1. Thursday February 21, 2013 Chapter 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. Intro to Thermodynamics
Wednesday February 17, 2016
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 transfers until thermal equilibrium is established.

6. Heat Transfer No 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

11. Practice Problem #1
A 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 18, 2016 Energy In a Cheeto Lab
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 Transfer No 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. 1 gram of water has a volume of 1 mL.
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. Lab Setup: Use about 20 mL of water 1 calorie = 4.184 Joules
All are units of heat energy.
1 calorie = Joules
Specific heat of water in calories: 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. How are the “joule”, “calorie”, and “Calorie” related?
Monday March 17, 2014
Warmup Question:
How are the “joule”, “calorie”, and “Calorie” related?
All are units of heat energy.
1 calorie = Joules
Specific heat of water in calories: 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. Cheeto lab due at this time!!!
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 Last Call: Cheeto Lab Heat Calculations WS
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. Heat of Fusion/Heat of Vaporization
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
liquid
gas
solid
Energy Increases!

38. PHASE CHANGES Freezing liquid to solid Energy released 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

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

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

44. Heat Transfer with Change of State Liquid Gas
Heat Transferred = (heat of vaporization)(mass)
Q = (DHvap)(m)
Example:
Water 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 Kahoot: Which Q is it? Go over Parts 1 and 2
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 Kahoot: Which Q is it? Go over Parts 1 and 2
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:

51. Complete Heat Calculations WS. Check your answers with the key.
Work Session
Complete Heat Calculations WS. Check your answers with the key.
Hint: Be sure all of your units are in sync before you solve!

52. Q=mcDT
Q=DHvap(m)
Q=mcDT
Q=DHfus(m)
Q=mcDT

53. Thursday March 20, 2014
A student uses the Q=mcDT equation to figure out how much heat is gained by a piece of ice as it melts into liquid. Why is this incorrect? The equation Q=mcDT cannot be used for a substance undergoing a phase change, only while it is in one specific phase because temperature does not change in a phase change.

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

55. Total Q partner activity
Tuesday March 3, 2015
EQ: What is difference between heat of fusion and heat of vaporization?
Calculating Total Q
Quiz
Total Q partner activity
ANNOUNCEMENTS:

56. Total Heat Calculations
How much heat is required to raise g of ice at a temperature of oC to room temperature of 21.0oC?

57. Q=mcDT
Q=DHvap(m)
Q=mcDT
Q=DHfus(m)
Q=mcDT

58. HEAT EQUATIONS Q = mcDT Q = (DHfus)(m) Q = (DHvap)(m)
For water: c = J/gC; DHfus = 334 J/g; DHvap = J/g
For ice: c = 2.06 J/g; For steam (gas): c = 2.02 J/g

59. TOTAL Q ASSIGNMENT With your partner:
Draw a sketch of the phase change graph and label the START and STOP points for your problems.
List the equations you would use to solve each step the problem.
Solve the heat for each step.
Find the total Q.