1. 1
   A saucepan of soup is being heated on a stove. The metal base and sides of the pan get hot, the handle (made of solid plastic) stays cool enough to hold, and the soup itself circulates as it heats.

   (a)

   Which method of thermal energy transfer is mainly responsible for the metal base of the pan becoming hot from the stove flame directly beneath it?

   [1 mark]

   • AConduction
   • BConvection
   • CEvaporation
   • DRefraction

   (b)

   Which method of thermal energy transfer is mainly responsible for the soup itself circulating and heating evenly throughout the pan?

   [1 mark]

   • ARadiation through the soup
   • BConduction through the soup only
   • CConvection
   • DSublimation

   (c)

   Explain, using at least two different methods of thermal energy transfer, why the plastic handle of the pan stays significantly cooler than the metal base and sides during cooking.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A double-glazed window with a dark-coloured metal frame is fitted to a house. On a sunny day, the metal frame becomes noticeably warmer than the surrounding painted wall, largely because of radiation.

   (a)

   Which property of the dark metal frame makes it absorb thermal radiation from the Sun effectively?

   [1 mark]

   • AIts smooth, shiny texture
   • BIts ability to conduct electricity
   • CIts high density compared with the wall material
   • DIts dark, dull surface colour

   (b)

   Once the metal frame has absorbed thermal energy from the Sun, which process then mainly transfers this energy from the frame into the room's air in contact with the inner surface of the frame?

   [1 mark]

   • AEvaporation of the metal frame
   • BConduction through the frame, followed by convection into the room air
   • CNuclear fission within the frame
   • DTotal internal reflection within the frame

   (c)

   Explain the complex sequence of thermal energy transfer methods involved: from the Sun's radiation reaching the outer frame, through the solid metal frame, to warming the air inside the room.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A campfire is burning wood at a campsite on a cool evening. People sitting around the fire feel warmth on their skin from the flames, the metal poker used to stir the fire becomes too hot to hold if left in the flames, and the air directly above the fire visibly shimmers and rises.

   (a)

   (a) Identify the main method of thermal energy transfer responsible for each of these three observations: the warmth felt on the skin of people sitting nearby, the poker becoming hot, and the shimmering, rising air above the fire.

   [3 marks]

   (b)

   Explain why a person sitting very close to the campfire but slightly to one side, out of the direct path of the rising hot air, still feels significant warmth, describing which method or methods of thermal energy transfer are responsible and why convection is not the main explanation in this position.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A car radiator is designed to cool the engine by circulating hot water/coolant from the engine through a network of thin metal tubes with attached metal fins, over which air flows as the car moves.

   (a)

   Explain fully how conduction, convection and radiation each contribute to transferring thermal energy away from the hot engine coolant and ultimately into the surrounding atmosphere, and explain why the design uses thin metal tubes with many fins rather than a single thick metal block.

   [6 marks]

   (b)

   An engineer proposes painting the metal fins and tubes of the car radiator matte black instead of leaving them their natural shiny metallic finish. Explain fully, considering conduction, convection and radiation, whether this change would be likely to improve or worsen the radiator's ability to cool the engine, and identify which of the three methods of thermal energy transfer would be most affected by this change.

   [6 marks]

   Total for question 4: 12 marks

End of questions