1. 1
   A sealed can of deodorant contains gas at a fixed volume. As the can is warmed near a radiator, the pressure inside the can increases.

   (a)

   What is the cause of this increase in pressure at the particle level?

   [1 mark]

   • AThe gas molecules move faster on average and collide with the walls more frequently and with greater force
   • BThe gas molecules increase in number as the can is heated
   • CThe gas molecules become heavier as the temperature rises
   • DThe gas molecules stop moving and settle at the bottom of the can

   (b)

   Which temperature scale is most directly related to the average kinetic energy of the gas molecules in the can?

   [1 mark]

   • ACelsius scale
   • BFahrenheit scale
   • CKelvin scale
   • Dnone of the scales relate to kinetic energy

   (c)

   The gas in the sealed can starts at a temperature of 20°C and a pressure of 250,000 Pa. It is warmed to 80°C at constant volume. Calculate the new pressure of the gas, showing your conversion to kelvin.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A diver's flexible balloon filled with air is taken from the surface of a lake down to a greater depth, where the surrounding water pressure is much higher, while the temperature of the air inside stays constant.

   (a)

   What happens to the volume of the balloon as it descends?

   [1 mark]

   • AThe volume becomes zero
   • BThe volume increases
   • CThe volume stays exactly the same
   • DThe volume decreases

   (b)

   Which equation correctly relates the pressure and volume of the fixed mass of gas in the balloon at constant temperature?

   [1 mark]

   • Ap1/T1 = p2/T2
   • Bp1V1 = p2V2
   • Cp1 + V1 = p2 + V2
   • Dp1V1 = p2/T2

   (c)

   At the surface, the balloon has a volume of 3.0 litres at a pressure of 101,000 Pa. At depth, the pressure increases to 303,000 Pa, with temperature unchanged. Calculate the new volume of the balloon.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A weather balloon is released from ground level and rises into the upper atmosphere, where both the temperature and the surrounding pressure are much lower than at ground level, causing the balloon to expand considerably.

   (a)

   Explain, in terms of the random motion of gas molecules, why a gas exerts a pressure on the walls of its container, and why the pressure inside the balloon changes as it rises.

   [3 marks]

   (b)

   At ground level, the gas inside the weather balloon is at a temperature of 290 K and a pressure of 100,000 Pa in a sealed rigid test chamber used to model the balloon's gas before launch. If this fixed volume of gas is cooled to a temperature of 232 K, calculate the new pressure of the gas, and explain what this calculation shows about the relationship between pressure and Kelvin temperature at constant volume.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A physics teacher demonstrates the idea of absolute zero to a class using a fixed volume of gas sealed in a rigid flask connected to a pressure gauge, cooling the flask in stages and recording the pressure at each temperature.

   (a)

   Explain what is meant by absolute zero, why it represents a limit that cannot be reached in practice, and how the teacher's experimental results (pressure decreasing as temperature falls) support the existence of this limiting temperature.

   [6 marks]

   (b)

   The teacher records the following approximate results: at 373 K the pressure is 140,000 Pa; at 273 K the pressure is 102,000 Pa; at 173 K the pressure is 65,000 Pa. Evaluate whether these results support the relationship that pressure is directly proportional to Kelvin temperature at constant volume, showing any relevant calculations, and suggest one improvement to the experimental method that would make the conclusion more reliable.

   [6 marks]

   Total for question 4: 12 marks

End of questions