Unit 6 Review- Thermal Physics

Name __________________________________________________________________ Date: _______________________ Period __________ Unit 6 Review- Thermal Physics Essential Skills that will be tested 6-1 6-2 6-3 6-4 6-5 Questions- (this is only a partial review- use your worksheets, notes, & labs too) 1. Fill in the following table information. Variable Name Variable Symbol Unit Name Unit Symbol Formula On Reference Sheet? Internal Energy Final Temperature n/a Work Heat Specific Heat n/a Mass n/a Initial Temperature n/a Change in Temperature Heat from the Hot Reservoir n/a Heat from the Cold Reservoir n/a Work by a Heat Engine Efficiency 2. What is temperature? 3. Rank the following temperatures: 100°F, 100°C, and 100 K. 4. A temperature change of 50 K is equivalent to a temperature change in which scale-Celsius or Fahrenheit? 5. What must you have in order for heat to flow? 6. What are the three types of heat flow? Provide an example of each. 7. What two things happen when 2 substances reach thermal equilibrium? 8. A 100 g sample of aluminum at 100°C is combined with a 100 g sample of water at 20°C. a. Which material, if either, will undergo the greater temperature change and why? 9. b. Which material, if either, will undergo the greatest heat transfer? c. Describe from the molecules perspective what is happening during this transfer of heat. Use the words temperature, average kinetic energy, heat, and thermal equilibrium in your response. You add 10,000 J of heat to a sample 2 kg sample of water and the temperature changes by 2.5°C. If you add the same amount of heat to a sample half that size, what will the temperature change be now? Why? 10. You are going to build a slide at a playground and your two option for materials are: Aluminum (specific heat = 897 J/kg º C) or Iron (specific heat 449 J/kg º C). Based on their specific heat, which would you chose & why? 11. (See your heat calculations worksheet for more practice with these types of problems) You combine 100 kg of water (specific heat = 4184 J/kg°C ) at 30°C with a piece of gold having a mass of 18.69 kg and initially at 10 °C. At thermal equilibrium, the water has a temperature of 12°C. a. Which substance will gain heat? How do you know? b. Which substance will lose heat? How do you know? c. Calculate the heat gained/lost by the water. d. How much heat was gained/lost by the gold? How do you know? ______________________________ e. What is the final temperature of the gold? ___________________ f. Calculate the specific heat of gold. 12. (See your 1st Law of Thermodynamics WS for more practice with these concepts). What remains constant in the following thermodynamic processes? a. isovolumetric: b. isothermal: c. adiabatic: d. isobaric: 13. A gas undergoes a thermodynamic process in which heat is added to the gas yet its temperature does not change. a. What is the name of this type of process? b. What else is happening to the gas for this to be true? Analyze the first law of thermodynamics to help you answer this question. 14. A gas undergoes a thermodynamic process in which the temperature is decreased yet heat is not added or removed. a. What is the name of this type of process? b. What else is happening to the gas for this to be true? Analyze the first law of thermodynamics to help you answer this question. 15. A gas undergoes an isobaric process where it experiences an increase in temperature while expanding. Is heat being added or removed during this process? Analyze the first law of thermodynamics to help you answer this question. 16. 7500 J of heat is removed from a gas while 4500 J of work is done on the gas. a. What is the change in internal energy of the system? b. Did the system’s temperature increase or decrease? How do you know? 17. (See your engines worksheet for more practice with this concept) When an engine is running, it extracts 400 J of energy from the hot reservoir and does 250 J of work each minute. a. How much heat was lost to the cold reservoir? b. What would the efficiency of this engine be? c. Can an engine ever be 100% efficient? Explain. d. How could you make this engine more efficient?