States of matter and the particle modelIB MYP Physics: Subtopic test

1. 1
   Ice cubes are taken from a freezer and left in a glass in a hot kitchen in Dubai. The ice slowly changes to water, and later some of the water disappears from the glass.

   (a)

   Which statement describes the particles in the ice cubes?

   [1 mark]

   • AThey are closely packed in a regular pattern and vibrate about fixed positions
   • BThey are close together in a random arrangement and slide past each other
   • CThey are far apart and move randomly at high speed
   • DThey are far apart in a regular pattern and do not move

   (b)

   What is the change of state from ice to water called?

   [1 mark]

   • AFreezing
   • BCondensation
   • CMelting
   • DSublimation

   (c)

   Describe how the arrangement and movement of the particles in the water differ from those in the ice.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Seoul looks at specks of smoke in a sealed glass cell under a microscope. The specks move in random zigzag paths. In another lesson, a teacher opens a bottle of perfume at the front of a still classroom, and after a minute students at the back can smell it.

   (a)

   What causes the smoke specks to move in random zigzag paths?

   [1 mark]

   • AThe specks are alive and swim around
   • BWarm air currents from the microscope lamp
   • CThe specks are attracted to the glass of the lens
   • DCollisions with fast-moving, invisible air particles

   (b)

   Which process explains why the perfume smell reaches the back of the classroom?

   [1 mark]

   • ACondensation
   • BDiffusion
   • CSublimation
   • DMelting

   (c)

   Explain why the perfume smell would reach the back of the room more quickly on a warmer day.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A class in Cape Town heats crushed ice gently in a beaker. A thermometer is held in the beaker and the temperature is read every minute. The temperature rises steadily from -8 °C to 0 °C in 4 minutes, stays at 0 °C for 6 minutes while the ice melts, rises steadily to 100 °C over 10 minutes, and then stays at 100 °C while the water boils.

   (a)

   Explain, using the particle model, why the temperature stays at 0 °C for 6 minutes even though the beaker is still being heated.

   [3 marks]

   (b)

   Suggest two improvements to the method, giving a reason for each.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A food company in Chile makes freeze-dried strawberries. The fruit is frozen, then placed in a low-pressure chamber and gently warmed. The ice in the fruit turns directly into gas, leaving dry, light fruit that keeps for years without a fridge. The process takes many hours and uses a large amount of electricity.

   (a)

   Explain, using the particle model, how the ice in the strawberries changes directly into gas, and describe what happens to the energy, arrangement and movement of the particles.

   [6 marks]

   (b)

   Evaluate whether freeze-drying is a good way to supply food to people living in remote areas.

   [6 marks]

   Total for question 4: 12 marks

End of questions