1. 1
   A perfume manufacturer notices that a customer standing several metres from an open bottle of perfume can eventually smell it spreading across a still room.

   (a)

   Which term describes the process by which perfume particles spread through the air to reach the customer?

   [1 mark]

   • ADiffusion
   • BFiltration
   • CDistillation
   • DChromatography

   (b)

   The perfume vapour spreads through the room because its particles are constantly moving. Which statement best describes the arrangement and motion of particles in a gas such as perfume vapour, compared with a liquid?

   [1 mark]

   • AGas particles are arranged in a regular lattice and do not move
   • BGas particles are close together and vibrate about fixed positions
   • CGas particles are far apart and move rapidly and randomly in all directions
   • DGas particles are closer together than liquid particles and move more slowly

   (c)

   The manufacturer also sells a heavier, more viscous perfume oil with a much larger relative molecular mass than the original perfume. Explain why this heavier perfume oil diffuses more slowly through the air than the lighter perfume.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A weather balloon is released at ground level and rises high into the atmosphere, where the air pressure is much lower than at ground level. As it rises the balloon steadily expands until it eventually bursts.

   (a)

   What happens to the volume of the fixed mass of gas inside the balloon as the external pressure decreases, if temperature is constant?

   [1 mark]

   • AThe volume decreases
   • BThe volume increases
   • CThe volume stays exactly the same
   • DThe gas turns into a liquid

   (b)

   Scientists also record that the temperature of the atmosphere falls steadily as the balloon rises. If the pressure on the gas inside the balloon were kept constant instead, what would happen to the volume of the gas as its temperature decreases?

   [1 mark]

   • AThe gas becomes denser but keeps the same volume
   • BThe volume increases
   • CThe volume stays exactly the same
   • DThe volume decreases

   (c)

   Using kinetic particle theory, explain why decreasing the external pressure on the balloon causes the trapped gas to increase in volume.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A metallurgist heats a solid block of tin from room temperature until it becomes a flowing liquid, and continues heating the liquid tin until it eventually boils.

   (a)

   Describe, in terms of particle separation, arrangement and motion, the changes that occur to the tin particles as the solid tin melts and then as the liquid tin boils.

   [3 marks]

   (b)

   The metallurgist records the temperature of the tin every minute while heating it and plots a heating curve. Explain why the temperature of the tin remains constant for a period of time while it is melting, even though heating continues throughout.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A gas cylinder manufacturer tests two identical rigid steel cylinders, X and Y, each fitted with a pressure gauge. Cylinder X is filled with pure hydrogen gas and cylinder Y is filled with pure carbon dioxide gas, at the same temperature and pressure, and both are opened simultaneously at one end of a long, still corridor via a narrow valve.

   (a)

   Explain, in terms of kinetic particle theory and relative molecular mass, why the smell of any leaking gas (imagine both gases had a smell) would reach the far end of the corridor from cylinder X before it would from cylinder Y, and describe how the rate of diffusion of a gas is affected by its relative molecular mass more generally.

   [6 marks]

   (b)

   The manufacturer also wants to understand how temperature and pressure affect the volume of gas stored inside cylinder X before it is opened. Using kinetic particle theory, explain the effect of (i) increasing the temperature of the gas at constant pressure, and (ii) increasing the pressure applied to the gas at constant temperature, on the volume occupied by a fixed mass of hydrogen gas.

   [6 marks]

   Total for question 4: 12 marks

End of questions