CAIE A Level Chemistry 9701 · States of matter
Helium gas is stored in a rigid steel cylinder at 20 °C and 150 kPa.
(a) Suggest how the kinetic theory model of an ideal gas explains the pressure that the helium exerts on the inner walls of the cylinder.
(b) The model treats the helium atoms as point particles with zero volume and assumes there are no forces of attraction between them. Suggest why each of these two assumptions is reasonable for helium in this cylinder.
7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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