1. 1
   A student sets up a simple calorimetry experiment, burning a sample of liquid fuel in a spirit burner beneath a metal can containing 100 g of water, and measuring the temperature of the water before and after heating for two minutes.

   (a)

   A student burns a sample of fuel beneath a metal can containing 100 g of water, using the flame to heat the water. Which equation should the student use to calculate the energy transferred to the water?

   [1 mark]

   • AQ = mc$\Delta$ T
   • BQ = m/c
   • CQ = m $\times \Delta$ T
   • DQ = c/$\Delta$ T

   (b)

   Which unit is most commonly used to express the energy value calculated in this type of experiment?

   [1 mark]

   • ANewtons (N)
   • BJoules (J) or kilojoules (kJ)
   • CMoles (mol)
   • DDegrees Celsius (°C)

   (c)

   The student records a temperature rise of 15°C in the 100 g of water. State what other piece of information the student needs to calculate the energy released by the fuel, and describe one source of error in this experimental method that could cause the calculated energy value to be lower than the true value.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Two students independently carry out the same calorimetry experiment to measure the energy released when burning ethanol. Student 1 heats water in a thin glass beaker, while Student 2 heats the same mass of water in a metal can, both directly above an identical spirit burner flame.

   (a)

   Two students compare their calorimetry results for the same fuel. Student 1 used a glass beaker and Student 2 used a metal can, with all other conditions identical. Which student is likely to obtain a more accurate value for the energy released by the fuel?

   [1 mark]

   • AStudent 1, because glass absorbs less heat than metal
   • BBoth students will get identical results, since the fuel is the same
   • CStudent 2, because metal conducts heat to the water more effectively than glass, transferring more energy to the water rather than losing it
   • DStudent 1, because glass is transparent and allows more light energy to reach the water

   (b)

   Both students notice that their calculated energy values are lower than the data-book value for the energy released by burning ethanol. What is the most likely explanation for this?

   [1 mark]

   • AEthanol cannot release energy when burned
   • BThe specific heat capacity of water used in the calculation was too high
   • CThe fuel released more energy than the data-book value predicted
   • DEnergy is lost to the surroundings as heat, rather than being fully transferred to the water

   (c)

   Suggest two changes to the experimental method that would reduce heat loss to the surroundings and give a more accurate energy value for both students.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician is testing the energy content of a new liquid fuel by burning a known mass beneath a metal can of water and measuring the temperature rise, in order to compare the fuel with existing products on the market.

   (a)

   A technician burns 1.2 g of a liquid fuel beneath a metal can containing 150 g of water. The temperature of the water rises from 18°C to 42°C. Using Q = mc$\Delta$ T with a specific heat capacity of water of 4.2 J/g°C, calculate the energy transferred to the water in joules, showing your working.

   [3 marks]

   (b)

   Using your answer to part (a), calculate the energy released per gram of fuel burned, and explain why this calculated value is likely to be lower than the true energy content of the fuel.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school science department wants to compare the energy content of methanol, ethanol and propanol using a simple calorimetry investigation, planning to burn each fuel in turn beneath an identical metal can of water.

   (a)

   A school science department wants to compare the energy released by three different alcohol fuels (methanol, ethanol and propanol) using simple calorimetry. Describe, in detail, a method the department could use to compare the fuels fairly, including how they would calculate the energy released per gram of each fuel, and identify the key variables that must be controlled.

   [6 marks]

   (b)

   Discuss the main sources of experimental error in this simple calorimetry method, and evaluate why the calculated energy values for all three fuels are likely to be lower than published data-book values, even if the method is carried out carefully.

   [6 marks]

   Total for question 4: 12 marks

End of questions