2. State the direction of heat transfer between the surroundings and the water in the bottle from 7 a.m. to 3 p.m.

Transcription

1 Base your answers to questions 1 through 3 on the information below. A student investigated heat transfer using a bottle of water. The student placed the bottle in a room at 20.5 C. The student measured the temperature of the water in the bottle at 7 a.m. and again at 3 p.m. The data from the investigation are shown in the table below. 1. Compare the average kinetic energy of the water molecules in the bottle at 7 a.m. to the average kinetic energy of the water molecules in the bottle at 3 p.m. 2. State the direction of heat transfer between the surroundings and the water in the bottle from 7 a.m. to 3 p.m. 3. Show a numerical setup for calculating the change in the thermal energy of the water in the bottle from 7 a.m. to 3 p.m.

2 Base your answers to questions 4 through 6 on the information below and on your knowledge of chemistry. 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. 4. Describe what happens to both the potential energy and the average kinetic energy of the molecules in the H2O sample during interval AB. 5. Using the graph, determine the total amount of heat added to the sample during interval CD. 6. 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. Base your answers to questions 7 and 8 on the information below and on your knowledge of chemistry. A student made a copper bracelet by hammering a small copper bar into the desired shape. The bracelet has a mass of 30.1 grams and was at a temperature of 21 C in the classroom. After the student wore the bracelet, the bracelet reached a temperature of 33 C. Later, the student removed the bracelet and placed it on a desk at home, where it cooled from 33 C to 19 C. The specific heat capacity of copper is J/g K. 7. Explain, in terms of heat flow, the change in the temperature of the bracelet when the student wore the bracelet. 8. Show a numerical setup for calculating the amount of heat released by the bracelet as it cooled on the desk.

3 Base your answers to questions 9 and 10 on Heat is added to a sample of liquid water, starting at 80. C, until the entire sample is a gas at 120. C. This process, occurring at standard pressure, is represented by the balanced equation below. H2O( ) + heat H2O(g) 9. In the box below, using the key, draw a particle diagram to represent at least five molecules of the product of this physical change at 120. C. 10. On the diagram below, complete the heating curve for this physical change. Base your answers to questions 11 through 13 on the information below. Heat is added to a 200.-gram sample of H2O(s) to melt the sample at 0 C. Then the resulting H2O( ) is heated to a final temperature of 65 C. 11. Determine the total amount of heat required to completely melt the sample. 12. In the space below, show a numerical setup for calculating the total amount of heat required to raise the temperature of the H2O( ) from 0 C to its final temperature. 13. Compare the amount of heat required to vaporize a 200.-gram sample of H20( ) at its boiling point to the amount of heat required to melt a 200.-gram sample of H2O(s) at its melting point.

4 Base your answers to questions 14 through 16 on on the information below. A gram sample of NaCl(s) has an initial temperature of 0 C. A chemist measures the temperature of the sample as it is heated. Heat is not added at a constant rate. The heating curve for the sample is shown below. 14. Determine the temperature range over which the entire NaCl sample is a liquid. 15. Identify one line segment on the curve where the average kinetic energy of the particles of the NaCl sample is changing. 16. Identify one line segment on the curve where the NaCl sample is in a single phase and capable of conducting electricity. 17. Base your answer to the following question on the following paragraph. The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the pressure on the surface of the liquid. The heat of vaporization of ethanol is 838 joules per gram. A sample of ethanol has a mass of 65.0 grams and is boiling at 1.00 atmosphere. Calculate the minimum amount of heat required to completely vaporize this sample of ethanol. Your response must include both a correct numerical setup and the calculated result.

5 Base your answers to questions 18 and 19 on the information below. At a pressure of kilopascals and a temperature of 373 K, heat is removed from a sample of water vapor, causing the sample to change from time gaseous phase to time liquid phase. This phase change is represented by the equation below. H2O(g) H2O( ) + heat 18. Determine the total amount of heat released by 5.00 grams of water vapor during this phase change. 19. Explain, in terms of particle arrangement, why entropy decreases during this phase change.

6 Base your answers to questions 20 and 21 on the information below. 20. In terms of energy flow,explain why the temperature of the water in the calorimeter increases.

7 21. In this investigation, the change in heat of the copper is greater than the change in heat of the water. What error could account for this apparent violation of the Law of Conservation of Energy? Do not use human error as part of the answer. Base your answers to questions 22 through 24 on the information below A 5.00-gram sample of liquid ammonia is originally at 210. K. The diagram of the partial heating curve below represents the vaporization of the sample of ammonia at standard pressure due to the addition of heat. The heat is not added at a constant rate. 22. Calculate the total heat absorbed by the 5.00-gram sample of ammonia during time interval AB. Your response must include both a correct numerical setup and the calculated result. 23. Describe what is happening to both the potential energy and the average kinetic energy of the molecules in the ammonia sample during time interval BC. Your response must include both potential energy and average kinetic energy. 24. Determine the total amount of heat required to vaporize this 5.00-gram sample of ammonia at its boiling point.

8 Base your answers to questions 25 through 28 on the information below. The temperature of a sample of a substance is increased from 20. C to 160. C as the sample absorbs heat at a constant rate of 15 kilojoules per minute at standard pressure. The graph below represents the relationship between temperature and time as the sample is heated. 25. What is the boiling point of this sample? 26. Use the key below to draw at least nine particles in the box, showing the correct particle arrangement of this sample during the first minute of heating. 27. What is the total time this sample is in the liquid phase, only? 28. Determine the total amount of heat required to completely melt this sample at its melting point.