100 g water thermometer stirrer calorimeter methane Fig. 1 shows an energy level diagram for the reaction between hydrogen and oxygen to make water. The lab...
Question 1 Report
Fig. 1 shows an energy level diagram for the reaction between hydrogen and oxygen to make water. The labelled vertical arrow represents an energy change. Table 1 lists the energy of the atoms and compounds involved.
| material | energy / kJ |
|---|---|
| hydrogen and oxygen reactants | 820 |
| water products | 250 |
(a) What is the energy change, in kJ, for this reaction? [1]
(b) Name the type of reaction shown by Fig. 1. [1]
(c) Use the table to suggest why energy is released overall. [2]
The diagram shows a researcher using a calorimeter to compare the energy released when two samples of methane burn. The mass of water is kept at 100 g in both tests. Table 1 gives the observations.
| test | mass of methane burned / g | water temperature rise / °C |
|---|---|---|
| A | 0.20 | 16 |
| B | 0.40 | 31 |
(a) What variable is changed between tests A and B? [1]
(b) Give one variable that is controlled. [1]
(c) Use Table 1 to suggest whether the results are consistent with more methane releasing more energy. [1]
(d) Suggest two ways energy is lost from this calorimeter. [2]
Answer Details
Hydrogen and oxygen energy diagram
- \[820\ \mathrm{kJ}-250\ \mathrm{kJ}=570\ \mathrm{kJ}\] The energy change is 570 kJ released. [1]
- The reaction is exothermic. [1]
- The products have less energy, 250 kJ, than the reactants, 820 kJ. The 570 kJ difference is transferred to the surroundings, so energy is released overall. [2]
Methane calorimeter
- The changed variable is the mass of methane burned. [1]
- A controlled variable is the mass of water, kept at 100 g. Initial water temperature or using the same calorimeter would also be valid. [1]
- Yes. Burning 0.40 g methane gives a 31 °C rise, compared with a 16 °C rise for 0.20 g, consistent with more methane releasing more energy. [1]
- Energy can be transferred to the surrounding air and can heat the calorimeter. Hot gases leaving the apparatus also carry energy away. [2]
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