Thursday February 21, 2013 Chapter 17: Thermochemistry

1. Thursday February 21, 2013Chapter 17: Thermochemistry • Calorimeter • Enthalpy • Heat capacity • Heat of combustion • Heat of reaction • Law of conservation of energy • Molar heat of condensation • Molar heat of fusion • Molar heat of solidification • Molar heat of solution • Specific heat • Standard heat of formation • Surroundings • System • Thermochemistry BRING TEXTBOOK TOMORROW TOO!

2. Wednesday February 18, 2015 EQ: How is specific heat related to conductivity? • Intro to Thermodynamics • Q Equation ANNOUNCEMENTS:

3. THERMOCHEMISTRY The study of the changes in heat in chemical reactions and physical processes.

4. Heat Energy HEAT is the form of energy that flows between 2 objects because of their difference in temperature. Other forms of energy — • light • electrical • kinetic and potential

5. Heat Transfer Heat transfers until thermal equilibrium is established.

6. Heat TransferNo Change in State Heat = (mass)(specific heat)(change in temperature) Q = mcDT Q: heat (joules) m: mass (grams) c: specific heat (J/goC or J/gK) DT: change in temperature (oC or K)

7. Specific Heat The amount of heat required to raise the temperature of 1 gram (or 1 kg) of a substance by 1 K (or oC)

8. Specific Heat

9. Specific Heat CONDUCTOR? INSULATOR? Is specific heat capacity related to heat conductivity? Iron Wood Air Aluminum Water https://www.youtube.com/watch?v=-wj2Oh50wsA

11. Practice Problem #1 A 15.75-g piece of iron is heated and as a result its temperature changes from 25°C to 175°C. Calculate the amount of heat absorbed by the iron.

12. Practice Problem #2 How much energy would be absorbed by 550 g of silver that is heated from 24oC to 45oC? (The specific heat of silver is 235 J/kgK)

13. Practice #3 25.0 g of mercury is heated from 25°C to 155°C, and absorbs 455 joules of heat in the process. Calculate the specific heat capacity of mercury.

14. Thursday February 19, 2015 EQ: How much energy is stored in a cheeto? How are food calories related to heat energy? • Energy In a Cheeto Lab ANNOUNCEMENTS:

15. Heat TransferNo Change in State Heat = (mass)(specific heat)(change in temperature) Q = mcDT Q: heat (joules) m: mass (grams) c: specific heat (J/goC or J/gK) DT: change in temperature (oC or K)

16. Which has more Calories? Crunchy or Puffy Cheetos All human activity requires “burning” food for energy. How much energy is released when food burns in the body? How is the caloric content of food determined? Lets investigate the caloric content of a popular snack food, Cheetos.

17. Lab Setup Safety Precautions • Wear Goggles • Tie back loose hair and sleeves • No phone cords or headphones in lab • No eating

18. Ticket Out the Door

19. Hint for #7 1 gram of water has a volume of 1 mL.

20. Specific Heat Practice WS Part 2 • 0.46 J/gC or 460 J/kgC • 0.14 J/gC or 140 J/kgC • 32oC • 0.131 J/gC or 131 J/kgC • 1540 g • 7600 J • 14000 J

21. HOMEWORK • Complete the back • Due tomorrow

22. Friday March 14, 2014 Define specific heat. The amount of energy required to raise 1 kg of a substance by 1 Kelvin. Put your vocabulary in the tray at this time!

23. Specific Heat The amount of heat required to raise the temperature of 1 gram (or 1 kg) of a substance by 1 K (or oC)

24. All are units of heat energy. 1 calorie = 4.184 Joules • Specific heat of water in calories: 1.00 cal/gC 1 food Calorie = 1000 calories Lab Setup: • Use about 20 mL of water

25. Please sit according to your lab station from Friday. Stations 3 and 4 Stations 5 and 6 Stations 1 and 2

26. Monday March 17, 2014 Warmup Question: How are the “joule”, “calorie”, and “Calorie” related? All are units of heat energy. • 1 calorie = 4.184 Joules • Specific heat of water in calories: 1.00 cal/gC • 1 food Calorie = 1000 calories

27. Lab Calculations

28. Today • Exchange data with the other group. • Use your data to make to make the calculations on the back. • Turn in. • Work on Heat Calculations WS

29. Tuesday March 18, 2014 How much energy would be absorbed by 550 g of silver that is heated from 24oC to 45oC? (The specific heat of silver is 235 J/kgK) Cheeto lab due at this time!!!

30. Heat of Fusion&Heat of Vaporization

31. Wednesday February 25, 2015 EQ: How much energy is stored in a cheeto? How are food calories related to heat energy? • Last Call: • Cheeto Lab • Heat Calculations WS ANNOUNCEMENTS:

35. Thursday February 26, 2015 EQ: What is difference between heat of fusion and heat of vaporization? • Review phase change • Heat of Fusion/Heat of Vaporization ANNOUNCEMENTS:

36. PHASE CHANGE gas liquid solid Energy Increases!

38. PHASE CHANGES Melting Solid to liquid Energy absorbed Freezing liquid to solid Energy released

39. Evaporation or Vaporization Liquid to gas Energy absorbed Condensation Gas to liquid Energy released

40. Sublimation Solid to gas

41. Deposition gas to solid http://www.youtube.com/watch?v=Hsu3JoXN-qU

42. A,C,E: temperature changes; phase is constant B,D: temperature is constant; phase changes

43. Heat Transfer with Change of StateSolid Liquid Heat Transferred = (heat of fusion)(mass) Q = (DHfus)(m) Example: Ice + 334 J/g (heat of fusion) -----> Liquid water

44. Heat Transfer with Change of StateLiquid Gas Heat Transferred = (heat of vaporization)(mass) Q = (DHvap)(m) Example: Water + 2260 J/g (heat of vaporization) -----> Steam

45. Which Q equation?? No Phase Change Phase change Q = mcDT solid/liquid: Q = (DHfus)(m) liquid/gas: Q = (DHvap)(m) For water: c = 4.18 J/gC DHfus = 334 J/g DHvap = 2260 J/g

46. Friday February 26, 2015 EQ: What is difference between heat of fusion and heat of vaporization? • Kahoot: Which Q is it? • Go over Parts 1 and 2 • Complete Part 3 ANNOUNCEMENTS:

49. Friday February 26, 2015 EQ: What is difference between heat of fusion and heat of vaporization? • Kahoot: Which Q is it? • Go over Parts 1 and 2 • Complete Part 3 ANNOUNCEMENTS: