1. 1
   A sealed gas cylinder in a factory contains a fixed mass of gas at constant temperature. A technician slowly pushes a piston into the cylinder, reducing the volume of the gas to half its original value.

   (a)

   According to the kinetic particle model, what happens to the pressure of the gas?

   [1 mark]

   • AThe pressure halves because there is less gas in the cylinder
   • BThe pressure doubles because the particles collide with the walls more frequently
   • CThe pressure stays the same because the temperature has not changed
   • DThe pressure doubles because each particle collides with more force

   (b)

   Which equation correctly relates the pressure and volume of the fixed mass of gas in the cylinder, provided the temperature remains constant?

   [1 mark]

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

   (c)

   Explain, in terms of the motion of gas particles, why the pressure of the gas increases when the volume of the cylinder is reduced at constant temperature.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A rigid metal canister of compressed air is left in direct sunlight on a warm day. The volume of the canister cannot change.

   (a)

   What happens to the pressure of the gas inside as its temperature rises?

   [1 mark]

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

   (b)

   What is 0 kelvin, the absolute zero of temperature, equal to on the Celsius scale?

   [1 mark]

   • A-273 degrees Celsius
   • B0 degrees Celsius
   • C-100 degrees Celsius
   • D273 degrees Celsius

   (c)

   The canister warms from 15 degrees Celsius to 45 degrees Celsius. Convert both temperatures to kelvin, and explain in terms of particle motion why the gas pressure inside the rigid canister increases as the temperature rises.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A scientist observes tiny smoke particles suspended in air through a microscope. The smoke particles are seen to move continuously in a random, jittering path, even though there is no draught in the room.

   (a)

   (a) State the name given to this type of motion, and explain what causes the smoke particles to move in this way.

   [3 marks]

   (b)

   Explain why this observation of the smoke particles is considered evidence for the kinetic particle model of matter.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A weather balloon is released from ground level, where the air pressure and temperature are higher, and rises to high altitude, where the air pressure and temperature are both much lower. The balloon is made of a flexible material, so its volume can change freely as it rises.

   (a)

   Using the kinetic particle model, explain fully why the volume of the gas inside the balloon changes as it rises from ground level to high altitude, describing the separate effects of the falling external pressure and the falling temperature on the gas particles inside the balloon.

   [6 marks]

   (b)

   A second, identical weather balloon is instead sealed inside a rigid, unstretchable box so that its volume cannot change at all as the box is carried up to the same high altitude. Explain fully what would happen to the pressure of the gas inside this rigid box as it rises, and explain why the behaviour of the gas in the rigid box is different from the behaviour of the free balloon described in part (a).

   [6 marks]

   Total for question 4: 12 marks

End of questions