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Transcript
12 THERMAL ENERGY Vocabulary Review Write the term that correctly completes the statement. Use each term once. convection heat engine second law of thermodynamics entropy heat of fusion specific heat first law of thermodynamics heat of vaporization thermal conduction heat radiation thermal equilibrium 1. _________________________ ____ is the state at which the rate of thermal energy transfer between two objects is equal and the objects are at the same temperature. 2. _________________________ The transfer of thermal energy between objects is called ____ . 3. _________________________ The amount of energy required to raise the temperature of one unit mass of a substance by one temperature unit is the ____ of the substance. 4. _________________________ The amount of energy needed to melt 1 kg of a substance is the ____ . 5. _________________________ The ____ states that the change in thermal energy of an object equals the heat added to the object minus the work done by the object. 6. _________________________ ____ is the transfer of kinetic energy when particles collide. 7. _________________________ ____ is a measure of the energy dispersal of a system. 8. _________________________ A device that converts thermal energy to mechanical energy is a(n) ____ . 9. _________________________ The ____ states that natural processes go in a direction that increases the total entropy of the universe. 10. _________________________ ____ is the motion of a fluid caused by temperature differences. 11. _________________________ The amount of energy required to convert 1 kg of a substance from a liquid to a gas is the ____ . 12. _________________________ The transfer of energy by electromagnetic waves is called ____ . Chapter 12 Thermal Energy 1 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 13. 16 12 SECTION 1 Temperature, Heat, and Thermal Energy In your textbook, read about the theory of thermal energy and temperature. For each statement below, write true or rewrite the italicized part to make the statement true. 1. _________________________ The temperature of an object is a measure of the total kinetic energy of the particles. 2. _________________________ The thermal energy in an object depends on the number of particles in the object and the temperature of the object. 3. _________________________ Two bodies are in rotational equilibrium if they are at the same temperature. 4. _________________________ A Kelvin is equal in magnitude to a Celsius degree. 5. _________________________ Absolute zero is equal to 0°C. 6. _________________________ The freezing point of water is 0°C or 212 K. 7. _________________________ Absolute zero is the point at which a substance has minimal thermal energy. In your textbook, read about specific heat. For each term on the left, write the letter of the corresponding item. 8. _____ unit of specific heat a. K 9. _____ heat b. S 10. _____ degree Celsius c. T 11. _____ Kelvin d. C 12. _____ entropy e. Q 13. _____ energy change f. J/(kg•K) 14. _____ temperature change g. E Answer the following questions. Use complete sentences. 15. Why is the Kelvin temperature scale rather than the Celsius temperature scale used in science? Use “kinetic energy” in your answer. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Chapter 12 Thermal Energy 2 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 12 16. The diagram shows the construction of the inner liner of a vacuum bottle. How does a vacuum bottle prevent the transfer of thermal energy: a. by conduction? __________________________________________ __________________________________________ b. by convection? __________________________________________ __________________________________________ __________________________________________ c. by radiation? _________________________________________________________________________ _________________________________________________________________________ 17. What is the specific heat of a metal if it takes 15,000 J of heat to raise the temperature of a 620-g sample from 15.0C to 85.0C? In your textbook, read about calorimetry. Use the following information to answer questions 18–21. A student uses a foam cup as a calorimeter. The student places 100.0 g of water at 20C in the cup. The student adds 100.0 g of lead shot at 120C to the cup. The water and shot are then allowed to reach thermal equilibrium. The specific heat of lead is 130 J/(kg•K). 18. Is Q for the water positive or negative? ____________________________________________________________________________________ 19. Is Q for the lead shot positive or negative? ____________________________________________________________________________________ 20. Assuming that no thermal energy is lost to the surroundings, how does the total energy of the system compare with the total energy of the water and lead before mixing? ____________________________________________________________________________________ 21. What is the final temperature of the water at thermal equilibrium? ____________________________________________________________________________________ Chapter 12 Thermal Energy 3 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 12 SECTION 2 Changes of State and Thermodynamics In your textbook, read about changes of state. Circle the letter of the choice that best completes the statement or answers the question. 1. The energy needed to melt 1 kg of a substance is called the _____ . a. heat of vaporization c. heat of fusion b. melting point d. freezing point 2. The temperature at which all added thermal energy is used to change a liquid to a gas is the _____ . a. boiling point c. heat of fusion b. melting point d. heat of vaporization 3. How does the amount of energy absorbed by 1 g of ice as it melts compare to the amount of energy released by 1 g of water as it freezes? a. More energy is released by the ice than is absorbed by the water. b. More energy is absorbed by the water than is released by the ice. c. The amounts of energy absorbed and released depend on the surrounding temperature. d. They are the same. 4. Which equation correctly relates heat, mass, and the heat of vaporization? a. Q m Hv c. Q m/Hv b. Q mHv d. Q Hv/m 5. As a liquid changes to a gas, _____ . a. both its kinetic and potential energy increase c. only its potential energy increases b. only its kinetic energy increases d. neither its kinetic nor potential energy increases 6. How does the amount of energy needed to melt 1 kg of ice at 0C compare to the amount of energy needed to change 1 kg of water to steam at 100C? The heat of fusion of water is 3.34105 J/kg, and the heat of vaporization of water is 2.26106 J/kg. a. It takes about two-thirds as much energy to boil the water as to melt the ice. b. It takes the same amount of energy to boil the water and melt the ice. c. It takes about two-thirds as much energy to melt the ice as to boil the water. d. It takes more than six times as much energy to boil the water as to melt the ice. Chapter 12 Thermal Energy 4 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 12 Answer the following questions. Show your calculations. 7. How much ice at 273 K can be melted by 5.00 103 J? 8. A 2.00 102 g sample of water at 60.0C is heated to steam at 140.0C. a. How much heat is absorbed? b. How much energy would be released if the steam at 140.0°C were cooled to water at 60.0C? In your textbook, read about the first law of thermodynamics, the second law of thermodynamics, and entropy. Answer the following questions. Use complete sentences. 9. State the first law of thermodynamics. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 10. Some people think that they can cool off a hot kitchen by leaving the refrigerator door open. Why is that not true? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 11. When paint dries, does its entropy increase or decrease? Is this an instance where the second law of thermodynamics does not apply? Explain your answer. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Chapter 12 Thermal Energy 5 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 12 For each statement, circle 1 or 2 to indicate whether the statement relates more closely to the first law of thermodynamics or the second law of thermodynamics. 12. The total entropy of the universe tends to increase. (1) (2) 13. A change in the thermal energy of a system depends on the work done by the system and the heat added to a system. (1) (2) 14. Thermal energy flows spontaneously from hot objects to cold objects. (1) (2) 15. The amount of useful energy tends to decrease. (1) (2) 16. A heat engine converts thermal energy to mechanical energy. (1) (2) 17. Using mechanical energy, a refrigerator removes thermal energy from warmer bodies. (1) (2) 18. The moving parts in an automobile engine generate waste heat. (1) (2) Answer the following questions. Use complete sentences. 19. Explain why a heat engine must have a heat sink. ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 20. How does energy efficiency relate to the first and second laws of thermodynamics? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 21. Why is it important for appliance and automobile manufacturers to make their products as energy-efficient as possible? ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Chapter 12 Thermal Energy 6 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.