal gas law be used to calculate the molar mass of a gas from
experimental data?

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