Heat transfer: conduction, convection and radiationIB MYP Physics: Subtopic test

1. 1
   A chef in Istanbul cooks soup on a hob using a stainless steel pan with a plastic handle. The base of the pan heats up very quickly, but the plastic handle stays cool enough to hold.

   (a)

   Which statement describes conduction?

   [1 mark]

   • AHot fluid rises and carries energy with it
   • BEnergy travels as infrared waves and needs no particles
   • CEnergy is passed from particle to particle by vibrations and collisions, without the substance itself moving
   • DHot particles travel from one end of the solid to the other end

   (b)

   Which particles move through a metal and make metals good conductors of heat?

   [1 mark]

   • AFree electrons
   • BProtons
   • CNeutrons
   • DMolecules of air

   (c)

   Explain why the metal base heats up quickly but the plastic handle stays cool.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A radiator is fixed to one wall of a classroom in Oslo, close to the floor. When it is switched on, the whole room soon warms up, even the corner furthest from the radiator.

   (a)

   What happens to the air next to the radiator when it is switched on?

   [1 mark]

   • AIt contracts, becomes denser and rises
   • BIt expands, becomes denser and sinks
   • CIt contracts, becomes less dense and sinks
   • DIt expands, becomes less dense and rises

   (b)

   Convection cannot happen in one of the following. Which one?

   [1 mark]

   • AA beaker of water
   • BA solid brick wall
   • CA room full of air
   • DA pan of cooking oil

   (c)

   Explain how the energy from the radiator spreads through the whole room.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates how the surface of a can affects how quickly it cools. She uses three identical metal cans with lids: one painted dull black, one painted white and one with a shiny silver surface. She fills each can with 200 cm³ of water at 80 °C and leaves them in the same room at 20 °C. After 10 minutes the water temperatures are 55 °C (dull black can), 63 °C (white can) and 68 °C (shiny silver can). Her hypothesis was that dull black surfaces lose energy fastest.

   (a)

   Identify the independent variable and the dependent variable in the investigation, and state one control variable.

   [3 marks]

   (b)

   Describe the trend in the results and explain it using ideas about infrared radiation. Evaluate the hypothesis and suggest one improvement to the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A town in Spain is deciding whether to require solar water heaters on all new homes. Each system has a black metal panel on the roof with water pipes running through it, and a storage tank for the hot water. The tank is built like a vacuum flask, with a double wall, a vacuum between the walls, shiny inner surfaces and a tight-fitting lid.

   (a)

   Explain how the design of the tank reduces energy transfer by conduction, convection and radiation.

   [6 marks]

   (b)

   Discuss the benefits and drawbacks of requiring solar water heaters on all new homes, and evaluate whether the town should introduce the rule.

   [6 marks]

   Total for question 4: 12 marks

End of questions