1. 1
   A student places a small crystal of solid iodine in a sealed glass tube and gently heats it. The iodine turns directly into a purple gas without any liquid appearing, and the gas later forms solid crystals again at the cooler end of the tube.

   (a)

   Which term describes the state in which particles vibrate about fixed positions but do not move from place to place?

   [1 mark]

   • ASolid
   • BLiquid
   • CGas
   • DPlasma

   (b)

   What is the name given to the change of state in which a solid turns directly into a gas without becoming a liquid?

   [1 mark]

   • AMelting
   • BSubliming
   • CFreezing
   • DCondensing

   (c)

   Describe how the arrangement and movement of the iodine particles change as the solid iodine turns into a gas.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A pan of water is heated on a stove until it boils, producing steam. Some of the steam rises and touches a cold window pane above the stove, where it forms small droplets of liquid water.

   (a)

   What is the name of the process in which a liquid changes into a gas at its surface, below the boiling point?

   [1 mark]

   • AFreezing
   • BCondensation
   • CEvaporation
   • DSublimation

   (b)

   What is the name of the process occurring when steam touches the cold window and forms liquid water droplets?

   [1 mark]

   • AMelting
   • BEvaporation
   • CSublimation
   • DCondensation

   (c)

   Explain the energy changes taking place as the water boils to form steam, and as the steam condenses on the cold window.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An ice cube is left on a kitchen worktop at room temperature. Over the next hour it turns into a puddle of water, and over the following day the puddle disappears completely.

   (a)

   Describe the changes of state that occur and name each change.

   [3 marks]

   (b)

   Explain, in terms of particle arrangement, movement and energy, why the ice melts and the resulting puddle then evaporates completely.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Substance X is a solid at room temperature. It is placed in a sealed container and heated steadily until it is well above its boiling point, while its temperature is monitored throughout.

   (a)

   Describe the changes to the arrangement and movement of the particles of X at each stage, and explain why the temperature of X does not rise while it is melting or boiling.

   [6 marks]

   (b)

   Explain how heating and cooling can be used to change the state of substance X, referring to the energy changes involved in both breaking and forming the forces of attraction between particles.

   [6 marks]

   Total for question 4: 12 marks

End of questions