1. 1
   A cyclist uses a hand pump with a sealed nozzle to inflate a bicycle tyre, and notices that the pump barrel feels warm after several minutes of vigorous pumping.

   (a)

   A sealed bicycle pump contains gas at room temperature. What best describes the motion of the gas molecules inside it?

   [1 mark]

   • AThey are stationary, fixed in position
   • BThey vibrate around fixed positions only
   • CThey move constantly in random directions at various speeds
   • DThey all move in exactly the same direction at the same speed

   (b)

   As the cyclist pumps harder and the gas in the pump is heated slightly, what happens to the average kinetic energy of the gas molecules?

   [1 mark]

   • AIt decreases
   • BIt stays exactly the same
   • CIt becomes zero
   • DIt increases

   (c)

   Explain, using the particle model, why pushing the pump handle down (doing work on the trapped gas) causes the temperature of the gas inside the pump to rise.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A deep-sea diver carries a sealed metal cylinder containing a fixed mass of compressed air. As gas is slowly released from the cylinder into a larger expandable chamber at constant temperature, its volume increases.

   (a)

   A diver's sealed metal air cylinder holds a fixed mass of gas at constant temperature. Which equation relates the pressure and volume of this fixed mass of gas at constant temperature?

   [1 mark]

   • ApV = constant
   • Bp + V = constant
   • Cp/V = constant
   • Dp − V = constant

   (b)

   As the gas from the cylinder expands into the larger chamber at constant temperature, what happens to its pressure?

   [1 mark]

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

   (c)

   The gas initially has a pressure of 800 kPa in a volume of 2 m³. It expands at constant temperature into a chamber with a volume of 8 m³. Calculate the new pressure of the gas.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A meteorologist releases a sealed weather balloon containing a fixed mass of gas, which rises slowly through the lower atmosphere while the surrounding air temperature remains roughly constant, and the balloon's volume is observed to increase noticeably as it climbs.

   (a)

   A weather balloon is sealed at ground level, trapping a fixed mass of gas inside it, and rises slowly through the atmosphere where the surrounding air temperature stays roughly constant for the altitude range being studied. Explain, in terms of the particle model, why the gas inside the sealed balloon exerts a pressure on the inside of its rubber skin.

   [3 marks]

   (b)

   As the balloon rises, the surrounding atmospheric pressure decreases, and the meteorologist observes that the balloon's volume increases as a result, even though the surrounding air temperature is roughly constant. Explain why the balloon's volume increases as the outside pressure decreases, referring to the pressure of the trapped gas and using ideas from pV = constant.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A sports scientist is investigating why a bicycle pump barrel becomes noticeably warmer after many rapid, repeated compressions of the trapped air compared with a single slow compression producing the same total volume change.

   (a)

   Explain, using the particle model of gases and the idea of work done on a gas, why rapid, repeated compression causes a greater temperature rise in the trapped air than a single slow compression, even though the same total volume change occurs each time.

   [6 marks]

   (b)

   The sports scientist suggests that wrapping the pump barrel in an insulating foam sleeve would make the difference in temperature rise between rapid and slow compression even more noticeable. Evaluate this suggestion, explaining your reasoning in terms of energy transfer between the gas and its surroundings.

   [6 marks]

   Total for question 4: 12 marks

End of questions