1. Base your answer to the following question on the information below and on your knowledge of chemistry.

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1 1. Base your answer to the following question on the information below and on your knowledge of chemistry. A beaker contains a liquid sample of a molecular substance. Both the beaker and the liquid are at 194 K. The graph below represents the relationship between temperature and times as the beaker and its contents are cooled for 12 minutes in a refrigerated chamber. Identify the physical change occurring during the time interval, minute 4 to minute Base your answer to the following question on the information below and on your knowledge of chemistry. At standard pressure, water has unusual properties that are due to both its molecular structure and intermolecular forces. For example, although most liquids contract when they freeze, water expands, making ice less dense than liquid water. Water has a much higher boiling point than most other molecular compounds having a similar gram-formula mass. Determine the total amount of heat, in joules, required to completely vaporize a 50.0-gram sample of H 2O( ) at its boiling point at standard pressure. Base your answers to questions 3 and 4 on the information below and on your knowledge of chemistry. A few pieces of dry ice,, at are placed in a flask that contains air at. The flask is sealed by placing an uninflated balloon over the mouth of the flask. As the balloon inflates, the dry ice disappears and no liquid is observed in the flask. 3. Write the name of the process that occurs as the dry ice undergoes a phase change in the flask. 4. State the direction of heat flow that occurs between the dry ice and the air in the flask.

2 5. Base your answer to the following question on the information below and on your knowledge of chemistry. Ethane,, has a boiling point of at standard pressure. Ethanol,, has a much higher boiling point than ethane at standard pressure. At STP, ethane is a gas and ethanol is a liquid. Compare the intermolecular forces of the two substances at STP. Base your answers to questions 6 through 8 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. 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. 7. Using the graph, determine the total amount of heat added to the sample during interval CD. 8. Describe what happens to both the potential energy and the average kinetic energy of the molecules in the H2O sample during interval AB.

3 9. Base your answer to the following question on the information below. Natural gas is a mixture that includes butane, ethane, methane, and propane. Differences in boiling points can be used to separate the components of natural gas. The boiling points at standard pressure for these components are listed in the table below. 11. 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. List the four components of natural gas in order of increasing strength of intermolecular forces. Base your answers to questions 10 and 11 on Heat is added to a sample of liquid water, starting at 80.ºC, until the entire sample is a gas at 120.ºC. This process, occurring at standard pressure, is represented by the balanced equation below. H2O( ) + heat H2O(g) 10. On the diagram below, complete the heating curve for this physical change.

4 12. Base your answer to the following question on the information below. Carbon forms molecular compounds with some elements from Group 16. Two of these compounds are carbon dioxide, CO2, and carbon disulfide, CS2. Carbon dioxide is a colorless, odorless gas at room temperature. At standard temperature and pressure, CO2(s) changes directly to CO2(g). Carbon disulfide is formed by a direct reaction of carbon and sulfur. At room temperature, CS2 is a colorless liquid with an offensive odor. Carbon disulfide vapors are flammable. Identify one physical property and one chemical property of CS2. Base your answers to questions 13 through 15 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. 13. Determine the total amount of heat required to completely melt this sample at its melting point. 14. What is the total time this sample is in the liquid phase, only? 15. 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.

5 Base your answers to questions 16 and 17 on the information below. The graph below shows a compound being cooled at a constant rate starting in the liquid phase at 75 C and ending at 15 C. 16. What kelvin temperature is equal to 15 C? 17. A different experiment was conducted with another sample of the same compound starting in the solid phase. The sample was heated at a constant rate from 15 C to 75 C. On the graph, draw the resulting heating curve. 18. Base your answer to the following question on the graph below, which represents the cooling of a substance starting at a temperature above its boiling point. What is the melting point of this substance? 19. What is the total amount of heat energy, in joules, absorbed by 25.0 grams of water when the temperature of the water increases from 24.0 C to 36.0 C?

6 Base your answers to questions 20 through 24 on the information below. A substance is a solid at 15 C. A student heated a sample of the solid substance and recorded the temperature at one-minute intervals in the data table below. 20. The heat of fusion for this substance is 122 joules per gram. How many joules of heat are needed to melt 7.50 grams of this substance at its melting point? 21. What is the evidence that the average kinetic energy of the particles of this substance is increasing during the first three minutes? 22. Based on the data table, what is the melting point of this substance? 23. Plot the data from the data table. Circle and connect the points. 24. On the grid above, mark an appropriate scale on the axis labeled Temperature ( C). An appropriate scale is one that allows a trend to be seen.

7 Base your answers to questions 25 and 26 on the information below. 25. 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.

8 26. In the space below show a correct numerical setup for calculating the number of joules of heat gained by the water. 27. Base your answer to the following question on the heating curve below, which represents a substance starting as a solid below its melting point and being heated at a constant rate over a period of time. How does this heating curve illustrate that the heat of vaporization is greater than the heat of fusion? Base your answers to questions 28 through 30 on the pictures below: 28. Contrast sample A and sample B, in terms of compounds and mixtures. Include both sample A and sample B in your answer. 29. Explain, in terms of the composition, why sample A represents a pure substance. 30. Explain how the average kinetic energy of sample B can be equal to the average kinetic energy of sample C.

9 Base your answers to questions 31 through 34 on the information below. Given the heating curve where substance X starts as a solid below its melting point and is heated uniformly: 31. Describe, in terms of particle behavior or energy, what is happening to substance X during line segment. 32. Using ( ) to represent particles of substance X, draw at least five particles as they would appear in the substance at point F. Use the box provided above. 33. Identify a line segment in which the average kinetic energy is increasing. 34. Identify the process that takes place during line segment DE of the heating curve.

10 35. A sample of water is heated from a liquid at 40 C to a gas at 110 C. The graph of the heating curve is shown below. a. On the heating curve diagram provided below, label each of the following regions: Liquid, only Gas, only Phase change b. For section QR of the graph, state what is happening to the water molecules as heat is added. c. For section RS of the graph, state what is happening to the water molecules as heat is added.