Chapter 8 Practice Paper: Thermal Processes — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   Energy transfer by heating stops between two objects when they reach

   1. Athe same temperature
   2. Bthe same size
   3. Cthermal contact with a third object
   4. Droom pressure
   ( )
2. 2

   In a solid metal, thermal energy is conducted mainly by

   1. Avibrating particles passing energy to neighbours, helped by free electrons
   2. Bthe metal expanding
   3. Cblobs of hot metal rising
   4. Dinfrared radiation trapped in the metal
   ( )
3. 3

   A convection current rises because heated fluid

   1. Ashrinks and is pushed up
   2. Bevaporates instantly
   3. Cglows
   4. Dexpands, becomes less dense, and floats above cooler fluid
   ( )
4. 4

   Which surface loses heat to its surroundings fastest by radiation?

   1. Ashiny white
   2. Bpolished silver
   3. Cdull black
   4. Dsmooth cream
   ( )
5. 5

   A vacuum flask keeps drinks hot mainly by

   1. Aletting heat escape slowly through thick plastic
   2. Bpreventing conduction and convection with a vacuum, and reflecting radiation with silvered walls
   3. Cburning a small fuel inside
   4. Dincreasing the drink’s specific heat capacity
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 1

   A metal spoon and a wooden spoon stand in the same pot of hot soup.

   1. (a)

      After a minute, the metal spoon handle feels much hotter than the wooden one. Explain why, in terms of particles.

      [3]
   2. (b)

      State why the soup at the top of the pot is cooler than the soup at the bottom, and name the process that would even it out if the soup were stirred.

      [2]
   3. (c)

      The cook’s hand, held near (but not touching) the pot rim, feels warmth. Name the process and state what carries the energy.

      [1]
2. 2

   Two identical metal plates — one dull black, one shiny silver — stand upright facing an electric heater at equal distances. Each plate has a blob of wax holding a coin on its back face.

   1. (a)

      State which coin falls first, and why.

      [2]
   2. (b)

      The heater is switched off and the plates are moved away, then heated from behind by flames instead. State which plate now radiates energy away faster, with a reason.

      [2]
   3. (c)

      State two factors, other than surface colour, that affect the rate at which a hot object transfers energy by radiation.

      [2]
   4. (d)

      Explain why radiation, unlike conduction, can transfer energy across a vacuum.

      [1]
3. 3

   Sea breezes blow onshore during the day at a beach resort and reverse at night.

   1. (a)

      Explain, using convection, why a sea breeze blows from the sea towards the land during the day. Take the Sun as heating both equally.

      [4]
   2. (b)

      State the direction of the breeze at night and explain the reason.

      [2]
   3. (c)

      Name the property of water (compared with land) that explains why the sea warms and cools more slowly.

      [1]