1. 1
   A plumber is comparing two possible liquids to fill a central heating radiator system: water (specific heat capacity 4200 J/kg°C) and a type of oil (specific heat capacity 2100 J/kg°C), for the same mass of 5 kg heated through the same temperature rise of 20 °C.

   (a)

   Which equation is used to calculate the change in thermal energy stored when the temperature of a substance changes?

   [1 mark]

   • AΔE = mcΔθ
   • BΔE = mL
   • CΔE = Pt
   • DΔE = QV

   (b)

   For the same mass and the same temperature rise, which liquid requires more energy to heat up?

   [1 mark]

   • AThe oil, because it has the lower specific heat capacity
   • BThe water, because it has the higher specific heat capacity
   • CBoth require exactly the same energy regardless of specific heat capacity
   • DNeither, because specific heat capacity does not affect energy needed

   (c)

   Calculate the energy needed to heat 5 kg of water through a temperature rise of 20 °C, and the energy needed to heat 5 kg of the oil through the same temperature rise.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In a school physics laboratory, a student uses an electrical immersion heater embedded in an aluminium block to determine the specific heat capacity of aluminium, recording the power of the heater, the time it is switched on for, the mass of the block, and its temperature before and after heating.

   (a)

   A student uses an immersion heater to heat a block of metal in the laboratory to determine its specific heat capacity. Which two quantities, besides the mass of the block and the energy supplied, does she need to measure directly?

   [1 mark]

   • AThe colour and shape of the block
   • BThe current and resistance of the immersion heater only
   • CThe initial and final temperature of the block
   • DThe volume and density of the block

   (b)

   The student calculates the energy supplied to the block using the power of the heater and the time it was switched on. Which equation should she use?

   [1 mark]

   • AE = P/t
   • BE = mcΔθ
   • CE = mL
   • DE = Pt

   (c)

   The heater has a power of 50 W and is switched on for 300 seconds. The 2 kg aluminium block rises in temperature from 20 °C to 42 °C. Use these results to calculate the experimental value for the specific heat capacity of aluminium.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A geography teacher explains to students why a coastal city has a much milder climate than an inland city at a similar latitude, pointing out that the nearby sea absorbs and releases large amounts of energy from sunlight each day with only a small change in its own temperature.

   (a)

   A coastal city's climate is milder than an inland city at a similar latitude because the nearby sea has a much higher specific heat capacity than the surrounding land. Explain, using the concept of specific heat capacity, why the sea's temperature changes much less than the land's temperature over the course of a day, for the same energy gained from sunlight.

   [3 marks]

   (b)

   Explain why the sea, having absorbed a large amount of energy during a hot day, continues to release energy slowly overnight and keeps the coastal city's night-time temperature milder than the inland city, using ideas about specific heat capacity and internal energy.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An engineer is designing a thermal energy storage system for a solar power plant that must store solar heat energy during the day and release it steadily overnight, and is choosing between molten salt and rock as the storage material, assuming equal mass and equal temperature range for both.

   (a)

   She is choosing between two candidate materials: molten salt, which has a higher specific heat capacity, and a type of rock, which has a lower specific heat capacity. Explain, using the concept of specific heat capacity and the equation ΔE = mcΔθ, why the molten salt would be the better choice for storing more energy for the same mass and temperature change.

   [6 marks]

   (b)

   The engineer's colleague suggests that using twice the mass of rock instead would make it just as good a choice as the molten salt system. Evaluate this suggestion, using the equation ΔE = mcΔθ and considering any practical drawbacks of increasing the mass of storage material.

   [6 marks]

   Total for question 4: 12 marks

End of questions