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Name ______________________________ Thermodynamics Unit Study Guide Chap. 21-24 Vocabulary Temperature Heat Internal energy Thermal equilibrium Specific heat capacity Convection Conduction Radiation Heat of fusion Heat of vaporization Thermal Expansion Adiabatic Heat engine Entropy Thermodynamics Problems 1. The hottest temperature ever recorded on a planet was 864 ºF on Venus by the Soviet Venera probe and the U.S. Pioneer probe. The coldest place in the solar system is Pluto where the temperature is estimated at -360.0 ºF. Calculate each of these temperatures in degrees Celsius and Kelvin. (F = (5/9)xC + 32). 5/9 x 864 + 32 = 512 ºC + 273 = 785 K 5/9 x -360 F +32 = -168 ºC + 273 = 105 K 2. A man consumes 2,500 Calories (food calories) in one day assuming that all of this energy was used, and converted into heat, how much heat (in J/s) did he give off that day? 2500 Cal Day X 1 day 24 hr 1 hr 3600 s 4.18J 1 cal = .12 J/s 3. Calculate the number of calories of heat needed to change 340 mL of water by 50 C. Recall that 100 mL of water = 100 g of water. 17,000 calories or 17 Calories 4. A 50 gram piece of aluminum is heated to 100C and then dropped into cool water where the aluminum’s temperature drops to 30C. How many calories does the aluminum loose to the water? (Specific heat capacity Al = 0.215 cal/gC). Q=mcT = 50g x .215 cal/gC x 70 = 752.5 calories 5. Calculate the Ideal efficiency of a heat engine that takes in energy at 450 K and expels it to a reservoir at 60 K. 450-60/450 x 100 = 86.6 % 6. Circle the letter that best describes what happens when heat is added to a system. a. Much of it is destroyed immediately b. It transforms to an equal amount of some other form of energy. c. Much of it is lost d. It is used to overcome friction 7. Is the following sentence true or false? The compression and expansion of gases within the cylinders of an automobile engine is nearly adiabatic. __TRUE TRUE__ 8. What happens to a gas when it adiabatically expands and does work on its surroundings? It loses internal energy and cools down 9. Circle the letter that describes the adiabatic form of the first law of thermodynamics. a. pressure = constant b. energy out > energy in c. change in air temperature is directly proportional to the pressure change d. energy in = energy out + work Use the illustration below to answer the next question. 10. Circle the letter that describes the process that occurs to create the warm wind. a. adiabatic expansion b. adiabatic compression c. isobaric contraction d. thermal gain from land 11. Circle the letter of the thermodynamic law that states heat will never of itself flow from a cold object to a hot object. a. 1st Law b. 2nd law c. 3rd law d. 4th law 12. Is the following sentence true or false? Many heat engines are able to convert all heat input into mechanical energy output. FALSE 13. Is the following sentence true or false? No heat engine can have an ideal efficiency of 100%. TRUE TRUE 14. Circle the letter that best describes how the second law of thermodynamics applies to order and disorder. a. For all systems, overall order is constant. b. Natural systems tend toward a state of greater disorder. c. Natural systems are equally likely to become more ordered or more disordered d. All natural systems tend toward increasing order 15. A sample of gas is contained in a sealed flask. Circle the letter with the greatest disorder. a. The sample at 25 C in the sealed flask b. The sample at 50 C in the sealed flask c. The sample immediately after opening the flask d. The sample after it expands to fill the room 16. more a. b. c. d. Circle the letter of each example of increasing entropy. There may be than one answer. Gas molecules escaping from a bottle An unattended house breaking down A plant using energy from the sun to form new cells A breeze blowing papers off of your desk