Starting as a solid at - 25°C, a sample of H2O is heated at a constant rate until the sample is at 125°C. This heating occurs at standard pressure. The graph below represents the relationship between temperature and heat added to the sample.
57 Describe what happens to both the potential energy and the average kinetic energy of the molecules in the H2O sample during interval AB. [1]
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The potential energy remains the same, but the average kinetic energy of the H2O molecules increases. There is no change in potential energy. There is an increase in the average kinetic energy. |
58 Using the graph, determine the total amount of heat added to the sample during interval CD. [1]
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7-9 kJ (8 kJ plus or minus 1) |
59 Explain, in terms of heat of fusion and heat of vaporization, why the heat added during interval DE is greater than the heat added during interval BC for this sample of water. [1]
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The heat of vaporization of water is 2260 J/g and the heat of fusion for water is only 334 J/g. The heat of fusion of water is much less than its heat of vaporization |