1. 1
   A chef heats 2 kg of water and 2 kg of cooking oil on separate identical hobs, supplying the same amount of thermal energy to each. Water has a much higher specific heat capacity than cooking oil.

   (a)

   Which statement correctly describes the result?

   [1 mark]

   • AThe oil reaches a higher final temperature than the water
   • BThe water reaches a higher final temperature than the oil
   • CThe water and the oil reach exactly the same final temperature
   • DNeither the water nor the oil changes temperature

   (b)

   Which equation correctly defines specific heat capacity, c, in terms of the energy supplied, delta E, the mass, m, and the temperature rise, delta theta?

   [1 mark]

   • Ac = delta E x m x delta theta
   • Bc = m x delta theta / delta E
   • Cc = delta E / (m x delta theta)
   • Dc = delta theta / (m x delta E)

   (c)

   The chef supplies 8400 J of energy to the 2 kg of cooking oil, which has a specific heat capacity of 2100 J/(kg degree C). Calculate the rise in temperature of the oil.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student sets up an experiment to measure the specific heat capacity of a metal block. The student drills two holes into the block, one for an electrical heater and one for a thermometer, and insulates the block with cotton wool.

   (a)

   What is the main purpose of the cotton wool insulation in this experiment?

   [1 mark]

   • ATo prevent the thermometer from measuring the temperature at all
   • BTo increase the specific heat capacity of the metal block
   • CTo conduct heat more quickly from the heater into the block
   • DTo reduce thermal energy losses from the block to the surroundings, so the measured temperature rise more accurately reflects the energy supplied by the heater

   (b)

   The student records the potential difference across the heater, the current through it, and the time for which it operates, in order to calculate the energy supplied. Which equation should the student use to calculate the electrical energy supplied by the heater?

   [1 mark]

   • AE = I + V + t
   • BE = IVt
   • CE = I/(Vt)
   • DE = V/(It)

   (c)

   The student measures a potential difference of 12 V and a current of 4 A through the heater, which operates for 300 seconds, producing a temperature rise of 20 degrees Celsius in the 1.5 kg metal block. Calculate the specific heat capacity of the metal, showing your working.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A city planner is comparing two possible materials for paving a large public square: dark asphalt, which has a low specific heat capacity, and light-coloured stone, which has a higher specific heat capacity. Both materials absorb similar amounts of solar energy during a sunny day.

   (a)

   (a) Explain, using the concept of specific heat capacity, why the asphalt surface is likely to reach a higher temperature than the stone surface by the middle of the afternoon.

   [3 marks]

   (b)

   After sunset, both surfaces begin to cool. Predict and explain which surface, the asphalt or the stone, is likely to stay noticeably warm for longer into the evening, and explain the reasoning in terms of specific heat capacity and stored thermal energy.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital uses an electric water heater to warm 5 kg of water from 20 degrees Celsius to 60 degrees Celsius for sterilising instruments, using the equation delta E = m x c x delta theta with the specific heat capacity of water taken as 4200 J/(kg degree C).

   (a)

   Explain fully how you would calculate the minimum electrical energy required for this process, including full working, and explain why the actual electrical energy consumed by the heater in practice is likely to be greater than this calculated value.

   [6 marks]

   (b)

   The hospital engineer suggests replacing the water heater's insulating jacket with a thinner, less effective one to reduce costs. Explain fully, using the concept of specific heat capacity and energy transfer, why this change would affect the efficiency of the heating process and the practical consequences for the hospital's electricity costs and the time taken to reach the required temperature.

   [6 marks]

   Total for question 4: 12 marks

End of questions