1. 1
   A block of ice is left in a warm room. It gradually melts into liquid water, and the water is then heated further until it boils and turns into steam.

   (a)

   A block of ice is left in a warm room. It gradually turns into liquid water. What is this change of state called?

   [1 mark]

   • AMelting
   • BFreezing
   • CCondensation
   • DEvaporation

   (b)

   Which of these properties correctly describes the ice, while it remains a solid?

   [1 mark]

   • AIt has a fixed shape but no fixed volume
   • BIt has a fixed shape and a fixed volume
   • CIt has no fixed shape but a fixed volume
   • DIt has neither a fixed shape nor a fixed volume

   (c)

   Describe the difference in the arrangement and motion of the particles in the ice (a solid) compared with the particles in the liquid water it melts into.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A scientist observes tiny smoke particles suspended in air under a microscope, using a smoke cell, and sees the smoke particles moving in a continuous, random, jittery path.

   (a)

   What is this observed motion called?

   [1 mark]

   • AConvection
   • BThermal expansion
   • CBrownian motion
   • DDiffusion

   (b)

   What directly causes the smoke particles to move in this random, jittery way?

   [1 mark]

   • AVibrations from the microscope itself
   • BThe smoke particles repelling each other by like electric charges
   • CConvection currents caused by heating the air from below
   • DRandom collisions with fast-moving, invisible air molecules

   (c)

   Explain how this observation of Brownian motion provides evidence for the kinetic particle model of matter.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A canister contains a fixed mass of gas. The engineer designing the canister also compares how easily a gas, a liquid and a solid of the same substance can be compressed into a smaller volume.

   (a)

   A canister contains a fixed mass of gas. Describe the arrangement, separation and motion of the particles that make up this gas.

   [3 marks]

   (b)

   Explain, in terms of the forces and distances between particles, why the gas in the canister can be compressed relatively easily into a smaller volume, whereas a solid or liquid sample of the same substance cannot be compressed significantly.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A materials science class is studying how the properties of solids, liquids and gases arise from the behaviour of their particles, using an experiment observing Brownian motion in a smoke cell as supporting evidence.

   (a)

   Describe, in terms of the arrangement, separation and motion of particles, the differences between the solid, liquid and gaseous states of a substance, and explain how these microscopic differences account for the differing properties (fixed or non-fixed shape, fixed or non-fixed volume, and ease of compression) of the three states.

   [6 marks]

   (b)

   Describe, in detail, an experiment using a smoke cell and a microscope to observe Brownian motion, and explain how the results of this experiment provide evidence for the kinetic particle model of matter.

   [6 marks]

   Total for question 4: 12 marks

End of questions